TY - JOUR
T1 - Effect of crystalline admixture and polypropylene microfiber on the internal sulfate attack in Portland cement composites due to pyrite oxidation
AU - Dobrovolski, Mateus E.G.
AU - Munhoz, Guilherme S.
AU - Pereira, Eduardo
AU - Medeiros-Junior, Ronaldo A.
PY - 2021
Y1 - 2021
N2 - 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.
AB - 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.
KW - Internal sulfate attack
KW - Pyrite
KW - Crystalline admixture
KW - Polypropylene microfiber
U2 - 10.1016/j.conbuildmat.2021.125018
DO - 10.1016/j.conbuildmat.2021.125018
M3 - Article
SN - 0950-0618
VL - 308
SP - 1
EP - 20
JO - Construction and Building Materials
JF - Construction and Building Materials
M1 - 125018
ER -