Validation of predicted stress in polypropylene fiber-reinforced self-consolidating concrete under restrained shrinkage conditions

Abstract

Self-Consolidating Concrete’s high cement paste volume raises concerns of increased shrinkage and cracking. Evaluating concrete shrinkage potential is critical to designing mixes that limit cracking. AASHTO T334 tests restrained shrinkage, providing a relative method for comparatively assessing the performances of various mixes. In this study, a series of self-consolidating mixes incorporating fibers was prepared, and their cracking resistances were evaluated using the modified AASHTO T334 test. The modified restrained ring test includes two types of strain gages, vibrating wire strain gage, and foil strain gage. Accordingly, the concrete and steel strains were directly measured by two types of strain gages that provided the crack initiation and propagation ages. The measured concrete strain (and stress) and the predicted concrete stress based on the strain in the steel ring were compared and validated. Crack ages, lengths, and widths were measured using a digital microscope with 10x-50x magnification to quantify the cracking resistance of FR-SCC mixes. The results show that the use of polypropylene fibers could reduce the cracking area by 33%, and the use of the strain in the steel ring without modification could underestimate the predicted strain in concrete.