Self-crack closing ability of mortar with different additives

บทคัดย่อ

Self-crack closing ability of cementitious materials has been studied in various aspects. However, most studies focus mainly on the cementitious material with only cement as a binder (without mineral additives), although many additives are commonly used at present. This research thus aims to investigate the effect of additives on this self-crack closing ability by observing and measuring crack width on the mortar specimens. Cracks were created on mortar specimens by splitting method at the age of 3 and 28 days. As most reports show that the best self-crack closing performance was achieved when a plenty of water was supplied, the cracked specimens were thus cured in water for investigation of the self-crack closing ability. According to the results, it was observed that all mortars showed self-crack closing ability to some extent, even the control mortar which had no additive. In addition, the results indicate that adding some types of additive improved the self-crack closing ability of mortar. For the range of 0 - 0.05 mm crack width, mortar with crystalline admixture showed the best performance to close its cracks at both cracking ages (3 and 28 days). However, for larger cracks, mortar with silica fume was more outstanding in terms of self-crack closing ability, especially when the crack was generated at the age of 28 days. Fly ash was found to be the worst additive to promote self-crack closing ability of mortar in most cases.