Application of natural zeolite in concrete structures

Natural zeolite is a type of mineralogical material containing large quantities of reactive SiO2and Al2O3. It is widely used in the cement industry as a cement blending material. This paper presents several research results on carrier effect of zeolite, including both physical functions and chemical functions, such as compressive strength, degree of pozzolanic reaction, porosity of zeolite modified cement pastes, alkaliaggregate reaction, and microstructure, that can be used in the manufacturing of new concrete products. These results are compared with those obtained from similar blended cement pastes prepared with silica fume and fly ash replacements. Based on the experimental results, it can be concluded that natural zeolite is a pozzolanic material, with a reactivity between that of silica fume and fly ash. Generally, in blended cement pastes with a lower water-to-cementitious materials ratio, the natural zeolite contributes more to the strength of the pastes. But in the pastes with a higher water to cementitious ratio and a lower cement replacement level it undergoes a higher degree of reaction. The micro-structural study on concrete with zeolite revealed that the soluble SiO2 and Al2O3 could react with Ca(OH)2 to produce C-S-H which densified the concrete matrix. Pozzolanic effect of zeolite improved the microstructure of hardened cement paste and reduced the content of the harmful large pores, hence made concretemore impervious.