Study of concrete shrinkage behaviour using the restrained squared eccentric ring test method

摘要

Four types of cement-based concrete specimens were analysed in this study - high-fluidity concrete, semi-dry concrete, high-fluidity crumb rubber concrete with a rubber content of 110 kg/m(3) and semi-dry crumb rubber concrete with a rubber content of 110 kg/m(3). The restrained squared eccentric ring test method was applied to measure the restrained shrinkage strains at early age (first 5 d) in the 0, 90 and 180 degrees zone of the specimens, as well as the time when the specimens cracked. All 12 specimens cracked near the 0 degrees zone, and the values of restrained shrinkage strains in the 0, 90 and 180 degrees zones showed a decreasing sequence. Compared with the ordinary concretes without crumb rubber, the restrained shrinkage of the crumb rubber concretes was reduced and the cracking time was prolonged. The restrained shrinkage strains in the 0, 90 and 180 degrees zone plotted against time showed a linear growth pattern. The ratio of shrinkage strain between the 0 degrees zone and the 90 degrees zone and that between the 0 degrees zone and the 180 degrees zone were practically invariable over time, suggesting that restrained shrinkage strains may be expressed mathematically by a product of a time-dependent function and a spatially dependent function, as postulated in a number of analytical studies.