3D CONCRETE PRINTING…” An automation in construction industry for affordable and sustainable houses’’

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Abstract - The aim of this project is to assess the feasibility of using fresh concrete as a material for additive manufacturing, specifically in 3D concrete printing. 3D concrete printing is an innovative construction method that offers several advantages in terms of construction time, cost optimization, design flexibility, error reduction, and environmental considerations. The quality of the final printed structure depends significantly on the properties of the fresh concrete, which should possess adequate workability to be extruded through an extruder head (printability) and maintain its shape once deposited without collapsing under subsequent loads (buildability). Due to the unavailability of a 3D concrete printer, physical printing was not possible. However, using readily available plumbing materials, a nozzle was constructed, and beams were printed to simulate the process. In this project, seven different concrete mixes were designed, varying the water-cement ratio and the percentage of superplasticizer. The workability of the fresh concrete used in additive manufacturing was evaluated through slump cone tests. Furthermore, tests were conducted to assess the compressive strength and flexural strength of the hardened concrete. Additionally, this research provides an overview of 3D printing and demonstrates the process of modelling a 3D building using AutoCAD software. The building design was converted from .DWG to. stl format for compatibility with 3D printing. To showcase the 3D printing process, a 1BHK plan was designed and 3D printed using FDM technology.

Key Words: 3D concrete printing, concrete, Additive manufacturing, 3DCP, construction, Affordable houses, automation in construction.

1. INTRODUCTION

The manufacturing method known as "Additive Manufacturing" or 3D printing is characterized by the addition of material in successive patterns to create the desired shape, in contrast to traditional manufacturing techniquesthatinvolveremovingmaterialfromapreformed block (known as "Subtractive Manufacturing"). In 3D printing,specializedsoftwareslicesthe3Dmodelintothin layers,typically0.01mmthickoreventhinner.Theprinter thentraceseachlayerontothebuildplate,andoncealayer

iscompleted,thenextlayerisaddedontopoftheprevious one,graduallybuildingthefinalobject.

Unlikesubtractivemanufacturingmethodssuchasmilling andcutting,whichgenerateasignificantamountofwasteas the excess material is typically discarded as scrap, 3D printingsignificantlyreduceswaste.Thisisbecausein3D printing, material is only placed in the specific locations whereitisneededtoformtheobject,leavingtherestofthe spaceasemptyorsupportmaterial,minimizingunnecessary waste.

Byutilizingadditivemanufacturingtechniques,3Dprinting offersseveraladvantages,includingreducedmaterialwaste, more efficient material usage, and the ability to create complex geometries and intricate designs that may be difficult or impractical to achieve through traditional manufacturingmethods.

AccordingtoaJuly2021reportbyGrandViewResearch,the Global 3D construction market is projected to experience remarkable growth of 91% between 2021 and 2028. This growthindicatestheincreasingrecognitionof3Dprintingas a potential solution to the challenges faced by the architecture,engineering,andconstructionindustries.

One of the significant advantages of 3D printing in construction is its potential to provide affordable housing andsheltersindisaster-strickenregionswheretraditional construction methods may be limited due to a lack of availablehumanresources.Additionally,thetechnologyhas thepotentialforfutureresearchinestablishingcolonieson themoonandotherextraterrestrialsettlements.

Lower construction costs and time are among the main benefits of 3D printing in construction. The ability to accurately calculate the required volume of construction material reduces waste and enhances cost efficiency. Moreover,therapidconstructionspeedassociatedwith3D printing is a significant advantage, contributing to the growingpopularityof3Dprintedbuildings.

Overall,theanticipatedgrowthoftheglobal3Dconstruction market highlights the potential of 3D printing to address

Prof. Hansraj Dikkar1 , Prof. Ravindra Patil1 , Apeksha Gaikar2 , Veena Aher2 , Pooja Kakad2 , Shweta Borade2

1Assistant Professor, Sandip Institute of Engineering and Management, Sandip Foundation, Nashik

2Student of Bachelor of Engineering, Department of Civil Engineering, Sandip Institute of Engineering and Management, Nashik, Maharashtra, India-422213

various challenges in the architecture, engineering, and constructionsectors,offeringbenefitssuchascostreduction, timeefficiency,andtheabilitytocreatestructureswithless waste.

The main objective of this work is to identify the optimal concrete mixture using easily available materials for 3D printingandevaluatethefreshandhardenedpropertiesof the designed mix. The assessment includes evaluating the printability and buildability of various concrete mixtures, and determining the best mix proportions for printing structures.

Experimentalresultsarepresentedinthisstudy,focusingon themixdesignandtestsconductedtoassesstheproperties ofbothfreshandhardenedconcrete.Theseresultsprovide valuableinsightsintotheperformanceandsuitabilityofthe designedconcretemixfor3Dprintingapplications.

Oneofthedrawbacksoftraditionalmanufacturingprocesses is the significant waste generated in the construction industry worldwide, leading to financial losses. Moreover, these waste materials contribute to environmental degradation.Incontrast,additivemanufacturingprocesses, suchas3Dprinting,produceminimalwastethroughoutthe constructionprocess.Additionally,3Dprintingallowsforthe creation of more complex shapes compared to other manufacturing methods. Many machines, buildings, and other constructions achieved through 3D printing are accomplished at lower costs compared to alternative options. The continuous advancements in the field of 3D printingareexpectedtofurtherreduceprices.

Theabilityof3Dprinterstoachievecomplexshapesisoneof their most intriguing features. This capability promotes innovation,flexibility,andtheabilitytomakeadjustmentsin designs, ultimately making the construction process more cost-effective.With3Dprinting,whatisseeninthedrawings canbereplicatedasaphysicalobject,bringingdesignstolife.

Overall,thisresearchaimstooptimizetheconcretemixture for3Dprinting,evaluateitsproperties,highlightthebenefits ofadditivemanufacturingintermsofwastereductionand costefficiency,andemphasizetheabilityof3Dprintersto create intricate and complex shapes in construction and design.

2. MATERIAL IN DETAIL

1. Cement

2. CoarseAggregate

3. FineAggregate

4. Superplasticizer

5. Sand

6. Water

These materials, when properly proportioned and mixed, contributetotheworkability,strength,anddurabilityofthe concrete used in 3D printing and other construction applications.Thespecificproportionsandcharacteristicsof these materials can vary depending on the desired propertiesofthefinalconcretemixture.

1. Cement:

UsingOrdinaryPortlandcement53gradeforyourresearch project is a common practice in construction. This type of cement is known for its high compressive strength and is suitableforawiderangeofapplications.Testingthecement as per the Indian Standard Specification (BIS-1489 part 1:1991)ensuresthatitmeetstherequiredqualitystandards and specifications set by the Bureau of Indian Standards (BIS).

Usingfractionsrangingfrom10mmto4.75mmascoarse aggregateisacommonpracticeinconcretemixtures.These fractionsprovidestructuralstabilityandcontributetothe overallstrengthoftheconcrete.

Inthisresearchproject,crushedBasaltrockisbeingusedas thesourceforcoarseaggregates.Basaltisacommonlyused rock material in construction due to its high strength and durability. It conforms to IS: 383, which is the Indian StandardSpecificationforcoarseaggregates.

To ensure the quality of the coarse aggregates, it is important to maintain the flakiness index and elongation index below 15%. The flakiness index measures the percentageofaggregateparticleswithathicknesslessthana specified ratio to their average size. The elongation index measuresthepercentageofaggregateparticleswithalength greater than a specified ratio to their average size. By keeping both these indexes below 15%, you are ensuring thatthecoarseaggregateshaveamorecubicalshapeandare less prone to elongation, which can affect the workability andperformanceoftheconcrete.

ByusingcrushedBasaltrockwithinthespecifiedsizerange andmaintainingtheflakinessandelongationindexesbelow 15%, you are ensuring the quality and suitability of the

Table 1:PhysicalPropertiesofordinaryPortlandcement

2. COURSEAGGREGATE:

coarse aggregates for our research on 3D printing with concrete.

Inthisresearchproject,thefractionsrangingfrom4.75mm to 150 microns are classified as fine aggregate. Fine aggregatesareessentialcomponentsofconcretethathelpto fill the spaces between the coarse aggregates and provide workabilityandcohesivenesstothemixture.

Forourproject,bothriversandandartificialsandarebeing usedasfineaggregates.Theselectionoffineaggregatesfrom different sources allows for comparative analysis and evaluation of their performance in the concrete mix. It is importanttoensurethatbothtypesofsandconformtothe requirements specified in IS: 383, which is the Indian StandardSpecificationforfineaggregates.

ConformingtotherequirementsofIS:383meansthatthe riversandandartificialsandusedasfineaggregateshave undergonescreeningprocessestoeliminateanydeleterious materialsandoversizedparticles.Screeninghelpstoremove impurities, such as organic matter, clay, silt, and other contaminants, ensuring that the fine aggregates meet the necessaryqualitystandards.

By using both river sand and artificial sand as fine aggregatesandadheringtotherequirementsofIS:383,you can ensure that the fine aggregates contribute to the workability, strength, and overall performance of the concreteinyourresearchon3Dprintingwithconcrete

4. Superplasticizer:

Zentrament F BV -SNF based high early strength super plasticizer.

Productproperties:

 Highearlystrengthsuperplasticizer

 Chloridefree

 Highly pumpable concrete requiring minimum compaction

 Reducingthebleedingandsegregationinconcrete

5. Water

Waterusedformixingandcuringofconcretecubeshallbe clean and free from oil, acids, alkalis, salt and organic materialorothersubstances.Portablewatershallbeused formixingofconcrete.Suspendedsolidmatterinthewater shall not exceed more than 200mg/l. The pH value of the watershallnotbelessthan6.

6. Sand

Manufacturedsandisfreeofsiltandclayparticles,andhas denserparticlepackingthannaturalsand.Italsooffershigh flexural strength, better abrasion resistance, higher unit weight and lower permeability. It is superior and costeffective alternative to natural sand, crushed stones and lightweight fine aggregate, for use in the manufacture of advanced building material derivatives such as concrete, mortars,rooftiles,tileadhesivesetc.

3. EXPERIMENTAL METHODOLOGY

(1) Collectionofmaterial

(2) Developingamixdesign

(3) Conductingtestsforfreshconcreteproperties

(4) Conductingtestsforhardenedconcreteproperties

(5) Discussionofresult

(6) Identifybestresult

Byfollowingthismethodology,theresearchaimstoidentify thebestconcretemixtureusingeasilyavailablematerialsfor additivemanufacturingandevaluateitsfreshandhardened properties. The results will provide insights into the printability, buildability, and overall suitability of the designedmixfor3Dprintingapplications.

The water-cement ratio was fixed between 0.3 and 0.35. Then, five trials were conducted by adding a superplasticizer. In one trial, the water-cement ratio was decreased to 0.28 with the addition of 3% of superplasticizer.

3. FineAggregate

Table 2:TechnicalDataforZentramentFBV

Table 3: MixDesignRatiosfor7TrialMixes

4. EXPERIMENTAL RESULT

4.1 FRESH CONCRETE PROPERTY

Theconcreteslumptestmeasurestheconsistencyoffresh concrete before it sets. It is performed to check the workabilityoffreshlymadeconcrete,andthereforetheease with which concrete flows. Slump test carried out using a frustum of cone, having a base diameter of 80mm, top diameter of 70mm and a height of 500mm, a base plate, measuring tape and a trowel. The procedure consists of firstlytheinsideportionoftheconemadewetandisplaced inaninvertedmanneratthecenterofbaseplateThenthe concreteisfilledinsideusingatrowelwithnocompactionto concrete. When the concreteisfilledtheconeisvertically lifted.Whentheflowstops,diameterattwoperpendicular directionsistakenandthemeaniscalculated.Allthetests wereconductedonallthemixesbeforecastingofspecimens andtheresultofslumptest.

Thenextstageinvolvesmixingofconcreteorcementitious materials for the printing. To check the printability and stabilityinlayerbylayerformationofthedevelopedmix,a concreteextruderwasdesigned.Sincewewerenothaving3 Dprinterbuttoshowtheflowability,printabilityweusethe availableCANWhichconsisthopperandnozzletoasshown infig.Theextrudabilityofthemixwascarriedoutusingthe concreteextruder.Themachineallowedthesmoothflowof mix through auger and then through the nozzle. As the distance between nozzle and printing surface was proper therewasnobreakintheflowofthemix.Therewasproper layerbylayeradhesionandnobleedingoccurredshowing themixwasofproperratio.

The flowability test was conducted for each mix and the resultswereobtained.Apropermixwasascertainedfirstly throughthisexperiment.ThefirstmixM1wasobtained a flowof0cmandthemixwasnotsohardsothattheycan’tbe usedfor3Dprintingconcrete.Furthermixeswereprepared by reducing water cement ratio. And increasing the % of SuperplasticizerMixM2andM3weretoowateryanditwas flowable. Then mix M4 was prepared and conducted flowabilitytest.Themixobtainedwasofproperconsistency. And slump cone test was performed and the result was obtainedas225mm.Thentheflowabilityobtainedwas7.2 andtheconsistencywasproperwithoutanybleeding.

4.2 HARDENED CONCRETE PROPERTIES

1 CompressiveStrengthTest

ThetestwascarriedoutasperIS:516-1959.Compressive strength tests were performed on cube samples using compressiontestingmachine.Threesamplesperbatchwere testedwiththeaveragestrengthvaluesreportedintable3.

1.Workability

Fig 1:flowabilitytest(ConcretePouring)

2. Flowability

Fig 2:flowabilitytest(ConcretePouring)

3.ConcreteExtruder

Fig 3:ConcreteExtruder

5. RESULTS AND DISCUSSION

(i)For Batch 1: The results obtained by the compressive strength test at the age of 7 days are good as per the acceptableresultattheageof7dayscuringis51.40N/mm2 requiredforM55gradeofconcreteandobtainedresultsare morethanthat.

(ii) Theresultsobtainedbythecompressivestrengthtestat theageof28daysaregoodaspertheacceptableresultat theageof28dayscuringis60.47N/mm2requiredforM55 gradeofconcreteandobtainedresultsaremorethanthat.

(iii)Theworkabilitywasdeterminedbyslumpconetest,the slumpvalueformixdesignofbatch1wegotwas225,which ismorethanarequiredslump.

(iv) the concrete was flowable and the concrete was also easilyextrudedfromtheconcreteextruder.

(v)Asconcreteisamaterialdesignforcompressivestrength, itgivessatisfactoryresultsafterreplacingglassaggregateto coarse aggregate and it doesn’t show the suitability of material.

FLEXURALSTRENGTHTEST:

Flexuralstrengthtestswereperformedonflexuraltesting machinehaving100KNcapacityusingbeamspecimen.Three samples per batch were tested with the average strength values reported in table 6.2. The flexural strength of the specimenshallbeexpressedasthemodulusofrupturefb, which,if‘a’equalsthedistancebetweenthelineoffracture andthenearersupport,measuredonthecenterlineofthe tensilesideofthespecimen,incm,shallbecalculatedtothe nearest0.5kg/sq.cmasfollows

fb=pl/bd2

Discussion of Result

(i)Theresultsobtainedbytheflexuralstrengthtestatthe ageof7daysaregoodaspertheacceptablerangeofresult requiredforM55gradeofconcreteandobtainedresultsare morethanthat.

(ii)Asconcreteisamaterialdesignforcompressivestrength, italsogivesgood resultsin flexural strengthanditshows thatthesuitabilityofmaterial.

6 CONCLUSION

Thestudywasconductedto discovera proper mix for3D printingconcrete.Nospecificmixwasmentionedinanyof thereferredarticles.Bytrialanderrormethod, amixwas

Fig 4.Compressivestrengthtest

Table 4: CompressionTestResult

Fig 5. FlexuraltestingMachine

Table 4: FlexuralStrengthTestResult

fixed by assessing the fresh properties. Through trial and errormethod,TotalSeventrialswereconducted.Thefirst twotrialswerecarriedoutwith10mmaggregate,sand,and cementtodeterminethewater-cementratio.Thus,thewater cementratiowasfixedbetween0.3and0.35.Thenfivetrials wereconductedbyaddingasuperplasticizer.Bydecreasing thewater-cementratioto0.28 withtheadditionof3%of superplasticizer. The assessment of fresh properties by conducting a flowability test was conducted. Through compressivestrengthtest,itwasobservedthatthemixM6 whose7-daycompressivestrengthwas60N/mm2.

Theresultswhichproventhequalityofthedesignedmixcan besummarizedasfollows:

1.Thecompressivestrengthtestresultwaslimitedto7Days and28days.

2.Bestw/cratiowasfoundtobe0.37.

3.TheexperimentalinvestigationsprovedthattheBestmix was M7 in terms of Bleeding, Shrinkage, segregation, and strength.

4.WatercementRatioplaysaveryvitalroleinconcretemic designforthe3DConcretePrinting.Thewater-cementratios between0.25-0.44.

5.3Dconcretehassomefeasiblefeaturessuchasflowability. These characteristics vary from traditional concrete. Therefore, the development of 3D concrete should be performedwithgreatercarebytakingthesecharacteristics intoaccount.

6. Theinitialcostofconcreteprintingtechnologyishighdue tothehighcostof3Dprintermachines.3Dconcreteprinting providesmanypotential cost-effectivenessadvantagesfor construction processes compared to conventional construction methods, considering the different cost elements(labor,equipment,materials,design,andplanning costs).

7. Itisnecessarytousetheminimumamountofwaterwith superplasticizersforbetterconcreteadhesion.Furthermore, wecanalsothataddingmaterialssuchasflyash,silicafume andslagcouldbenefitthemixtureif5to30percentofthe total binder volume were added. And the cement will be usedinlessamount.

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