Ba(OH)2-activated hemihydrate phosphogypsum-based slag concrete: Influence of water-binder ratio on compressive strength, water resistance and microstructure

The quaternary cementitious system exhibited better performances and optimizing water-binder ratio was a low energy consumption approach to improve the properties of cementitious materials. This study presented an innovative quaternary cementitious system of Ba(OH)₂-activatied hemihydrate phosphogypsum-based slag concrete(HPG-SC) to achieve the modification mode of Ba alkali on HPG-SC “primary modification” + “secondary activation”. The experiments were conducted on HPG-SCs to reveal the effects of water-binder ratio on compressive strength, water resistance and microstructure of HPG-SC. The experimental results showed that compressive strength and water resistance increased firstly and then decreased as the water-binder ratio increased from 0.27 to 0.39. The 28-day compressive strength and air-dried softening coefficient of W-0.33 were 34.8 MPa and 0.85, respectively. The effect mechanisms of water-binder ratio were explained from the micro-morphologies, pore diameter and porosity. The water-binder ratio adjusted the hydration rate of cementitious system to increase the compactness and compressive strength. Moreover, the lowest first peak diameter was observed and the lower porosity was 43.32 % in W-0.33 specimen. Therefore, HPG-SC showed better compressive strength and water resistance at the suitable water-binder ratio, and was beneficial for the application in construction engineering.