• Composites Research
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• v.17 no.3
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• pp.8-14
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• 2004

The effect of moisture absorption on the mechanical properties in carbon fiber reinforced composites has been investigated with various moisture environment such as sea water, tap water and distilled water. It also has been studied about the influence of drying of the immersed specimen for a certain period of time on the mechanical properties. As a result, we found that the ratio of moisture absorption mainly depended on the immersion time in the moisture environment and that of the immersed specimen for a certain period of time decreased with the drying time. We also found that tensile strength decreased with the increasing of the ratio of moisture absorption and the tensile strength decreased by moisture absorption recovered up to some extent by drying the specimen.

• Advances in materials Research
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• v.6 no.4
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• pp.329-341
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• 2017

The challenge of replacing conventional plastics with biodegradable composite materials has attracted much attention in product design, particularly in the tensile-related areas of application. In this study, fibres extracted from oil palm empty fruit bunch (EFB) were treated and utilized in reinforcing polyester matrix by hand lay-up technique. The effect of fibre loading and combined influence of alkali and silane treatments on porosity and water absorption parameters, and its correlation with the tensile behaviour of composites was analyzed. The results showed that tensile strength decreased whilst modulus of elasticity, water absorption and porosity parameters increased with increasing fibre loading. The composites of treated oil palm EFB fibre exhibited improved values of 2.47 MPa to 3.78 MPa for tensile strength; 1.75 MPa to 2.04 MPa for modulus of elasticity; 3.43% to 1.68% for porosity and 3.51% to 3.12% for water absorption at respective 10 wt.% fibre loadings. A correlation between porosity and water absorption with tensile behavior of composites of oil palm EFB fibre and positive effect of fibre treatment was established, which clearly demonstrate a connection between processing and physical properties with tensile behavior of fibre composites. Accordingly, a further exploitation of economic significance of oil palm EFB fibres composites in areas of low-to-medium tensile strength application is inferred.

• Structural Engineering and Mechanics
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• v.51 no.3
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• pp.403-412
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• 2014

In this paper, enhancement of corrosion and chloride resistance of high performance self compacting concrete (SCC) through incorporating nanosilica into the binder has been investigated. For this purpose, different mixtures were designed with different amounts of silica fume and nano silica admixtures. Different binder contents were also investigated to observe the binder content effect on the concrete properties. Corrosion behavior was evaluated by chloride penetration and resitivity tests. Water absorption and capillary absorption were also measured as other durability-related properties. The results showed that water absorption, capillary absorption and Cl ion percentage decreased rather significantly in the mixtures containing admixtures especially blend of silica fume and nano silica. By addition of the admixtures, resistivity of the SCC mixtures increased which can lead to reduction of corrosion probability.

• International Journal of Concrete Structures and Materials
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• v.10 no.2
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• pp.249-256
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• 2016

This paper deals with the effects of silica fume content and polymer-binder ratio on the properties of ultrarapid-hardening polymer-modified mortar using silica fume and ethylene-vinyl acetate redispersible polymer powder instead of styrene-butadiene rubber latex to shorten the hardening time. The ultrarapid-hardening polymer-modified mortar was prepared with various silica fume contents and polymer-binder ratios, and tested flexural strength, compressive strength, water absorption, carbonation depth and chloride ion penetration depth. As results, the flexural, compressive and adhesion strengths of the ultrarapid-hardening polymer-modified mortar tended to increase as increasing polymer-binder ratio, and reached the maximums at 4 % of silica fume content. The water absorption, carbonation and chloride ion penetration resistance were improved according to silica fume content and polymer-binder ratio.

• Elastomers and Composites
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• v.54 no.3
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• pp.201-208
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• 2019

Superabsorbent hydrogel (SAH) is a lightly crosslinked hydrophilic functional polymer material comprising a flexible chain structure, which can absorb and retain high amounts of water or aqueous fluids even under high pressure. Therefore, it is important to improve their characteristics such as absorption performance, residual monomer content, and water permeability. SAH nanocomposites were prepared using clay mineral as an inorganic filler and the influence of post-treatment processes such as quenching and aging process on their properties was studied. In addition, surface-crosslinking process was applied to improve the absorption performance associated with mechanical properties and water permeability. The structure of the SAH was characterized using attenuated total reflectance Fourier transform infrared spectroscopy, X-ray diffraction analysis, and scanning electron microscopy.

• Journal of the Korean Wood Science and Technology
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• v.47 no.5
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• pp.567-578
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• 2019

A common problem with fast-growing hardwoods is dimensional instability that limits use of their wood. In this study, we investigated the effects of pre-drying methods, temperatures, and heating duration on the specific gravity, water absorption, and dimensional stability of three tropical fast-growing hardwoods, jabon (Neolamarckia cadamba Roxb.), sengon (Falcataria moluccana Miq.), and mangium (Acacia mangium Willd.). Wood samples were pre-dried by two methods (fan and oven at $40^{\circ}C$), and heat treatments were performed at three temperatures (120, 150, and $180^{\circ}C$) for two different time periods (2 and 6 hours). The specific gravity, water absorption, dimensional stability, and structural changes of the samples were evaluated. The results revealed that heat treatments slightly reduced the specific gravity of all three wood species. In addition, the heat treatments reduced water absorption and significantly improved dimensional stability of the samples. Oven pre-drying followed by heat treatment at $180^{\circ}C$ for 6 hours resulted in good physical improvement of jabon and sengon wood. Fan pre-drying followed by heat treatment at $180^{\circ}C$ for 2 hours improved the physical properties of mangium wood. The heat treatment shows a promising technique for improving the physical characteristic of fast growing hardwoods.

• Journal of the Korean Wood Science and Technology
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• v.47 no.4
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• pp.472-485
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• 2019

When wood plastic composites (WPCs) have been used for a certain period of time, they become waste materials and should be recycled to reduce their environmental impact. Waste WPCs can be transformed into reinforced composites, in which fillers are used to improve their performance. In this study, recycled WPCs were prepared using different proportions of waste WPCs, nanoclay, and glass fiber. The effects of nanoclay and glass fiber on the microstructural, mechanical, thermal, and water absorption properties of the recycled WPCs were investigated. X-ray diffraction showed that the nanoclay intercalates in the WPCs. Additionally, scanning electron micrographs revealed that the glass fiber is adequately dispersed. According to the analysis of mechanical properties, the simultaneous incorporation of nanoclay and glass fiber improved both tensile and flexural strengths. However, as the amount of fillers increases, their dispersion becomes limited and the tensile and flexural modulus were not further improved. The synergistic effect of nanoclay and glass fiber in recycled WPCs enhanced the thermal stability and crystallinity ($X_c$). Also, the presence of nanoclay improved the water absorption properties. The results suggested that recycled WPCs reinforced with nanoclay and glass fiber improved the deteriorated performance, showing the potential of recycled waste WPCs.

• Advances in concrete construction
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• v.14 no.3
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• pp.215-225
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• 2022

Thermal comfort and energy conservation are critical issues in the building sector. Energy consumption in the building sector should be reduced whilst enhancing the thermal comfort of occupants. Concrete is the most widely used construction material in buildings. Its thermal conductivity (k-value) has a direct effect on thermal comfort perception. This study aims to find the optimum value of replacing the normal aggregate with lightweight expanded clay aggregate (LECA) under high strengths and low thermal conductivity, density and water absorption. The k-value of the LECA concrete and its physical and mechanical properties have varying correlations. Results indicate that the oven-dry density, compressive strength, splitting tensile strength and k-value of concrete decrease when normal coarse aggregates are replaced with LECA. However, water absorption (initial and final) increases. Thermal conductivity and the physical and mechanical properties have a strong correlation. The statistical optimisation of the experimental data shows that the 39% replacement of normal coarse aggregate by LECA is the optimum value for maximising the compressive and splitting tensile strengths whilst maintaining the k-value, density and water absorption at a minimum.

• Computers and Concrete
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• v.21 no.3
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• pp.345-353
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• 2018

This paper approaches to improve the mechanical and durability properties of low calcium fly ash geopolymer concrete with the addition of Alccofine as a mineral admixture. The mechanical and durability performance of GPC was assessed by means of compressive strength, flexural strength, permeability, water absorption and permeable voids tests. The correlation between compressive strength and flexural strength, depth of water penetration and percentage permeable voids are also reported. Test results show that addition of Alccofine significantly improves the mechanical as well as permeation properties of low calcium fly ash geopolymer concrete. Very good correlations were noted between the depth of water penetration and compressive strength, percentage permeable voids and compressive strength as well as between compressive strength and flexural strength.

• Advances in concrete construction
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• v.7 no.2
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• pp.107-115
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• 2019

The possibility of using a combination of mineral admixtures as a replacement for cement may reduce the $CO_2$ emission which causes global warming and climatic changes on the environment. By using the combination of different byproducts from various industries, for replacing cement in concrete leads to saving in energy and natural resources. In this article, an attempt has been made to study the mechanical and water absorption properties of concrete incorporated with combination of Fly ash (FA), Alccofine (ALC) and Collodial Nano Silica (CNS) at 7, 28 and 56 days curing period. Cement has been partially replaced by combination of FA at 25%, ALC at 10% and CNS at 0.5%, 1%, 2% and 3% with water cement ratio of 0.43. The result indicates that the incorporation of combination of FA, ALC and CNS can be very effective in improvement of mechanical and water absorption properties of concrete. The Mix with a combination of 25% FA, 10% ALC and 1% CNS is most effective in improvement of mechanical and water absorption properties as compared with all other mixes.