Combining thermodynamic modeling and experiments to characterize the effect of ceramic polishing powder in cement-based materials

Abstract

Ceramic polishing powder (CPP), a by-product of ceramic tile production, has the potential to prepare building materials. While the hydration and thermodynamic properties of CPP remain largely unexplored, thereby limiting its widespread application. This study utilized R3 tests to demonstrate that CPP exhibits pozzolanic activity comparable to that of fly ash. Then it analyzed the effects of substituting 10–20 % of cement with CPP on the hydration products, microstructure, and mechanical properties of composite materials, utilizing a synergistic approach that combines thermodynamic simulations with experimental investigations. The findings showed that adding CPP does not generate new crystalline products but enhances the formation of C-S-H through the pozzolanic reaction, which consumes calcium hydroxide. However, adding over 25 % CPP significantly lowered the pH of the pore solution, altering hydration products and causing volume contraction. In addition, CPP improved the microstructure at later ages, particularly by increasing micropores, leading to enhanced mechanical properties at 28 and 90 days. For instance, at a w/b ratio of 0.5, the 90 days compressive strengths of composite mortars CPP10, CPP15, and CPP20 were recorded at 67.0 MPa, 63.3 MPa, and 65.1 MPa, respectively. These values represented increases of 17.3 %, 10.9 %, and 14.0 % over the control group (57.1 MPa). Conversely, this also resulted in increased autogenous shrinkage due to higher capillary pressure. Notably, the 6 days shrinkage of CPP15 and CPP20 was about 50 % higher compared to that of the pure cement mortar. These findings highlight the necessity of balancing CPP content for optimal performance.