The Influence Of CaO Content On Durability Of Geopolymer Concrete

Slag-based geopolymer cement is a new green cement which is synthesized mainly from natural aluminum silicate mineral materials or industrial solid waste, actived by alkaline solution,has a property like ceramic, whose molecular structure is made up of [SiO4] and [AlO4] tetrahedron, showing three-dimension network structure.Geopolymer was produced by utilizing metakaolin, slay and fly ash as the main raw materials. In this work, the main research is the influence of CaO content and n(SiO2)/n(Al2O3) on mechanical properties and durability of geopolymer. The research of alkali-aggregate reaction of geopolymer is using rapid mortar bar method, electric throughput method is used in the research of chloride ion reaction, and the characteristic of geopolymer is analyzed by SEM.The research shows that the influence of CaO content on mechanical properties is not significant when the geopolymer polymer is formed at early stage, as the increasing of CaO content, the growth of comperssive strength of geopolymer paste is slow. To28d age, the influence of CaO content on mechanical properties is prominent, the28d compressive strength is decrease at first before development. When CaO content of the raw materials is20%, the compressive strength is max.41.10Mpa, CaO content is15%corresponding strength minimum,26.5Mpa. With the increasing of n(SiO2)/n(Al2O3). the3d,7d compressive strength is decrease, and the28d compressive strength is increasing.With the increasing of CaO content, the linear expansion rate of geopolymer is sustained growth. The inhibiting AAR reaction effect is the best, when the fly ash content is58.18%, the linear expansion rate is0.005%. The linear expansion is decrease at first before development at the growth of n(SiO2)/n(Al2O3), and the peak is depended the CaO content.The performance of resistance to chloride ion is development at the growth of CaO content. When CaO content of the raw materials is20%, the electric throughput of14d geopolymer is minimum,3402C. With the increasing of n(SiO2)/n(Al2O3), the performance of resistance to chloride ion is decrease at first before development. CaO content is the mainly reason to decide the peak.SEM analysis shows high CaO content when inorganic minerals polymer structure is more compact. With the growth of age, the surface structure gradually completed. The structure is formed by ionic and covalent bond, the compressive strength increases, and the resistant to chloride ion penetration ability is enhancement.