Effect of Lightweight Aggregates Incorporation on the Mechanical Properties and Shrinkage Compensation of a Cement-Ground Granulated Blast Furnace Slag-Phosphogypsum Ternary System

Shrinkage-induced cracking is a common issue in concrete structures, where the formation of cracks not only affects the aesthetic appearance of concrete but also potentially reduces its durability and strength. In this study, the effect of ceramsite sand addition on the properties of a ternary system of cement-ground granulated blast furnace slag (GGBFS)-phosphogypsum (PG) is investigated. In particular, the fluidity, rheology, hydration heat, compressive strength, autogenous shrinkage, and drying shrinkage of the considered mortar specimens are analyzed. The results indicate that an increase in PG content leads to a decrease in fluidity, higher viscosity, lower exothermic peak, and lower compressive strength. However, the shrinkage of the mortar specimens is effectively compensated. The incorporation of internal curing water from ceramsite sand improves fluidity, decreases both yield stress and viscosity, enhances the degree of hydration, and induces mortar expansion. However, the inferior mechanical properties of the ceramsite sand generally produce a decrease in the compressive strength.