In this study, diatomite was used in cement mortar to improve the frost resistance durability. Experimental results showed that using diatomite instead of a small amount of silica fume (such as the samples in D-33.3%) can effectively enhance the frost resistance of cement mortar. To comprehensively understand the modification mechanism of diatomite, pore structure of cement mortar considering the effect of freeze-thaw cycles was studied by means of mercury intrusion porosimetry (MIP) and nitrogen adsorption-desorption measurement (NAM). Moreover, cumulative pore volume distribution (CPVD) results had the respective suitable measurement range using MIP and NAM due to the difference of calculation methods. Thus, to obtain more accurate results, the modified CPVD was proposed by the combination of MIP and NAM results. Furthermore, several characteristic pore volumes (including gel pores, transition pores, capillary pores and large pores) were determined according to the mentioned modified CPVD. Finally, multifractal analysis was carried out to explore the pore structure evolution mechanism, where the heterogeneity and connectivity of pore structure inside cement mortar containing diatomite subjected to freeze-thaw cycles were investigated based on the results of modified CPVD.

在这项研究中，硅藻土被用于水泥砂浆中，以提高其抗冻耐久性。实验结果表明，使用硅藻土代替少量硅粉（如D-33.3％的样品）可以有效提高水泥砂浆的抗冻性。为了全面了解硅藻土的改性机理，通过压汞法（MIP）和氮吸附-脱附测量（NAM）研究了考虑冻融循环影响的水泥砂浆孔隙结构。此外，由于计算方法的差异，使用MIP和NAM的累积孔体积分布（CPVD）结果具有各自合适的测量范围。因此，为了获得更准确的结果，结合了MIP和NAM结果提出了改进的CPVD。此外，根据所提及的改进的CPVD确定了几个特征孔体积（包括凝胶孔，过渡孔，毛细管孔和大孔）。最后，进行了多重分形分析，探讨了孔隙结构演化的机理，根据改性CPVD的结果，研究了含硅藻土的水泥砂浆冻融循环后孔隙结构的异质性和连通性。