Marine sponge spicules-inspired magnesium oxychloride cement with both enhanced water resistance and compressive strength via incorporating acid-activated palygorskite

The high energy consumption, large CO2 emission and mass pollutant release during the preparation process of Ordinary Portland cement (OPC) promote the development of sustainable magnesium oxychloride cement (MOC), which can increase the potash industrial waste utilization and alleviate ecological problems. However, MOC is limited by the poor water resistance, and integrating high water resistance with compressive strength for the MOC still remains a challenge. Herein, inspired by marine sponge spicules, acid-activated palygorskite (APal) was introduced into MOC to construct the inorganic fiber reinforced structure, thus both the water resistance (enhanced from 0.37 to 0.71 in water resistance coefficient) and compressive strength (37.1% increase) were improved. This improvement can be due to the physical filling, surface complexation, electrostatic adsorption interaction and fiber reinforcement of APal, as well as the transformation to gel-like phase 5. Especially, this strategy offers a new and effective approach to enhance the water resistance of MOC that although phase 5 content exhibit a reduction trend in soaked MOC-APal, the composite still present enhanced water resistance. This may be attributed to the sponge spicules-inspired fibrous structure serving as an effective supporting skeleton to provide a certain mechanical strength for soaked MOC-APal.