Feasibility of producing two-stage (preplaced aggregate) concrete by gravity process

摘要

Two-stage concrete or Preplaced aggregate concrete ("PAC") is produced by first preplacing the coarse aggregates into the formwork and then injecting a grout to fill in the voids between the aggregates. The involvement of unique and complex machinery for injecting grout has resulted in underutilization of PAC despite its high potential. This study aims to investigate the feasibility of producing PAC using simple construction technique.A suitable grout mix with a desired flowability and strength was applied via gravity process and pumping process to produce PAC using four different sizes of coarse aggregates that is, 45 mm, 37 mm, 20 mm and 14 mm. 20 mm coarse aggregate size was found to be the optimum size for the production of PAC by both gravity process and pumping process displaying compatible performance. Pumping process is recommended for aggregates smaller than 20 mm as it ensures better penetrability of the grout through the aggregates. PAC displays better dimensional stability with drying shrinkage less than half of that produced by conventional concrete.