چكيده به لاتين
This research work presents a study is on the synthesis and characterization of acid-resistant geopolymer binder. In the first stage, based on preliminary experiments on the reactivity and suitability of different geopolymer precursors, taftan pozzolan, waste-glass powder (WGP), clay brick waste powder (CBWP) and fly ash (FA) were selected as geopolymer source materials. Some commercially available additives such as calcium alumina cements (Fundo, Secar 71 and Secar 80) and phosphorous slag were also incorporated into the dry binders in order to increase the reactivity of source materials. The selected blends were then activated by aqueous solution of NaOH and sodium silicate with different Na2O contents and SiO2/Na2O ratios and the effects of a number of major factors such as chemical composition of the source materials and the nature and concentration of alkali activators on the compressive strength of resultant geopolymer mortars were investigated. Besides, the optimized geopolymer mortars tested for workability, setting time, free-alkali content and tendency towards efflorescence formation. X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses were also performed to characterize the molecular- and micro- structures of the produced geopolymers. In the next stage, the optimized geopolymer specimens (WGP-, CBWP- and FA-based geopolymer mortars) were immersed in HCl and H2SO4 solutions of pH=1 and pH=3 for 6 and 24 months, respectively, to monitor changes in the physical and mechanical properties of the mortars. These experiments were repeated with Portland cement and high alumina cement mortars as control specimens. Microstructural and characterization tools were also employed to examine the compositional and microstructural changes of the geopolymers. The findings showed the superior performance of WGP- and FA-based geopolymer mortars against both acidic solutions compared to the control mortars, as indicated by the significant lower strength loss and lower mass change. Meanwhile, the CBWP-based geopolymer mortar was less susceptible to acid attack than the control mortars; however, superior enhancement in durability properties was not achieved in this case. The results, finally, demonstrate a new potential of value-added reuse application for WGP and FA (by adding suitable additives) in production of acid-resistant geopolymer binders.