Effect of Recycled Coarse Aggregates in Concrete

Effect of Recycled Coarse Aggregates in Concrete

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  Prepared by Nirmal KrishnanA K
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  INTRODUCTION  Concrete  World’ssecond most consumed material.  Basic need for urban development.  Out of all construction materials concrete is the main constituent.  It is estimated that 25 billion tonnes of concrete is manufactured each year.  Ingredients  Cement  Aggregate  Water  Admixtures
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  INTRODUCTION (contd.)  Constructionand demolition waste  Demolition waste  Construction waste  Road work waste  Other construction waste  Environmental problems  Scarcity of landfills  Non biodegradable  Solution  RECYCLE  REUSE
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  RECYCLING OF CONCRETE BENEFITS  Saves landfill space  Use as gravel reduces need for gravel mining  Use as base material for roadways reduce the pollution involved in trucking material  Recycling of 1 ton of concrete could save 1360 gallons of water, 900 Kg of CO2  Rubblization
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  RECYCLED AGGREGATES  Productionof recycled aggregates  Uses of recycled aggregates  Types of recycled aggregates  Recycled coarse aggregate(RCA)  Recycled fine aggregate(RFA)
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  METHODS TO PRODUCERECYCLED AGGREGATES  HEATING AND RUBBING METHOD  ECCENTRIC-SHAFT ROTOR METHOD  MECHANICAL GRINDING METHOD  ELECTRIC PULSE POWER METHOD
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  LITERATURE REVIEW Sl.no AuthorYear Work done 1 P.C Khergamwala et al 2013 Studied on recycled coarse aggregates from fresh concrete waste 2 N. Sivakumar et al 2013 Study on recycled coarse aggregate made from demolition waste 3 Mamery Sérifou et al 2014 Studied about the possibility of using fresh concrete waste as recycled aggregates in concrete 7
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  CASE STUDY  CASESTUDY 1-EXPERIMENTAL STUDIES ON HIGH STRENGTH CONCRETE BY USING RECYCLED COARSE AGGREGATE  CASE STUDY 2-EFFECT OF RECYCLED COARSE AGGREGATES ON CHARACTERISTIC STRENGTH OF DIFFERENT GRADES OF CONCRETE
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  CASE STUDY 1 High strength concrete(HSC) Concrete with characteristic compressive strength higher than 40MPa Materials used Cement Water Fine aggregate Coarse aggregate Mix design 1:1.97:3.35 wc ratio 0.4
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  Mix  HSC  0%recycled coarse aggregates  10% recycled coarse aggregates  20% recycled coarse aggregates  30% recycled coarse aggregates  40% recycled coarse aggregates  50% recycled coarse aggregates  50% recycled coarse aggregates with reduced w/c ratio
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  TEST ON HSC TESTON FOR DURABILITY HSC  Acid resistance test  Saturated water absorption test  Porosity test TEST FOR STRENGTH ON HSC  Slump test  Compression test  Indirect tensile test  Modulus of elasticity
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  SLUMP TEST  Slumpcone or Abrams cone  Filling and tamping of mix  Removal of cone  Measurement of slump  Result Fig.1 Graph showing the result of slump test (Source: N.Sivakumar et al, 2014)
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  COMPRESSION TEST  Compressiontesting machine  Specimen 150mm CUBE  After 24 hours immerse in water for curing  Strength after 7 and 28 day curing  Load till failure  Compressive strength is the ratio between load at failure to cross sectional area
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  Fig.3 Variation ofcompressive strength after 28 days (Source: N.Sivakumar et al, 2014) Fig.2 Variation of compressive strength after 7 days (Source: N.Sivakumar et al, 2014)
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  Fig.4 Graph showingpercentage of Compressive Strength remained (Source: N.Sivakumar et al, 2014)
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  INDIRECT TENSILE TEST Compression testing machine  Cylinder of size 300mm AND 150mm diameter  After 24 hours immerse in water for curing  Strength after7 and 28 day curing  Loading as specified in figure  Load till failure Fig.5 schematic representation of indirect tensile test
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  Fig.6 Variation ofTensile strength after 7 days (Source: N.Sivakumar et al, 2014) Fig.7 Variation of Tensile strength after 28 days (Source: N.Sivakumar et al, 2014)
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  Fig.8 Graph showingpercentage of Tensile Strength remained (Source: N.Sivakumar et al, 2014)
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  MODULUS OF ELASTICITYTEST  Compression testing machine  Specimen 152mm diameter and 312mm long cylinder  Fix the specimen in the compressometer and place it in compression testing machine  Measure the average deformation of two diametrically opposite locations to the nearest 5 millionths of strain  The modulus of elasticity is calculated  Obtain a stress-strain curve
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  Fig.9 Stress andStrain Relationship for 0% RCA replacement(Source: N.Sivakumar et al, 2014) Fig.10 Stress and Strain Relationship for 50% RCA replacement (Source: N.Sivakumar et al, 2014)
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  Fig.11 Graph showingvariation of modulus of elasticity (Source: N.Sivakumar et al, 2014)
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  ACID RESISTANCE TEST Specimen 150mm cubes  Weighed  Immersed in 3% Sulphuric acid for 45 days  Surface dried and weighed  The percentage loss in weight and the percentage loss in compressive strengths are calculated
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  Table.1 Reduction inCompressive Strength based on Acid resistance Test (Source: N.Sivakumar et al, 2014) Percentage replaced 28 day compressive strength (MPa) After 45 days immersion of cubes in Sulphuric acid solution Percentage reduction in weight Compressive strength (MPa) Percentage reduction in compressive strength compared to 28 day strength 0 42.1 0.42 38.3 9.03 10 38.2 0.47 33.8 11.52 20 35.3 0.51 31.1 11.9 30 32.5 0.56 28 13.85 40 30 0.59 25 16.67 50 26.6 0.63 21.3 19.92 50 % with reduced water content 37 0.52 32 12.33
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  SATURATED WATER ABSORPTIONAND POROSITY  Procedure SPECIMEN 100mm CUBES After 24 hours immerse in water for curing After 28 and 90 days of curing Weighed and dried at 1050C Continued till weight at consecutive days remains same Cooled at room temperature and immersed in water Continued till weight at consecutive days remains same
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  SATURATED WATER ABSORPTIONAND POROSITY (contd.)  Saturated water absorption Percentage water absorption = (𝑊𝑠−𝑊𝑑) 𝑊𝑑 x 100  Porosity Effective porosity = (Ws –Wd ) (𝑊𝑠−𝑊𝑠𝑢𝑏) x 100
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  Table.2 Test forsaturated water absorption & porosity (Source: N.Sivakumar et al, 2014) Percentage replaced Saturated water absorption Percentage increase in saturated water absorption Effective porosity Percentage increase in Effective porosity 0 1.10 0 3.30 0 10 1.24 12 3.51 6 20 1.38 25 3.85 16 30 1.56 41 3.90 18 40 1.66 50 3.97 20 50 1.74 57 4.05 22 50% with reduced w/c ratio 1.37 24 3.59 9
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  CASE STUDY 2 Materials  Cement :- OPC grade 43  Fly ash :- the 45 micron passing fraction in the unprocessed fly ash was more than 90 percent  Fine aggregates :-specific gravity 2.61  Coarse aggregates :-  Natural aggregates specific gravity:2.7  Recycled coarse aggregates made from laboratory waste and left over fresh concrete specific gravity:2.45  Water
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  MIX DESIGN MIX MIX PROPORTION FLY ASH% CONSTITUTIONS(Kg/M3) W/C RATIO CEMENT SAND AGGREGATES M20 1:1.5:3.4 25 400 600 1360 0.5 M30 1:1.25:2.75 25 450 562.5 1237.6 0.5 Table.3 Mix proportions for different mixes (Source: P.C Khergamwala et al, 2013)
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  Mix  M20 concrete 0% recycled coarse aggregates  25% recycled coarse aggregate  50% recycled coarse aggregate  75%recycled coarse aggregate  100%recycled coarse aggregate  M30 concrete  0% recycled coarse aggregates  25% recycled coarse aggregate  50% recycled coarse aggregate  75%recycled coarse aggregate  100%recycled coarse aggregate
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  COMPRESSIVE STRENGTH TEST Cubes of size 150 mm are casted for all the mixes  Immersed in water for curing  Compressive strength at 7 day and 28 days of curing is fount out using compression testing machine  Compressive strength is the ratio between load at failure to cross sectional area  Percentage reduction in characteristic compressive strength is calculated
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  Table.4 Compressive strength(N/mm2) of concrete mixes (Source: P.C Khergamwala et al, 2013) Recycled aggregate (%) M20 Compressive strength % Reduction in fck M30 Compressive strength % Reduction in fck 7 days 28days 7 days 28 days 0 18.2 25.9 - 23.5 34.2 - 25 17.4 25.8 0.4 20.4 32.1 6.1 50 18.7 26.7 3% increase 21.9 33.3 2.6 75 12.4 18.6 28.2 17.2 26.7 21.9 100 16.4 21.3 17.8 21.2 29.8 12.9
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  Fig.12 Compressive strengthof concrete at 7 days(Source: P.C Khergamwala et al, 2013) Fig.13 Compressive strength of concrete at 28 days (Source: P.C Khergamwala et al, 2013)
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  SUMMARY  Specific gravityof RCA is lower and Water absorption of RCA is higher than natural aggregate.  The compressive strength of concrete containing 25% and 50% RCA is in close proximity to that of normal concrete.  For M 20 it was seen that compressive strength increased by 3 % with addition of RCA but only up to 50%.  When amount of RCA is increased above 50%, it adversely affects the compressive strength of concrete.
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  CONCLUSIONS  Recycled aggregatescan be used as an alternative for natural aggregates.  By using there recycled aggregates we can save our precious land from dumping C&D wastes as landfills.  In modern times broken brick, marble, plastic, etc. are used as aggregates.  So these recycled aggregates can be used as fine aggregate as well as coarse aggregates.
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  CONCLUSIONS (contd.)  ForHSC 30%-40% recycled coarse aggregates with reduced wc ratio may give same output as normal concrete gives.  For low grade concrete 50% RCA replacement will give almost equal results as normal concrete gives.  Problem in recycled aggregate concrete is that due to the low wc ratio the workability will be very low  Due to high water absorption rate of recycled aggregates the water content in the mix should monitored carefully
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  REFERENCES  Pinal C.Khergamwala, Dr. Jagbir Singh, Dr. Rajesh Kumar International 6, “Effect of Recycled Coarse Aggregates on Characteristic Strength of Different Grades of Concrete” Journal of Civil Engineering and Technology, volume 4.  N.Sivakumar, S.Muthukumar, V.Sivakumar D.Gowtham, V.Muthuraj “Experimental Studies on High Strength Concrete by Using Recycled Coarse Aggregate” International Journal of Engineering and Science, vol.4, issue 01.  Mamery Sérifou, Z. M. Sbarta, S. Yotte, M. O. Boffoué,2 E. Emeruwa, and F. Bos “A Study of Concrete Made with Fine and Coarse Aggregates Recycled from Fresh Concrete Waste” Journal of Construction Engineering Volume 2013, Article ID 317182.  S. K. Singh, and P. C. Sharma (2007) “Use of Recycled Aggregates in Concrete- A Paradigm Shift”  http://www.buildingresearch.com.np