Effect of the quantity of sand on the compressive strength of two-stage concrete

Traditional concrete is made by mixing all the ingredients in a mixer. Then the mixed concrete is placed in a formwork. Two-stage concrete is constructed by first placing the coarse aggregate into 30 x 30 x 30 cm moulds and then grouting the voids of the coarse aggregate with a special grout mixture. Since a large volume of the two-stage concrete is occupied by coarse aggregate, it is likely that variations in coarse aggregate content will significantly influence the strength of the concrete. The stresses are mainly transferred by the coarse aggregate skeleton to the grout. The quantity of sand does not influence the compressive strength of two-stage concrete, but influences the physical properties of the mixture (grout), e.g. fluidity and sedimentation, because the grout must be sufficiently liquid to fill the voids in the aggregate skeleton. The paper describes aspects of the effect of the quantity of sand on the compressive strength of the two-stage concrete method.