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

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Experiment previously showed several findings that the strength of cold-formed steel cross-section are not the same, where web strength and flange strength do not give the same response when receiving the axial load. This occurs not only because of a shift in the center point of the force due to deformation of the cross section, but also due to different strengths in cross-section, especially on the web section and flange section. To find out more details of this case, the experiment carried out the tensile test for mechanics property and compression test with an axial load to find which parts are weaknesses, then used as a reference in combining the profile. The compression test results showed significant increase in compression capability between single profile with double profile back to back (Dbb) or double profile flange to flange (Dff) with ratio 1: 2.24 and 1: 2.44 respectively. There is a non-linear increase in the value of Aeff and Ieff when becomes combine profiles (double, quadruple, hexatruple), so this can be the basis for increasing the combine profile capacity to be able to withstand larger loads. This experiment can show a basic performance of CFS, where are weak section parts of a profile can be used as a reference to put combine profile to increase compression capacity. With a numerical analysis approach compared to the experimental results, the combination of Cold-formed steel profile is established as a column for the low-rise building structure.

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