Self-healing characteristics of engineered geopolymer composites incorporating metakaolin and fly ash under different environments

The crack distribution and self-healing characteristics of engineered geopolymer composites using metakaolin and fly ash (PVA/MK-FA EGC) at various pre-loadings of 1%, 2% and 3% under air and wet/dry conditioning cycles were investigated at age of 3 days, 7 days and 28 days. The results show that PVA/MK-FA EGC combines the advantages of traditional engineered cementitious composite(ECC) and geopolymer, exhibiting obvious multiple cracking pattern and a strain-hardening behavior. The crack spacing is in the range of 2-5 mm and the maximum residual crack width is below 25 μm, which provide more favorable conditions for self-healing. After self-healing under different environments, number of crack decreases significantly. The ultimate tensile strain can exceed 3.8%, and both ultimate tensile strain and tensile strength capacity of the majority specimens at reloading are higher than the control specimens. Air conditioning can favor the self-healing of the PVA/MK-FA EGC materials. The surface of the particles in the crack is covered with geopolymeric gel, which may enhance the bond of fiber and matrix, resulting in the recovery of the mechanical properties.