Effect of Stress–Strength Ratio and Fiber Length on Creep Property of Polypropylene Fiber-Reinforced Alkali-Activated Slag Concrete

Alkali-activated slag (AAS) is an environmentally friendly green cementitious material that can replace ordinary Portland cement (OPC) and has attracted extensive research by scholars all over the world. However, research regarding its creep performance has been lacking, which in turn affects its further application. The creep of alkali-activated slag concrete is large, and fiber addition has been shown to improve this problem. Polypropylene (PP) fiber has good alkali resistance and is economical. This paper studies the effect of the stress–strength ratio and fiber length on the creep property of PP fiber-reinforced alkali-activated slag (FRAAS) concrete. At the stress–strength ratio of 0.15, PP fiber addition is able to greatly reduce the creep of concrete. When the stress–strength ratio increases, the shorter fiber loses the anchoring force and the holes caused by the longer fiber crack. This in turn leads to the deterioration of the inhibition effect on concrete creep. The CEB-FIP 2010 model is highly accurate, but the final value prediction is small. The early prediction value of the GL2000 model is rather large and conservative. The creep coefficient of the prediction model and the measured secant modulus of PP FRAAS concrete with different fiber lengths under different stress–strength ratios may solve the issue of creep prediction.