Shrinkage Cracking and Crack Control in Restrained Reinforced Concrete Members

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Title: Shrinkage Cracking and Crack Control in Restrained Reinforced Concrete Members

Author(s): Shami Nejadi and Ian Gilbert

Publication: Structural Journal

Volume: 101

Issue: 6

Appears on pages(s): 840-845

Keywords: crack control; cracking; creep; reinforced concrete; restraint; shrinkage; slab; time-dependent

Date: 11/1/2004

Abstract:
Cracking caused by shrinkage in restrained reinforced concrete members is considered both experimentally and analytically. Eight longitudinally restrained slab specimens with different reinforcement layouts were monitored for up to 150 days to measure the effects of 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. An analytical model developed previously to study the problem by Gilbert is modified and recalibrated and the experimental results and analytical predictions are compared. The effects of varying the quantity of reinforcing steel, the bar diameter, and the bar spacing are studied to gain a clearer understanding of the mechanism of direct tension cracking caused by restrained shrinkage and the factors affecting it.