Ubagaram Johnson Alengaram

Properties of high-workability concrete with recycled concrete aggregate

This study presents the effects of recycled concrete aggregate (RCA) on the key fresh and hardened properties of concrete. RCA was used to produce high-workability concrete substituting 0-100% natural coarse aggregate (NCA) by weight. The slump and slump flow of fresh concretes were determined to ensure high workability. In addition, the compressive, flexural and splitting tensile strengths, modulus of elasticity, and permeable voids of hardened concretes were determined. The test results revealed that RCA significantly decreased the workability of concrete. RCA also affected the compressive strength, modulus of elasticity, and permeable voids of concrete. At the age of 28 days, the concrete with 100% RCA provided 12.2% lower compressive strength and 17.7% lesser modulus of elasticity than the control concrete. Also, 100% RCA increased the permeable voids of 28-day old concrete by 8.2%. However, no significant negative impact of RCA was observed on the flexural and splitting tensile strengths of concrete.

Near Surface Mounted Composites for Flexural Strengthening of Reinforced Concrete Beams

Existing structural components require strengthening after a certain period of time due to increases in service loads, errors in design, mechanical damage, and the need to extend the service period. Externally-bonded reinforcement (EBR) and near-surface mounted (NSM) reinforcement are two preferred strengthening approach. This paper presents a NSM technique incorporating NSM composites, namely steel and carbon fiber-reinforced polymer (CFRP) bars, as reinforcement. Experimental and analytical studies carried out to explore the performance of reinforced concrete (RC) members strengthened with the NSM composites. Analytical models were developed in predicting the maximum crack spacing and width, concrete cover separation failure loads, and deflection. A four-point bending test was applied on beams strengthened with different types and ratios of NSM reinforcement. The failure characteristics, yield, and ultimate capacities, deflection, strain, and cracking behavior of the beams were evaluated based on the experimental output. The test results indicate an increase in the cracking load of 69% and an increase in the ultimate load of 92% compared with the control beam. The predicted result from the analytical model shows good agreement with the experimental result, which ensures the competent implementation of the present NSM-steel and CFRP technique.

Flexural Behaviour of Concrete Beams Bonded with Wire Mesh-Epoxy Composite

This paper investigates the flexural performance of plain concrete beams bonded with wire mesh-epoxy composite. A total of four beam specimens were prepared and tested. Three specimens were bonded with same amount of wire mesh-epoxy composite with varying composite width and one plain concrete specimen was used as a control. The effect of wire mesh-epoxy composite on enhancing the flexural behaviour of concrete beams as well as the effect of different configurations of composite was studied. Test results showedthat the wire mesh-epoxy composite increased the flexural strength of concrete beams. The increase in energy absorption of bonded beams was remarkable. In addition, specimen with large composite width showed better behaviour with respect to energy absorption capability.

The Effect of Palm Oil Fuel Ash as a Cementreplacement Material on Self-Compacting Concrete

In this study ground palm oil fuel ash (POFA) has been used as cement replacement in percentages of 0%, 10%, and 20% in a self-compacting concrete (SCC). Fresh properties such as slump flow, T50, V-funnel, J-ring, L-box and segregation index; concrete properties such as drying shrinkage strain, initial surface absorption test (ISAT) as well as compressive strength were investigated. Test results showed that substitution of cement with POFA up to 20%, the fresh properties of the concrete fulfilled the requirements of a self-compacting concrete. The results revealed that concrete has higher compressive strength, lower drying shrinkage, and lower initial surface absorption than control mix. The results indicated that POFA can be used up to 20% as a cement replacement material for producing self-compacting concrete.