Papers by Author: M.A. Megat Johari

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Authors: A.M. Zeyad, M.A. Megat Johari, Norazura Muhamad Bunnori, K.S. Ariffin, Nurdeen M. Altwair
Abstract: Palm oil fuel ash obtained from palm oil mill was treated via screening, grinding and heating to improve its pozzolanic reactivity. The characteristics of the palm oil fuel ash before and after treatment were monitored to assess the changes in the properties of the palm oil fuel ash. The resulting ultrafine palm oil fuel ash was then utilized to produce high strength concrete by replacing the ordinary Portland cement at 0, 20, 40 and 60% on mass-for-mass basis. The results show that the treatment process undertaken reduces the particle size, diminishes the unburned carbon content, while at the same time increases the glassy phases. The utilization of the ultrafine palm oil fuel ash in high strength concrete was observed to improve workability especially at higher ultrafine palm oil fuel ash content. In addition, the long-term compressive strength of the high strength concrete was significantly increased with the ultrafine palm oil fuel ash inclusion. Further, the long-term rapid chloride permeability was significant reduced especially at higher ultrafine palm oil fuel ash content of 60%, which could be translated into superior durability performance.
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Authors: Ibrahim Mohamad H. Wan, B.H. Abu Bakar, M.A. Megat Johari, P.J. Ramadhansyah
Abstract: The aim of this study is to investigate the behaviour of the calcium silicate brick masonry wall exposed to sulphate condition. This paper presents some result about the effect of sodium sulphate attack on the elasticity of the calcium silicate brick masonry structures. All specimens were cured under polythene sheet for 14 days in environmental controlled room with temperature of 25± 2°C and 80 ± 5% relative humidity. After curing, the specimens were exposed to sodium sulphate solution before tested at 14, 28, 56 and 180 days respectively. As a result, the modulus of elasticity of the calcium silicate brick masonry wall reduces with the increase of sulphate concentration.
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Authors: Ibrahim Mohamad H. Wan, B.H. Abu Bakar, M.A. Megat Johari, P.J. Ramadhansyah
Abstract: This paper presents the behaviour of moisture movement of calcium silicate brick masonry walls exposed to sodium sulphate environment. The walls were exposed to three sodium sulphate conditions with sulphate concentrations of5%, 10% and 15%. For comparison, some walls were also exposed to dry and wet condition which acts as a control conditions. All specimens were prepared and cured under polythene sheet for 14 days in a controlled environmental room and maintained at relative humidity and temperature of 80 ± 5% and 25 ± 2°C, respectively. After the curing period, the specimens were exposed to sodium sulphate as well as drying and water exposures, during which moisture movement was measured and monitored for a period of up to 7 months. As a result, the moisture expansion was observed and recorded for all masonry wall specimens after exposed to the sulphate condition.
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Authors: Nurdeen M. Altwair, M.A. Megat Johari, Syed Fuad Saiyid Hashim, A.M. Zeyad
Abstract: Palm oil fuel ash (POFA) was used to produce engineered cementitious composite (ECC) in this research where ECC mixtures containing different volume of POFA (up to 55% by weight) of cement, were prepared. Mechanical properties of the resulting ECC mixtures were assessed using the compression, flexural and uniaxial tensile tests. The findings of the study show that the use of POFA improves the mechanical properties of the ECCs. The ECC mix with 1.2 POFA/cement ratio achieved a compressive strength of 30 MPa at 28 days, which is within the normal range of concrete strength for many applications. Moreover, the results portray that the use of POFA should be helpful for achieving strain-hardening behaviour. The increase in the POFA content concomitantly increased the flexural deflection and tensile strain capacities of the POFA-ECC. Furthermore, crack width of the ECC was significantly decreased with an increase of POFA content. In addition, the resulting POFA-ECC is expected to enhance the material greenness and durability.
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Authors: Nurdeen M. Altwair, M.A. Megat Johari, Syed Fuad Saiyid Hashim
Abstract: The present paper is a part of an extensive study on green palm oil fuel ash engineered cementitious composites conducted at Universiti Sains Malaysia. It specifically investigates the effects of waterbinder ratio (w/b) and palm oil fuel ash (POFA) on the drying shrinkage of engineered cementitious composites (ECCs). W/b values of 0.33, 0.36, and 0.38 were selected. ECC mixes were proportioned to have various ratios of POFA ranging from 0 to 1.2 from the mass of cement. The drying shrinkage measurements were taken at 4, 11, 18, 25, 57, and 90 days. The experimental results show that w/b has a significant effect on the drying shrinkage of the ECC mixtures. Drying shrinkage is remarkably reduced with a decrease in the w/b. The results also showed that drying shrinkage of the composites is considerably reduced when POFA is used in the matrix. The measured drying shrinkage strain at 90 days is only 920×10-6 µε to 1216×10-6 µε for ECC mixtures with high POFA content. The shrinkage strain of the ECC mixtures without POFA at 90 days is nearly 1597×10-6 µε to 1910×10-6 µε.
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Authors: Bassam A. Tayeh, B.H. Abu Bakar, M.A. Megat Johari, A.M. Zeyad
Abstract: The weak interfacial transition zone between new and old concrete is always paid much attention and controls many properties of repaired concrete, The present work reports a study on the influence of the silica fume on the adhesion of reactive powder concrete (RPC), as a concrete restoration material, with the ordinary concrete (OC) substrate. The results showed that, the silica fume presence in the interfacial transition zone significantly enhances the adhesion strength between RPC and OC substrate. Furthermore, the silica fume particles consume calcium hydroxide, which is in attendance in the interfacial transition zone, and make the zone more dense, uniform and tough.
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