Research on the Performance of Titanium Gypsum Concrete Based on Calcium-Silicon-Sulfur Ratio

Based on the high sulfur content in titanium gypsum, the concept of the calcium-silicon-sulfur (Ca/Si/S) ratio was proposed. The Ca/Si/S ratio of concrete was adjusted by changing the titanium gypsum, fly ash, and cement content. The effects of different Ca/Si/S ratios on the mechanical properties, hydration products, and concrete microstructure were investigated by nuclear magnetic resonance, uniaxial compression, and scanning electron microscopy. The result shows: (1) The compressive strength of concrete mixed with titanium gypsum increases first and then decreases with the Ca/Si/S ratio decrease. When the Ca/Si/S ratio is 1:0.85:0.10, the strength reaches the peak and is lower than the blank group. (2) The microstructure indicates the addition of titanium gypsum can effectively stimulate the activity of fly ash. Still, too much or too little titanium gypsum will hamper concrete strength development. (3) Titanium gypsum concrete's nuclear magnetic resonance T2 spectrum has two characteristic peaks. With the Ca/Si/S ratio decreasing, the micropores in the concrete expand towards the macropores. The compressive strength is negatively correlated with the proportion of macropores and is positively correlated with the proportion of no-capillary pores.