LAUSR

ABSTRACT Since the existence of cracks reduces the concrete service life, the self-healing ability of concrete has attracted the attention of researchers. In this article, effects of fly ash and steel/polypropylene fibres on the self-healing ability of concrete were investigated separately and together. The cylindrical specimens were pre-cracked by means of a tensile strength test at 28 days. Secondary tensile test was performed immediately after pre-cracking and 28 and 56 days after re-curing in water. Also, to monitor microcracks in concrete after pre-cracking and during the self-healing period, the ultrasonic pulse velocity and permeability tests were conducted. The results showed that 15% fly ash replacement led to 94% reduction in permeability and almost complete recovery in secondary tensile strength after 8 weeks of re-curing. Although the specimen with polypropylene lost lower tensile strength among specimens with fibre immediately after pre-loading (22%), the improvement rate of those during the self-healing period was only 27%.