Experimental research on aggregate restrained shrinkage and cracking of early-age cement paste

Abstract

This study conducted mesoscale experimental research to investigate the effect of aggregate restraint on local deformation and cracking of early-age cement. The digital image correlation (DIC) method and a microscope were utilized to measure the deformation and cracking of the specimens. The principal strain was analyzed, and the effect of aggregate geometries and the interface transition zone (ITZ) on restrained shrinkage was discussed. Additionally, a cracking index was proposed to quantify the degree of cracking. The results reveal that aggregates without sharp edges lead to later cracking. Elliptical aggregates may offer weaker restraint than circular. The shrinkage at the corner is generally larger, and the direction changes more sharply. As the internal angle of the regular polygon increases, the deformation required for initial cracking increases. A linear relationship between the cracking index and cracking width is established, based on which quantitative analysis of the cracking degree can be conducted.