Influence of recycled waste concrete powders on the performances of sulphoaluminate cement

The effect of recycled waste concrete powders (RWCPs) with different particle sizes on the properties of sulphoaluminate cement (SAC) was tested in order to extend the application avenues of RWCPs. RWCPs with particle sizes of 10μm, 40μm and 80μm were used to replace SAC in the proportion of 0 %, 1 %, 5 %, 10 % and 30 % by mass, respectively. The influence of RWCP on SAC hydration was investigated in terms of fluidity, setting time, compressive strength, hydration product, heat of hydration and microstructure. The experimental results showed that RWCPs had a detrimental effect on SAC fluidity and the effects increased with decreasing particle size. RWCPs with 10μm and 40μm up to 5 % dosing can shorten the setting time of SAC, while others have prolonged effects. RWCPs with 10μm and 40μm increased the compressive strength of the cement within the dosage range, while 80μm had a reinforcing effect only up to 10 % dosage. The heat of hydration and XRD tests showed that RWCPs with 10μm and 40μm promoted the hydration of SAC in the range of 10 % dosing, and the ettringite (AFt) generation was also promoted by SEM. The test results showed that RWCP can be used as a potential SCMs to achieve low carbon emissions of SAC, which not only reduces the cost of cement, but also achieves the life cycle utilization of solid waste. •We investigated the effect of RWCPs with different particle sizes and dosages on the properties of SAC.•We found that RWCPs with 10μm and 40μm improved the properties of SAC significantly.•The reason for this improvement is mainly. attributed to nucleation and filling effects.