Effects of steam curing on the pore structure of recycled aggregate concrete

Abstract

The pores in steam-cured concrete affect its strength and durability, and optimisation of the steaming system can improve the pore structure to some extent. However, the influence mechanism of evaporation on recycled aggregate concrete (RAC) remains unclear. In this paper, the effects of curing temperature (20°C, 40°C, 60°C and 80°C), steam curing time (6 h, 9 h and 12 h) and pozzolans (slag powder and fly ash) on the compressive strength and pore structure of RAC were studied. The microstructure characteristics such as pore size and pore size distribution were analysed by mercury injection porosimetry. The results show that steam curing can significantly improve the compressive strength and reduce the most probable aperture and average pore sizes of RAC. Moreover, the effect of slag powder on RAC pore structure is better than that of fly ash. Also, there is a linear correlation between the compressive strength and the average pore size of steam-cured RAC. This could be an important parameter for constructing future steam-cured RAC strength prediction models.