Chloride resistance of blended ash geopolymer concrete (chloride resistance & microstructural analysis)

Abstract

- Chloride attack on concrete is a mechanism of deterioration which causes corrosion of steel reinforcement. Geopolymer, an alternative aluminosilicate binder material, has attracted attention for its structural and durability performance as well as for environmental benefits in reducing the CO2 emissions associated with concrete production. However, the understanding of its behaviour in the chloride resistance of geopolymer concrete especially from mixtures of pulverized fuel ash (PFA) and palm oil fuel ash (POFA) is scarce. In this study, geopolymer concrete using blended ashes from agro-industrial waste were tested for chloride content using ASTM 1543-10a (Standard Test Method for Determining the Penetration of Chloride Ion into Concrete). The geopolymer concrete samples were prepared using a mix of the PFA and POFA as the main binder components at the range of alkaline/binder ratio of 0.4 together mixed with coarse and fine aggregates. The ambient temperature (26-30°C) of curing regimes was used. The specimens were cast in 100mm3 molds. After achieving the targeted compressive strength (25-30 MPa), the specimens were immersed for 18 months to 2.5% solution of sodium chloride (NaCl). The normal OPC concrete with similar compressive strength were also prepared for direct comparison. X-ray diffraction (XRD), Fourier Transformed Infrared Spectrometer (FTIR), Thermogravimetry analyser (TGA-DTG) and Field Emission Scanning electron microscopy images with energy dispersive X-ray (FESEM-EDX) were performed to analyze the microstructural characterisation of the materials. In particular, geopolymer concrete had shown a better resistance to chloride penetration as compared to OPC concrete.