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VOLUMEN 1 - NÚMERO 2
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Lic. Luis Tomás Castro Hidalgo Rector UJED M.I. José Vicente Reyes Espino Secretario General UJED Dr. José Gerardo Ignacio Gómez Romero Dirección General de Administración UJED M.C. Alberto Diosdado Salazar Director FICA M.C. Julio Gerardo Lozoya Vélez Secretario Académico FICA M.C. Julio Roberto Betancourt Chávez Jefe de la División de Estudios de Posgrado FICA Ing. Francisco Javier Facio Palacios Secretario Administrativo FICA Dr. Noé Villegas Flores Director de Revista Ingeniería Civil Sostenible Dra. Ana Carolina Parapinski dos Santos Jefe de Edición Portada: Prueba Módulo de elasticidad Fotografía: Ana Carolina Parapinski dos Santos El contenido de los artículos firmados es únicamente responsabilidad del autor(es) y no de los editores. El material impreso puede reproducirse mientras sea sin fines de lucro y citando la fuente. ISSN en trámite – País de edición MÉXICO – www.ingenieríacivilsostenible.com Revista Ingeniería Civil Sostenible. Avenida Universidad s/n Frac. Filadelfia, Gómez Palacio, Durango, MÉXICO. contacto@ingenieriacivilsostenible.com (52) 871-715.20.17. C.P. 35010
COMÉXICO Ingeniería Civil Sostenible Vol.1 – No. 2
Marzo/ Agosto 2012
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EDITORIAL Revista Ingeniería Civil Sostenible ISSN en registro – www.ingenieriacivilsostenible.com Facultad de Ingeniería, Ciencias y Arquitectura Vol. 1, No. 2 Marzo- Agosto 2012 EDITORIAL CON SEJOTORIA
Concrete Microstructure Study with high-reactivity metakaolin, proceeding from Industrial tailing.
6-17
PAULO SÉRGIO L. SOUZA, DENISE C. C. DAL MOLIN, CLÁUDIO DE S. KAZMIERCKZAK & RUAN FABRÍCIO G. MORAES
Empleo de bloques de concreto elaborados con escombros de construcción en zonas sísmicas 18-29 RAÚL GONZÁLEZ HERRERA, JESSICA NAD-XELLY ALEGRÍA NUCAMENDI, CARLOS MANUEL GARCÍA LARA, PEDRO VERA TOLEDO & JORGE ALFREDO AGUILAR CARBONEY
Measuring the Early Shrinkage of Mortars 30-41 MARKUS GREIM
Assessment of the modulus of elasticity in concrete with high reactivity metakaolin from industry tailing
42-52
PAULO SÉRGIO LIMA SOUZA; DENISE C.DAL MOLIN & MARCOS ANDERSON GUEDES FERNANDES
INFORMACIÓN PARA AUTORES
53-54
RICS es una revista semestral, de difusión científica y tecnológica de la Facultad de Ingeniería Civil, Ciencias y Arquitectura de la UJED sin fines de lucro, editada por el cuerpo académico de Tecnología del Concreto.
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BIENVENIDA DEL DIRECTOR DE LA REVISTA
Welcome message from the Editor-in-Chief It has been two years since I was given the privilege to serve as the Chief Editor of the Journal of Sustainable Civil Engineering. It has been a great pleasure for me to have done my duty for the journal despite the constant demand that it required. One of my major goals for the journal is that it should continue to provide a scholarly treatment of pressing contemporary issues that affect engineering and developing new materials in construction civil. So, the journal’s editorial focus covers several areas: Cement and concrete, durability of construction materials, management of industrial wastes of construction, recycled studies of materials and process of construction composites, infrastructure studies and seismic performance in infrastructure. We hope to be able to bring about gradual changes in the near future for a successful indexation and more importantly for the improvement of the journal. I would like to express my gratitude and thankfulness to those who have supported me during the last two years and to those who are going to be with me in our journey of bringing the journal to another height. Finally, we wish to encourage more contributions from the scientific community to ensure a continued success of the journal. Authors, reviewers and guest editors are always welcome. We also welcome comments and suggestions that could improve the quality of the journal.
Dr Noé Villegas Flores Editor-in-Chief Universidad Juárez del Estado de Durango University Avenue. Frac Filadelfia s/n Gómez Palacio City, Durango MÉXICO Email: nvillegas@ujed.mx www.ingenieriacivilsostenible.com
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Consejo asesor y comité científico Jayagopal S. PSG College of Technollogy, INDIA Virginie Wiktor. TU Delft, HOLANDA Alfredo Reyes Salazar. Universidad Autónoma de Sinaloa, MÉXICO Roberto César de Oliveira Romano, Universidade de Sao Paolo, BRASIL Antonio Aguado de Cea. Universidad Politécnica de Cataluña, ESPAÑA Edna Possan. Universidad Federal de la Integração Latinoaméricana, BRASIL Ramón Corral Higuera. Universidad Autónoma de Sinaloa, MÉXICO Ravindra Raja. Nanyang Tecnological University, SINGAPORE Urs Mueller. BAM Federal Institute for Materials Research andTesting, ALEMANIA Tezozomoc Pérez López. Universidad Autónoma de Campeche, MÉXICO Carlos Felipe Urazan Bonells. Universidad La Salle Bogotá, COLOMBIA Iris Mujica Flores. Logistíca y distribución La Gran Catalana. ESPAÑA Néstor Guzmán Chacón. Universidad de San Simón, BOLIVIA Delva Guichard Romero. Universidad Autónoma de Chiapas, MÉXICO Rajeswary Narayanasamy. Universidad Juárez del Estado de Durango, MÉXICO Mauricio Centeno Ortiz. VIATEST, MÉXICO Carlos P. Barrios Durstewitz. Universidad Autónoma de Sinaloa, MÉXICO Katarina Malaga. Cement and concrete Institute CBI, SUECIA Luis Agullo Fité. Universidad Politécnica de Cataluña, ESPAÑA José Angel Ortiz Lozano. Universidad Autónoma de Aguascalientes, MÉXICO Edgar Vladimiro Mantilla Carrasco. Universidade Federal de Minas Gerais, BRASIL Mario Walter Efraín Toledo. Universidad Salta, ARGENTINA José Castañeda Ávila. Universidad Autónoma de Chihuahua, MÉXICO Vesa Penttala. Alto University, FINLANDIA Gláucia María Dalfré. Universidade do Minho, PORTUGAL Diego Miramontes de León. Universidad Autónoma de Zacatecas, MÉXICO Luis Augusto Conde Mendes Veloso. Universidade Federal do Pará, BRASIL Francisco Alberto Alonso. Universidad Autónoma de Chiapas, MÉXICO Luis Gil Espert. Universidad Politécnica de Cataluña, LITEM, ESPAÑA Edder Alexander Velandia Duran. Universidad de La Salle, COLOMBIA Jorge Luis Almaral Sánchez. Universidad Autónoma de Sinaloa, MÉXICO Oscar Gónzalez Cuevas. Universidad Autónoma de México, MÉXICO Erick Maldonado Bandala. Universidad Veracruzana, MÉXICO Ma. Cruz Alonso Alonso. Instituto de Ciencias de la Construcción Eduardo Torroja- CSIC, ESPAÑA Citlali Gaona Tiburcio. Centro de investigación en materiales avanzados, MÉXICO José Mora Ruacho. Universidad Autónoma de Chihuahua, MÉXICO Patricia Elke Rodríguez Schaeffer. Universidad Autónoma de Chiapas, MÉXICO Luis Francisco Chapa González. Universidad Autónoma de Nuevo León, MÉXICO María de la Consolación Trinidad Gómez Soberón. Universidad Autónoma Metropolitana, MÉXICO Miguel Ángel Baltazar Zamora. Universidad Veracruzana, MÉXICO
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Paulo S. L. Souza; Denise C. C. Dal Molin; C. de S. Kazmierckzak & R. F. G. Moraes
Concrete Microstructure study with high-reactivity metakaolin, proceeding from Industrial tailing Paulo S. L. Souza1; Denise C. C. Dal Molin2; C. de S. Kazmierckzak3; R. F. G. Moraes4
Received Article: January 20, 2012 Acceptance article: June 14, 2012
Abstract: This work aimed at studying the concrete microstructure, intending to verify its behavior regard to the high-reactivity metakaolin use (HRMK). To obtain this mineral addition we have adopted as raw material the paper industry tailing, afterwards a calcination and milling process, it changes into HRMK. To accomplish work, the HRMK content have been varied, and also the ratio water/cement and the body-tests disruption ages. In order to accomplish this objective we have used the diffraction of xray, porosimetry by titration and mercury intrusion. The study has indicated that the use of HRMK provokes alterations within the concrete microstructure within the chemical aspect, due to the pozolanic activity where new compositions appearance is evidenced as the gehlenite and the C4AH13. Within the physical aspect also changes have been evidenced regard to of the filer effect. The work has been concluded with some commentaries over the obtained outcomes. Keywords: high-reactivity metakaolin, microstructure, calcium hydroxide, calcium silicate hydrated, gehlenite.
1. INTRODUCTION In the early twentieth century, the use of concrete has always been seen with reservation when using them within tall buildings, regard to the difficult of obtaining high material resistance. Nevertheless, since the second half of this century the situation has begun to change, providing to obtaining concrete with high resistance, called Hrc. This change is mainly due to the use of mineral addition and better understanding by the researchers, the reaction that occur within the cement hydration process and the concrete internal structure. Currently, even with the adv ances in concrete microstructure, there is still some gaps within knowledge, especially when it relates to the use of new materials within the concrete, such as high reactivity metakaolin (HRMK). The HRMK, besides having technical advantages, is able to be gathered from the paper industry tailing. This tailing is basically made by processed kaolin of an extremely limpid, white, thin and pure kaolin (high content of Kaolinite -Al23.2SiO2.2H2), being transformed into aluminium-silicate pozzolanic throughout a calcinations process (from 700 to 800ºC) and Civil Eng., Dr. Professor and researcher at NUHAM-UFPª; e-mail: paseliso@ufpa.br Civil Eng. Dr. Professor and researcher at UFRGS-NORIE. e-mail: dalmolin@vortex.ufrgs.br 3 Civil Eng. Dr. Professor and researcher at UNISINOS-RS e-mail: claudiok@unisinos.br 4 Civil Eng. Student and researcher at NUHAM-UFPa. e-mail: ruanmoraes@yahoo.com.br 1 2
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Paulo S. L. Souza; Denise C. C. Dal Molin; C. de S. Kazmierckzak & R. F. G. Moraes milling. According to the reported of the first work, this tailing comes from an industry located in the northwest of Pará State, which nowadays storage them within tailing dams. Nevertheless, this storage process has been changed into an environmental problem due to the demand of large areas of deforestation. Thus, the main goal of this study has been to determine the variation found within the concrete microstructure throughout the X-ray diffraction, titration and porosimetry by mercury intrusion, from the HRMK adding coming from the paper industry tailing. 2. METHODOLOGY 2.1 Material Characterization We have used quartz-washed sand, mined from Jacuí River and crushed rock of basaltic origin, whose characteristics, are placed within table 1. We have used the Portland cement of high initial resistance (CPV-ARI). The HRMK was obtained the calcinations to750 ºC and afterwards milling process. Within figure 1 there is the x-ray diffraction of the material afterwards calcinations, where we may realized low crystallization of its structure. The main characteristics of the cement and the HRMK are placed within the table 2. Table 1 – Values gathered within the used aggregates physical characteristics
Description
Sand
Specific mass - NBR 9937 (ABNT, 1987)
2,62 kg/dm3
Unit mass – NBR 7251 (ABNT, 1982)
1,51 kg/dm3
Thinness modulus – NBR 7217 (ABNT, 1987) Maximum diameter – NBR 7217 (ABNT, 1987)
2,43 2,4 mm
Crushed rock 2,71 kg/dm3 1,44 kg/dm3 6,85 19 mm
Table 2 - Main characteristics of the cement and the HRMK used.
Chemistry SiO2 (%) AL2O3 (%)
Cement 19,51 4,17
HRMK 42,19 39,24
Fe2O3 (%) P2O5 (%)
2,85
1,88
MgO (%)
1,32
0,21 0,20
TiO2 (%)
-
1,49
SO3(%) CO2 (%)
2,72
Mechanical and Physics
Cement 4.570
HRMK 10,59 18.770
9,16
4,65
Resistance to Cement Compression – 1st day
19,00
-
-
Resistance to Cement compression – 3rd day
30,70
-
CaO Free
2,08 1,48
-
Resistance to Cement compression – 7th day
34,00
-
CaO Total
64,32
0,02
Pozzolanic Activity (%)
Specific area (m²/kg)
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Figure 1 – Pozzolan X-ray diffraction, afterwards the calcinations process
A super-plasticizer compounded of sulphonated naphthalene has been used, made from 37 to 39% of solids. To determine the final amount of water to be added to the mixture, we have used the value of 38% of solids to correct the ratio Water/Binder. 2.2 Experimental Program and elaboration and cement mixture procedure To assess this material influence, we set up controllable variables. We have used the following levels for each controllable variable, as it follows. HRMK content of replacement: 0%, 10%, 20%, and ; ratio w/(c+HRMK): 0.25 and 0.60; age 1, 14 and 28 days. We have adopted a dosage method proposed by MEHTA and AITCIN (1990). The control of the workability, the value of 120 20 mm has been used to accomplish the assay of trunk cone depletion, according to the NBR 7223 (1992), this procedure has been the guideline to the additive content definition to be used. The table 3 presents the amounts of materials, where we have highlighted that the amount of final water includes the added water within the additive. Table 3 - Proportion of the materials for the concrete output.
Ratio w/(c+MCAR) 0.25 0.60
HRMK %
Water (kg/m³)
Cement (kg/m³)
HRMK (kg/m³)
Sand (kg/m³)
0 10 20 0 10 20
144 143 140 214 210 208
575 517 460 358 323 287
46 93 29 58
654 654 654 773 773 773
Coarse Aggregate (kg/m³) 1085 1085 1085 962 962 962
The molding and the process of cure have followed the procedures of NBR 5738 (1984). Within 24 hours of cure into a laboratory, the dismounting was made and the bodytests placed into a humid chamber until the specific date. The paste have had the same consumption of cement of the concrete, being that the pastes have decreased the water amount to be placed, due to the absorption of coarse
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Paulo S. L. Souza; Denise C. C. Dal Molin; C. de S. Kazmierckzak & R. F. G. Moraes aggregate and sand. The samples on the assay date have been prepared to use of ethyl alcohol. For the diffraction of X-rays and titration has been carried out afterwards grinding and screening of the samples. Within table 4 we have got the concrete assay and within the paste. Table 4 - Variables analyzed within microstructure assay.
Content of HRMK (%) 0 10 20
Ratio w/(c+MCAR) 0,25 0,60
Age (days) 1 14 28
Assays
Mixture
Porosimetry by mercury intrusion. Diffraction of X-rays, titration
Concrete Paste
3. OUTCOMES 3.1 X-Ray Diffraction We have adopted diffractometer D5000, Siemens, type Kristaloflex (CuK radiation, 30 ma current and voltage 40 kV) scan with step of 0.02 and collection time of 1 second per step. The use of this technique, defined as indirect interpretation, aims at obtaining information on the mineralogy of the products formed within the mixtures hydration process with and without the HRMK. The diffractograms outcomes are placed within Figure 2. Within the diffractograms placed within Figure 2, we have verified a higher intensity of the peaks for the Ca(OH)2 within the mixtures with a higher ratio w / (c + MCAR), which reflects its larger dimension due to higher ratio water / solids within these fresh mixtures, allowing a higher growth and higher perfection of the crystals surface of Ca(OH)2. Parallel to this, we have also noted a higher presence of volatile constituents of the anhydrous cement within mixtures with the smaller ratio w/(c + HRMK), as the C2S (larnite), the halloysite and bassanite, due to non hydration of these compounds, lack of water. Regarding to the HRMK influence within the mixtures hydration process, we verify that the changes outcome from the use of this material present itself differently within the age groups. On the 1st day, within the two ratios w/(c + MCAR), there has been little change within the mixtures mineralogy, regardless to the content of replacement, indicating the slow start of the pozzolanic reaction. On the 14th day we have verified within the two ratios w/(c + HRMK) studied changes within the mixtures hydration process, decreasing the intensity of the Ca(OH)2 peaks and the increase of the C-S-H peaks, as well the appearance of other compounds, such as hydrated (C2ASH8) and C4AH13. On the 28th day, we have got apparently a similar behaviour to that found on 14th day, and at this age we have already noted a higher intensity of peaks relating to the new compounds. At whole ages, the changes have been more evident with the content of replacement increasing and the ratio w/(c + HRMK).
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Paulo S. L. Souza; Denise C. C. Dal Molin; C. de S. Kazmierckzak & R. F. G. Moraes The highlighted alterations, mainly on the 14th and 28th day, are jointly with filer effect responsible for the matrix densification, which may outcome within improving mechanical concrete properties with HRMK, for the reference mixture. This improvement in mechanical properties may still present, as the outcome, the presence of hydrated gehlenita within HRMK mixtures, which according to Taylor (1992), is more resistant than the C-S-H.
Figure 2 - Diffractograms of Paste: (a) w/(c+HRMK) of 0,25 on the 1st day; (b) w/(c+HRMK) of 0,60 on the 1st day; (c) w/(c+HRMK) of 0,25 on the 14th day; (d) w/(c+HRMK of 0,60 on the 14th day; (e) w/(c+HRMK) of 0,25 on the 28th day; (f) w/(c+HRMK) of 0,60 on the 28th day.
Another important issue concerning to the HRMK, is related to the compounds formed by the reaction of pozzolanic material. Within this context, we may verify that usually has not been identified the presence of hydrated gehlenite and C4AH13 on the 1st day. These compounds presence has been highlighted only on the 14th day. The hydro-grenade presence has not been noted within this compound. Regarding to C-S-H and hydrated gehlenite, we realize that the identification proved to be somewhat harmed by the fact that these compounds present low crystallinity, and do not present accurate peaks when exposed to x-rays. Moreover, we have got peaks regard to these
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Paulo S. L. Souza; Denise C. C. Dal Molin; C. de S. Kazmierckzak & R. F. G. Moraes compounds coinciding with other peaks. According to the AMERICAN PUBLIC HEALTH ASSOCIATION (1985), this coincidence makes the diffraction of x-rays does not allow the perfect identification of these compounds. These factors have indicated the need for other forms of identification, such as thermal differential analysis (TDA), that could identify, more clearly, the presence of C-S-H and the appearance of hydrated gehlenita. 3.2. Thermo differential (TDA) and thermo gravimetric (TGA) analysis This analysis has also aimed at verifying the HRMK influence within the cement hydration process, as well, ratify the presence of compounds and the behavior evidenced within the x-rays diffraction. For the analysis, we have used the thermo balance NETZSCH model STA 409C and alumina crucibles for samples, and we have used as parameters to be attained at a nitrogen atmosphere, heating rate of 10 oC / min and maximum temperature 1100 oC. We have adopted within the pastes analyzed the same variables used within the xrays diffraction assay. The TDA outcomes are placed within the figure 3.
Figure 3 - Paste of TDA (a) w/(c+HRMK) of 0,25 on the 1st day; (b) w/(c+HRMK) of 0,60 on the 1st day; (c) w/(c+HRMK) of 0,25 on the 14th day; (d) w/(c+HRMK of 0,60 on the 14th day; (e) w/(c+HRMK) of 0,25 on the 28th day; (f) w/(c+HRMK) of 0,60 on the 28th day.
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Paulo S. L. Souza; Denise C. C. Dal Molin; C. de S. Kazmierckzak & R. F. G. Moraes Within Figure 3 we have observed again the differences within the outcomes coming from the changes of the replacement content, the ratio w/(c + HRMK) and age (degree of hydration). We have got, within whole mixtures, the presence of two endothermic peaks appearing around 130 ° C and 480 º C, regarding to presence of C-S-H and Ca(OH)2, respectively. This analysis also points itself again a higher intensity of the Ca(OH)2 peaks within mixtures with higher ratio w/(c + HRMK), evidenced again a higher presence of this compound. Regarding to analysed age, we have got within its minority an increase within the C-S-H peak and a decrease of Ca(OH)2 peak, within the two ratios w/(c + HRMK), with the HRMK replacement content, confirming the pozzolanic effect, highlighted within the x-rays diffraction. In addition to the C-S-H and Ca(OH)2 we have also verified the presence of ettringite within the mixture of reference and gehlenita (C2ASH8) and C4AH13 presence within HRMK mixtures. Nevertheless, the presence of these compounds within HRMK mixtures has occurred, as evidenced within the diffractogram, only within mixtures with higher ratio w/(c + HRMK). Regarding to gehlenita, we may verify the presence of this compound only on 14th day, which is consistent with the reported by FRIAS and CABRERA (2001), nevertheless, differs from that reported by AMBROISE et al. (1994), which only identifies this phase are superior than 28 days and replacement content of 20% and 25%. Regarding to C4AH13, we have had the only finding of this compound on the 28th Day, differing from that reported by FRIAS and CABRERA (2001), which identifies this compound only at the higher ages. We believe that the differences related to the period of appearance of certain compounds may be caused by factors such as: conditions for conducting the assays and the HRMK composition, cement and temperature, which may speed up or slow down the hydration process and pozzolanic reactions. Within whole HRMK mixtures, as well within diffractograms, we have not realized the presence of hydro grenade. 3.3. Titration The completion of this assay has aimed at attempting to quantify the consequences outcome from the pozzolanic reaction of HRMK, at the X-ray diffraction and thermo gravimetry analysis, regard to consumption of calcium hydroxide, so, reduction of this compound due to pozzolanic reaction of HRMK. This assays, has been based on the alkali extraction with distilled water for a period of approximately 48 hours, and titration with acid of known concentration. The Ca(OH)2 content within mixtures regard to the ratio w/(c + HRMK) of 0.25 and 0.60, are placed within Figure 4. Based on the presented figures within Figure 4, we have got again endorsed some evidence placed within the x-rays diffraction. Regard to the Ca(OH)2 content, we have verified that actually there was a greater output of this compound within larger ratios w/(c + HRMK), caused by the justifications stated within items 3.1 and 3.2. Regarding to the HRMK pozzolanic effect this has been quantified with the Ca(OH)2 decrease, which usually decreased with increasing HRMK content of replacement. Despite this Ingeniería Civil Sostenible Vol.1 – No. 2
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Paulo S. L. Souza; Denise C. C. Dal Molin; C. de S. Kazmierckzak & R. F. G. Moraes
2.00
2.00
1.50
1.50
1 day
1.00
14 days
Ca(OH)2(%)
Ca(OH)2(%)
decrease, we have verified differences regard to that reported by other references, referred to the Ca(OH)2 consumption, thus Kostuch et al. (2000) has verified that the total consumption of this compound to the 28th day, when the use of the replacement content of 20%.
1.00 0.50 0.00
Age
28 days
0.50 0.00
0
10
20
0
Proportion of substitution (%) (a)
10
20
Proportion of substitution(%)
(b)
Figure 4 - Consumption of Ca (OH)2 within the mixture as: (a) ratio w/(c+HRMK) of 0,25 (b) ratio w/(c+HRMK) of 0,60.
The pozzolanic effect has shown itself again more intense within the higher ratios w/(c + HRMK), and the two ratios studied, we have had the greatest pozzolanic effect intensity within the first 14 days, meeting as described by KHATIB and WILD (1996), regard to the pozzolanic reaction period of this material. Another point to be discussed within the titration has been the HRMK influence within the alkalinity mixtures. This analysis aimed to verifying the mixture pH, since this parameter is extremely important for chemical protection of the concrete reinforcement, within the case of carbonation corrosion. The values obtained within this assay are placed within Figure 5. 13.50
13.00
13.00
Idades 1 day
pH
pH
13.50
12.50
14 days
12.50
12.00
28 days
12.00 0
10
20
Proportion of substitution (%) (a)
0
10
20
Proportion of substitution (%) (b)
Figure 5 - pH Values, measured by titration, withiin mixtures with: a) ratio w/(c+HRMK) of 0,25 (b) ratio w/(c+HRMK) of 0,60.
According to the figures presented within Figure 5, we verify that the decrease in pH has occurred, regardless to the ratio w/(c + HRMK) used, but remained more intense within the larger ratios w/(c +HRMK) and within the first fourteen days. The pH reduction within the mixtures, due to the Ca (OH)2 consumption within the HRMK pozzolanic reaction, has outcome within little decrease within alkalinity, not influencing significantly the chemical IngenierĂa Civil Sostenible Vol.1 – No. 2
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Paulo S. L. Souza; Denise C. C. Dal Molin; C. de S. Kazmierckzak & R. F. G. Moraes reinforcement protection. KOSTUCH et al.KOSTUCH et al. (2000) also obtained similar pH values with the use of HRMK contents of 10% and 20%. 3.4 Porosimetry by mercury intrusion The pursuit of this analysis was mainly due to the need to verify the filer effect of HRMK use. Within the carry out of the assays we have used the MASTER PORE 33 of QUINTACHRONE, with a contact angle of 140º and a pressure range from 0 to 33,000 psi, using samples obtained from concrete. The assay implementation has been developed within two stages. Thus, the intrusion of mercury within the sample has occurred under low pressure (0 to 50 Psi) until this pressure has become ineffective within the assay course and, therefore be transported to the second pressure cell, where the intrusion mercury has occurred under high pressure (50 to 33,000 psi). As an outcome of this process, we have got the pore size distribution and total porosity of the samples. For the total porosity of the samples analyzed, we have summed the volume of mercury introduced, both the low and high pressure. The total porosity of the samples is placed within Table 6. Table 6 - Total Porosity Values of the samples.
Ratio w/(c+HRMK) 0,25
0,60
Mixtures Reference 10% of HRMK 20% of HRMK Reference 10% of HRMK 20% of HRMK
Total Porosity total (%) 14 28 1 day days days 4,40 4,81 4,91 8,55 9,42 7,25
3,22 3,33 3,04 7,33 6,07 7,48
3,23 3,32 2,93 6,71 5,6 6,02
Regarding to the behaviour of total porosity, as expected, we have verified that normally has occurred to reduction regard to the ratio w/(c + HRMK), with the increase of the replacement content and the hydration degree. Although, this behavior has not been valid for whole of total porosity presented. This issue may be the outcome of the assay inherent variability, due to several factors, such as the wall effect, derived from the paste contact with aggregate or the molding surface, which may cause an increase within the pore region or localized failure. The decrease within total porosity with the HRMK use has also been reported by KOSTUCH et al. (2000) and FRIAS and CABREARA (2000), when the use of replacement content of 20% and 5%, 10%, 15% , 20% and 25% of HRMK, respectively. Even with the behavior of the total porosity as expected, we have decided to use the distribution of pore size as a manner to better analyze the influence of the variables studied. This option has been based on some outcomes reported by METHA and MONTEIRO (1994), who claim not to be the total porosity, but the pores size distribution that effectively controls the strength and durability According to the authors, this distribution may be divided into macro-pores ( > 0.05 Ingeniería Civil Sostenible Vol.1 – No. 2
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Paulo S. L. Souza; Denise C. C. Dal Molin; C. de S. Kazmierckzak & R. F. G. Moraes m) and micro-pores (<0.05 m), which exert huge influence on the strength and durability and drying shrinkage and fluency, respectively. The charts with the concrete samples pores distribution studied are placed within Figure 6. a)
b)
c)
d)
e)
f)
Figure 6 - Pores Average Diameter Values (a) w/(c+HRMK) of 0,25 on the 1st day; (b) w/(c+HRMK) of 0,60 on the 1st day; (c) w/(c+HRMK) of 0,25 on the 14th day; (d) w/(c+HRMK of 0,60 on the 14th day; (e) w/(c+HRMK) of 0,25 on the 28th day; (f) w/(c+HRMK) of 0,60 on the 28th day.
Within figure 6, we verify the influence on the parameters studied of pore size distribution, where we realize small presence of macro-pores within samples with age increase, the content of replacement increase and decrease of the ratio w/(c + HRMK). This refinement of the pores has also been reported by KHABIT and WILD (1996) between 14th and 28th days within cement pastes with 5%, 10% and 15% of HRMK and DELVASTO and MORALES (2000), when the use of several contents of replacement within mortars. The minor presence of macro-pores and consequent densification of the matrix not only has been confirmed on the first day, since we have verified that the content of replacement increase has not outcome in a reduction within the presence of macro-pores. Ingeniería Civil Sostenible Vol.1 – No. 2
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Paulo S. L. Souza; Denise C. C. Dal Molin; C. de S. Kazmierckzak & R. F. G. Moraes This different behavior is due to the inefficiency of the HRMK filer effect to replace the cement. In addition to the low efficiency of the filer effect, also is caused, a minor pozzolanic velocity reaction that day, we have verified in the x-ray diffraction and thermal differential analysis. The two situations are mostly from larger particle size of HRMK regard to the active silica. 4. FINAL CONSIDERATIONS Thus, the accomplishment outcomes from this work are stated below: -
Within x-rays diffraction assay, we may highlight a greater presence of C-S-H peaks and Ca(OH)2 within the larger ratios w/(c + HRMK) and pozzolanic effect outcome from the HRMK use. We have highlighted the appearance of gehlenita and C4AH13.
-
Within thermo differential analysis (TDA) and thermo gravimetric analysis (TGA) we have ratified the evidence obtained within the diffraction of x-rays.
-
Within titrations, we have quantified the decrease in Ca(OH)2 outcome from the HRMK use. We have also verified the decrease in pH without affect the alkalinity of the mixtures.
-
Within the porosimetry by mercury intrusion has ratified the HRMK filer effect by the decrease of total porosity and pore distribution regard to the mixtures of references.
5. ACKNOWLEDGEMENT The author’s would like to thanks the financial support supplied by the CNPq (National Council of Scientific and Technological Development) for the accomplishment of this work.
6. REFERENCES [1] AMERICAN CONCRETE INSTITUTE. Committee 363 R. State-of-the-art report on high strength concrete. ACI manual of concrete practice, Detroit, 1991, part 1. 48p. [2] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Argamassas e concreto – determinação da resistência à tração por compressão diametral de corpos-de-prova cilíndricos: NBR 7222. Rio de Janeiro, 1994. [3] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Agregados em estado solto. Determinação da massa unitária: NBR 7251. Rio de Janeiro, 1982. [4] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Agregados – Determinação da composição granulométrica: NBR 7217. Rio de Janeiro, 1987.
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Paulo S. L. Souza; Denise C. C. Dal Molin; C. de S. Kazmierckzak & R. F. G. Moraes [5] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Agregados – Determinação da massa específica do agregado miúdo por meio do frasco de Chapman: NBR 9776. Rio de Janeiro, 1986. [6] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Agregados-Determinação da absorção e da massa específica do agr. graúdo: NBR 9937. Rio de Janeiro, 1987. [7] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Concreto - Determinação da consistência pelo abatimento do tronco de cone: NBR 7223. Rio de Janeiro, 1992. [8] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Concreto – Determinação da resistência à tração na flexão em corpos-de-prova prismáticos: NBR 12142. Rio de Janeiro, 1992. [9] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Concreto - Determinação do módulo de deformação estática e diagrama – Tensão-Deformação: NBR 8522. Rio de Janeiro, 1984. [10] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Confecção e cura de corpos-de-prova de concreto cilíndricos ou prismáticos: NBR 5738. Rio de Janeiro, 1984. [11] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Ensaio de compressão de corpos-deprova cilíndricos de concreto: NBR 5739. Rio de Janeiro, 1980. [12] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Projeto de estruturas de concreto: NBR 6118. Rio de Janeiro, 2001. [13] COMITE EURO-INTERNATIONAL DU BETON. CEB-FIP model code 1990. Lausanne, 1991. 159p. (Bulletin d’information, 203). [14] DAL MOLIN, D.C.C. Contribuição ao estudo das propriedades mecânicas dos concretos de alta resistência com e sem adição de microssílica. São Paulo, 1995. 286 p. Tese de Doutorado – Escola Politécnica da USP. [15] METHA, P.K.; AÏTCIN, P.C. Principles underlying output of high-performance concrete. Cement, Concrete and Aggregates, Philadelphia, v.12, nº 2, p. 70-78, Winter, 1990. [16] MEHTA, P.K.; MONTEIRO, P.J.M. Concreto: estrutura, propriedades e materiais. São Paulo: PINI, 1994. [17] SENSALE, G.R.B de. Estudo comparativo entre as propriedades mecânicas dos concretos de alta resistência com cinza de casca de arroz. Porto Alegre, 2000. 181 p. Tese de doutorado. PPGEC - UFRGS.
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R. González Herrera, J. Nad-Xelly Alegría Nucamendi, C.M. García Lara, P. Vera Toledo y J.A. Aguilar Carboney
Empleo de bloques de concreto elaborados con escombros de construcción en zonas sísmicas R. González Herrera1, J. Nad-Xelly Alegría Nucamendi, C.M. García Lara, P. Vera Toledo y J.A. Aguilar Carboney
Recibido: 3 de marzo de 2012 Aceptado: 8 de julio de 2012
Resumen: Este artículo presenta la situación persistente en torno a los residuos de construcción (RC) empleados para la elaboración de bloques de concreto, se muestra su potencial de reciclaje como materia prima, que puede incluso ser empleada en zonas sísmicas; lo cual se desarrolla con un trabajo experimental donde se propone una dosificación para bloques, con la cual cumplan con las características técnicas establecidas en las normas mexicanas [1 y 2]. Adicionalmente, se compararon los resultados contra los obtenidos en bloques convencionales que se fabrican en Tuxtla Gutiérrez, Chiapas, México, lugar donde se desarrolló el estudio. Los resultados obtenidos son alentadores en resistencia mecánica y facilidad constructiva, así como competitivos en costos. Palabras clave: Residuos de construcción, bloques de concreto, construcción sismo resistente.
1. INTRODUCCIÓN La Ley General para la Prevención y Gestión Integral de los Residuos (LGPGIR) [3], define cuatro tipos de residuos: Residuos de Manejo Especial, Residuos Incompatibles, Residuos Peligrosos y Residuos Sólidos Urbanos. Los Residuos de Manejo Especial son considerados como aquellos generados en los procesos productivos, que no reúnen las características para ser considerados como peligrosos o como Residuos Sólidos Urbanos, o que son producidos por grandes generadores de Residuos Sólidos Urbanos [3]. Dentro de los Residuos de Manejo Especial se encuentran los Residuos de la Construcción (RC). Los residuos generados durante estas actividades consisten generalmente en residuos de materiales utilizados para construir como madera, tabla roca, residuos de albañilería, metales, vidrio, plásticos, asfalto, concretos, ladrillos, bloques, cerámicos, entre otros. En la tabla 1 se presenta la clasificación de los residuos de construcción y los porcentajes de materiales que los componen físicamente. Otros documentos normativos que hablan de este tipo de residuos de manera directa o indirecta son los siguientes: Reglamento de la Ley de Residuos Sólidos del Distrito Federal [4], Norma Ambiental del Distrito Federal NADF-007-RNAT-2004 [5], Ley General del Equilibrio Ecológico y la Protección al Ambiente [6], Ley General del Equilibrio Ecológico y la Protección al Ambiente del Estado de Chiapas [7] y la Ley de Residuos Sólidos del Distrito Federal [8].
1
Facultad de Ingeniería, Escuela de Ingeniería Ambiental, UNICACH, Tuxtla Gutiérrez, Chiapas, México. E-mail: ingeraul@yahoo.com
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R. González Herrera, J. Nad-Xelly Alegría Nucamendi, C.M. García Lara, P. Vera Toledo y J.A. Aguilar Carboney Analizando la tabla 1 puede observarse que a partir de la composición física de los residuos de construcción, cerca del 7% de éstos (tabla roca, yeso, madera, cerámica, plástico, papel, poliestireno, cartón, acero, asfalto, entre otros) no podrían emplearse para elaborar un bloque de concreto, en tanto que el 49% de dichos residuos sí son propicios para tal fin (pedacero de bloques de concreto y tabique, y otros elementos de concreto). Sin embargo al menos el 44% (producto de excavación y pedacero de tabique) sería adecuado para elaborar tabiques, tejas, entre otros elementos de barro. De la composición física presentada en la tabla 1 se concluye que el 93% de estos residuos puede ser tratado para ser empleados en la elaboración de bloques de concreto y tabiques de barro y con ello disminuir la extracción de materiales pétreos (arenas y gravas) en nuevos bancos de materiales. Tabla 1 - Composición física de los residuos de construcción. [9] Composición física Material de excavación Concreto Block-tabique Tabla roca-yeso Otros (madera, cerámica, plástico, piedra, papel, varilla, asfalto, lámina)
Porcentaje 44% 25% 24% 5% <2%
2. ANTECEDENTES DEL RECICLAJE DE RESIDUOS DE CONSTRUCCIÓN En los países desarrollados la mayor fuente de residuos industriales generados volumétricamente son los producidos por la industria de la construcción, “evaluándose en torno a 450 Kg/Hab/Año” [10]. Al descubrirse que una cantidad importante de estos residuos se podían reutilizar, algunos países han procurado producir menos cantidades y han comenzado a realizar estudios y proyectos para investigar cuales son las posibilidades de reciclaje de estos; aunque por el momento sólo se recicla un porcentaje menor en comparación con la producción de residuos, sin embargo, “La mayoría se deposita o se usa como relleno sin dar los pasos necesarios para evitar la agresión medioambiental” [11]. Algunos de los beneficios que se pueden obtener al reciclar los RC son ahorros en el transporte de las materias primas, sobre todo en lugares en donde haya un déficit de estas, además de que este tipo de residuo siempre y cuando no esté contaminado puede ser reciclado en el mismo lugar en donde se esté trabajando o incluso en sus proximidades, y finalmente dejar de extraer materiales áridos en nuevos bancos con lo que se ayuda a evitar erosión, remociones de masa, etc. Según reporta la Secretaría de Desarrollo Social (SEDESOL) del gobierno federal mexicano, solamente existe un relleno sanitario para residuos industriales no peligrosos en México, ubicado en el estado fronterizo de Tamaulipas. Por tanto, en la mayor parte del país no existen sitios para un manejo adecuado. Puede asumirse que estos residuos no peligrosos se quedan en las fuentes donde están los productores, en rellenos municipales y/o en basureros abiertos. Se estima que 1 m3 de obra construida, genera 0.068 m3 de RC, asimismo Ingeniería Civil Sostenible Vol.1 – No. 2
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R. González Herrera, J. Nad-Xelly Alegría Nucamendi, C.M. García Lara, P. Vera Toledo y J.A. Aguilar Carboney un peso volumétrico 1.5 ton/m3, por lo que 1 m3 de obra construida genera 102 kg de RC [12]. En el estado de México se estableció la primera planta mexicana de tratamiento de residuos de construcción, denominada: Concretos Reciclados, nació en el año 2004 y tiene capacidad para procesar 2 mil toneladas de desechos de la industria de la construcción. En esta empresa se desarrollan productos para la construcción como: Bases y Sub-bases para calles, caminos y estacionamientos; material para construcción de terraplenes; material fino para cubierta en rellenos sanitarios, construcción de andadores y ciclopistas; materiales intermedios para camas de tuberías, rellenos, filtros o piedraplenes e incluso bases de cimentaciones. “El precio es de un tercio del valor de los materiales vírgenes con cualquier curva granulométrica” [13]. 2.1. Elaboración de mampuestos con residuos En Ecuador tras un proceso experimental [14] que buscaba emplear residuos de construcción para comparar estos mampuestos respecto a las normas ecuatorianas, los resultados indicaron una viabilidad técnica y económica para la producción de blocks, sin embargo, las resistencias alcanzadas fueron bajas no obstante que cumplían con las normas técnicas ecuatorianas. Otros intentos se generaron en Argentina para elaborar blocks para muros divisorios o para zonas no sísmicas con polímeros de PET a medida de elementos de aislamiento térmico y acústico, la resistencia fue suficiente y el proceso de construcción adecuado para reducir polímeros, adicionalmente son ligeros, lo cual facilita su construcción [15]. Otros esfuerzos logran bloques con refuerzo de fibras vegetales, la resistencia es más bien baja hasta 20 Kg/cm2 (2 MPa), los resultados son aceptables para zonas no sísmicas o viviendas rurales que era el objetivo del estudio [16]. En Chiapas se elaboró una propuesta de bloques de concreto y deja la interrogante de ver si estas piezas pueden emplearse en zonas sísmicas, lo cual redundó en el presente artículo [17].
3. PROCESO METODOLÓGICO El proceso parte desde la elección aleatoria de los sitios de recolección de los RC con los que posteriormente se elaboran los blocks, se consideró recolectar los residuos en direcciones opuestas unas con otras para que de esta manera se pudiera lograr un mejor muestreo del tipo de residuos obtenidos en la ciudad de Tuxtla Gutiérrez, las direcciones de los sitios de recolección fueron Infonavit del Rosario en Av. Rosa de Vietnam y calle Rosa del Oriente; 9 norte entre 8 y 9 poniente y por último 19 poniente entre 11 y 12 sur, véase figura 1, donde se presenta un croquis de localización de las tres ubicaciones.
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R. González Herrera, J. Nad-Xelly Alegría Nucamendi, C.M. García Lara, P. Vera Toledo y J.A. Aguilar Carboney
Figura 1 - Residuos de construcción recolectados en los tres sitios señalados en Tuxtla Gutiérrez, Chiapas, México.
Después de la recolección de los RC, se criba todo el residuo sin previa trituración para saber qué porcentaje de finos pasaba por las mallas, lo que posibilita identificar la presencia de finos (arcillas y limos) y otros elementos no deseables; una vez obtenidos los valores necesarios se trituran con ayuda de marros y un pisón y se criban nuevamente los RC. Tabla 2 - Composición de las mezclas para los blocks. Composición de la mezcla
Número de mezcla I II III
Composición 4 latas de RC + 2 latas de arena + 1/2 bulto de cemento 4 latas de RC + 3 latas de arena + 1/2 bulto de cemento 4 latas de RC + 6 latas de arena + 1/2 bulto de cemento
Número de RC 1
2
3
Proporción de la mezcla
1.I
2.I
3.I
8:4:1
1.II
2.II
3.II
8:6:1
1.III
2.III
3.III
8:12:1
Una vez triturado y cribado el escombro, se elaboran los blocks obteniéndose, de tres tipos de escombro y tres tipos de dosificaciones por volumen nueve tipos de blocks, lo que se explica en la tabla 2. Con estos 9 tipos de blocks se realizan un total 100 blocks, los cuales, al elaborarse cumplen en cuanto a su volumen, pero debido a que la composición de los residuos empleados era de distinto origen, algunos residuos pesan más que otros y al sacar la composición porcentual en cuanto al peso se obtuvo la tabla 3 en la que se expresa cómo está constituido cada block.
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R. González Herrera, J. Nad-Xelly Alegría Nucamendi, C.M. García Lara, P. Vera Toledo y J.A. Aguilar Carboney Tabla 3 - Composición porcentual en peso de los blocks.
Tipo de block
RC
Arena
Cemento
Cantidad de blocks
1.I
56.05%
30.68%
13.26%
6
1.II
48.60%
39.90%
11.50%
4
1.III
34.74%
57.04%
8.20%
8
2.I
54.90%
31.48%
13.62%
6
2.II
47.43%
40.80%
11.76%
6
2.III
33.69%
57.95%
8.35%
6
3.I
51.63%
33.76%
14.60%
6
3.II
44.18%
43.33%
12.49%
5
3.III
30.82%
60.46%
8.72%
8
4. PRUEBAS EXPERIMENTALES DE LAS PIEZAS Se realizaron las pruebas en el laboratorio de materiales de la Universidad Autónoma de Chiapas, se verifica que las pruebas se realicen según las normas mexicanas [18] en la que se toman las dimensiones de los blocks. Al realizar esta prueba se logró detectar que los blocks de fábrica que se compraron para servir como comparación con los blocks producto de reciclaje, se les desprendían pequeños residuos al estarlos manipulando, además de que fueron únicamente estos los que al transportarlos sufrieron pérdida de material, situación totalmente contraria a los hechos con RC ya que estos mantuvieron su integridad al ser transportados y al estarlos manipulando no presentaban pérdida de partículas. Lo anterior se puede explicar por los bajos niveles de cemento. Los resultados que se obtuvieron en esta prueba fueron medidas de 12x20x40 ± 1 cm debido a que todos los blocks fueron hechos con el mismo molde y los blocks que se adquirieron también eran de las mismas medidas, para poder tener mejores resultados al comparar a los dos tipos de blocks. Después se desarrolló la prueba de absorción inicial y se prepararon los blocks para realizar la absorción total en 24 horas siguiendo la metodología mencionada en la Norma Mexicana [19]. Los resultados muestran que los blocks absorbieron alrededor de 0.5 a 3 Kg de agua, estando los blocks convencionales y los elaborados con RC en los mismos rangos. Después de haber sacado los blocks del horno se prepararon para la prueba de compresión realizando el cabeceo con azufre como lo indica la Norma Mexicana [20], y al término de realizar el cabeceo se colocaron los blocks en la prensa para realizarles la prueba de compresión (véase figura 2), los resultados obtenidos muestran que los blocks convencionales soportan una compresión entre las 5 y 8.2 Ton, mientras que los que fueron elaborados con RC lograron soportar compresiones en el rango de las 5 a 42 Ton; teniendo así una clara superioridad frente a los convencionales. Ingeniería Civil Sostenible Vol.1 – No. 2
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R. González Herrera, J. Nad-Xelly Alegría Nucamendi, C.M. García Lara, P. Vera Toledo y J.A. Aguilar Carboney No obstante que la diferencia entre la resistencia a compresión de los blocks convencionales y los elaborados por los residuos de construcción fue aproximadamente hasta uno a cinco, la diferencia de costos es de alrededor de uno a dos, lo que indica claramente la ventaja de los elaborados con residuos, sin embargo no son los residuos de construcción lo que les dio la ventaja, si no la cantidad de cemento que es unas tres veces mayor que la que tradicionalmente se coloca y que se tuvo mayor cuidado en todo el proceso de fabricación.
Figura 2 – (a) Cabeceo de las piezas con azufre para homogenizar la superficie sometida a esfuerzos de compresión; (b) Prueba de compresión a uno de los blocks en el laboratorio de la UNACH.
Respecto a las pruebas de los muretes a compresión y de las piezas a flexión y corte, no se pudieron realizar en el año 2010 [17], debido a que no estaban funcionando la prensa universal principal y otros equipos del Laboratorio de Materiales de la Facultad de Ingeniería de la UNACH, por lo que se aprovechó a realizar las pruebas posibles en las condiciones en que se encontraba el laboratorio, sin embargo para este artículo se continuo con el trabajo experimental y se logró obtener resistencias a flexión, tensión y tensión diagonal (cortante) teniendo resultados similares a los mostrados para los mampuestos convencionales.
5. RESULTADOS EXPERIMENTALES DE LAS PIEZAS Al realizar las pruebas a los blocks se logró observar y concluir muy claramente que los convencionales a pesar de ser elaborados en fábrica no están exentos de contener otro tipo de materiales, además de cemento y arena ya que se apreció la presencia de residuos de madera, papel, algunas conchas, las que se encontraban contaminado a la arena al realizar la mezcla. De esta manera se demuestra que tampoco existe el cuidado de retirar esas impurezas que contienen los materiales con los que se elaboran estos blocks; además de que debido a la demanda de estos productos se descuida su proceso y se reduce la calidad, teniendo como resultado blocks que no cumplen con la norma, por los contaminantes presentes y su baja resistencia. Los bloques presentaron un comportamiento frágil debido a la mala mezcla y poco contenido de cemento de la pieza. La falla frágil mostrada por las piezas al romperse en dos partes, se debe a planos de falla que se dieron por una mezcla inadecuada o por no haberse Ingeniería Civil Sostenible Vol.1 – No. 2
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R. González Herrera, J. Nad-Xelly Alegría Nucamendi, C.M. García Lara, P. Vera Toledo y J.A. Aguilar Carboney triturado lo suficiente las partículas grandes de escombro, lo que se puede observar en la figura 3.
Figura 3 - Block posterior a la prueba de compresión, muestra falla frágil al romperse en dos partes con daño concentrado y no distribuido en el cuerpo de la pieza.
Largo en Cm
A continuación se presentan una serie de gráficas con los resultados obtenidos en las distintas pruebas realizadas a los blocks que se generaron para poder realizar un análisis de estos. En la figuras 4a, 4b, 4c y 4d, donde se muestra las medias de las dimensiones geométricas para cada uno de los tres lados y para los 9 tipos de combinaciones de los blocks elaborados y los testigos experimentales que son los de fábrica, podemos observar la media, la desviación estándar y el coeficiente de variación, donde el peso y el espesor son las variable con mayor variación.
blocks
Cm
Figura 4 (a) - Histograma de la variación del largo de los blocks sometidos a las pruebas.
blocks
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R. González Herrera, J. Nad-Xelly Alegría Nucamendi, C.M. García Lara, P. Vera Toledo y J.A. Aguilar Carboney
Cm
Figura 4 (b) - Histograma de la variación del ancho de los blocks puestos a prueba.
blocks
Kg
Figura 4 (c) - Histograma de la variación del espesor de los blocks puestos a prueba.
blocks Figura 4 (d) - Histograma de la variación del peso de los blocks sometidos a las pruebas.
Las variaciones en el esfuerzo de compresión están entre 18.29 a 70.73 Kg/cm2 (1.8 a 7.1 MPa) en los blocks elaborados con residuos de construcción, mientras que el promedio de los bloques testigos solo alcanzaron los 14.47 Kg/cm2 (1.4 MPa), ver la figura 5. En este proceso se observó que entre mayor es la cantidad de arena, es mayor la resistencia, lo cual se debe a que los escombros de construcción trabajan como agregado grueso y la mezcla por lo tanto presenta una mejor graduación, sin embargo que llega un punto, donde no hay balance entre agregado grueso y fino, lo cual es el interés de un siguiente estudio y fue abordado de manera sencilla [14].
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R. González Herrera, J. Nad-Xelly Alegría Nucamendi, C.M. García Lara, P. Vera Toledo y J.A. Aguilar Carboney Resistencia a compresión (kg/cm2)
Figura 5 - Resistencia a compresión de los blocks en Kg/cm2.
Porcentaje
Los resultados de la absorción inicial, están graficados en las figuras 6a y 6b, donde se muestra las medias de las absorciones para los 9 tipos de combinaciones de los bloques elaborados y los testigos experimentales que son los de la fábrica, podemos observar la media, la desviación estándar y el coeficiente de variación, donde se aprecia una absorción inicial prácticamente igual en las piezas de fábrica y en las de RC y una variación muy amplia en las piezas de residuos de construcción y en las de fábrica y solo un comportamiento adecuado en las combinaciones que tienen más arena y que también presentan una mayor resistencia.
blocks Figura 6 (a) - Porcentaje de absorción total de agua en 24 horas.
Figura 6 (b) - Comparación de absorción máxima inicial de agua en g/min.
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R. González Herrera, J. Nad-Xelly Alegría Nucamendi, C.M. García Lara, P. Vera Toledo y J.A. Aguilar Carboney La absorción inicial representa la cantidad de agua tomada del mortero en el pegado de las piezas, para esta característica no hubo diferencia entre las piezas elaboradas con RC y las de fábrica, sin embargo, la absorción total representa la porosidad de la pieza, entre más agua absorbe hay más poros internos en la pieza ó hay mayor cantidad de material plástico, lo cual representa una característica de los RC, por lo que la cantidad de arena (la cual no absorbe agua) es clave en la dosificación de las piezas, para dar un menor peso (lo cual es bueno por cuestión sísmica al presentar una menor masa inercial), mayor resistencia y homogeneidad en la mezcla, así como una absorción adecuada. 6. CONCLUSIONES Se elaboraron 100 bloques y se compararon contra 20 bloques de fábrica. En cuanto al peso y las medidas de los bloques, se observa que no hay variación en las condiciones de largo y ancho, como si lo hay en el espesor, pero con mayor claridad en el peso, ya que las piezas elaboradas con RC resultaron más densas y pesadas en cuanto más porcentaje en volumen de escombros tenían. Para la absorción inicial no hubo diferencia entre las piezas elaboradas con RC y las de fábrica, sin embargo, en la absorción total representa la porosidad de la pieza, hay una diferencia importante por el material plástico contenido en los RC. Respecto a la resistencia a compresión varía entre 18.29 a 70.73 Kg/cm2 en los blocks elaborados con RC, mientras que el promedio de los blocks de fábrica solo alcanzaron los 14.47 Kg/cm2, no obstante solo un 30% cumplió lo mínimo solicitado en [2] (60 Kg/cm2). Entre mayor es la cantidad de arena, mayor la resistencia, lo cual, se debe a que los residuos de construcción trabajan como agregado grueso y la mezcla por lo tanto presenta una mejor graduación. En esa misma proporción se encuentran las resistencias a flexión y tensión (cercano al 15% de la resistencia a compresión) y la de cortante (aproximadamente el 8% de la resistencia a compresión). Respecto a la pregunta planteada se puede decir, que los bloques de concreto elaborados si pueden ser empleados en zonas sísmicas con seguridad, la clave no son los residuos, sino el diseño de la mezcla y la cantidad de cemento. En esta investigación se presentan las siguientes recomendaciones para posibilitar un mejor control en todo el proceso en el tema de reciclaje de RC:
Creación o modificación de normas para poder controlar más eficientemente el vertido de RC y de esta manera poder usar un mecanismo de reciclaje para evitar que su mala disposición siga afectando al medio y a la sociedad.
Elaborar programas de concientización para enterar a la sociedad de la actual situación de estos residuos, ya que gran cantidad de la sociedad no conoce la magnitud del impacto que se provoca al verter de manera incontrolada los RC, y sobre todo no conocen la gran capacidad de reciclaje de estos residuos.
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R. González Herrera, J. Nad-Xelly Alegría Nucamendi, C.M. García Lara, P. Vera Toledo y J.A. Aguilar Carboney Mejorar el control de calidad por parte de las fábricas encargadas de la elaboración de blocks, mediante la exigencia de pruebas que avalen la resistencia que mínima pueden vender, las pruebas deben estar a cargo de las autoridades, ya que con la realización de este proyecto se pudo observar que no se tiene un buen control de calidad, ya que es importante para la resistencia, seguridad y durabilidad de las construcciones.
Legislar la explotación de los bancos de materia prima, ya que por este motivo también se causa una gran afectación al medio ambiente y tampoco se puede tener un control sobre este. Al ser fácil la explotación de nuevos bancos se limita la fabricación y empleo de RC.
7. REFERENCIAS [1] NORMA MEXICANA NMX-C-404-ONNCCE-2005. Industria de la construcción: Bloques, tabiques o ladrillos y tabicones para uso estructural. Especificaciones y métodos de prueba. [2] NORMAS TÉCNICAS COMPLEMENTARIAS PARA DISEÑO DE MAMPOSTERÍA DEL REGLAMENTO DE CONSTRUCCIONES DEL DISTRITO FEDERAL NTC-DM-RCDF-2004. Reglamento de Construcciones de Tuxtla Gutiérrez 2004. [3] LEY GENERAL PARA LA PREVENCIÓN Y GESTIÓN INTEGRAL DE LOS RESIDUOS. 2006. Ley publicada en el DOF el 8 de Octubre del 2003. Ultima reforma publicada el 22 de mayo del 2006. [4] REGLAMENTO DE LA LEY DE RESIDUOS SÓLIDOS DEL DISTRITO FEDERAL. 2008. Publicado en la Gaceta Oficial del Distrito Federal el 7 de octubre de 2008. [5] NORMA AMBIENTAL DEL DISTRITO FEDERAL NADF-007-RNAT-2004. Clasificación y especificaciones de manejo para residuos de la construcción en el Distrito Federal. Publicada el 12 de julio de 2006 en la Gaceta Oficial del Distrito Federal. [6] LEY GENERAL DEL EQUILIBRIO ECOLÓGICO Y LA PROTECCIÓN AL AMBIENTE. 2007. Diario Oficial de la Federación 28 de enero de 1988; última reforma publicada DOF 5 de Julio del 2007. [7] LEY DEL EQUILIBRIO ECOLÓGICO Y LA PROTECCIÓN AL AMBIENTE DEL ESTADO DE CHIAPAS. 1999. Última reforma publicada en el Periódico Oficial del Estado: 24 de febrero de 1999. [8] LEY DE RESIDUOS SÓLIDOS DEL DISTRITO FEDERAL. 2003. Gaceta Oficial del Distrito Federal el 22 de abril del 2003. [9] REVISTA INGENIERÍA CIVIL 325 MAYO. 1996. Colegio de Ingenieros Civiles de México.
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R. González Herrera, J. Nad-Xelly Alegría Nucamendi, C.M. García Lara, P. Vera Toledo y J.A. Aguilar Carboney [10] INSTITUTO JUAN DE HERRERA. 1997. Ciudades para un Futuro más Sostenible. Boletín Especial sobre residuos. Producción de residuos de construcción y reciclaje. 30 de septiembre de 1997, Madrid. España. [11] LAURITZEN, E., NIELS, J.H. 1997. Producción de residuos de construcción y reciclaje, número 8 revista Residuos. Instituto Juan de Herrera. Av. Juan de Herrera 4. 28040 Madrid. España, septiembre de 1997. [12] ESQUINCA, F., ESCOBAR, J.L., HERNÁNDEZ, A., VILLALOBOS, J.J. 2008. Caracterización y generación de los residuos sólidos de Tuxtla Gutiérrez, Chiapas. Secretaría de Ecología, Recursos Naturales y Pesca/SMISA Sección Chiapas, 2008. [13] HERNÁNDEZ, J.D., RODRÍGUEZ, M.A., MACHT, A., RAMOS, E. 2008. El manejo de los residuos de la construcción en el estado de México. Marco de la cooperación técnica alemana en México. Desarrollo local sostenible. Vol. 1n No 3, Septiembre del 2008. [14] CRUZ, C.E., HIDALGO, A.R., MASSON, O.A., ZUÑIGA, J., HARO, A. 2006. Elaboración de mampuestos con residuos reciclados de la construcción civil y comparación con las normas INEN Y ASTM. Tesis de licenciatura en Ingeniería Civil, Escuela Politécnica del Ejército, Sangolquí. [15] GAGGINO, R. 2007. Tecnología de reciclado para la auto-construcción de viviendas. Revista I+A (Investigación más acción) de la facultad de Arquitectura, Urbanismo y Diseño, año 11, número 11, Argentina. [16] BUZÓN, J. 2009. Uso del cuesco de la palma africana en la fabricación de adoquines y bloques de mampostería. Seventh LACCEI Latin American and Caribbean Conference for Engineering and Technology (LACCEI, 2009) “Energy and Technology for the Americas: Education, Innovation, Technology and Practice”. Junio 2-5 de 2009, San Cristóbal, Venezuela. [17] GONZÁLEZ, R., ALEGRÍA, J.N., BORRAZ, M.A., AGUILAR, J.A., VERA, P., GARCÍA, C.M. 2010. Empleo de blocks elaborados con residuos de construcción en Chiapas. XVII Congreso Nacional de Ingeniería Estructural, León, Guanajuato, México, Noviembre de 2010. [18] NORMA MEXICANA NMX-C-038-ONNCCE-2004. Industria de la construcción: Determinación de las dimensiones de ladrillos, tabiques, bloques y tabicones para la construcción. [19] NORMA MEXICANA NMX-C-037-ONNCCE-2005. Industria de la construcción: Bloques, ladrillos o tabiques y tabicones - Determinación de la absorción de agua y absorción inicial de agua. [20] NORMA MEXICANA NMX-C-036-ONNCCE-2004. Industria de la construcción: Bloques, tabiques o ladrillos, tabicones y adoquines - Resistencia a la compresión - Método de prueba.
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Markus Greim
Measuring the Early Shrinkage of Mortars Markus Greim1 Recibido: March 22, 2012 Aceptado: July 7, 2012
Abstract: All mortars are changing their volume from the moment the binder particles came in contact with water until several months and years. In most practical application this expansion and shrinkage must be minimized. Many theoretical models are describing the cause of this effects, but specially the mechanism in the first hours are not completely understood yet. One demanding prerequisite for controlling the shrinkage of mortars are measurement instruments that are able to measure shrinkage and expansion from the early beginning of hydration and setups that are able to simulate environmental conditions in the field application. Up to now shrinkage and expansion of building materials is measured by simple mechanical instruments like cantilevers. Therefore a certain strength of the material is necessary. There is a survey given about more modern sensors and instruments measuring also the early shrinkage before the setting point. Beneath others a contactless LASER based measurement method with a cone-formed formwork is presented avoiding the problems shown above. Key words: Early shrinkage, mortars, measuring
1. TAXONOMY OF SHRINKAGE MEASUREMENT SYSTEMS As long as a material is in the fluid state shrinkage is not causing a problem. The only thing you have to keep in mind is, that a length change on each site of a 1 cubicmeter cube of 1/1000 is already a volume change of When the material is setting and/or is in contact with a material that has no shrinkage or expansion, strain inside the material or in the contact zone will appear. As soon as this tension will be over the actual tensile strength of the material, the material structure will be damaged, usually by the occurring of cracks. Therefore it’s obvious not only to measure the free shrinkage but also the strain has that occurred. It’s called measurement of the blocked or restrained shrinkage. The tensile strength and the materials volume is changing most in the first hours after mixing, so restrained and free shrinkage should be observed as early as possible in the hydration process. The process of crystal grow itself is influenced by the environmental conditions like temperature, humidity, freeze thaw cycles, penetration of gas, or salty or acid liquids. This environment must be kept constant to detect the shrinkage of the material itself. But on the opposite the length change may be an indicator for the resistance against an environmental attack on the material. For example for detecting the alkali silica reaction or for indicating the freeze/thaw resistance of concrete.
1
Director Gerente de Schleibinger. Germany; email: greim@schleibinger.com Ingeniería Civil Sostenible Vol.1 – No. 2
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Markus Greim Figure 1 shows free shrinkage over the time in a general way. We must distinguish 3 ranges of of material strength for using different measurement techniques: -
Fluid (F) Starting of setting (S) Hardened material (H)
These 3 ranges may be subdivided depending on the material geometry and environmental conditions. For example: -
Rigid volume, no evaporation Low volume, high surface, high evaporation High or low temperature Periodical temperature changes Humidity gradient Temperature gradient
The appropriate shrinkage measurement instruments are also shown.
Figure 1 - Shrinkage over time
2.
LENGTH CHANGE MEASUREMENT SENSORS
Common for all systems is the requirement to measure very small length or volume changes over the time. A resolution better then 1μm is usually requested. As comparison: A human head hair has a mean diameter of about 120 μm, the wave length of red light is 0.7 μ m. The measuring period is quite long, from several hours and days up to one year and more. So the sensor must also give very stable, non drifting results over a long time. The scale of the Measurement setup is from several centimeter small specimen in a laboratory setup up to
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Markus Greim deformation measurement of real big structures like dams and bridges. The mostly very slow movement of the material is an advantage from the measurement technology point of view. We can distinguish two kind of measurement transducers for the length change: 1. Systems that are in a direct mechanical contact with the material. 2. Systems measuring without touch the distance between the sensors and the surface of the specimen. If the specimen is submersed in a fluid phase the volume change can be measured indirectly by the buoyant force, for example with a balance. The tables 1 and 2 give a survey about the several mechanical touching and touchless sensors.
Table 1 - Survey about sensors for contacting distance measurement
Table 2 - Survey about sensors for non-contacting distance measurement
3.1 Contacting Sensors 3.1.1 Calipers Calipers are quite robust, but a low accuracy and may not be read out automatically, out fashioned.
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Markus Greim 3.1.2 LVDTs The Linear Variable Differential Transformers has a movable ferromagnetic core. Depending on the position of the core the voltage inducted from the primary to the secondary coil is changed. Mostly pen sized with a diameter of 8mm. 3.1.3 Strain Gages A strain gage is a thin foil, sized several millimeters, with a electrical resistor network printed on. If a thin wire is elongated the diameter of the wire will decrease and the resistance will increase. Most common application is measuring the forces on a structure by detecting the deformation with a strain gage. Special strain gages for cementitious system are available. Used for measuring restrained shrinkage. 3.1.4 Fiber Bragg Gratings On a thin glass fiber on a length of some centimeters the inner glass structure is changed to a kind of optical grading [3]. Under a mechanical tension the distance of the slits of the gratings and therefore the spectrum of the light, which is crossing the grating, is changed. One single glass fiber of several hundred of meter length may carry several of this length change sensitive areas. Main application is the monitoring of large structures over months and years. 3.2 Contactless Sensors 3.2.1 Ultrasound Ultrasound sensors are well known from the car park assistance systems. These systems are measuring the time of flight of sound pulse. The results are quite independent of the surface properties of the reflecting material, but the accuracy and the resolution is quite poor. 3.2.2 Inductive Sensors A conductive element near by an electro magnetic oscillating circuit is moving the frequency and damping the voltage depending on the distance from the coil. Very robust, but needs a high conductive target. 3.2.3 Laser TOF The Time Of Flight of a short light pulse is measured. Due to the high speed of light the time is in the range of several pico (10�12) seconds. High measurement range, but the resolution is quite low (0.1 mm). It is well suited for big structures.
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Markus Greim 3.2.4 Laser Triangulation There is known distance between the light emitter and the detector. Based on the elementary trigonometry laws the distance between the emitter and the target can be calculated. Systems have a low absolute measurement range, but a high resolution, better then the wave length of the used light. 3.2.5 Capacitive Measurement The capacity of an electrical capacitor is directly proportional to the area of the capacitor plate and inversely proportional to the distance of the plates. This method is the most accurate method known up to know. The absolute measurement range is less than some millimeters, but the resolution and accuracy are in the nanometer (10-9m) range. 3.3 Future Developments in Sensor Technology For some applications the accuracy and resolution of the LASER sensors or the LVDTs is not high enough. Capacitive sensors, as written, would be an improvement. But up to now this technology is quite difficult to handle for practical applications, and the results were strongly influenced, by changes in in the resistance of the material surface. Latest developments, integrating different technologies into one singe sensor are very promising. Also the Fiber Bragg sensors directly embedded inside the specimen are a very interesting technology. Up to now economic reasons are limiting the application of these sensors to a few big construction projects. 3.
MEASURING SYSTEMS
It is obvious that for the fluid state and the early setting state touching sensors are not appropriate. The sensor can't be actuated by adherence if the material is still fluid. If the system is hardened a mechanical coupling is easily possible. This sensors are generally speaking cheaper or have a higher accuracy at the same costs as the non-contact sensors. So using mechanical sensors is recommended more from the economical point of view as for technical reasons. The optimal measurement system is a combination of the appropriate setup and the best fitting sensor. As in all practical applications a lot of details must be regarded and also the economical requirements to build such a system for a reasonable price. This will be illustrated on some examples for systems designed for the fluid, setting and hardened state of material for different environmental conditions. 3.1 Gauge for hardened specimen To measure the every day length of a mortar or concrete beam is an apparent easy task. The standard EN 12617-4 [6] is describing such a test procedure. Here an accuracy of ±1.00 μm is required. This can not be fulfilled by any mechanical indicating caliper, and also the best standard electronic digital caliper with LC display, as used in the machine industry, Ingeniería Civil Sostenible Vol.1 – No. 2
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Markus Greim have (for my knowledge) an absolute accuracy over the whole measurement range not better then ± 1.25 μm. Another very important point is the thermal length change of all materials. Concrete, mortar and steel have a thermal expansion coefficient of about 12 μm/m/K, stainless steel 16 μm/m/K and even quartz glass of 0.5 μm/m/K.. As calibration reference bar a so called Invar (Fe: 65%, Ni: 35%) steel bar is required. Also this kind of material is changing with 2 μ m/m/K [9]. Modern carbon fibers have an coefficient of 0.2 μm/m/K. As composite materials CFRP rods can even have negative thermal expansion coefficients. A steel carbon construction can achieve a thermal expansion nearly zero. Figure 1 (upper right) shows a setup made of steel and carbon. 3.2. Shrinkage Drain Measuring the shrinkage and expansion during hydration can be done in a kind of mold for the fresh material, which is equipped with a length change sensor. For this purpose at least one side of the mold must be movable. Figure 2 shows an 25 cm long example of such a setup. One meter long drains are common usage. The length It must be kept in mind that shrinkage and expansion is generally in all 3 dimensions. But this volume change is not absolutely isotropic. For this reason the mold is covered inside with a non sucking but compressible rubber sheet (about 1..2 mm) to avoid blocking in the drain.
Figure 2 - Shrinkage Drain
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Markus Greim The support for the movable anchor has some loss also in the y and z direction also to avoid blocking in these extra directions. Therefore a gap between the anchor plate and the wall of the drain is necessary, which can be easily sealed with some simple elastic material like ordinary grease (see figure 4). The anchors are a little bit elastic itself to regard that that there is also a length change between the start and endpoint of the anchor. The sensor has an accuracy of about ±1μm at a stroke of 5mm. This kind of setup gives reliable data after certain level of strength of the material. To compare the shrinkage values of different materials, you need also results of strength development, for example done with the Vicat apparatus. 3.3. Corrugated Polyethylene Molds Jensen [10] suggested the use of a corrugated polyethylene mould (see figure 3 insted a steel mold). First results are given about 30 minutes after mixing for cement paste [12]. One disadvantage of this setup for mortar is that aggregates placed in the fins are blocking shrinkage, especially if the material is segregating. 3.4. Bending drain The ordinary shrinkage drain, as it is described above, is normally used at constant temperature, constant humidity and a covered surface of the material to avoid evaporation. Sometimes the simulation of real world conditions is more interesting. To build in a screed in a house with a floor ground heating is a demanding job [11]. Starting the heating will result in temperature and later on in humidity gradient in the material. Anisotropy shrinkage, higher on top surface then on the bottom layer will result in a bending. Is the cementitious material with a size of 100x10x6 cm³fixed at 10 cm before the end, forces on anchor more then 100 N. Would this setup made of 2 mm tin of steel bending would be several 100 μm, that’s in the range of the common bending at all. The solution is a setup (see figure 4) where the forces are transferred to a rigid u-shaped steel foundation [7].
Figure 3 - Shrinkage measurement with corrugated polyethylene moulds [12]
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Markus Greim For the length and height change measurement the same LVDTs as for the bending drain can be used. In the bottom of the drain a computer controlled electrical heating unit can simulate different heating up and cooling down profiles over several days.
Figure 4 - Bending Drain
3.5. Shrinkage Ring The Shrinkage Ring is a setup for measuring restrained shrinkage. This means, the material is in a fix mechanical contact with an infinite stiff mechanical structure so no shrinkage and expansion is possible, instead of length change the forces are measured. Such a system could be realized for example by an active controlled mechanical structure, where a hydraulic ram compensates each movement and the the forces are measured indirectly over the hydraulic pressure. Such systems have been realized [4] but the technical and the economical expense is quite high. The standard ASTM C 1581-04. “Standard Test Method for Determining Age at Cracking and Induced Tensile Stress Characteristics of Mortar and Concrete under Restrained Shrinkage [1] is describing a simpler setup. The material is placed between two concentric steel rings. The outer ring has an inner diameter of 406 mm the inner ring an outside diameter of 330 mm. So the specimen is like a donut with 38 mm thickness. The inner steel ring has a wall thickness of 13 mm with strain gages applied for measuring forces (see figure 5). As mentioned before strain gage is basically not measuring forces but even also a length change. A typical strain of 100 μm/m is an absolute length change at the given geometry of about 116 μm. So shrinkage is only partly restrained.
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Markus Greim
Figure 5 - Bending Drain
3.6 Shrinkage Cone For measuring shrinkage and expansion for the fluid or just setting material we must use a non-contact measurement procedure. The standard ASTM C 827-95a “Change in Height at Early Ages of Cylindrical Specimens from Cementitious Mixtures”[2] describes a method where a ball with a diameter about 10 mm and a density of 1.2 kg/dm³ is laid onto the surface of the material which is filled into a cylindrical mold, between 100 and 300 mm height. With a light source and a lens the ball is projected onto the wall, where the movement should be indicated with a pencil each hour. Beside the outfashioned distance measurement technology, the disadvantage of this method is the use of a rigid cylindrical mold. Under the prerequisite of an isotropic shrinkage and expansion the material is not only expanding in the vertical but also in the horizontal direction. As long as all material is fluid enough, we will get only a height change, the material which is moving horizontal is also lifted up, like in a thermometer. As son as the material has a certain stiffness we get an undefined relocation of the material. On the surface we will get a kind of spherical calotte. Higher in the center by an expansion and lower for a shrinking material. The measured height change is therefore a mix of the vertical length change and the total volume change. You can avoid this if you are using a mold formed like a bottom up pyramid or cone. Under the presumption that with an isotropic form volume change the angles of a body keep the same smaller cone is only changing its height, there is no relocation of material [8] (see figure 6). It can be mathematical shown that the volume change is the cube of the height change and vice versa (Equation 1): A practical realization of this setup is shown in figure 7. The double wall cone formed vessel may be temperature controlled. A polypropylene foil is avoiding wall friction. A triangulation LASER sensor is measuring the height change with an accuracy of some μm. To avoid evaporation on the top surface it may be covered by transparent silicone oil, or a
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Markus Greim stainless steel foil. A standard plastic foil is not diffusion resistant. A reflector may be used if there is a risk of air bubbles growing where the LASER beam is targeting the surface.
(Equation 1)
Figure 6 - Under the prerequisite of an isotropic shrinkage (expansion) the radius r and the height h of a cone shrink (expand) the same percentage: h´ = k * h and r´ = k * r (k for example 80%)) V´=V = 0.83 = 0:512
Figure 7 - The Shrinkage Cone as exploded view. Cone formed vessel, partition foil, specimen and optional reflector
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Markus Greim 3.7 Thin Layer Shrinkage Measurement System To measure the early shrinkage of Self Levelling Underlayments (SLUs) R. Zurbriggen [5] suggested a setup shown in figure 8. Here the material is placed in a flexible thin mold with big surface (ca. 600 cm²) and low volume (ca. 0.2 l ). LASER triangulation sensors on each end of the mold are measuring the distance to a lightweight Styrofoam reflector. The sum of both distances is the total length change. To get a correlation between the shrinkage and the weight loss, the mold is placed onto a balance.
Figure 8- Basic principle of the thin layer shrinkage measurement system as described at [5]
4. CONCLUSION Very slow movements over a long time are not accessible for our human visual sense or sense of touch. Making reliable measurement of shrinkage and expansion of building materials is a trivial task only for the first glimpse. Not only the selection of the right sensor is important, but the system setup itself should be designed very carefully. 5. REFERENCES [1] ASTM C 1581-04. “Standard Test Method for Determining Age at Cracking and Induced Tensile Stress Characteristics of Mortar and Concrete under Restrained Shrinkage”, 2004 [2] ASTM C 827-95a (Reapproved 1997) “Standard Test Method for Change in Height at Early Ages of Cylindrical Specimens from Cementitious Mixtures”, 1997. [3] Bludau W, “Lichtwellenleiter in Sensorik und optischer Nachrichtentechnik”, Springer Berlin 1998. [4] Breitenbücher R, “Zwangsspannungen und Rissbildung infolge Hydratationswärme” Dissertation TU München, München, 1989. [5] Bühler E, Zurbriggen R, “Mechanisms of early shrinkage and expansion of fast setting flooring compounds”Tagung Bauchemie, 7./8. Oktober 2004 in Erlangen Neubauer J, GoetzNeunhoeffer F, hrsg. Von der GDCh-Fachgruppe Bauchemie, 2004.
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Markus Greim [6] EN 12617-4:2002, “Products and systems for the protection and repair of concrete structures. Test methods, Part 4: Determination of shrinkage and expansion”. [7] Gerstner B, Haltenberger H, Teubert O, Greim M, “Device for measuring deformation of mortar in two directions under different temperature conditions has sensors for simultaneous measurement of vertical and horizontal mortar movement”German Paten Application DE000010123663A1, 2001. [8] Greim M, Teubert O, “Appliance for detecting initial expansion and shrinkage behavior of building materials based on contactless measurement of change in filling level of container of fresh material specimens until set”, German Patent Application DE000010046284A1, 2000. [9] Ilschner B, Singer RF, "Werkstoffwissenschaften und Fertigungstechnik: Eigenschaften, Vorgänge, Technologien" Springer Berlin 2010. [10] Jensen OM, Hansen PF. “A Dilatometer for Measuring Autogeneous Deformation in Hardening Portland Cement Paste” Materials and Structures : Research and Testing. 28:406409, 1995. [11] Lorenz OK, Schmidt M, “Aufschüsseln schwimmend verlegter Zementestriche”, ibausil,Internationala Baustofftagung September 1997, hrsg. Stark J. Band 1, 1997. [12] Lura P, Durand F , Jensen OM, “Autogenous strain of cement pastes with superabsorbent polymers”, International RILEM Conference on Volume Changes of Hardening Concrete: Testing and Mitigation, Jensen OM, Lura P, Kovler K (eds), RILEM Publications SARL 2006
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Paulo Sérgio Lima Souza1; Denise C.Dal Molin2; Marcos Anderson Guedes Fernandes3
Assessment of the modulus of elasticity in concrete with high reactivity metakaolin from industry tailing Paulo Sérgio Lima Souza1; Denise C.Dal Molin2; Marcos Anderson Guedes Fernandes3 Received Article: January 8, 2012 Acceptance article: July 25, 2012
Abstract: This paper aims at assessing the use of HRMK within the concrete and verifying its influence within the modulus of elasticity of concrete. To obtain this mineral addition was adopted as raw material, a paper industry tailing, afterwards calcinations and milling process to be transformed into HRMK. To accomplish this work, the content of the HRMK replacements has been varied, as well as the water/concrete ratio and the ages of disruption of the body-test. The methodology used has been based on laboratorial assays and statistical tools in order to the legality of the outcomes. The study has stated that the isolated effect of the controlled variables and some interactions between these variables influence within this property among these isolated effects, it has been evidenced that the variations of HRMK percentages from 0% to 20% outcomes in additions until 9% within the values obtained from the assay of the elasticity modulus. Key words: High reactivity metakaolin, elasticity modulus
I.
INTRODUCTION
The knowledge of the elasticity modulus is the great importance for the implementation of the project, whereas its value helps to predict the deformation, the knowledge of the tensions between the concrete and steel structure, and pre-stressed concrete, besides contributing to the calculation of tensions outcome from shrinkage and settling. Although, this knowledge is still at an early stage regarding to the behavior of this property by using highly reactive pozzolanics, especially, when it focuses on the use of high reactive metakaolin (HRMK). The HRMK, besides its technical advantages is able to be obtained from the paper industry tailing. This tailing is basically made by processed kaolin of an extremely limpid, white, thin and pure kaolin (high content of Kaolinite -Al23.2SiO2.2H2) being transformed into aluminium-silicate pozzolanic throughout a milling and calcinations process (from 700 to 800ºC). According to what has been reported on the first paper, this tailing comes from an industry located northwest of the State of Pará, which currently holds it within tailing dams. However, this storage process has become an environmental problem due to the demand of large areas of deforestation.
Civil Eng. Professor and researcher at NUHAM-UFPa. E-mail: paseliso@ufpa.br Civil Eng. Professor and researcher at UFRGS-NOIRE. E-mail: dalmolin@vortex.ufrgs.br 3 Civil Eng. Student and researcher at UFPa. E-mail: guedesfernandes@gmail.com 1 2
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Paulo Sérgio Lima Souza1; Denise C.Dal Molin2; Marcos Anderson Guedes Fernandes3 Thus, the main objective of this study has aimed at determining the variation within the modulus of elasticity of concrete from the inclusion of HRMK coming from the tailings of paper industry. 2. METHODOLOGY 2.1 Characterization of the Material Quartz-washed sand, mined from Jacuí River and crushed rock of basaltic origin have been used, which characteristics, are placed within Table 1. The Portland cement of high initial resistance (CPV-ARI) has been used. Afterwards, the HRMK has been obtained from the process of milling and calcinations to 750 ºC. Within Figure 1 there is the x-ray diffraction of the material afterwards calcinations, where low crystallization of its structure has been realized. The main characteristics of the cement and the HRMK are presented within the Table 2. Table 1 – Values obtained from the aggregates used and its physical characteristics Description Sand Crushed rock Specific Mass - NBR 9776 (ABNT, 1986) 2,62 kg/dm3 2,71 kg/dm3 NBR 9937 (ABNT, 1987) Mass Unit – NBR 7251 (ABNT, 1982) 1,51 kg/dm3 1,44 kg/dm3 Thinness Modulus - NBR 7217 (ABNT, 1987) 2,43 6,85 Maximun diameter - NBR 7217 (ABNT, 1987) 2,4 mm 19 mm ABNT (Brazilian Association of Technical Standards) Table 2 -Main Characteristics of cement and HRMK used. Chemestries
Cement
HRMK
Mechanical and Physics
Cement
Cement
SiO2 (%)
19,51
42,19
Screen residues 75 m (%)
-
10,59
AL2O3 (%)
4,17
39,24
Specífic area (m²/kg)
4.570
18.770
Fe2O3 (%)
2,85
1,88
Average Diameter (m)
9,16
4,65
-
0,21
Resistance to Cement Compression – 1st day
19,00
-
MgO (%)
1,32
0,20
TiO2 (%)
-
1,49
Resistance to Cement compression – 3rd day
30,70
-
SO3(%)
2,72
-
2,08
-
Resistance to Cement compression – 7th day
34,00
-
CaO Free
1,48
-
CaO Total
64,32
0,02
P2O5 (%)
CO2 (%)
Pozzolnic Activity (%)
94,15
A super-plasticizer compounded of sulphonated naphthalene has been used, made from 37 to 39% of solids. In determining the final amount of water to be added to the mixture, the value of 38% of solids to correct the ratio w/(c+HRMK) has been adopted. Ingeniería Civil Sostenible Vol.1 – No. 2
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Paulo Sérgio Lima Souza1; Denise C.Dal Molin2; Marcos Anderson Guedes Fernandes3
Figure 1 – Pozzolan X-ray diffraction, afterwards the calcinations process
2.2. Experimental program To assess the influence of this material has been necessary set up the controllable variable of the research. Five levels for each controllable variable have been used, as follows: HRMK content of replacement: 0%, 5%, 10%, 15% and 20%; ratio w/(c+HRMK): 0.25, 0.28, 0.35, 0.46 and 0.60; age: 1, 7, 14, 28 and 91 days. Due to the number of existing variables, a statistical project has been adopted, which had the splitting up as the methodology. Two different body-tests from different mixed concrete for each combination have been used. More details about the experimental program were published by SOUZA (2003). A dosage method proposed by MEHTA and AITCIN (1990) was adopted. The mix design method considering the MEHTA and AÏTCIN (1992) has been used. As control of the workability, the value of 20 has been used to accomplish the assay of trunk cone depletion, according to the NBR 7223 (1992) and this procedure has been the guideline to the definition of additive content to be used. The table 3 presents the amounts of materials, where it is highlighted that the amount of final water includes the water added within the additive. In the implementation of the concrete mixture, a vertical shaft concrete mixer has been used, and performing the following sequence of materials: coarse aggregate; half of sand; a portion of water; cement; HRMK; half of the small aggregate; the rest of water. The moulding and curing process followed the procedures of NBR 5738 (1984). Within 24 hours of curing into a laboratory, the dismounting was made and the body-tests placed into a humid chamber until the moment of the assay of the strength to compression. It was performed according to the NBR 8522 (1984).
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Paulo Sérgio Lima Souza1; Denise C.Dal Molin2; Marcos Anderson Guedes Fernandes3 Table 3 – Output of Proportion of the materials for the concrete. Coarse Aggregate
Ratio
HRMK
Water
Cement
HRMK
Sand
W/(c+MCAR)
%
(kg/m³)
(kg/m³)
(kg/m³)
(kg/m³)
0
144
575
-
654
1085
10
143
517
46
654
1085
20
140
460
93
654
1085
5
153
520
22
669
1069
10
152
492
44
669
1069
15
151
465
66
669
1069
0
171
491
-
700
1038
10
171
442
40
700
1038
20
167
393
79
700
1038
5
193
399
17
739
997
10
191
378
34
739
997
15
189
357
51
739
997
0
214
358
-
773
962
10
210
323
29
773
962
20
208
287
58
773
962
0,25
0,28
0,35
0,46
0,60
3.
(kg/m³)
ANALYSIS OF OUTCOMES
The assay outcomes of the modulus of elasticity have been obtained from LVDT (linear variable differential transformer) The mathematical framework of this property is placed within equation 1 and presents one value of r² of 88,70%. The value is statistically consistent; therefore, it shows that 89% of the variability of the outcomes is due to the isolated effect of the variables and the interaction between them, resulting that the values obtained from this framework are very close to those have obtained from the assay. Nevertheless, in order to achieve these values, throughout the equation 1, the controlled variables for levels between 0, 5 and 1, 5 have been codified; in order the constants of the equations have presented the same order of magnitude. Table 4 presents real and codified levels of each variable. Eq= 14, 1332 +0, 00163592/ (Contenr4*Age8) –0, 00496357*AC3/Age9+17, 3975*Content, 2 +9, 76265/WC0,5 –1,83621*Content 0,01*WC3 -0,0496533/Age8
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Table 4 - Real e Codified Levels of the controlled variable used Ratio w/(c+MCAR) – AC
Real Level Codified Level
0,25 0,50
Age (days)
Real Level Codified Level
1 0,50
Content of replacement (%)
Real Level Codified Level
0 0,50
0,28 0, 585 7 0, 565 5 0,75
0,35 0, 785 14 0, 645 10 1,00
0,46 1,10
0,60 1,50
28 0,80
91 1,50
15 1,25
20 1,50
The parameters of the equation have presented p-values at levels below to 0, 05, demonstrating that the proposed framework is statistically significant to a reliable level of 95%, where is not advisable to suppress any of the variable used. Within the analysis of variance of the framework, a high value of F, regard to the calculated F value has been obtained, and it rejects the null hypothesis, and there is no relationship between the controlled variable and the considered response. Within this analysis the p-value was zero, indicating that there is a statistically significant relationship between the controlled variable and the considered response. 3.1 Effect of the ratio w/(c+HRMK) and age (hydration degree) within the concrete elasticity modulus. Figure 2 presents the trend charts of the isolated effect behavior of the ratio w/(c+ HRMK) and the isolated effect of age of disruption, respectively, within the modulus of elasticity. The charts have been obtained from the equation 1, varying the codified values of the focused effect and remaining the other variables of the equation within the average point of the interval codified of each one of them.
Figure 2 - Elasticity Modulus regard to the isolated effect: (a) ratio Water/(c+HRMK) (b) Age of disruption
As expected, the chart (a) of the isolated effect of the ratio w/(c+HRMK) of Figure 2, presents a decrease of the modulus of elasticity values according to the increase of the ratio values. Within the higher ratios w/(c+HRMK) presents a large cement grains spacing resulting Ingeniería Civil Sostenible Vol.1 – No. 2
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Paulo Sérgio Lima Souza1; Denise C.Dal Molin2; Marcos Anderson Guedes Fernandes3 in a larger presence of, principally, within the transition zone, the calcium hydroxide and ettringite, outcoming within a bond weakness within the hardened concrete. Regarding to the chart (b), referred to the isolated effect of the age disruption within Figure 2, the outcomes are also inside the expectations, that is, the values are increasing according to the increases of age of disruption. Within this chart, the evolution age of the modulus of elasticity that has been verified is accentuated, and 68% within the 1st day is reached from the value reached on the 28th day. It is interesting to highlight that the behaviour has presented within the chart placed within Figure 2 incline itself to vary due to other variables, such as the content of replacement of the HRMK.
Modulus of elasticity (GPa)
The interaction between the ratio w/(c+HRMK) and the age of disruption, placed in figure 3, has been necessary to the maintenance of the other variable (content of replacement) of the equation within the average point. 50
50
Age (days)
0.25
30
0.28
20
0.35
28
10
0.46
91
0
7
30
14
20 10 0 0.00
40
1
40
0.20
0.40
0.60
w/(c+HRMK)
0.60
0
20
40
60
80
100
0.80
Ratio w/(c+MCAR)
Age (days)
Figure 3 - Modulus of Elasticity due to the interaction ratio W/(c+HRMK) x age of disruption: (a) chart Eq (ratio w/(c+HRMK); (b) chart Eq (age of disruption).
According to this interaction, a second chart placed within the figure 3 presents, a slower growth of the modulus of elasticity on the first ages when higher values of the ratio w/(c+HRMK) is adopted. On the other hand, low ratios w/(c+HRMK); the growth of the values of the modulus of elasticity tends to be higher within the first ages. Within both situations there has been a much reduced growth after the 28th day.
3.2. Effect of metakaolin of high reactivity addition within the concrete elasticity modulus To obtain the contribution from each replacement content of HRMK, within the modulus of elasticity placed within Figure 4, the disruption age on the 28th day has been fixed, in order to obtain the average contribution between the ratios w/(c+HRMK) used, on the 28th day of the concrete age, for the whole content of replacement studied.
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50
Sc (GPa)
45
100%
40
103%
105%
107%
5%
10%
15%
109%
35 30 25 20 -10%
-5%
0%
20%
25%
Content of Replacement
Figure 4 Modulus of Elasticity regard to the isolated effect of the content of replacement.
According to the values placed within the figure 4, an improvement of this property has been obtained from the increase of the replacement content of HRMK within the concrete. The current contribution of the HRMK use is alike those obtained by QIAN and LI (2001) and ZHANG and MALHORTRA (1995), and inferior the values placed by CALDARONE at al. (1994). These differences may be stated to the physical and chemical characteristics variation of HRMK. Comparing to the improvement obtained from the HRMK to other pozzolans of high reactivity, a different fulfillment of the outcomes obtained from this paper may be realized. In the case of active silica, Dal Molin (1995) also noticed the significance of this variable, where on the 28th day it has been obtained, within a content of addition of 10%, an average improvement among the various ratios w / (c + as) used, approximately 4% compared to the concrete of reference, rather than the improvement obtained from this paper, despite of the HRMK replacement that has been used. Regarding to the ash of rice husk, and based on the mathematical frameworks related by SENSALE (2000), on the 28th day there is a decrease of the modulus of elasticity values, and this decrease, increases due to increase of the content of replacement. Afterwards this age, this behaviour tends itself to be altered, where may be obtained, on the 91th day, an increase of the values, regard to the concrete of reference, within an increase of the replacement content. Despite of this increase to the higher ages, the average contribution obtained from the researcher was still lower than that obtained from this paper using HRMK, on the 91th day. The difference obtained from the behavior between the high reactivity pozzolan may be due to the thinness of active silica compared to HRMK and ashes of rice husk. This situation conceives of the HRMK particle and the ashes of rice rusk provide a performance of this material not only as a filer, but also like micro-aggregate within this mixture. Within the HRMK case, the best performance also may be due to the fact of the property effect, of the products outcome of the pozzolan reaction of this material, such as gelignite.
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Paulo Sérgio Lima Souza1; Denise C.Dal Molin2; Marcos Anderson Guedes Fernandes3 3.3 Effect of addition of metakaolin of high reactivity regard to the ratio w/(c+MCAR), modulus of elasticity of concrete.
Content (%)
50
0
40
5 10
30 20 0.00
15 20
0.20
0.40
0.60
0.80
Ratio w/(c+HRMK)
Modulud of elasticity (GPa)
Modulus of elasticity (GPa)
Within Figure 5 may be seen the effect of this interaction on the modulus of elasticity. The values to assembly the charts have been obtained from the variation of the codified values of the ratio w/(c+HRMK) for each codified value of the content of replacement, maintaining itself the other variable (age) on the average rank. w/(c+HRMK) 50 0.25 0.28
40
0.35
30
0.46 0.60
20 0
5
10
15
20
25
30
Content of Replacement (%)
Figure 5 - Modulus of Elasticity regard to the interaction content of replacement x ratio W/(c+HRMK): a) chart fc (ratio w/(c+HRMK)) b) chart fc (content of replacement).
According to the figure 5, a better efficiency of HRMK regard to use of higher ratios w/(c+HRMK) has been verified. This behaviour may be justified by the fact that within the majority of the ratios w/(c+HRMK), there is a higher porosity, that causes the highest efficiency of the pozzolanic effect by the fulfilling of the emptiness of the mixture, as well as by the filer effect. The comparison of the outcomes with outcomes of other papers that have focused the HRMK use is difficult due to the fact there are no other papers that approach this interaction regard to the modulus of elasticity. Ranking the age within the average point has made that those values placed within the chart of figure 5 be different from the14th day. For the minors or higher ages this behaviour may be different, as have been verified within the interaction between the content of replacement of HRMK and the age of disruption, as following. 3.4 Effect of addition of metakaolin of high reactivity regard to the age, within modulus of elasticity of concrete. The charts of Figure 6 present the modulus of elasticity behavior regards to this interaction and have been obtained from the variation of the codified values of the content of replacement for each codified value of age, maintaining itself the other variable (ratio w/(c+HRMK) within the average point.
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Paulo Sérgio Lima Souza1; Denise C.Dal Molin2; Marcos Anderson Guedes Fernandes3
Figure 6 - Modulus of Elasticity regard to the interaction content of replacement x age of disruption: (a) chart Fc (content of replacement) (b) chart age.
The charts of figure 6 presents that, the increase of the content of replacement has performed a decrease of the modulus values on the first age only. Afterwards the 14th day, the values increase has remained practically unmodified, regardless of the content of replacement that has been adopted. Therefore, a mixture of HRMK an average growth of the modulus values has been obtained of 69% for the 28th day, and 89% for ages of 1 and 7 days, whereas within the mixtures without HRMK the growth has been of 82% and 93% for those ages. Within other ages, the average increase has been 97% and 101% for ages of the 14 and 91 days, respectively, regardless of content of replacement. This behaviour is alike to those gathered by CALDARONE at al. (1994) and QIAN and LI (2001). Regarding to the concrete of reference, within the early ages may be observed that the replacement of cement by HRMK tends to cause a decrease in the values of the modulus. This decrease tends to be again, the outcome of microfiler failure effect in order to compensate the removal of cement, as well as the slowing of pozzolanic reaction of HRMK. On the 14th day, it has already been observed an increase in the value of the modulus with the increase of the content of replacement , where it has been verified an average improvement of 5%, 6%,and 7% to the ages of 7, 14, 28 and 91 days, respectively. ZHANG e MALHOTRA (1995) and QIAN and LI (2001) obtained alike improvements, principally to the ages of 28 days, with HRMK use. Other papers made by CALDARONE at al. (1994) also found improvement within this property, however, it has been noticed that the improvements compared to the reference concrete has been 35%, 36% and 27% at ages 7, 28 and 90 days respectively, that is, higher those obtained from this study. This variation may be credited to the differences that exist within the HRMK used within the referred papers, such as thinness and content of Al2O3, that has great influence within the effect to filer and pozzolanic, respectively, as well as the type of adopted cement. Placing the ratio w/(c+HRMK) on the average point, the values placed on the Figure 5.16 are regard to the ratio 0, 35. For lesser and higher ratio w/(c+HRMK), this behavior may be different.
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Paulo Sérgio Lima Souza1; Denise C.Dal Molin2; Marcos Anderson Guedes Fernandes3 In general, the modulus of elasticity, the outcomes have obtained the optimum content of replacement may exceed the maximum value placed on this paper, and, thus higher than the optimum content placed for the active silica, according to SABIR (1995 ), this should be inferior than 16%, by focusing on the improvement within the modulus of elasticity. 4.
FINAL CONSIDERATIONS
Thus, the accomplishment outcomes from this paper are stated below: 1. The values of the modulus of elasticity have risen when it increases its age, and has diminished with the increase of the ratio water (c+HRMK), as expected. 2. The interaction between the ratio w/(c+HRMK) and the age (degree of hydration) a different growth behavior of the modulus of elasticity has happened, for the several studied ratios w/(c+HRMK). Within the smallest ratios w/(c+HRMK) the growth has been higher within the first ages, whereas within the highest ratios w/(c+HRMK) the growth has been slower. Within both situations, it has obtained little growth between the 28th and the 91st day. 3. The isolated effect assessment of the content of replacement of cement for HRMK, there has been an improvement, directly proportional, to the content of replacement adopted, getting to obtain an average improvement of 9%, amongst the several ratios w/(c+HRMK) used, on the 28th day of age with a content of replacement of 20%. 4. The interaction between the ratio (w/c+HRMK) and the content of replacement has also shown itself significant. Within this interaction, that within the smallest ratios w/(c+HRMK) the improvement within the current modulus of elasticity has been verified due to the increase of the content of replacement that has been inferior to those obtained from the highest ratios w/(c+HRMK). 5. The interaction of age with the content of replacement, there has been a different growth of the modulus of elasticity, related to the ages studied. Within the 1st and 7th day, values with increasing of content of replacement have been verified, while within other age, as well an increase within values with the increasing of the content of replacement of HRMK. In general, it may conclude, throughout the framework obtained, that the HRMK tends to outcome in improvements within this property. This improvement, besides outcome within technical advantages, still provides an excellent option to use tailings that causes large environmental damage. Nevertheless, even with the outcomes, it shall emphasize the need for additional research in order to consolidate the knowledge obtained from this paper. 5. ACKNOWLEDGEMENT The authors’ thanks the financial support supplied by the CNPq (National Council of Scientific and Technological Development) for the accomplishment of this paper.
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Paulo Sérgio Lima Souza1; Denise C.Dal Molin2; Marcos Anderson Guedes Fernandes3 6. REFERENCES [1] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Agregados em estado solto – Determinação da massa unitária: NBR 7251. Rio de Janeiro, 1982. [2] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Agregados – Determinação da composição granulométrica: NBR 7217. Rio de Janeiro, 1987. [3] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Agregados – Determinação da massa específica do agregado miúdo por meio do frasco de Chapman: NBR 9776. Rio de Janeiro, 1986. [4] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Agregada-Determinação da absorção e da massa específica do agr. graúdo: NBR 9937. Rio de Janeiro, 1987. [5] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Concreto - Determinação do módulo de deformação estática e diagrama – Tensão-Deformação: NBR 8522. Rio de Janeiro, 1984. [6] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Concreto - Determinação da consistência pelo abatimento do tronco de cone: NBR 7223. Rio de Janeiro, 1992. [7] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Confecção e cura de corpos-de-prova de concreto cilíndricos ou prismáticos: NBR 5738. Rio de Janeiro, 1984. [8] CALDARONE, M.A.; GRUBER, K. A.; BURG, R.G. High-reactivity Metakaolin: A New Generation Mineral Admixture. Concrete International. v.16, n.11, p. 37-40, Nov. 1994. [9] DAL MOLIN, D.C.C. Contribuição ao estudo das propriedades mecânicas dos concretos de alta resistência com e sem adição de microssílica. São Paulo, 1995. 286 p. Tese de Doutorado – Escola Politécnica da USP. [10] METHA, P.K.; AÏTCIN, P.C. Principles underlying output of high-performance concrete. Cement, Concrete and Aggregates, Philadelphia, v.12, n.2, p.70-78, Winter, 1990. [11] QUIAN, X.; LI, Z. The relationships between stress and strain for high-performance with metakaolin. Cement and Concrete Research. v. 31, n. 11, p1607-1611, 2001. [12] SABIR, B.B. High-strength condensed silica fume concrete. Magazine of Concrete Research. Sep, 1995, v.47, n. 172, p 219-226. [13] SENSALE, G.R.B de. Estudo comparativo entre as propriedades mecânicas dos concretos de alta resistência com cinza de casca de arroz. Porto Alegre, 2000. 181 p. Tese de doutorado. PPGEC - UFRGS. [14] SOUZA, P.S.L. Verificação da influência do uso do metacaulim de alta reatividade na propriedades mecânicas do concreto de alta resistência. Porto Alegre, 2003. 203 p. Tese de Doutorado – PPGEC da UFRGS. [15] ZHANG, M.H.; MALHOTRA, V.M. Characteristics of thermally activated alumino-silicate pozzolanic material and its use in concrete. Cement and Concrete Research, v. 25, n. 8, p.17131725, Jul 1995.
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INFORMACIÓN PARA AUTORES enviar sólo las que realmente —teniendo en cuenta la reproducción— sean útiles, claras y representativas. Las Tablas, Figuras y fotografías se aportarán en hojas separadas del texto y deben enviarlas en formato jpg o tiff. 12.- Fórmulas y expresiones matemáticas. En unas y otras debe perseguirse la máxima claridad de escritura, procurando emplear las formas más reducidas o que ocupen menos espacio. En el texto se indicarán por corchetes. Se deberá emplear editor de ecuaciones para su formulación. 13.- Preparación de envíos. Como parte del proceso de envío, los autores deben comprobar que cumplen con todas las condiciones siguientes. En caso de no seguir estas indicaciones, los envíos podrán ser devueltos a sus autores. a) El envío no ha sido publicado previamente ni se ha enviado previamente a otra revista (o se ha proporcionado una explicación en Comentarios al editor). b) El archivo enviado está en formato Microsoft Word. c) Se han proporcionado los URL para las referencias siempre que ha sido posible. d) El texto tiene interlineado simple, el tamaño de fuente es de 11 puntos, letra Arial. e) El texto cumple con los requisitos bibliográficos y de estilo indicados en las Normas para autores según APA. Para los envíos a secciones en las que se aplica la revisión por pares, se han seguido las instrucciones de la sección Para asegurar una revisión ciega). Para una revisión ciega es necesario que el documento enviado no contenga ninguna referencia de los autores. Envíen los datos del autor en un fichero aparte con nombre, apellidos, breve currículum, dirección electrónica y postal y adscripción académica o profesional. 14.- Todos los artículos originales que se publican en Revista de Ingeniería Civil Sostenible, quedan sometidos a discusión y al comentario de nuestros lectores. Las opiniones deben enviarse, por duplicado, dentro del plazo de tres meses, contados a partir de la fecha de distribución de la Revista. 15.- Contenido científico. Las colaboraciones publicadas en cada número deberán ser resultados originales producto de investigaciones científicas, así como otras contribuciones originales significativas en el área de ingeniería civil y de acuerdo a la temática de la revista.
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INGENIERIA
CIVIL
S O ST E N I B L E
REVISTA DE INVESTIGACIÓN CIENTÍFICA Y TECNOLÓGICA
FACULTAD DE INGENIERÍA, CIENCIAS Y ARQUITECTURA UNIVERSIDAD JUÁREZ DEL ESTADO DE DURANGO
NÚMERO 2
MARZO – AGOSTO 2012