MECHANICAL PROPERTIES OF MODIFIED SUPERSULFATED CEMENT MORTAR

Supersulfated cement (SSC) is a green and environmentally friendly material that contains limited or no clinkers, with lowhydration heat release and favorable sulfate corrosion resistance. However, SSC requires modification because its poor mechanical property has restricted its promotion and application to a certain extent. Mix proportion design and mechanical properties of Bayer red mud and water glass-modified SSC were explored in this study, and the results were discussed by microanalysis. Results showed that the increase of red mud content prolongs the setting time of SSC, thereby indicating that early-stage mechanical properties (within 3 days), especially ultraearly-stage mechanical properties (within hours), need further improvement. However, mechanical properties of SSC mortar at different stages improve after three days, and further improve with the simultaneous addition of water glass and red mud. The optimal mix proportion of SSC obtained using Taguchi method is presented as follows: slag (70 wt. %), gypsum (15 wt. %), OPC (5 wt. %), red mud (10 wt. %), and water glass with a modulus of 1.8 (2.0 wt. %). Meanwhile, the compressive strength of specimen at this mix proportion reaches 42.12 MPa at 28 d. Mechanical properties improve because system alkalinity is further enhanced, additional gel products are generated, and the hardened body presents a tight binding state due to the simultaneous addition of red mud and water glass.