Effect of Alkali Concentration on Strength Development in Jointly Activated Pond Ash-GGBFS Mixtures through Geopolymeric Reactions

Abstract

This paper presents research findings of the effect of mutual activation of pond ash and ground granulated blast furnace slag (GGBFS) in the development of unconfined compressive strength (UCS) with the addition of NaOH as an alkali activator at concentrations of 2, 4, 6, 8, and 10M. Compressive strength tests were carried out on alkali-activated samples of pond ash-GGBFS mixtures compacted at their respective optimum moisture content (OMC), maximum dry density (MDD) and were kept cured in polythene at ambient temperature. The strength of un-mixed pond ash activated with NaOH at molarity of 6 and above shows significant UCS when curing time increases up to 56 days. However, a great increase in strength of geopolymer mixtures was observed with increase in GGBFS content. The majority of samples of pond ash-GGBFS mixtures activated at 4M NaOH showed the highest strength in comparison to higher concentrations of 6, 8, and 10M NaOH with increasing GGBFS content and curing time. To confirm the occurrence of geopolymeric reactions during alkali interaction with pond ash-GGBFS mixtures, the samples were also characterized by the Fourier Transform Infrared Spectroscopy (FTIR), X-ray Powder Diffraction (XRD) and Scanning Electron Microscopy with Energy Dispersive X-Ray Analysis (SEM/EDX) data. In the present study the alkali activated pond ash-GGBFS mixtures have also been tried to evaluate their utilization as construction materials in civil engineering applications.