Abstract: The first part of the study deals with testing of Recycled Aggregate Concrete (RAC) mixes with Recycled Coarse Aggregate (RCA) in Air Dry (AD), Saturated Surface Dry (SSD), Saturated Surface Wet (SSW) and Surface Wet (SW) conditions and at different levels of replacement for Natural Coarse Aggregate (NCA), so as to assess their influence, on fresh and hardened properties of RAC. The second part, deals with testing of concrete mixes with Recycled Fine Aggregate (RFA) at different replacement levels for Natural Fine Aggregate (NFA). Two fractions of coarse aggregates are used in the mix design viz., 60% (< 20 mm and > 10mm) and the remaining 40 % (< 10 mm and > 4.75mm). At any replacement level of RCA, slump is found to be lowest in AD condition and highest in SSW. The slump is found to reduce with increase in RCA content. At all RCA replacement levels, the AD condition, yields maximum compressive strength, followed by SSD (-11%), SW (-25%) and SSW (-30%). The test results with respect to compressive strength at 7 and 28 days, density and split tensile strength are statistically analysed, to determine their correlation as well as the ratio between them. An empirical equation is proposed to compute the normalized value taking into account the prime variants of the study. It is also observed that, slump value decreases as the percentage replacement of RFA increases and reaches zero for 100% replacement. At all levels of RFA replacement, concrete mixes possess, higher 28 days strength, than the mix with NFA. A linear equation is proposed to compute the normalized 28 days strength for different RFA replacement levels. It is concluded that, since quantum of concrete waste generation is obviously much less than concrete requirement in construction sector, the possible replacement levels may be fixed as 20% RCA and RFA. Test results for such replacement levels indicate, that RAC possesses very similar properties of Natural Aggregate Concrete (NAC), except for workability requirements, which can be circumvented with the use of 0.8% superplasticizer (SP).
Keywords: Concrete waste, Recycled Coarse Aggregate (RCA), Recycled Fine Aggregate (RFA), Recycled Aggregate Concrete (RAC), Air Dry (AD), Saturated Surface Dry (SSD), Saturated Surface Wet (SSW), Surface Wet (SW), Natural Fine Aggregate (NFA), Natural Coarse aggregate (NCA), Natural Aggregate Concrete(NAC).
Title: Experimental Studies on Utilization of Recycled Concrete Aggregates in various moisture conditions and Recycled Fine Aggregates in Normal Grade Concrete Mixes
Author: Vinay Kumar B M, H Ananthan, KVA Balaji
International Journal of Civil and Structural Engineering Research
ISSN 2348-7607 (Online)
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