Abstract:

In this paper, two devices were respectively developed for the measurements of early-age shrinkage stress and non-contact shrinkage. Then, by exposing the casting surface to the dry environment, the early-age elastic modulus and free shrinkage of the high-strength concrete with the water-to-cement ratios of 0. 26 and 0. 40 were determined respectively using the two devices. Moreover, the inner shrinkage stress and stress gradient of the restrained specimens were investigated through a modified restrained ring test, and the early-age cracking tendency of the restrained high-strength concrete was finally investigated based on the above-mentioned experiments. The results indicate that, for the high-strength concrete, when the water-to-cement ratio decreases, the early-age free shrinkage, the elastic modulus and the inner shrinkage stress under restrained condition all increase, and that the potential of plastic shrinkage cracking on the drying surface improves. It is thus concluded that the high-strength concrete with a low water-to-cement ratio exhibits high tendency of early-age cracking.

Key words: high-strength concrete, shrinkage, early-age cracking, restrained ring test, dry condition