Early Cracking of Cementitious Materials Based on Stress Concentration Method

The traditional ring constraint shrinkage test method for detecting shrinkage cracking of cementitious materials has been found to have low cracking sensitivity and random occurrence of cracks. To address these problems, this study proposed an improvement ring constraint shrinkage test apparatus. The apparatus was used to analyze the stress distribution at key nodes and cross sections by theoretical and finite element methods. The study also counted the cracking time and crack location distribution of the improvement ring constraint specimens by test results. The findings showed that the average cracking time of the cement mortar that improved ring specimens was 52.4 % shorter than that of the conventional ring specimen. This significant reduction in the test observation period indicates that the improvement ring constraint shrinkage test method is highly efficient. Moreover, 98 % of the crack offset was within 27.35 mm of the expected cracking location, and the offset distance was negligible compared with the conductive coating length. These results suggest that the improvement ring constraint shrinkage test method can effectively limit the location of specimen cracking.