Alteration of the Pore Structure of Cement Pastes under Extreme Pressures

Understanding the behavior of cementitious material under extreme loading is vital for the dynamic design of structures. In such conditions, deformations are confined, and compression is accompanied by pore closure of pores rather than cracking. This study analyzed pore structure changes in response to high oedometric compression of cement pastes. The effects of water-to-cement (w/c) ratio, saturation, and coating were investigated using mercury intrusion porosimetry (MIP). Compression decreased the porosity of all samples, but less so for saturated than unsaturated samples. Pore sizes of unsaturated samples were also reduced by compression, resulting in a narrow pore size distribution. Conversely, the compression of saturated samples resulted in a wider pore size distribution with a shift to larger pores due to the migration of water from smaller to larger pores under pressure. The effect of coating observed only at the highest w/c ratio may be associated with the decrease in permeability with the decrease in w/c ratio. Results were verified using residual volumetric strain values, demonstrating a good correlation with MIP measurements.