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The ability to improve the tendency of hardened concrete in compression at elevated temperature was studied. Five mixes of fly ash were cast with a replacement amount of 0%, 10%, 20%, 30%, and 40% by cement mass. They were exposed to 400°C and held for 2 hours after water curing. The specimens have been cooled down to room temperature and then undergo a compressive test. This research aims to study the physical and mechanical properties of fly ash concrete after being exposed to elevated temperatures. A digital microscope was used to analyse the formation mechanism of microstructure in concrete. Fly ash was used to produce high fire resistance concrete with 100 mm x 100 mm x 100 mm concrete cube. Sample 4 with 30% fly ash has the highest compressive strength with 26 MPa after 28 days and 21 MPa after exposed to 400°C. The results show that concrete containing a high amount of fly ash has several improvements when exposed to elevated temperature. The concrete specimens were used to validate an interfacial transition zone (ITZ) in concrete. The microstructure features were discussed concerning their influence on the strength development of concrete.

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In this work, Mg and Zn powder were used to prepare the Mg-Zn/β-TCP composites with different β-TCP composition by using powder metallurgy technique. The composite were mixed using ball mill and compacted at 500 MPa. The composites sintered at 450 °C in tube furnace for two hours. The effects of properties on Mg-Zn with different composition of β-TCP were studied. The results on the effect of β-TCP composition were analyzed in terms of density and microstructural analysis.

Rice husk (RH) is an agricultural waste transformed to produce secondary by-products and is widely accepted as a substitution of cement or concrete mixtures. This paper deals with the optimal level of SiO2 content due to various incineration conditions of rice husk grown in Perlis, Malaysia. RH was burnt in a controlled environment with a targeted temperature of 650, 750 and 850 °C at various incineration period between 1 and 6 h. All the ashes were assessed for visual inspection and physiochemical and mineralogical properties using X-ray fluorescence (XRF) and X-ray diffraction (XRD). From the analysis, a significant amount of SiO2 in the range of 89–93 wt % was successfully obtained with the preferable properties of supplementary cementitious materials: amorphous silica with high reactivity, ultrafine size, and large surface area. Contrary, the burning temperature of 850 °C greater than 4 h incineration period is not advisable to be used as it transformed into a crystalline phase. No obvious color changes were observed for the ashes as the amount oxide compound of K2O causes carbon entrapped in surface melting. To sum up, 650 °C incineration for 1 h shows an optimum result, and the RH is bearable to reduce the negative impact on the environment.

Cement industry is a major carbon dioxide emission contributor, which could be reduced by implementing supplementary cementitious materials. Rice husk ash (RHA) exhibits high pozzolanic characteristics when properly produced using controlled incineration. In this study, rice husk (RH) collected from rice milling industry in Perlis, Malaysia was burned at 650 °C for 1 hour. The completed burning process produced dark-grey 78 μm sized amorphous ash particles containing almost 89% silica content. To understand the compressive strength in early age mortar, varying composition of RHA between 5 to 20% was purposely replaced with OPC. It was found that replacing RHA at 5% produced the highest strength followed by RHA replacement up to 15% in relation to the conventional OPC mortar. However, adding up to 20 % results in a steep decrease in the compressive strength due to the densification and space ratio factors in the mortar. In addition, the environmental performance of 20% RHA mixture were unsatisfactory as it is associated with the control mixture. In conclusion, mortar containing 5% RHA replacement shows acceptable properties similar to conventional cement mortar. Further analysis needs to be carried out to understand the hydration mechanism that affected their performance.

Abstract.One of the key performances of repaired reinforced concrete is its ability to withstand corrosion due to harmful ions and should be compatible with substrate and repaired concrete structures. This research investigates the prediction of corrosion risk on repaired RC by comparing performance between PMM and conventional OPC as chosen materials for repairing RC structures under influenced of chloride ions. The effect of chloride ions on repaired RC will be analyzed according to microstructural analysis, half-cell potential and chloride content by weight of cement. For analysis, substrate concrete containing 9 kg/m 3 chloride ions with W/C ratio 60% acts as the reference specimen. Meanwhile, for comparison purpose; two conditions of repaired RC namely OPC with W/C ratio 40% (R-0.4OPC) and PMM (R-PMM) that contain chloride free ions using similar casting and curing techniques were prepared respectively. Based on the results obtained, porosity and microstructural images using BSE were alternated under influenced of chloride ions since it correlated with surface charge of CSH due to Ca/Si amount in each specimen. The correlation between free and total chloride ions in concrete reveals the phenomena of co-matrix in R-PMM specimen since least chloride ions found in repaired section compared to R-0.4OPC specimen. The most striking result is R-PMM specimen able to resist chloride ions ingress in its repaired section but for HCP results obtained the R-PMM specimen beyond its threshold of passivity even though its porosity value is the lowest. To sum up, penetration of chloride ions throughout the specimens according to the wet chemical analysis giving effects to the porosity and microstructure. The R-PMM specimen was good in resistance of chloride ions to the repaired part but it was not the final predictions on its ability to withstand corrosion resistance.

Fly Ash (FA) is one of the waste materials generated from the combustion of solid waste through incinerator and contains hazardous substances. Further treatment to the ash needs to be done to avoid further environmental destruction. As an alternative solution for this problem, FA is used as a replacement material for cement in the mortar. The main objective of this study is to explore the potential use of FA as partial replacement of cement in mortar. The percentage of FA used to replace the cement in this study is 0%, 5%, 10%, 15% and 20%. Several important tests were conducted to identify main properties of the mortar such as compressive strength, water absorption, density and ultra-pulse velocity. Mortar containing 15% of fly ash has the highest of compression strength which is 35 MPa after 28 days. Besides, the mortar containing 5% of fly ash has the highest result of water absorption test and density test whereas mortar containing 20% of fly ash has the highest value for pulse velocity after 28 days. Thus, mortar containing fly ash has good physical and mechanical properties.