Study on properties and pore structure characteristics of cement-based materials with limestone powder

In order to study the effect of limestone powder as an auxiliary cementing material replacing part of cement on the properties and pore structure of cement mortar, the working performance, mechanical properties and pore structure characteristics of cement mortar with 0%, 10%, 20% and 40% substitutions of limestone powder were tested. The experimental results show that with the increase of the amount of limestone powder, the fluidity of mortar increases continuously and the water retention also becomes better. The addition of limestone powder improves the workability of mortar, but with the increase of limestone powder, the compressive strength of mortar decreases continuously. The results of low field NMR show that the porosity of cement mortar increases firstly and then decreases with the increase of limestone powder content. Compared with the reference mortar, its porosity is improved to some extent, however the pore throat distribution indicates that the increase of porosity is caused by the increase of small pores between 0.01μm and 0.16μm. The harmful macropores between 0.16μm and 0.63μm in mortar are reduced, which indicate that the addition of limestone powder can effectively improve the pore diameter distribution of mortar.