Results and discussions

The failure load of specimens after the healing process was shown in Figure 2.They were normalized by the strength of the ordinary mortar without preloading.To get rid of the effect of strength variation with time,properties of undamaged specimens cured for the same days were considered.

Figure 2(a)illustrated the results of specimens after the first healing.Most specimens recovered very well in strength when compared with the undamaged ones showed by blank columns.Among them,specimens with FA replacement ratio of 35% performed best,whose flexural strength improved by 22%,17% and 16%,when preloading levels of 30%,60%and 80% were applied,respectively.In Figure 2(b),different from those in Figure 2(a),the remaining strength was lower than the reference(white),demonstrating the decline of self-healing effect under repeated loadings.However,specimens with FA replacement ratio of 35%under 80%fmax did not comply with the findings,whose strength went up by 11%.The interesting phenomenon could be resulted from the pozzolanic reaction of FA[3,8,9],where healing products like C-S-H gels were generated to fill the crack.Adequate space was required to activate this reaction.Under the high preloading level such as 80%,the key requirement was satisfied.

Figure 2　Strength restoration