Influence of sodium sulfate on hydration and microstructure of cement high volume fly ash system under steam curing

摘要

The influence of sodium sulfate (SS) addition on hydration and microstructure development of the cement high volume fly ash (CHVFA) system under steam curing is investigated in this paper.The compressive strength of CHVFA mortars was tested with different SS dosages. Results show that the addition of SS increases the strength obviously when its content is less than 2 %, and that further increase in SS content is not conducive to the development of the positive effect of SS is analyzed by X-ray diffraction (XRD), differential scanning calorimety-thermogravimetry (DSC-TG), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and nuclear magnetic resonance (NMR). The results reveal that SS incorporation accelerates the hydration of cement and fly ash, decreases the porosity and the content of calcium hydroxide (CH) and increases the polymerization degree of C-S-H, thus enhancing the compressive strength of mortars.