Pore characteristics of different phase in nano-modified concrete and their influences on the compressive strength

To comprehensively understand the influence of nanoparticles on pore characteristics of concrete; vacuum saturation, mercury intrusion porosimetry and scanning electron microscopy were used to analyze the pore characteristics of concrete block, mortar phase and ITZ phase, respectively. The results indicated that with the best dosages nano-SiO (2) and nano-TiO (2) can reduce the porosity of concrete block by 15.6% and 3.5%, the porosity of cement mortar by 34.7% and 16.6%, and the porosity of ITZ by 92.0% and 65.6%, respectively. Besides, nanoparticles can also decrease the most probable pore aperture and the critical aperture in mortar phase, and can decrease the pore number in ITZ phase. After that, influences of these porosities on compressive strength have been analyzed by grey theory. Test results of compressive strength indicated that by reducing the porosities nano-SiO (2) and nano-TiO (2) can most improve the compressive strength by 15.79% and 9.22%, respectively. Correlation degrees between the porosities and the growth rate of compressive strength indicated that improving the structure of ITZ was the most effective mean to enhance the compressive strength by nanoparticles. Correlation degrees between the porosities and the compressive strength indicated that the porosity of mortar phase was a good choice to estimate the compressive strength. The studies were meaningful and helpful for investigating the properties of concrete by nanoparticles.