Abstract
The drying shrinkage of concrete has a negative effect on its structural performance. In cases where the concrete is restrained, which includes most structures, shrinkage may result in appreciably sized cracks. These cracks affect the aesthetics of the structure and have negative durability related implications.
This paper discusses the results of an investigation which was aimed at quantifying the influence of aggregate stiffness on the drying shrinkage behaviour of plane concrete.
The experimental programme included measurements of drying shrinkage on concrete specimens of two different strength grades for each of three different commonly used South African aggregate types (quartzite, granite and andesite) under controlled conditions. In addition, elastic modulus tests were conducted on cores of the aggregate types assessed.
The test results indicated that, for each aggregate type, the specimens with the higher water cement ratio exhibited less drying shrinkage than those with the lower water cement ratio. Furthermore, the concretes containing quartzite aggregate exhibited less shrinkage than both the granite and andesite concretes, at both water cement ratios. A positive correlation (r = 0.84) was established between the Relative Shrinkage Coefficient (which accounts for different water/ cement ratios) and the elastic modulus of the aggregate.