Shrinkage cracking in restrained reinforced concrete members

The problem of cracking caused by shrinkage in restrained reinforced concrete members is discussed and examined both experimentally and analytically. A total of eight fully restrained slab specimens with different reinforcement layouts were monitored for up to 150 days to measure the effects of drying shrinkage on the time-dependent development of direct tension cracking. Strains in both the reinforcement and the concrete were monitored throughout the tests. The age of the concrete when each crack developed, the crack locations and the gradual change in crack widths with time were also recorded. The effects of varying the quantity of reinforcing steel, the bar diameter and the bar spacing were studied in order to gain a clearer understanding of the mechanism of direct tension cracking caused by restrained shrinkage and the factors affecting it. An analytical model developed previously to study the problem (Gilbert, 1992) is also described and the experimental results and analytical predictions are compared.