8 - Fly ash-incorporated recycled coarse aggregate-based concrete

Abstract

This chapter focuses on the feasible use of partial cement substituted by fly ash in 100% recycled coarse aggregate-based concrete (feasible use of fly ash in recycled aggregate concrete [FARAC]). The effect of particle packing method of mix proportioning is explored. Performance of such sustainable concrete is assessed for both strength and durability. At material level, this chapter examines fresh and hardened concrete properties. Microstructural analysis provides some insights for macrolevel behavior. Finer spherical fly ash particles and triple mixing method improve workability of recycled aggregate concrete (RAC). The negative effects of RAC on compressive strength (CS) is only significant at early ages (7 days), which reduces with adequate curing in RAC with 30% fly ash. Split tensile strength and the ratio of split tensile to CS decreases, which implies reduction of the rate of development of tensile strength at higher CS in RAC. Presence of fly ash in RAC causes densification of pores, thereby increasing the resistance to chemical attack. Fly ash used as cement substitution also proves to be beneficial as far as the creep and shrinkage of concrete is concerned. Adverse effects at material level can be accounted for with necessary design considerations for safe application of FARAC as structural components (beam, column, and slabs).