Mohd Faidz Mohd Zain

Concrete using waste oil palm shells as aggregate

Abstract Concrete with oil palm shells (OPS) as coarse aggregate was investigated for its workability, density, and compressive strength development over 56 days under three curing conditions. The effect of fly ash as partial cement replacement was also studied. Fresh OPS concrete was found to have better workability while its 28-day air-dry density was 19–20% lower than ordinary concrete. Compressive strength after 56 days was found to be 41–50% lower than ordinary concrete. These results were still within the normal range for structural lightweight concrete. Fly ash was found to lower the compressive strength of OPS concrete, which was the opposite of its effect on normal concrete.

Prediction of splitting tensile strength of high-performance concrete

Splitting tensile strength (STS) is one of the concrete mechanical properties that are used in structural design. It can be related to numerous parameters, which include compressive strength, water/binder (W/B) ratio and concrete age. Until now, most researchers estimated the STS directly from compressive strength data. This paper suggests formulae that relate STS with that of compressive strength, W/B ratio and concrete age. The predicted STS can be obtained accurately using these formulae. It is proposed that the equation with the concrete age (t) parameter be used in predicting the STS of high-performance concrete (HPC).

A study on the properties of freshly mixed high performance concrete

The physical properties of freshly mixed high performance concrete were investigated. Physical state and quality of fresh concrete were monitored batch by batch. The properties of fresh high performance concrete were determined in respect of slump, slump flow, V-funnel flow, air content, temperature, and unit weight. It was observed that the properties are interrelated, particularly the flow and the air content. The indication of flowability was more pronounced in terms of V-funnel flow than slump flow. This result suggests that the traditional slump test is not efficient to evaluate the workability and flowability of high performance concrete.

Effects of mineral and chemical admixtures on high-strength concrete in seawater

Abstract The effects of mineral and chemical admixtures namely fly ash, ground granulated blast furnace slag, silica fume and superplasticizers on the porosity, pore size distribution and compressive strength development of high-strength concrete in seawater curing condition exposed to tidal zone were investigated. In this study, three levels of cement replacement (0%, 30% and 70% by weight) were used. The total cementitious content used was 420 kg/m 3 . A water/binder ratio of 0.4 was used to produce concrete having a target compressive strength ranging between 54 and 63 MPa at the age of 28 days. At the age of 364 days, the compressive strength of the specimens produced ranged between 59 and 74 MPa. The pore size distribution of both high-strength concrete (MSS-0 and MSS-40) was significantly finer and the mean volume pore radii (MVPR) at the age of 6 months were reduced about three times compared to NPC concrete. Results of this study indicate that both concrete mixes (30% and 70%) exhibited better performance than the NPC concrete in seawater exposed to tidal zone. Hence, it is believed that both high-strength concrete produced would withstand severe seawater exposure without serious deterioration.

Development of high performance concrete using silica fume at relatively high water-binder ratios

Abstract The aim of this study was to investigate the possibility of developing high performance concrete (HPC) using silica fume (SF) at relatively high water–binder ratios. For this purpose, water–binder ratios of 0.45 and 0.50 were considered. Test specimens were air and water cured and exposed to a medium temperature range of 20°C to 50°C. The compressive strength, modulus of elasticity and initial surface absorption (ISA) of hardened concrete were determined in the laboratory. Test results indicated that concrete under water curing offers the best results. The highest level of compressive strength and modulus of elasticity and the lowest level of ISA were produced by SF concrete under water curing and at temperature of 35°C. Data collected also revealed that, under controlled curing conditions, it is possible to produce HPC at relatively high water–binder ratios.

Effect of curing conditions on the properties of OPS-concrete

Abstract The effect of six types of curing conditions on pulse velocity and compressive strength of OPS-concrete (oil palm shell as coarse aggregate) and control concrete has been studied. The development in the pulse velocity and the compressive strength of OPS-concrete is more in full water curing followed by partial plastic, full plastic and partial water curing. Compressive strengths of OPS-concrete, ranges 20– 24.25 N / mm 2 for 28-day, were satisfactory for structural lightweight concrete. In this study, it appears that strength development is impeded due to early drying and due to the presence of organic OPS aggregate.

Physical properties of high-performance concrete with admixtures exposed to a medium temperature range 20 °C to 50 °C

This paper discusses two physical properties, namely, compressive strength and modulus of elasticity of high-performance concrete made with four types of concrete mixes exposed to temperatures within the range 20°C to 50°C under three types of curing methods. The results showed that the compressive strength of concrete incorporating mineral admixtures practically reached above 100 MPa from the age of 7 days. The highest levels of strength and modulus of elasticity were produced by silica fume (SF) concrete under water and wrapped curing at temperature of 35°C. This indicates that the high pozzolanic reactivity and microfiller effect of SF at medium temperature has modified the open channels at the transition zone in SF concrete. The medium temperature environment associated with proper curing has played an important role in the hydration process that produced the hardened concrete with higher strength and elasticity.

The influence of medium temperature environments on the water permeability of high performance mortar

In this study, the durability of normal portland cement mortar and silica fume mortar are characterized by measuring the water permeability under four different types of curing temperatures. It is observed that the water permeability of normal portland cement mortar increases as temperature increases up to 75°C. However, the water permeability of silica fume mortar decreases as the temperature increases. This indicates that the high pozzolanic reaction and microfiller effect of silica fume at medium temperature has modified the open channels at the transition zone of silica fume mortar, making it much denser and stronger and leading to a fine and discontinuous pore structure.