Optimization of calcium carbonate whisker reinforced cement paste for rheology and fracture properties using response surface methodology

摘要

Cement paste is generally used as a grouting joint material for concrete structures. A good rheology property guarantees the workability of fresh cement paste, and an excellent fracture toughness that reflects the good crack resistance of hardened cement paste. Calcium carbonate whisker (CW) is an inorganic mineral reinforcing material with excellent micromechanical performance, microcrack resistance and environmentally friendly nature. In this study, the rheological and three-point bending tests were conducted on CW reinforced cement paste (CWRCP) to evaluate workability and mechanical properties. The results showed that the yield stress (τ_0) and plastic viscosity (μ) were increased with addition of CW. This was because of the large specific surface area of CW which consumed free water and reduced lubricity between cement particles; and meanwhile, fibrous CW overlapped into net and prevented the flow of fresh cement paste. The addition of CW increased the fracture toughness (K_(IC)) of cement paste due to its microscopic crack resistance effect. Also, the environmental scanning electron microscopy (ESEM) analysis was performed to study the microstructural characteristics. The response surface methodology (RSM) was used to evaluate the influence of CW content (ν_(cw)) and water-cement ratio (w/c) to response parameters. Additionally, multiobjective optimization technique was performed to determine best settings for design variables which satisfied ideal response parameters. Conclusively, the optimal solution of CWRCP is beneficial to acquire ideal response goal and provides the basis for engineering applications.