Shrinkage of Hong Kong granite aggregate concrete

In the design of many concrete structures, it is important to assess the amount of shrinkage that could occur because shrinkage could lead to extensive cracking or substantial prestress loss. A number of shrinkage models have been developed all over the world but they differ widely from each other, indicating that the shrinkage of concrete is dependent on the characteristics of the materials used and the local conditions. Early experimental studies in Hong Kong suggested that the shrinkage of Hong Kong concrete is considerably larger than that estimated using shrinkage models developed elsewhere. This is probably due to the local granite aggregate used. In order to resolve this problem and develop a shrinkage model for Hong Kong, a comprehensive testing programme using fibre-optic strain gauges to measure the shrinkage strain was launched. The shrinkage measurement lasted over 3.5 years and covered concrete mixes with and without pulverised fuel ash added and with paste volume varying from 30 to 40%.