Development of drying shrinkage model for alkali-activated slag concrete

The current study aims to develop a drying shrinkage model for alkali-activated slag concrete (AASC). Three water-to-binder (W/B) ratios (0.44, 0.47 and 0.50), two fly ash contents (0 and 25%) and three silica fume contents (0, 5% and 15%) were studied. Slump, compressive strength and the drying shrinkage test lasting for over 300 d were performed. The results showed that: (1) Increasing both the W/B ratio and fly ash content increased the slump of the concrete, while a 5%-10% silica fume had little effect; (2) The compressive strength of the concrete was decreased with increasing both the W/B ratio and fly ash content, while it was improved with the addition of 5% silica fume; (3) Inclusions of fly ash and silica fume contributed to the reduction of the final drying shrinkage; (4) The current prediction models for drying shrinkage behavior of Portland cement-based concrete was not suitable for AASCs. Based on the results, a novel drying shrinkage prediction model with higher reliability for sodium silicate-activated slag-based concrete cured at the standard environment (20 +/- 2 degrees C and RH of 60 +/- 5 %) was developed, which is mainly derived from the model of ACI 209. The well-fitted results of this developed model fully indicated the relatively wide applicability of this model. However, given the complexity of the binder composition of AASC, this model still needs to be further upgraded in future.