This article evaluated the effect of improved autogenous mortar self-healing in the alkali-aggregate reaction (AAR). Prismatic mortar specimens were cast with different contents of polypropylene microfiber and crystalline admixture. The crack-induction method (for subsequent self-healing) was the AAR accelerated mortar bar test itself. After AAR-testing, the specimens were submitted to wetting and drying cycles to stimulate the self-healing mechanism. These two approaches (AAR and self-healing steps) were alternately repeated four times. The results showed that the reference mortar and the mixture with 1% of polypropylene microfiber had the highest and lowest levels of expansion, respectively. The expansion rate was lower for the combined mixtures, although the initial values of length change were high. The visual inspection confirmed that improved autogenous self-healing could close cracks caused by AAR and promote microstructural densification.

Internal sulfate attack (ISA) occurs in cement composites due to the presence of mineral sulfide in aggregates, such as pyrite (FeS2). The oxidation of the pyrite releases sulfate ions, which react with hydrated phases of Portland cement and produce expansive phases such as ettringite and gypsum. The objective of this article was to study the influence of crystalline admixture and polypropylene microfiber on the internal sulfate attack in Portland cement composites due to pyrite oxidation. Mortars with 10% pyrite content (by sand weight) were evaluated and compared with reference mortars (without pyrite). Pyrite oxidation was stimulated through wetting and drying cycles at 40 °C. Transport properties (water absorption by immersion, sorptivity, ultrasonic pulse velocity, and electrical resistivity), length change, flexural tensile strength, and microstructural properties were monitored for up to 24 weeks. Pyrite promoted degradation in all mortars over time. Mortars with microfibers had the lowest expansion due to the availability of voids for the consolidation of expansive phases. However, the high porosity and permeability of the material facilitated the entry of water and diffusion of oxygen. A large number of expansive phases and cracks were found in these mortars. The presence of soluble alkaline phases promoted the interaction between crystalline admixture and pyrite, accelerating the ISA.