引气剂对延缓高海拔强碱环境下碱-硅酸反应的影响

Effect of Air-entraining Agent on Mitigating Alkali-Silica Reactions under High-Altitude Alkaline Environment

青藏高原盐渍土地区的碱金属离子含量很高,属于强碱环境,碱活性骨料分布广,极易引起混凝土发生碱-硅酸反应(ASR)。为确定引气剂延缓ASR的机理,设计了掺入矿物掺合料(SCM)的混凝土配比,并加入引气剂,研究了腐蚀溶液中的混凝土试件,包括1.5 a的强度发展和1 a的碱金属离子扩散浓度,并研究了砂浆棒试件210 d的膨胀率发展和龄期长达6 a的微观形貌。结果表明:相较于未使用引气剂的试件,掺量为0.05%的引气剂未引起混凝土试件(含气量5.4%)的强度损失,且有效降低了砂浆棒试件的膨胀率。此外,引气气孔成为了ASR产物的储仓,若混凝土碱量不变,则可控制碱活性骨料周边的ASR作用程度,延缓ASR胀裂的速率,有效改善SCM对ASR的抑制作用。

The saline soil areas of Qinghai-Tibet Plateau,China,are in a strong alkali environment due to the high contents of alkali metal ions,which can easily cause the alkali-silica reaction(ASR)in concrete.To investigate the mechanism of the air-entraining agent in mitigating the ASR,a mix of concrete blended with supplementary cementitious materials(SCM)in the presence of air-entraining agent was designed.The strength development during 1.5 a and the diffusion concentration of alkali metal ions at 1 a of the concrete specimens in corrosive solution were analyzed.The expansion development of the mortar-bar specimens for 210 d and their microscopic morphology at 6 a were investigated.The results show that the air-entraining agent at 0.05%dosage does not cause the strength loss of concrete specimens(when gas content is 5.4%)and effectively reduce the expansions of mortar-bars specimens.In addition,the air-entraining pores become a reservoir of ASR products,controlling the extent of ASR around the alkali-active aggregates as the alkali of concrete is constant,delaying the cracking rate duo to ASR,and then improving the inhibitory effect of SCM on ASR.