A methodology to assess crack-sealing effectiveness of crystalline admixtures under repeated cracking-healing cycles

This paper analyzes the autogenous and stimulated self-sealing capacity of steel fiber reinforced concretes, with and without crystalline admixtures, under repeated cracking and healing cycles. To this purpose, the performance under cracking and healing cycles was investigated on 150 × 150 × 50 mm3 specimens, cracked by means of an indirect tensile test called Double Edge Wedge Splitting (DEWS) test. Two concrete mixes (with and without crystalline admixtures) and three healing exposure conditions were investigated: water immersion, open-air exposure and wet/dry cycles. Initially, the specimens were cracked up to a crack opening of 0.25 mm and were then subjected to the different aforementioned exposure conditions for 1, 3 and 6 months. At the end of each period, the specimens were cracked again and were subjected to the different exposure conditions for an additional 1 or 2 months, repeating the cracking and healing procedure up until a total duration of one year. The crack closure was analyzed using image processing methods. The results show that, for the same healing period, the specimens immersed in water reached the largest crack closures. In addition, it was observed that the crystalline admixture may favor long-term self-sealing capacity under repeated cracking and healing events.