Improving the performance of coal gangue permeable concrete by using cellulose

Coal gangue pervious concrete (CGPC) is a building material that can address urban flooding and the heat island effect. It also provides a new approach for the treatment of coal gangue. However, the high fluidity of the slurry causes it to settle at the bottom of the CGPC, blocking a large number of pores and reducing the permeability coefficient, which limits its wide application. In this study, coal gangue was used as the aggregate, and hydroxypropyl methyl cellulose (HPMC) and ultrafine fly ash (UFA) were added to explore the synergistic regulation effect of the two on the performance of CGPC. The results showed that HPMC reduced the fluidity of the slurry and significantly increased the permeability coefficient, but led to a decrease in the compressive strength of CGPC. When the UFA replacement rate was 10%, the compressive strength of CGPC reached 21.7 MPa, the permeability coefficient was 3.1 mm/s, which was 70% higher than that of the control group, and the porosity was 22%. Microscopic analysis showed that HPMC slowed down the hydration rate of cement; the synergistic effect of HPMC and UFA improved the structure of the interfacial transition zone and reduced micropores.