This paper presents an experimental study on the effects of zirconia silica fume on the composite properties and cracking patterns of fiber-reinforced alkali-activated slag-based composites. Four mixtures were prepared with added zirconia silica fume and varying water-to-binder ratio. Polyethylene fiber was used as a reinforcing fiber for all the mixtures at a volumetric ratio of 2.0% cubic specimens and uniaxial tensile specimens were prepared to evaluate their density, compressive strength, and tensile behavior. The test results demonstrated that the compressive strength, tensile strength, and tensile strain capacity of the composite can be simultaneously improved by incorporating zirconia silica fume. A mixture incorporating zirconia silica fume showed high-ductile behavior of 26.5% higher tensile strength, and 13.7% higher tensile strain capacity than the mixture without zirconia silica fume. The composite with added zirconia silica fume also showed excellent cracking patterns, i.e., narrow crack spacing and crack width.

This paper presents a direct comparison of the mechanical and crack-healing properties of strain hardening cementitious composites (SHCC) under water submersion in a laboratory and in a natural environment outdoors. Portland cement, slag, crumb rubber powder, and hybrid polyethylene and polyvinyl alcohol fibers were used for the SHCC, and mixture proportions were determined. Specimens were exposed to different environmental conditions. A sequence of experimental tests including those for density, compressive strength, and tensile properties was performed to assess the mechanical properties of the SHCC. To confirm the healing feasibility of the SHCC, crack width reduction, stiffness recovery, and tensile performance at post-healing were adopted. The test results showed that underwater conditions are better than natural conditions in improving both the mechanical and crack-healing properties of SHCC. Specifically, the SHCC cured in natural conditions had a lower compressive strength, tensile strength, and tensile strain capacity than that cured in underwater conditions by 10%, 4%, and 3%, respectively. The SHCC cured in underwater conditions had a healing threshold of crack width of 60 µm, while the SHCC cured in natural conditions had very limited crack-healing capacity. Additionally, stiffness recovery of the SHCC cured in underwater conditions was higher than that cured in natural conditions.