Improvement of mechanical properties of concrete canvas by anhydrite-modified calcium sulfoaluminate cement

A carefully designed formulation of dry cement powder for concrete canvas, which is expected to have both high mechanical strengths and short setting times, is obtained by partially replacing calcium sulfoaluminate cement (CSA) with anhydrite at four levels (0%, 10%, 20% and 30% by mass of CSA cement). The influence of anhydrite fineness on the mechanical properties of concrete canvas and its mechanical anisotropy are both investigated. X-ray diffraction analysis and isothermal calorimetry are used to investigate the underlying mechanism. Results reveal that increasing anhydrite content or fineness improve the mechanical strengths of concrete canvas and shortened its setting times. However, a slight decrease of mechanical strength occurs at the later age when the replacement level was 30 wt%. A large amount of unhydrated particles is found in hardened specimens. The concrete canvas shows higher mechanical strengths in the warp direction than in the weft direction, and it exhibits the lowest compressive strength in the through-the-thickness direction.