Partial replacement of cement by ground granulated blast furnace slag and silica fume in two-stage concrete (preplaced aggregate concrete)

An experimental investigation was carried out to enhance the properties of two-stage concrete, also known as preplaced aggregate concrete (PAC), by adding ground granulated blast furnace slag (GGBS) and silica fume (SF) as partial replacement of cement at different proportions. PAC was produced using the gravity process by first placing the coarse aggregates into the formwork and then injecting a grout to fill in the voids in-between the aggregates. Partial replacement of cement by GGBS and SF at 30 and 10%, respectively were found to be a suitable mix for PAC. Even though incorporation of GGBS and SF increased the shrinkage, strength and durability were improved. Generally, shrinkage produced by PAC was significantly lower than that of conventional concrete. By applying preplaced aggregate with an improved composition of grouts, properties of concrete, like strength and permeability, can be enhanced with shrinkage kept within an acceptable level.