Influence of high-volume mineral mixtures and the steam-curing temperatures on the properties of precast concrete

摘要

The compressive strengths of concrete and hardened paste, the resistance to chloride ion of concrete, the pore structure of hardened paste are tested to investigate the influence of high volume mineral admixture on the la put ties of concrete and hardened paste under steam-curing condition. Three binders used are the pure cement, the binder containing high content of GGBS, and the binder containing high content of fly ash. Two steam-curing temperatures used are 60 degrees C and 80 degrees C. The results show that the addition of high volume GGBS tends to decrease the early strength of concrete slightly, but it refines the pore structure of hardened paste and improves the compressive strength and resistance to chloride ion penetration of concrete at late ages. The addition of high volume fly ash tends to decrease the early strength of concrete sharply, but its negative effect on the strength of concrete decreases obviously with the prolonging of age and it can refine the pore structure of hardened paste and improve the resistance to chloride ion penetration of concrete in some cases. Increasing the steam-curing temperature has negative effect on the pore structure of hardened pure cement paste and the resistance to chloride ion penetration of the pure cement concrete at late ages, but the addition of high volume GGBS or fly ash can eliminate this negative effect.