Mechanistic Understanding of Creep in Basalt Fiber-Reinforced Alkali-Activated Slag Concrete: Quantitative Assessment of Stress–Strength Ratio and Fiber Length Effects

Creep is a critical property affecting the behavior of alkali-activated materials (AAM). AAM exhibit significant creep, hindering their applicability in prestressed structures. Fiber addition to concrete is known to decrease its creep. In this study, basalt fibers were used in developing fiber-reinforced alkali-activated slag (FRAAS) concrete to reduce the resulting creep. Basalt fibers of varying lengths and stress-to-strength ratios were incorporated, and the resulting concrete creep was evaluated. The results showed that the fiber length should not be very long at the same dosage. An appropriate fiber length is conducive to increasing the compressive strength and reducing creep. Although creep decreases when the fiber length is significantly extended, the long fibers decrease the compressive strength and weaken the inhibition effect at a high stress-to-strength ratio. The fiber length minimally influenced the creep coefficient of the FRAAS concrete. Further, a prediction model was proposed for the creep coefficient. The accuracy and rationality of the developed model were corroborated by measuring secant moduli of concrete incorporating different fiber lengths under various stress levels.