Properties of ultra-high performance fiber reinforced cementitious composites made with gypsum-contaminated aggregates and cured at normal and elevated temperatures

Abstract

Aggregates in many parts of the Middle East are contaminated with gypsum. Therefore, in this study the effects of using gypsum-contaminated natural sand on the compressive strength and expansion of ultra-high performance fiber reinforced cementitious composites (UHPFRCCs) were investigated over a period of one year. Two groups of UHPFRCCs were designed with binary and ternary cementitious blends of Portland cement, silica fume, and/or ground granulated blast furnace slag. Each group consisted of five mixes with different SO3 contents of between 0.11% and 4.5% by weight of natural sand. For each mix, the samples were either water cured or steam cured over a 48h period. The microstructure of the cementitious composites was also studied by the SEM–EDX. Besides, some findings of UHPFRCCs were compared to those of Portland cement mortars. Test results indicated that UHPFRCCs showed a strength gain, particularly under steam curing and an insignificant expansion even in the presence of excess sulfates, in contrast to the mortars.