Tennessee Concrete Winter 2022 Magazine

TENNESSEE CONCRETE magazine is published for the Tennessee Concrete Association—

3026 Owen Drive Antioch, TN 37013

Phone: 615.360.7393 Fax: 615.360.6670 Website: www.tnconcrete.org

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WINTER 2022, Vol. 36, no. 3  Tennessee CONCRETE

Sam Pittenger TCA President

Moving back to Davidson County:

3026 Owen Dr. Suite 101 Antioch, TN 37013

Annual Concrete Design Awards will be held during lunch

PRESIDENT’S MESSAGE

THANK YOU TO TCAs ANNUAL SPONSORS

By the time you read this TCA should be moved into their new home. We are back in Davidson County in the Cane Ridge/ Antioch community where your TCA staff is busy outfitting our new Concrete Lab and Training Room, along with the rest of the space.

I would like to say a special Thank You to all of our TCA members who contributed to help us outfit the Lab! And, please feel free to stop in and visit our new space on your next trip to Nashville. Our new address is 3026 Owen Drive, Suite 101, Antioch, TN 37013. The office is conveniently located just off of I-24, Exit 62, on the southeast side of Nashville.

I would also like to thank all of TCA’s Annual Sponsors, both Presenting and Platinum. For 2022, we had a total of 18 annual sponsors — a record number! Our Annual Sponsors show their commitment to our organization with financial support above and beyond their annual dues. Their support makes it possible for TCA to provide a higher level of service to all of member companies, so please support our sponsors by giving them the first opportunity to earn your business. We are signing up Annual Sponsors for 2023 right now. Please consider adding your organization to this great group of TCA supporters.

are already working for us. We have a great morning session lined up with some outstanding speakers (see the Annual Convention schedule included in this issue) who will address labor force demographics, fire and building codes, and improving your personal use of technology. Plus, we will hear an update of the CIM program from CIM Director Jon Huddleston.

Our Annual Concrete Design Awards presentation will be held during lunch, so if you haven’t sent your projects in to be considered put that on your immediate TO-DO list! The Design Awards celebrate the best projects and the best people in our industry — make sure your projects and people don’t get left out.

Our afternoon session this year is special and is designed to help you start the process of improving your organization’s retention program. This will be a hands-on workshop lead by retention specialist Cara Silletto of Magnet Culture. This workshop is designed for you and your workforce team to kickstart your efforts and to keep the great people you already have. So, please consider bringing your key workforce people to the TCA Convention to be part of this dynamic opportunity.

Sponsors

Finally, I would like to extend my personal invitation for you to attend our 2023 Annual Convention (February 8–9, 2023, at Franklin/ Cool Springs Marriott). Our focus this year will be on Workforce with special attention on how we can retain the employees who

WINTER 2022, Vol. 36, no. 3

All of this is included in your Annual Convention registration (thanks in large part to that great group of TCA Annual Sponsors!) so get your team signed up today.

Looking forward to seeing you at the Convention! ■

A special thanks to TCA's Annual

2022 DRAWING TO A CLOSE

2022is rapidly drawing to a close. It has been (and continues to be) a busy year for the concrete industry across the state in spite of numerous challenges like material availability and of course finding and keeping good people. Concrete production in Tennessee through mid-year is slightly above the record concrete production that we posted in 2021 in spite of all these challenges. The outlook for 2023 is clouded by a number of unknowns but most forecasters are not predicting a dramatic drop off in construction activity, even though many are predicting a slowdown in the rate of growth, or even a small (3 to 5 percent) decline in overall construction activity.

Even if we see a slight drop in construction activity the concrete industry (and most other industries) will continue to scramble to find enough people to operate their business. The NRMCA reports in their recently released Mixer Driver Recruitment and Retention Survey that our industry continues to lose drivers at a high rate with a 28 percent quit rate (above the national average for all industries of 25 percent). The survey also documents that our overall number of drivers in the concrete industry is not growing while the amount of concrete production continues to grow year-over-year. This means that the majority of ready mix producers (about 70 percent) report they don’t have enough drivers to fully service their business and are losing yardage because they don’t have enough drivers to carry those loads.

The survey also documents that the median age of a ready mix operator is 47 years old, slightly above the national average for all industries. This means that half of our current driver pool is over 47 years old and we will lose many drivers from our pool as they retire, in addition to the large number who quit for

other reasons. While this is not necessarily a new problem it will become an increasingly urgent problem for one very important reason — demographics.

U.S. population growth has been below replacement level for nearly 50 years with the end result of having fewer people enter the workforce than will be exiting the workforce, especially as the Baby Boomer generation retires. For industries like construction this is especially troubling as we typically hire our replacement workers from this youngest portion of the population. We will be facing this shortage of new workers for many years and there is no quick fix.

While this is sobering it is also something we can see coming and thus plan for. TCA is putting together our 2023 Annual Convention program with this in mind so I encourage you to attend and soak up timely, relevant information that will be critical to your future planning for your organization. Our kick-off speaker (on Thursday, Feb. 9, 2023) is an expert on demographics and how this will impact the workforce of the very near future. Plus, we have put together an entire afternoon session that will focus on retaining the workforce you already have — one person retained is one that you don’t have to replace. This session will be interactive and hands on, not just a slide deck. It is designed to guide your organization through the process of creating your own retention plan so you will leave the session with a critically important building block for your organization’s future. Plan to bring your workforce team to the Convention so you can participate in this vital workshop.

TCA’s ability to bring this caliber of speakers to our membership is due in large part to our Annual Sponsors — so a big shoutout to those 18 companies that became Annual Sponsors in 2022. We are recruiting 2023

Annual Sponsors right now so please consider joining this elite group of TCA members!

Plan to stop by and visit TCA in our new space located at 3026 Owen Drive, Suite 101, Antioch, TN 37013. We look forward to giving you a personal tour!

REGISTRATION FEES AND SPONSORSHIP OPPORTUNITIES

• Annual Convention Registration: $575

• Annual Convention Award Winner Lunch Ticket: $150 Intended for family members of winners, co-workers, and extended project members beyond the Ready Mixed companies. Not needed with full convention ticket purchase!

• Eats & Drinks Sponsor: $375

• Tabletop Sponsor: $995 Includes one full convention registration and a tabletop for display at convention.

• Tabletop Sponsor Plus: $995 Includes one full convention registration and a tabletop for display at convention.

SCHEDULE

Wednesday Evening

5:30–6:30 Statewide Eats and Drinks Reception (near the bar)

Thursday Morning • Afternoon • Evening

7:30* Breakfast Buffet open 8:00 TCA Annual Membership Meeting and Election 8:15 Morning Technology Tip with Beth Z

8:30 The Demographic Drought: Bridging the Labor Gap with Ron Hetrick (via Zoom)

9:30 CIM Program Update with John Huddleston

10:00 Break (15 minutes)

10:15 Fire & Building Codes: How they Impact our Concrete Markets with Shimim Rashid-Sumar, NRMCA VP of Codes

11:15 Morning Summary and Lunch Instructions

11:30–1:00* Annual Concrete Design Awards Banquet

1:15–4:15* Retention Workshop—Keeping Your Valuable Workforce with Cara Silletto (NOTE: This is a hands-on workshop. You will leave with a plan to improve retention in your organization! Bring your team, e.g., HR, managers, etc., and get started on your plan to keep your workforce)

Friday Morning

8:00–Noon TCA Board of Directors Meeting & Breakfast (Invitation Only)

SPRINGS

700 Cool Springs Boulevard Franklin, TN 37067

ROOM BLOCK

Visit our website tnconcrete.org to access Room Block for the dates of Feb. 8–10. Rooms are $189. For a room outside those dates, please call the hotel directly at (615) 261-6100.

NEW! SPECIAL ONE-ON-ONE COACHING SESSIONS

30-minute time slots - $49

Each additional track 3–5 p.m. (Only 4 slots available for each track.)

TECHNOLOGY UP

How to use your tech more effectively. Coaching provided by Beth Z — Your Nerdy Best Friend.

SOCIAL MEDIA

Increase your understanding and improve your message. Coaching provided by Onwrd&Upwrd.

MARRIOTT FRANKLIN COOL

by

GOING BEYOND ACI 332:

Commercial/Residential

Enhanced Durability Concrete: Phase III — The Effect of Limited

ABSTRACT

An absence or shortened amount of curing time for Portland cement concrete can reduce the potential degree of hydration in that concrete. Adequate curing can increase the potential for hydration, the chemical reaction between cement and water, and thus potentially increase the amount of hydration products. Hydration products not only increase strength, they also occupy the void space left by water used for hydration, creating a less permeable concrete matrix. Through these mechanisms, curing can increase both the strength and durability.

Curing concrete is often overlooked in practice due to its time-consuming process. Although the curing process can potentially slow down the progress of a project, it is crucial for the strength and durability development of concrete. Using a variety of common mixes (commercial 3500, commercial ACI, and CRED) and exposing them to limited various amounts of curing, the objective of this research is show how curing effects 28-day hardened properties.Six batches of each mixture were

used. Sixteen four-inch by eight-inch cylinders were cast from each batch. The cylinders from each batch were divided into four sets of four and each cured for a different length of time (0, 3, 7, and 14 days). Surface resistivity, compressive strength, and split tensile strength were determined at 28 days. The effects of extended amounts of curing increased the benefits of strength and durability properties in 38 out of 54 instances.

The compressive strength yielded the most improvement due to longer amounts of immersion curing, however split tensile and surface resistivity also had improvements in results based on curing time.

INTRODUCTION AND LITERATURE REVIEW

The process required to adequately cure concrete can be seen by many contractors as overwhelming or not worth the time and money. Common curing methods such as water ponding and the installation of wetted burlap, both for extended amounts of time, can stall the progress of a project and lead to scheduling problems. However, the process of curing concrete ensures adequate strength

Tennessee CONCRETE

Curing

development and promotion of durability characteristics (1). A concrete’s strength is undoubtedly an important characteristic and is a main describing factor in its production, while the durability of a concrete impacts the longevity of a concrete’s service life. An absence or shortened amount of time allowed for curing can lead to a decrease in both the strength and durability in concrete (2).

The introduction of external water after a concrete’s final set provides moisture that can be used to keep the relative humidity (RH) of the concrete’s matrix high and provide extra water to further promote the hydration of Portland cement (2). The longer this external water is present, the more opportunity the concrete has to reach a higher degree of hydration. Hydration products take the place of the space previously occupied by the mixing water, so this promotion of hydration leads to more products being available to occupy what would have been permeable pore space, making the concrete stronger and less susceptible to harmful chloride ion penetration (3). Chloride ion penetration and sorptivity are durability problems in concrete that can lessen the service life of concrete and have been seen to be higher with concrete being only air cured (4).

An absence of external water after a concrete’s final set, or air cured, has been seen in studies, such as a comparative study by Goel, to cause a lesser compressive and tensile strength than a concrete that has been cured via water immersion or under plastic film. This decrease in strength properties was seen in early age (3-7 days) as well as late age (28-56 days) testing, the latter of which produced the biggest difference due to the higher degree of hydration from the immersion groups (5). According to a study by Senbetta, a poorly cured concrete contained a chloride ion concentration of nearly 50% greater than a concrete that was well cured (6). This characteristic can lead to severe durability concerns for a concrete and lead to a shortened service life.

MATERIALS AND PROCEDURE

The materials used in this experiment are shown in Table 1, Column 1. The three mixes chosen to be used in this study have been used in two previous phases of research and are meant to

WINTER 2022, Vol. 36, no. 3

Robert Tyler Hughes, L. K. Crouch, Daniel Badoe, Kyle Wendt, Alan Sparkman and John Pearson

Type I/II PC, (lbs/CY) 375 451 312

Class F Fly Ash, (lbs/CY) 0 0 187.2

Class C Fly Ash, (lbs/CY) 150 113 0 Metakaolin, (lbs/CY) 0 0 20.8

No. 57 Stone, (SSD lbs/CY) 1816 1854 1911 River Sand, (SSD lbs/CY) 1281 1217 1252 Water (lbs/CY) 250 250 203

Design Percent Air 6 5 6 Air Entrainer, (oz/cwt) 1.1 1.1 0.6 Mid-Range Water Reducer (oz/cwt) 4.2 7.4 8.8 High-Range Water Reducer (oz/cwt) 0.0 0.0 7.3

WINTER 2022, Vol. 36, no. 3

represent a spectrum of low to high end performance based off of strength and durability characteristics. This spectrum is displayed left to right across the top of Table 1. The percent substitution of Class F fly ash in CRED is still beyond the maximum percentage allowed by ACI 332 for concrete subjected to RF3 and RF4 exposure classes, as it was in Phases I and II (8).

Six 1.06-cubic foot batches of each mixture were made with each batch consisting of sixteen four-inch by eight-inch cylinders. Sets of four cylinders within each batch were subjected to a certain amount of immersion curing time, namely 0, 3, 7 and 14 days. The lime-water immersion curing conforms to ASTM C192 specifications (9). Once the sets of cylinders had reached their prescribed amount of curing, they were removed from the immersion tank and left to air cure at room temperature. This curing schedule can be seen in Table 2.

At 28 days, three out of four cylinders of each set were tested for chloride ion penetration via surface resistivity (SR). SR measures the concrete’s resistance to harmful chloride ion penetration, so the higher the SR value, the less permeable the concrete is. In order to conform to SR’s test method, AASHTO T358-17, of testing saturated cylinders, every cylinder was placed back into the curing tank 48 hours prior to testing (10). This was done so as not to provide any additional curing as well as to provide moisture for adequate testing. Compressive strength and tensile strength

were also tested at 28 days, directly after SR had taken place due to its non-destructive nature. Two cylinders of each set were tested in compression, and the other two were tested in tension. Compressive strength was tested in accordance to ASTM C39, and tensile strength was tested in accordance to ASTM C496 (11, 12).

RESULTS

The results for SR of each mixture at each curing age is shown in Table 3. Tables 4 and 5 display the results for compressive strength and tensile strength, respectively.

QUALITY OF RESULTS

Tables A-1, A-2, and A-3 in Appendix A show the comparison of actual and allowable ranges for each hardened state test. The allowable ranges were calculated via multiplying the mean result of each batch by a factor for maximum acceptable range from ASTM C670 that depends on the number of test results, as well as a coefficient of variation factor (COV) from each test’s individual test method criteria (13). Note that the test method for split tensile strength, ASTM C496, does not include a COV factor for four-inch by eight-inch cylinders, however it does recommend a factor for six-inch by twelve-inch cylinders (12). This recommended factor

CONCRETE

WINTER 2022, Vol. 36, no. 3

by Robert Tyler Hughes, L. K. Crouch, Daniel Badoe, Kyle Wendt, Alan Sparkman and John Pearson

RESULTS,

80

25 was used in this quality analysis in order to provide a means of check on the ranges of the split tensile results.

The red shaded cells in Tables A-1, A-2, and A-3 in Appendix A represent instances when the range obtained exceeded the allowable range. Green shaded cells represent instances when the range obtained was lower than the upper limit set by the allowable range.

Four out of thirty-six cases across all mixtures and tests are seen to have an actual range greater than the allowable range. Commercial 3500 and CRED with zero days of immersion curing experienced one batch having lower than normal compressive breaks. CRED with three and seven days of immersion curing experienced singular batches having higher than normal tensile strengths for their curing age. This is thought to be a symptom of sample size; however, the exact cause is unknown but considered not to be a problem.

ANALYSIS OF RESULTS

A statistical analysis of the hardened property results for each mixture was conducted to determine which mix performed better with a certain duration of curing. A statistical t-test with the assumption of unequal variances was conducted in order to accomplish this. When the absolute value of the calculated t-statistic was found to be less than the critical t-value at the corresponding degree of freedom, the results corresponding to this specific comparison were deemed to be not statistically different

(NSD). When the absolute value of the calculated t-statistic was found to be greater than the critical t-value at the corresponding degree of freedom, the results corresponding to this specific comparison were deemed to be statistically significantly different (SSD). Once a comparison is deemed SSD, a closer look at the compared mean property values is required to declare which is superior or inferior.

The primary objective of this research involves comparing the results of different ages of curing within the same mixture as well as showing how different immersion curing periods affect the hardened property results. These comparisons are shown in Tables 9, 10, and 11. A secondary objective involves comparing results from the same curing age but between the three different mixes, which shows how each mixture compares to each other under the same limited curing conditions. These comparisons are shown in Tables 12, 13, and 14.

All mixtures in this study have been used in previous studies and were chosen for this experiment to represent a range of performance (from poorest to best performing: Commercial 3500, Commercial ACI, CRED). It is through research highlighted in the literature review that the hypothesis of samples being cured via immersion longer will perform better than samples that have not been cured via immersion for as long as that sample can be used. For Tables 9 through 12, green shaded cells represent an instance when the comparison is SSD and the result which has been immersion cured for the smaller period of time is inferior. The percent difference in means of the comparison is shown in

WINTER 2022, Vol. 36, no. 3

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GOING BEYOND ACI 332: Commercial/Residential

DISCUSSION

these tables as well. Orange shaded cells represent an instance when the comparison is NSD. For Tables 13 through 15, green shaded cells represent an instance when the lower-ranking mix is SSD and inferior to the higher-ranking mix at that level of curing age. The percent difference in means of the comparison is shown in these tables as well. Orange shaded cells represent an instance when the comparison is NSD.

TABLE 9. STATISTICAL COMPARISON OF

The effect of limiting the curing time a concrete can go through in early stages dampens its ability to promote strength and durability characteristics, as seen by the previous tables. Not allowing excess water to enter the concrete’s matrix after final set in order to increase both the rate and degree of hydration decreases the amount of strength gaining hydration product, calcium silica

RESULTS WITHIN EACH MIXTURE

Robert Tyler Hughes, L. K. Crouch, Daniel Badoe, Kyle Wendt, Alan Sparkman and John Pearson

TABLE 12. STATISTICAL COMPARISON OF SR RESULTS WITHIN CURING AGES

COMPARISON

0 3 7 14

Commercial 3500 vs. Commercial ACI Inferior -22.7% Inferior -11.7% NSD NSD

Commercial 3500 vs. CRED Inferior -205.3% Inferior -168.1% Inferior -161.9% Inferior -161.7%

Commercial ACI vs. CRED Inferior -148.8% Inferior -140.0% Inferior -164.7% Inferior -155.7%

TABLE 13. STATISTICAL COMPARISON OF COMPRESSIVE STRENGTH RESULTSWITHIN CURING AGES

COMPARISON

Commercial 3500 vs. Commercial ACI

0 3 7 14

Inferior -33.6% Inferior -26.8% Inferior -25.9% Inferior -21.3%

Commercial 3500 vs. CRED Inferior -74.5% Inferior -56.9% Inferior -55.2% Inferior -50.0%

Commercial ACI vs. CRED Inferior -30.6% Inferior -23.7% Inferior -23.3% Inferior -23.7%

TABLE 14. STATISTICAL COMPARISON OF TENSILE STRENGTH RESULTS WITHIN CURING AGES

COMPARISON CURING AGE (DAYS) 0 3 7 14

Commercial 3500 vs. Commercial ACI Inferior -30.9% Inferior -19.8% Inferior -11.8% Inferior -16.6%

Commercial 3500 vs. CRED Inferior -48.4% Inferior -27.4% Inferior -24.2% Inferior -28.1%

Commercial ACI vs. CRED Inferior -13.3% NSD Inferior -11.1% Inferior -9.9%

hydrate (CSH). With less CSH comes less strength bonds and more permeable pore space where these bonds would have taken place.

When examining the sole effect of curing time, as is done in Tables 9 through 11, it is seen that SR responded better to curing time in the commercial 3500 and CRED mixes than the commercial ACI. This could possibly be attributed to the mix design, as ACI has a higher amount of Portland cement than the other mixes, giving it much more opportunity to start making partial bonds through hydration and providing less permeable pore space. Commercial 3500 and CRED both responded well to SR in terms of immersion curing age, as 5 out of 6 cases in both mixtures proved the higher curing age to be beneficial.

The effect of providing more curing time had the greatest impact on compressive strength, as seen in Table 10. The commercial

3500 mixture’s results indicated that every instance of comparison shows more immersion curing time leads to an SSD and higher compressive strength than those with less immersion curing time. Commercial ACI and CRED both experienced 5 out of 6 cases where more immersion curing time lead to an SSD and higher compressive strength as well.

Tensile strength performed well in both commercial 3500 and commercial ACI, with more curing time leading to SSD and higher tensile strengths in 4 and 5 out of 6 cases, respectfully. The CRED mixture seen split responses, with 3 out of 6 comparisons showing that an extended amount of immersion curing time caused SSD and higher tensile strengths than those with less immersion curing time.

The analysis shown in Tables 12 through 14 reaffirm the hierarchy of the mixtures shown in phase one of this research.

WINTER 2022, Vol. 36, no. 3

by Robert Tyler Hughes, L. K. Crouch, Daniel Badoe, Kyle Wendt, Alan Sparkman and John Pearson

GOING BEYOND ACI 332: Commercial/Residential

Enhanced Durability Concrete: Phase III — The Effect of Limited Curing

Figures 1 and 2. Display how an increase in the amount of time a concrete is allowed to cure leads to higher strength and durability results.

development. While the effects appear more prominent for compressive strength, tensile strength also has a similar strength development relationship.

CONCLUSIONS

Using three mixtures that are meant to represent a broad spectrum of commercial and residential concrete and subjecting them to four different time periods of immersion curing, it can be concluded that:

Figure 2. Tensile Strength Results Compared to Days of Immersion Curing

• More immersion curing time can benefit both strength and durability properties.

Figure 1 (Left) displays the smaller amount of change seen in SR results when considering longer amounts of immersion curing time. This is due in part to the smaller value in number of SR when compared to larger numbers such as compressive or tensile strength. Figure 1 (Right) and Figure 2 provide a good visual on the effects that extended curing time has on strength

• If using the lower end of the commercial and residential concrete spectrum, which could be considered objectionable, simply curing for three days instead of not curing at all could lead to increase in compressive strength of up to 20%.

• Using a concrete on the high end of the commercial and residential spectrum, such as CRED, increases the resistance to chloride ion permeability, thus increasing the durability of the concrete without regard to the amount of immersion curing time.

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GOING BEYOND ACI 332: Commercial/Residential

Enhanced Durability Concrete: Phase III — The Effect of Limited

3. E. Senbetta, “Curing and Curing Materials.” eds. P. Klieger and J. Lamond STP169C-EB Significance of Tests and Properties of Concrete and Concrete-Making Materials. West Conshohocken, PA: ASTM International, 1994. 478-483. Web. 10 Aug 2021. <https://doi.org/10.1520/STP36442S>

4. Radlinski, Mateusz, and Jan Olek. “Effects of Curing Conditions on the Properties of Ternary (Ordinary Portland Cement/Fly Ash/Silica Fume) Concrete.” ACI Materials Journal , vol. 112, no. 1, 2015, pp. 49–58., doi:10.14359/51687307.

5. Goel, Ajay, Jyoti Narwal, Vivek Verma, Devender Sharma, and Bhupinder Singh. “A Comparative Study on the Effect of Curing on the Strength of Concrete.” International Journal of Engineering and Advanced Technology (IJEAT) 2 (2013): 401-406.

6. Senbetta, E. & Malchow, G. (1987). “Studies on Control of Durability of Concrete Through Proper Curing.” Symposium Paper, 100, 73-88. https://www.concrete.org/publications/int ernationalconcreteabstractsportal/m/details/id/3306

7. ACI Committee 332. (2014). ACI 332-14: Residential Code Requirements for Structural Concrete. Farmington Hill, MI: American Concrete Institute.

8. ACI Committee 332. (2020). ACI 332-14: Code Requirements for Residential Concrete. Farmington Hill, MI: American Concrete Institute.

9. ASTM Standard C192. (2018). “Standard practice for making and curing concrete test specimens in the laboratory.” ASTM International, West Conshohocken, PA, 2018. doi: https://doi. org/10.1520/C0192_C0192M-18

10. AASHTO T 358-17. “Standard Method of Test for Surface Resistivity Indication of Concrete’s Ability to Resist Chloride Ion Penetration.” American Association of State Highway and Transportation Officials. Provisional Standards, 2017 edition, April 2017.

11. ASTM Standard C39. (2018). “Standard test method for compressive strength of cylindrical concrete specimens.” ASTM International, West Conshohocken, PA, 2018. doi: https://doi.org/10.1520/C0039_C0039M-18

12. ASTM Standard C496. (2017). “Standard test method for splitting tensile strength of

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Curing

13. cylindrical concrete specimens.” ASTM International, West Conshohocken, PA, 2017. doi: https://doi.org/10.1520/ C0496_C0496M-17

14. ASTM Standard C670. (2015). “Standard practice for preparing precision and bias statements for test methods for construction materials.” ASTM International, West Conshohocken, PA, 2015. doi: https://doi.org/10.1520/ C0670-15

ACKNOWLEDGEMENTS

The authors appreciate the financial and technical support provided by the Tennessee Concrete Association.

The authors would like to thank Denny Lind of BASF for extensive donations of chemical admixtures to the project. Also, the authors would like to thank Martin Medley for donations of materials used in this project.

In addition, the authors would like to thank Mark Davis for his patience and skill in fabrication, maintenance, and repair of the equipment.

Further, we appreciate the financial support of the TTU Department of Civil and Environmental Engineering.

Finally, the authors appreciate the administrative, financial and information technology support provided by the TTU Center for Energy Systems Research, particularly Dr. Satish Mahajan, Robert Craven, Barbara Fenlon, and Anysa Milum.

AUTHOR INFORMATION

Robert Tyler Hughes, E.I.T. is a civil engineering master’s student at Tennessee Technological University.

L. K. Crouch, Ph.D., P.E. is a professor of Civil Engineering at Tennessee Technological University.

Daniel Badoe, Ph.D. is a professor of Civil Engineering at Tennessee Technological University.

Kyle Wendt is a future civil engineering master’s student and current civil engineering student at Tennessee Technological University.

Alan Sparkman, CAE, LEED AP, CCPf, is executive director of the Tennessee Concrete Association.

John Pearson, P.E. is the technical services director of the Tennessee Concrete Association.

Robert Tyler Hughes, L. K. Crouch, Daniel Badoe, Kyle Wendt, Alan Sparkman and John Pearson

THE RIGHT TOOL FOR THE JOB

Those of you who know me know that I enjoy slow smoking meat on my homemade, offset, wood-fired smoker. Controlling the temperatures across the cooker for a 14-hour cook can be a challenge, but it is a challenge that I have come to enjoy. Although I started out with just a single dial thermometer mounted in the chamber lid, I quickly came to realize that one thermometer would just not suffice. I now have probes made specifically for checking the temperatures at cooking grate level, probes to monitor the internal temperature of the meat, and infrared thermometers to check the surface temperatures on the tuning plates or on the outside of the smoke chamber or firebox. If you are like my wife, you have probably already become bored with this topic. But there is a reason for my ramblings. Every one of these thermometers has a specific purpose. If you use the wrong tool, you will very likely get the wrong answer and you may end up making bad decisions based upon this information. Case in point, not too long ago I was over at a friend’s house, and he was cooking steak on his new outdoor griddle. He was quite proud of his griddle and especially proud of his new infrared surface thermometer which he believed somehow could magically provide a measure of the internal temperature of the steaks. I looked on in horror as I watched him check surface temperatures of the meat during the cook, knowing that he thought he was getting the internal temperature of the meat. For very thin pieces of meat, a surface thermometer might get you close, but should not be relied upon for food safety or quality. Fortunately, I like my steaks on the rare side, and no one ended up getting sick. I am just glad he was not cooking chicken.

I have seen the same type of issue come up in concrete testing. I have had people insist that my reported concrete temperatures must be in error because my reading did not match what they were getting with their infrared surface thermometer. Infrared surface thermometers are great for their intended purpose and can provide some very quick information, but they cannot be used to determine the concrete temperature for acceptance. For a representative concrete temperature, the probe must be protected from the influence of the ambient air. ASTM C1064 Temperature of Freshly Mixed Hydraulic Cement Concrete requires a thermometer long enough that the sensor can be submerged at least three inches into the concrete with at least

three inches of concrete cover in all directions. For concrete with larger aggregate, this distance increases to at least three times the nominal maximum size of the aggregate. This would mean for a 3-inch nominal max aggregate, nine inches of cover would be required in all directions. Surface thermometers, despite their speed and convenience, are not a reliable means to measure representative concrete temperatures for the purpose of acceptance testing.

These types of issues are not limited to temperature tests. The other fresh property tests for concrete have specific equipment requirements that are prescribed for a reason. Don’t get me wrong, sometimes I question the logic of certain requirements or restrictions included in the ASTM standards. I am not sure why it is acceptable to use the tamping rod, a float, or trowel to finish a concrete cylinder while a strike-off bar is not included in the list of acceptable tools for this purpose. By similar logic, one may question why a strike-off bar can be used for strike-off when determining air content by the pressure method, but a strikeoff plate is required for the density (unit weight) test. However, when you take the time to consider how the tests are performed, it becomes evident that strike-off is a much more critical process for the density test. Since density relies upon the relationship of weight to volume, an accurate density result relies on having the measure completely full (but not overfilled). A small error in strike-off will be magnified by a factor of four when the ¼ cubic foot air-pot base is used as the measure, thus skewing the results.

ASTM committees and subcommittees are continually reviewing and revising the specifications to improve the standards by removing overly restrictive requirements while also being clear and specific enough to ensure accuracy and repeatability. We must resist the temptation to make modifications based upon our assumptions or presumptions. Occasionally, and under certain conditions, you may get lucky and your error may not have immediate negative consequences. However, just like undercooked food, your actions may come back to you or others with some rather unpleasant consequences.

TECHNICAL DIRECTOR’S MESSAGE—JOHN B. PEARSON, P.E.

CIM UPDATE

by Jon Huddleston, Associate Professor & CIM Director

Officials at Middle Tennessee State University cut the ribbon Thursday, October 13, to officially open the new $40.1 million School of Concrete and Construction Management Building on the west side of campus. The 54,000-square-foot facility will be an integrated and experiential learning laboratory for the 136 current Concrete Industry Management majors, and a major change from their approximately 9,000 square feet of space in the Voorhies Engineering Technology building.

Among the building’s many features are a 200-seat lecture hall, four basic materials and building labs, a dedicated mechanical electrical plumbing, or MEP, classroom, a covered amphitheater, and two computer labs, including a virtual design and construction lab capable of advanced building models and construction simulations as well as an augmented virtual reality lab for immersive experiences.

University President Sidney A. McPhee calls it “the beginning of a new chapter in the success of our MTSU CIM (Concrete Industry Management) and CCM (Commercial Construction Management) programs. … With today’s dedication, we are publicly reaffirming

our commitment to maintaining the nation’s finest program in Concrete and Construction Management.”

McPhee said he was “amazed at the many ways concrete was utilized in the design and construction. Students will see firsthand how the many forms of concrete can add value and creativity to a structure. The building is a true living laboratory, with examples of various construction techniques and operating systems operating in full view of students.”

WINTER 2022, Vol. 36, no. 3

McPhee saluted industry partners who raised over $5 million in matching funding for the project and who “have been incredibly generous with their time and resources, enabling us to have an amazing facility for our students.”

The builder was Birmingham, Alabama-based Hoar Construction. Orcut/Winslow was the architect. Construction began in January 2021 and finished in September.

The new facility marks an expansion of the university’s Corridor of Innovation in the heart of campus, anchored by the state-ofthe-art Science Building. In coming years, SCCM will have a new neighbor as the Applied Engineering Building will be built in that same area of campus.

MTSU ribbon cutting Front of Building

MTSU ribbon cutting Dr. McPhee Speaking

Current Junior in CIM Aric Rickman speaks at ribbon cutting representing current students

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