Low cost and effective methodology to improve the physical properties of recycled aggregates with the use of rice husk ash- lime slurry

Abstract

The objective of the present study is to develop a cost effective methodology to improve the overall quality of RCA, which can be easily incorporated into the manufacturing process of RCA. The treatment technique proposed in this work is based on a coating technique where different slurry ratios (i.e., Liquid: Solid) having varying proportions of RHA (rice husk ash) and Lime was used to coat the RCA. The different slurry ratios (i.e., Liquid: Solid) used in this research are 0.625, 0.75, 0.875 and 1.000. For each slurry ratio the solid composition was varied by varying the Lime: RHA (rice husk ash) composition as followed 20%: 80%, 40%: 60%, 50%: 50%, 60%: 40% and 80%: 20%. The RHA was ground using a LAAV (Las Angeles Abrasion Value) machine. The water absorption and the specific gravity of the treated RCA were tested. To understand the strength factor of each coating scenario of RCA, mortar cubes of 50x50x50 mm3 was casted and cured for 28 days and the compressive strength was obtained. By observing the results it can be seen that when the slurry is thinner the water absorption capacity of the treated RCA reduces. The optimum water absorption reduction of treated RCA is obtained at the slurry ratio 1.000 and it varied from 22-27%. When considering the mortar strength of each scenario it can clearly be seen that in slurry ratios 0.625, 0.75 and 0.875 the strength is optimum when the solid composition of RHA: Lime is 40%: 60%. More the added RHA, the lesser the strength gain, which implies the coating around the treated RCA gets weaker as the amount of RHA is increased. Therefore it’s best to choose the solid composition (i.e.: RHA Lime) as 20%: 80%, 40%: 60% and 50%: 50% to obtain good results. It also should be noted that the strength variation of all scenarios falls in the range of 1.07± 0.26- 2.65± 0.14 N/mm2 which represents a very small variation. Hence it’s best to use a thin slurry as 1.000 having a solid composition of RHA: Lime as 20%: 80%, 40%: 60% and 50%: 50% to coat the RCA.