Effect of sand, fly ash, and coarse aggregate gradation on preplaced aggregate concrete studied through factorial design

In casting preplaced aggregate concrete (PAC), coarse aggregates are preplaced into formworks then grouts are injected to fill voids. This casting method depends on the ability of the grout to fill voids, which depends on grout workability and coarse aggregate shape and gradation. The effects of fly ash replacement and sand content on low W/B (0.33) PA grout properties is studied, along with the effects of coarse aggregate gradation on PAC mixtures. Significant factor effects and interactions are identified through statistical factorial design of experiment. Results show that inclusion of sand reduces fresh grout workability while fly ash replacement in binders compensates for the loss of workability. The increase in sand content increases mechanical strength of PAC, while coarse aggregate gradation has no significant effect in PAC mechanical strength. Optimized sand and fly ash proportions improve strength up to 43%, 49% and 90% of compressive, tensile and flexural strength respectively, compared to pure cement PAC mixtures.