Effect of fibre dosage and stress-strength ratio on creep of polypropylene fibre-reinforced alkali-activated slag concrete

The use of alkali-activated slag (AAS), an eco-friendly cementitious material, to replace ordinary Portland cement in construction can reduce the energy consumption, CO₂ emissions, and solid dust pollution and promote the recycling of ground granulated blast furnace slag, which represents an industrial solid waste. However, the creep of AAS concrete is a critical long-term property that has rarely been investigated. Creep is related to the structural safety, including that of large pre-stressed concrete structures. AAS concrete exhibits a higher creep and lower elasticity modulus compared to OPC concrete, and the addition of fibres is an effective solution to this problem. In this study, the effects of fibre dosage and stress-strength ratio on the creep properties of polypropylene (PP) fibre-reinforced AAS (FRAAS) concrete were investigated. Thirty-two creep samples with four fibre dosages and four stress–strength ratios were subjected to tests for approximately 350 d. The PP FRAAS concrete did not exhibit any significant linear creep behaviour. With the increase of fibre dosage, the inhibition effect of fibres first became stronger and then became weaker. The inhibition effect of the fibres was gradually intensified with the increasing stress–strength ratio. As the fibre dosage increased from 0 to 0.9%, the creep coefficient gradually decreased. Based on the experimental results, a method of predicting the creep of PP FRAAS concrete was developed.