粉煤灰和抛光渣抑制碱硅酸反应及其机理研究

采用砂浆棒快速法,分别以0%、20%、30%、40%的粉煤灰和抛光渣等质量取代水泥制备砂浆试件,进行膨胀率及强度测试,借助扫描电镜(SEM)、能谱分析(EDS)和X射线衍射(XRD)等方法对碱环境下集料与胶凝材料界面过渡区的微观结构、元素组成和生成物进行分析,研究粉煤灰和抛光渣抑制碱硅酸反应(ASR)的内在机理.结果表明:粉煤灰和抛光渣均可有效抑制ASR,综合考虑粉煤灰、抛光渣对ASR的抑制作用和对材料强度的影响,粉煤灰、抛光渣取代率宜取20%～30%;掺粉煤灰和抛光渣均可使界面过渡区结构更致密;界面过渡区钙硅比和钠硅比明显降低;钾硅比和铝硅比在界面过渡区有突变,K和Al在界面过渡区富集,原因为K~+比Na~+更倾向于与Al_2O_3结合.尽管抛光渣碱含量较高,但其中高含量的SiO_2、Al_2O_3及活性集料中的SiO_2可与体系中的Na~+、K~+共同作用,在界面过渡区生成体积稳定的架状结构硅酸盐矿物钾霞石KAlSiO_4和霞石(K,Na)AlSiO_4,从而抑制ASR.

Mechanism of Fly Ash and Ceramic Polishing Powder on Inhibition Alkali Silica Reaction

The mortar specimens were prepared by replacing 0%, 20%, 30%, and 40% of cement with the same amount of fly ash and ceramic polishing powder. The expansion ratio and strength were measured. The microstructure, element composition, and products of interfacial transition zone between aggregate and cementitious material were analyzed by scanning electron microscope(SEM), energy disperse spectroscopy(EDS) and X ray diffraction(XRD). The intrinsic mechanism of alkali silica reaction(ASR) inhibition by fly ash and ceramic polishing powder was studied. The results show that ASR can be effectively inhibited by introduction of fly ash or ceramic polishing powder in mortar bars. Considering the effects of fly ash or ceramic polishing powder on ASR inhibition and the strength, it is recommended that replacement ratio of fly ash or ceramic polishing powder should be 20%30%. The structure of the interfacial transition zone becomes denser. Calcium silicon ratio and sodium silicon ratio significantly decrease in the interfacial transition zone of the material. Because K+ is more likely to bind to Al2O3 than Na+. K and Al are enriched in the interfacial transition zone, which makes potassium silicon ratio and aluminium silicon ratio mutate at the region in the interfacial transition zone. Although the ceramic polishing powder has a higher alkali content, the reaction of the SiO2, Al2O3 in the ceramic polishing powder and the reactive aggregates with Na+ and K+ in the system generates kalsilite(KAlSiO4) and nepheline((K, Na) AlSiO4) in the interfacial transition zone, which are volume stabilized tectosilicate minerals, thus ASR can be inhibited.