摘要: The influences of different replacement levels of rice husk ash (RHA) blended cement concrete subjected to 5% Na2SO4 solution via wetting-drying cycles was evaluated in this study. RHA was used as a Portland cement Type I replacement at the levels of 0%, 10%, 20, 30%, and 40% by weight of binder. The water-to-binder ratio was 0.49 to produce concrete having target strength of 40 MPa at 28 days. The performance of RHA blended cement concrete on compressive strength, reduction in strength and loss of weight was monitored for up to 6 months. The results of the compressive strength test have been shown that use of RHA in blended cement has a significant influence on sulfate concentration. When increasing the replacement level of RHA, the strength of concrete also increases in comparison to OPC concrete (except RHA40) even exposed to 5% Na2SO4 solution. On the other hand, the reduction in strength and weight loss of specimens increased with increase in the exposure time. Generally, it can be said that the incorporation of rice husk ash as cement replacement significantly improved the resistance to sulfate penetration of concrete. Finally, RHA cement replacement in concrete mixed provided better resistance to sodium sulfate attack up to 6-month exposure.
摘要: With the increasing building activities in both developed and developing countries, the utilization of supplementary cementing materials will continue to increase in the years to come because of their technical, economical and ecological advantages. One of such pozzolanic materials is palm oil fuel ash (POFA) which has been identified to be a good cement substitute in mortar and concrete mixes. This paper highlights some laboratory test results on the deformation characteristics of concrete containing high volume palm oil fuel ash. Concrete specimens containing 50% POFA were made and tested for compressive strength, modulus of elasticity, shrinkage and creep. The results were compared with that of control specimen i.e. concrete made with 100% ordinary Portland cement (OPC). It has been observed that POFA concrete had lower compressive strength compared to OPC concrete. Along with lower strength development, the modulus of elasticity of concrete containing 50% ash was found to be lower. Although a relatively higher creep strain was been recorded in POFA concrete, there has been no significant difference of drying shrinkage in concrete with or without palm oil fuel ash.
摘要: This paper presents the detection of impact damage in a natural fibre reinforced composite plate under low velocity impact damage. Lead Zirconate Titanate (PZT) sensors were placed at ten different positions on each plate in order to record the response signals. The response signals captured from each sensor were collected for impacts performed by a data acquisition system. The impacted plates were examined with optical microscope to examine the damaged areas. It was found that the damaged size grew proportionally with impact force. The results also revealed that PZT sensors can be used to detect the damage extent with the waveform of sensor signals implying the damage initiation and propagation which detected above the damage force of 150N.
摘要: The purpose of this research is to enhance the toughness of richly-filled wood plastic composites (WPC) by using ultrafine acrylonitrile butadiene rubber (NBR) particles. The WPC was prepared by using poly (vinyl chloride) (PVC) matrix filled with Iron wood (Xylia xylocarpa) flour at 40 phr (WPC40) and 60 phr (WPC60). To enhance the impact strength, various contents of the ultrafine NBR were incorporated as an impact modifier from 1-11 phr. Experimental results indicated that the NBR toughened-WPCs were tougher than that of the unmodified ones, by increasing the tensile elongation at break. The impact strength of the WPCs modified with only 5 phr of NBR was notably enhanced around 26 and 7% for WPC40 and WPC60 respectively. Rheological results revealed that the ultrafine NBR functioned not only as an impact modifier but also as a processing aid with shorter processing time and lower melt torque.
摘要: Open cell foams, made on the basis of polyurethane foams replication method are well known and had been widely used since decades. The advantage of the network-like metal foams is it exhibits a natural bone-like structure which enables ingrowth of bone cells and blood vessels. The aim of the present study is to develop SS316L foam with an open cell structure by using powder metallurgy routes via foam replication method. The SS316L slurry was produced by mixing SS316L powder with Polyethylene Glycol (PEG), Methylcellulose (CMC) and distilled water. The composition of the SS316L powder in the slurry was varied from 40 to 60 wt. %. Then, polymeric foam template was impregnated in SS316L slurry and dried at room temperature. Sintering was carried out in a high temperature vacuum furnace at 1300°C. The microstructure of the SS316L foam produced was observed by Scanning Electron Microscope (SEM) and the elemental analysis was carried by Energy Dispersive X-ray (EDX). It was found that pore size are within 200-400μm and the average pore size is 293μ. The detected elements in the SS316L foam were C, Al, Ca, O, Cr, Fe, Mo, Ni and Si.
摘要: This paper focuses on the pore structure parameters of mortars produced with manufactured sand and natural sand via water saturation and MIP methods. Test results show that, total porosity, as well as compressive strength, of manufactured sand mortar, is higher than that of natural sand mortar at fixed w/c and s/c ratio. Furthermore, considerable volume of large pores present in specimens of manufactured sand at higher w/c ratio rather not at the lower w/c ratio, which caused by the larger binder-aggregate interface. Manufactured fine aggregate in mortar probably accelerate hydrated reaction of cement, which result in the most probable pore size is finer than that of natural sand mortar. It can be concluded that the threshold region becomes flatten and threshold radius increases due to the aggregate volume concentration rises. Finally, a new theoretical model with a double-lognormal distribution function is demonstrated to be reasonable to fit pore size distribution in mortars.
摘要: Controlled permeability formwork liner (CPFL) is the functional material similar to nonwoven fabrics and its filtration and drainage performance is dominated by the pore size distribution (PSD) of matrix. In this paper, suction table method, generally used to measure soil pore diameter, is improved for testing PSD of CPFL and experimental data was compared to the results from four other normal experimental methods, i.e., wet sieving method, bubble point method, mercury intrusion porosimetry (MIP) method and image analysis. The comparison indicates that PSD of CPFL obtained from suction table show good accuracy and repeatability. Furthermore, a modified mathematical model derived from Rawal model and Fature model is proved to be suitable for determinating PSD of the matrix of CPFLwith bilayer structure, and have a good agreement with the experimental data from suction table.
摘要: The nanoscale materials have a large surface area for a given volume. The larger particle size has some disadvantages such as it can increase the sensitivity to defects. Thus, in this study, the titanium dioxide was synthesized using new method of sol gel assisted with the milling process to investigate its structural and surface morphology. FESEM results show the agglomeration of the particles produces the large particle size of TiO2. In the milling process, longer milling time of 6 h does not affects much on the size of the particles of TiO2, but more affects on its surface morphology of TiO2. The effect on the milling amount of TiO2 also were studied where 4 gram TiO2 shows the highest agglomeration of the sample and 6 gram TiO2 shows the smooth surface compared to others. Finally, the best structure of TiO2 was added into the PMMA to investigate the effects of TiO2 on the composite surface morphology.
摘要: In this paper, empirical models are proposed using multiple non linear regressions technique to predict the influence on the Youngs modulus and the tensile strength of the natural fiber reinforced plastic composites (NFRPC). Maleic Anhydride grafted polypropylene (MAPP) has been a proven coupling agent (CA) used to improve the interfacial bonding between the fibers and the plastics material. It is important to include the factor of coupling agent, when making predictions the properties of the composites through the models. For the development of the model, data was collected from various research journals presented in literature. Non linear regression analysis was performed to obtain the empirical model using polymath scientific software. The results were found to be within the acceptable range.