RECYCLED CONCRETE AGGREGATE IN NATURAL AGGREGATE

By:C SHIVA KRISHNA,1005-14-74108,UCE(A), Osmania University

Under the guidance of:Mrs .P.ANURADHA,Assistant Professor,Civil Engineering,UCE(A), Osmania UniversityRECYCLEDCONCRETE AGGREGATE Introduction Objective of studyChallengesMethodology of studyManufacture of RCAProperties of RCAResults and Discussions Conclusion Future ScopeReferences

CONTENTS4th March 20151005-14-741120INTRODUCTIONRecycled concrete aggregate is defined as the aggregate obtained after the demolition of a structure or leftover concrete after hardening. Concrete is the 2nd largest consumed material after waterProduction: 25 billion tonnes per yearIn Newzealand 27% of waste generated is from CDWRecycling is preferred option than landfill or charges or leviesSustainable Development requiredOld buildings are demolishedExtensive use of Natural Resources

Why Recycle?4th March 20151005-14-741120Sustainable practices are desirableReuse and conserve natural resourcesCost savings over traditional methodsUse of RA in concrete and asphalt showed comparable performance over virgin aggregates.

Continued.4th March 20151005-14-7411205To study the properties of RCATo compare the concrete with recycled aggregate over natural aggregateTo provide a common provision so that waste generated will be recycled completely

OBJECTIVE OF STUDY4th March 20151005-14-741120CheaperTransportation- Easy to obtainEco-FriendlyPreserves the use of Landfill for materials which cannot be recycledADVANTAGES OF RCA4th March 20151005-14-741120Resistance to changeLack of experience Inadequate codes, specifications and standardsInconsistent aggregate gradingLower and variable qualityCHALLENGES FOR USING RECYCLED CONCRETE AGGREGATES

4th March 20151005-14-741120METHODOLOGY4th March 20151005-14-741120CONCRETE MIX PROPORTIONS:

Depends on replacement of coarse aggregate with RCA20% replacement: specific gravity of RCAHigher replacement: shape, grade & texture of RCA

The addition of a fly ash can be used to increase workability without increasing the mix-waterMANUFACTURE OF RECYCLED AGGREGATECONCRETE CONCRETE4th March 20151005-14-741120

4th March 20151005-14-741120There are two processes1ST Process (Two-stage mixing approach)

Stage 1: 60 second mixing- half mix water added- thick layer of cement slurry formed

Stage 2: Adding remaining water-strengthened interfacial zone- improved performance in RCA

CONCRETE MIXING PROCESS4th March 20151005-14-741120Mixture Procedure (Two-Stage Mixing Approach)

Recycled coarse + cementing material1 min50% water1 minVirgin coarse + sand+ 50%water2 minmixmixmix* Control concrete was mixed following the commonly used mixing procedure 4th March 20151005-14-74112013

2nd ProcessDry mixing of RCA before adding the other ingredients- higher compressive & tensile strength & modulus of elasticity- improves shape of recycled aggregate4th March 20151005-14-741120FRESH CONCRETE PROPERTIES

Concrete Density: Fresh density of recycled aggregate concrete at 100% replacement of coarse aggregate will generally be 5% to 10% lower than the corresponding natural aggregate

Workability: Recycled aggregate concrete made from crushed leftover concrete may in general require a small cement adjustment to compensate for increase in water demand. Concrete made from demolition concrete, which generally has a harsher texture from the increased adhered mortar will have an even higher water demand.Properties of RCA4th March 20151005-14-741120PROPERTIES OF HARDENED CONCRETE

Tensile Strength: Tensile and flexural strengths of recycled aggregate concrete at 100% replacement level have been found to have the same or at most 10% lower strength than the natural aggregate concrete

Modulus of Elasticity: reduction in the modulus of elasticity (MOE) of recycled aggregate concrete at 100% replacement level compared to its natural aggregate equivalent by between 6% and 33%.

4th March 20151005-14-741120Drying Shrinkage: Twenty to 50% higher shrinkage levels are reported in recycled concrete aggregate mixes at 100% replacement level when compared to their natural aggregate counterpart

Creep: 30% to 60% greater creep compared with natural aggregate concrete depending on the replacement level

Abrasion Resistance: small differences in the abrasion resistance of concrete for up to 30% replacement level of recycled coarse aggregate4th March 20151005-14-741120Durability: there was no reduction in freeze thaw resistance or increase in permeability or penetrability in the concrete for recycled aggregate replacement levels of up to 30%.4th March 20151005-14-741120

Table showing properties of materials 4th March 20151005-14-741120WATER ABSORPTION OF RCAAggregateWater Absorption CapacitySand2.43%CA-162.73%CA-71.90%Recycled Agg.5.51%4th March 20151005-14-741120

RESULTS OF TESTSSlump test result analysis4th March 20151005-14-741120

Compression test result analysis

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Split tensile strength result analysis

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Flexural strength result analysis4th March 20151005-14-741120

Hardened Density Test4th March 20151005-14-741120

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4th March 20151005-14-74112027As the demolition & construction waste is increasing recycling of aggregate is the best option available instead of landfillingRecycling of aggregate is a Eco-friendly process so as to save natural resourcesReplacement of natural aggregate with RCA gives:As RCA compressive strength by 40-50%As RCA split tensile strength As RCA flexural strength by about 70%As RCA densitySlump value of RCA is less than natural aggregate

CONCLUSION4th March 20151005-14-741120As the waste generating from construction sector is increasing there is a great need of spreading awareness for the recycling of aggregatesSo there should be brought a provision leading to the 100% recycling of concrete aggregateSCOPE FOR FUTURE STUDY4th March 20151005-14-741120International journal on Influence of recycled concrete aggregates on strength parameters of concrete by Jitender Sharma1, Sandeep Singla2- september 2014Best Practice Guide for the use of Recycled Aggregates in New Concrete by CCANZAchtemichuk, S.; Hubbard, J.; Sluce, R.; and Shehata, M. H., The Utilization of Recycled Concrete Aggregate to Produce Controlled Low-Strength Materials without Using Portland Cement,, V. 31, No. 8, pp. 564-569Engr.Bilal Riaz Chughtai Mechanical Properties Of Recycled Aggregates ConcreteREFERENCES4th March 20151005-14-741120

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