Quantitative assessment of plastic shrinkage cracking and its impact on the corrosion of steel reinforcement

Chengqing Qi, Purdue University

Abstract

Fresh concrete may be susceptible to plastic shrinkage cracking. Cracks that develop at an early-age can significantly impact the durability of concrete structures. While fiber reinforcement has been advocated as a promising solution to mitigate the problem of plastic shrinkage cracking, little guidance exists to determine which type and what quantity of fiber should be used. This study has developed a quantitative approach to determine the efficiency of fiber reinforcement for plastic shrinkage crack reduction. A test procedure was developed where a restrained slab specimen was exposed to a drying environment immediately after casting. After 24 hours, a semi-automated image analysis technique was used to process digital images of surface crack widths. The crack width data extracted from these images were analyzed using a modified Weibull distribution function. The three characterization parameters that were used in the modified Weibull function, scale parameter (β), shape parameter (α), and PCrack, were related to mean crack width, crack width distribution range, and crack frequency respectively. Statistical analysis methods were used to determine the repeatability of the restrained slab test as a proposed standard plastic cracking test method. Finally, the impact of premature cracking on the corrosion of steel reinforcement was quantitatively assessed. The experimental results indicate that the time to corrosion initiation decreases in the presence of premature surface cracking. As crack width decreases and cover thickness increases, the resistance to the corrosion of steel reinforcement is improved.

Degree

Ph.D.

Advisors

Weiss, Purdue University.

Subject Area

Civil engineering

COinS