Effect of Eggshell Powder on Sulfate Resistance of Metakaolin Cement-based Materials

Purposes This work has been carried out to determine the optimal composite mix ratio of eggshell powder and metakaolin as cement replacement materials for simultaneously enhancing the compressive strength of cement mortar and the sulfate resistance of cement paste. Methods Eggshell powder and metakaolin were used to replace cement to make specimens, and the strength of cement mortar and sulfate resistance of cement paste were tested separatehy. Findings The strength test results show that 20% metakaolin content increases the cement strength most significantly, and the cement strength decreases significantly when the metakolin content increases to 30%. When the 20% metakaolin content is fixed and 5% eggshell powder is added, the cement mortar still maintains the strength close to that of cement mortar with 20% metakaolin. When the content of eggshell powder increases to 10%, the cement strength decreases obviously. The sulfate resistance test results show that the additions of 10% and 20% metakaolin lead to the volume expansion and fragmentation of cement-based materials in sulfate environment. After adding eggshell powder, this phenomenon is alleviated. The specimens with eggshell powder and pure cement show the same sulfate resistance. Conclusions When the eggshell powder and metakaolin are compounded in an appropriate proportion, the strength of cement-based matenals can be improved and their sulfate resistance can be maintained at the same time.