Effect of grout proportions on strength of two-stage concrete

The objective of this paper was to study the manufacture of suitable grouts for two-stage (pre-placed aggregate) concrete using different admixtures to improve flowability of grout and hence the strength of two-stage concrete. The hypothesis of two-stage concrete is different from conventional concrete, because the particle-to-particle contact of coarse aggregate shrinkage is lower than that of normal concrete. The most important aspect of two-stage concrete strength still remains unclear. The strength of two-stage (pre-placed aggregate) concrete has been described in different ways, by experiment or theory. As no reliable data are available showing the strength of two-stage (pre-placed aggregate) concrete, it was necessary to investigate its strength at different mixes. This paper deals with the effect of different types of admixture on the concrete strength of two-stage (pre-placed aggregate) concrete. The paper also presents experimental results of pre-placed crushed aggregate concrete using 36 different grout mixture proportions. A total of 360 standard concrete cylinders were tested in unconfined compression and tensile strength at 28 days. On the basis of these results, a relationship between the tensile strength and compressive strength of two-stage (pre-placed aggregate) concrete has been statistically derived.