Effect of curing regimes on chloride binding capacity of geopolymer

Abstract

Chloride attack on reinforced concrete is considered the most important aspect in concrete durability investigation. This study is carried out to investigate effect of curing condition on the chloride binding capacity of fly ash geopolymer pastes containing a range of cast in chloride contents (NaCL), varying from 1%, 2% and 4% by mass of binder. The applied curing regimes were normal, oven, steam and microwave. The impact of induced chlorides on the compressive strength and on the chloride binding capacity of fly ash geopolymers under different curing conditions is determined. A detailed microstructure and phase composition analysis were conducted through SEM and XRD tests. It was observed that applying thermal curing conditions could increase the chloride binding capacity to the formed geopolyric hydration product. High curing temperatures promote the precursor dissolution reactions and will increase the overall generation of polymerization reaction products, while under normal curing a lot of fly ash grains did not fully react. Therefore, thermal curing is important in the activation of geopolymerization process that increase aluminosilicate gel and result in dense and less porous geopolymer matrix and yields in high compressive strength. This results in the physical adsorption and chemical binding of chloride ions on the gel surface, and hence reducing the rate of chloride ingress. It was concluded that the ingress of chlorides can be particularly controlled better through binding the free chloride ions under steam and microwave curing in the fly ash geopolymer concrete.

Keywords

• Chlorid resistant
• Fly ash
• Microwave curing
• Binding capacity