Observations on the density and quality of concrete

Abstract

Although fully compacted lower density concrete is made with lower density aggregates and, of necessity, these aggregates are of high porosity, this does not necessarily reduce the quality of the concrete. On the contrary, good quality structural concrete made with manufactured aggregates of relative density about 1.5, is at least as good as — and seems to be intrinsically better than — similar concrete made with normal weight aggregates. This results from the higher cement content and lower water-cement ratio used, from the lower E values of the aggregates, from the availability of water from aggregate pores and from the reduced tendency to cracking. Evidence is presented which suggests that in-situ lower density structural concrete has properties much closer to those assumed by the designer than is the case with normal weight concrete.