Experimental Study on the Effect of Ultrafine Mineral Admixtures on the Mechanical Properties of Cement Mortar

Abstract

Objective: The effect of ultrafine mineral admixtures on the mechanical properties of grouting mortar was studied. Methods: In this paper, the compressive strength and flexural strength of the mortar with different contents of ultrafine mineral admixture replacing cement were tested respectively, and the heat of hydration was tested. XRD and SEM were used to analyze the changes in the microstructure characteristics after the addition of ultrafine mineral admixture. Results: after the addition of 5% ultrafine mineral admixture, the fluidity of cement slurry decreased by 25. 3%, and the fluidity gradually decreased with the gradual increase of ultrafine mineral admixture. With the addition of superfine mineral addition, The compressive strength increased steadily and gradually decreased thereafter, while the content of superfine mineral added was 20%, the strength of rubber sand reached the maximum value at 28 days, which increased by 23. 76% compared with the test block without admixture. The flexural strength of 3d and 7d of rubber sand was weakened by the incorporation of ultrafine mineral admixture, and the flexural strength of 28d increased slowly with the incorporation of ultrafine admixture, and the flexural strength value reached the maximum when the dosage was 25%. The heat of hydration and microstructure analysis showed that the sand system produced more hydrated calcium silicate gel filling into the structure of the sand after the addition of ultrafine mineral admixture. Conclusion: a certain amount of ultrafine mineral admixture has remarkable influence on the compression strength of rubber sand, and the flexural strength of 3d and 7d is weakened, and increases the flexural strength of 28d.