## 5 Conclusions  
The capillary water absorption performance of cement-based materials is influenced by various factors. In the present study, the capillary water absorption coefficient of cement-based materials with different W/B and various preloads was measured using the weight method, and the pore structure of specimens was determined using MIP. The following conclusions were drawn by analyzing the relationship between the capillary water absorption coefficient and the different influencing factors. (1) With the increase in the W/B, the total porosity of cement-based materials increased, and the connectivity between the pores increased. The higher the W/B was, the more rapid was the acceleration of the rate of water uptake during the initial absorption period. (2) When the dosage of fly ash did not exceed the critical value, the capillary water absorption coefficient of all cement-based material samples decreased with increasing dosages of fly ash, which was beneficial and improved the impermeability of cement-based materials. However, when the dosage of fly ash exceeded the critical value, the capillary water absorption coefficient of cement-based materials increased rapidly with increasing dosages of fly ash. Figure 13: Relationship between the pore fractal dimension and the capillary water absorption coefficient. (3) With an increasing ground granulated blast furnace slag content, the capillary water absorption coefficient of the cement-based material decreased rapidly. Adding fly ash or ground granulated blast furnace slag effectively reduced the capillary water absorption coefficient of cement-based materials. Compared with the effect of fly ash, the ground granulated blast furnace slag exerted a more obvious effect on reducing the capillary water absorption coefficient. (4) The experimental results showed that with an increasing preload, the capillary water absorption of the cement-based material first decreased and then increased. When the preload was low, the internal pores of the cement-based material closed, resulting in a decrease in the capillary water absorption coefficient. When the preload exceeded the critical value, as the preload increased, new microcracks formed and expanded inside the cement-based material, and the capillary water absorption coefficient increased. (5) With increasing pore volumes in the pore size range of 10-50 nm, the capillary absorption coefficient showed an increasing trend; with the increase in the pore volume in the ranges of 50\(\sim\)100 nm and 100-1000 nm, the capillary absorption coefficient first increased and then decreased slightly. Therefore, the ability of cement-based materials to absorb water is correlated mainly with pores with diameters ranging from 10-1000 nm. With the increase of the pore fractal dimension, the capillary water absorption coefficient continued to increase. This study serves as an important step towards a more complete understanding of the capillary water absorption characteristics of concrete. Although the results of the present study are valid for the range of parameters we considered herein, further experiments should be conducted to confirm and expand the knowledge obtained from this study. Conceptualization, Y.W. and M.A. ; methodology, Y.W., M.A., Z.Y. and H.H. ; formal analysis, L.L. ; investigation, L.L., Y.S. and H.H. ; data curation, L.L., Y.S. and H.H. ; writing--original draft preparation, Y.W. and L.L. ; writing--review and editing, Y.W., M.A. and Z.Y. All authors have read and agreed to the published version of the manuscript. This research was funded by the Fundamental Research Funds for the Central Universities, grant number 2019 RC007; the National Natural Science Foundation of China, grant number 52108189; and the Beijing Natural Science Foundation, grant number 8192032. Not applicable. The data supporting the findings of the study are available within the article. Financial support from the Fundamental Research Funds for the Central Universities (Grant No. 2019 RC007), National Natural Science Foundation of China (Grant No.