Papers by Keyword: Flexural Strength

Abstract: PC is a type of concrete which is well known for its low strength and high infiltration rate. PC is made up of cement, coarse aggregate, water and with little or no fine, that is the reason PC is also known as no fine concrete. The fine content in PC tends to improve the strength of the concrete yet it adversely affects the infiltration of the PC. Therefore, in this study the pumice stone fine was incorporated in pervious concrete to make a PC with improve strength without sacrificing its infiltration. This experimental investigation helps to explain the effect of pumice stone when used as fine aggregate on the density, void content, compressive strength, flexure strength, and infiltration rate of PC. All PC mixtures were proportioned with a fixed water-to-cement ratio (w/c) of 0.30. The fresh and hardened voids of PC containing pumice fine were up to 9% greater than the PC without fine resulting in about 11% reduction in the hardened density of PC with fine. Moreover, the compressive strength of pervious concrete with incorporation of pumice fine shows a significant increase of about 30% compressive and 40% flexural strength. Moreover, the infiltration rate of PC made with pumice fine showed about 60% improvement. Therefore, pumice fine is a great option for incorporating in PC to improve its overall performance.

Abstract: In addressing the imperative need for sustainable and cost-effective solutions in pavement development, this study investigates the effect of incorporating high-volume coal thermal by-products (i.e., fly ash [FA] and bottom ash [BA]) on the engineering properties of sustainable concrete pavement. In detail, FA was used to substitute 50% by mass of ordinary Portland cement, while BA was used to replace 50% and 100% (by volume) of natural fine aggregate in the concrete mixtures. The performance of concrete was evaluated through a test series of slump, fresh unit weight, compressive and flexural strengths, dry density, and surface abrasion. Further, based on the experimental results, the potential applications of concrete in real practice were suggested. As a result, the incorporation of FA and BA improved the workability and reduced the unit weight of fresh concrete mixtures. Both the dry density and surface abrasion of concrete were also reduced with the inclusion of high-volume FA and BA. This study found that concrete incorporating 50% FA and 50% BA exhibited the highest strength and acceptable surface abrasion level, satisfying the Vietnamese standard requirements for use in the sustainable construction of level-4 pavement.

Abstract: Nowadays the construction of palm oil industry mills is advancing rapidly and the next one is Refined Palm Oil (RPO). Refined Palm Oil (RPO) is one of the derivatives of palm oil processing. One option to use structures in the construction of palm oil mills is to use concrete. Plant parts that have concrete components often suffer damage, cracks and reduced concrete strength.This study is intended to examine the mechanical properties of concrete including compressive strength, flexural strength and porosity in concrete in the RPO environment, examining changes in the weight of coarse and fine aggregates immersed in RPO. This study used concrete experiments in RPO baths with 3 combinations, 54 samples and 2 types of concrete plan life, then analyzed in the laboratory. The parameters measured are changes in aggregate weight, porosity, bending strength and compressive strength of concrete. The results showed that the higher the percentage of RPO immersed in concrete, the lower the compressive strength, bending strength and porosity of the concrete. Fine aggregate undergoes weight change when immersed in RPO for 28 and 56 days, while coarse aggregate undergoes no weight change

Abstract: This study presents an experimental investigation of the load-bearing behavior and drainage ability of pervious concrete (PC) produced using local materials in Vietnam with differently designed porosities of 15% (R15), 20% (R20), and 25% (R25). The PC samples were cast at the laboratory and cured in open air before being tested for drainage ability, flexural and compressive strengths, and dry density. The relationship between load and displacement of the PC was also analyzed in this study. Results showed that the designed porosity significantly affected the mechanical strength, density, and infiltration rate of the PC. In detail, the compressive strength of PC ranged from 1 to 5 MPa while the flexural strength values were 0.86, 0.99, and 1.71 MPa for samples designed at the respective porosities of 25%, 20%, and 15%. In addition, the dry density of PC specimens (1560-1688 kg/m³) decreased with an increase in the designed porosity. The infiltration rate values were measured at 19.4, 38.3, and 1215 cm/min corresponding to the R15, R20, and R25 specimens. Besides, the load-displacement curves under flexure and compression revealed a significant impact of void contents on the strength-bearing capacity of PC as the R15 specimen exhibited the highest slope, indicating the higher brittle behavior and lower deformation. Overall, the experimental results further demonstrated the high applicability of the PC for various construction applications in real practice.

Abstract: The utilization of Fiber Reinforced Concrete (FRC) as a structural material is steadily on the rise. Conventional concrete is characterized by its brittleness, displaying a flexural strength that falls within the range of 10-15% of its compressive strength. Incorporation of fibers into concrete enhances various mechanical properties, including tensile strength, flexural strength, and ductility. An advantageous feature of FRC is its capacity to consider cracked concrete below the neutral axis in the cross-section of a beam to some extent. Important factors influencing the flexural strengths of both Plain Concrete (PC) and FRC include the modulus of rupture, corresponding deflection, toughness index, energy absorption, and density. This results in a diminished requirement for additional reinforcement in beams. The modified stress-strain diagram proposed by Bashara proves valuable in integrating the effect of FRC on the tension side, an aspect previously neglected due to the inherent weakness of PC in tension. The ongoing literature review seeks to comprehensively explore the potential of fiber-reinforced concrete in beams situated below the neutral axis, concentrating on articles published in highly reputable journals over the past decade.

Abstract: Wind energy has been making its way into renewable energies until today, experiencing a continuous growth worlwide that leads to the urgent task of reflecting on and solving the issue of the recycling of the wind turbine blades. Their complex composition causes that currently there is no a widely acepted solution for it. This study evaluates the incorporation of waste from the crushing of wind turbine blades, which contains fibers, into self-compacting concrete, which can be used for producing any construction element. Therefore, five concrete mixes were made with different percentages of this waste, including a reference mix without this waste. The addition of waste increased the content of fibers in the concrete, which in turn implied an increase in the water/cement ratio. This situation led to a worsening of the mechanical performance of concrete as the waste amount increased, although it was partially compensated by the stitching effect of the fibers. The concrete mix with 1.5% in volume of this waste exhibited flexural and compressive strengths very similar to those of the reference concrete. This shows that incorporating the waste from the crushing of wind turbine blades can allow to produce structural self-compacting concrete.

Abstract: Machine tool housing design is pivotal in optimizing manufacturing processes, focusing on functionality, ease of assembly, and alignment precision. Current materials face challenges in static, dynamic, and thermal behaviors, impacting machining quality. The properties of ultra high-performance concrete (UHPC) such as high strength, low porosity, and corrosion resistance make it ideal for machine tool applications, promising increased precision and efficiency while reducing material costs and labor. Its recyclability adds environmental benefits. Incorporating UHPC in machine tool structures, including hybrid materials like Carbon Fiber Reinforced Plastic (CFRP), achieves superior static, dynamic, and thermal stability. Experimental results demonstrate UHPC’s compressive strengths (17,000-22,000 psi), surpassing conventional materials, and its ability to enhance machine tool performance and sustainability. This research highlights UHPC as a transformative material for resilient, precise, and eco-friendly manufacturing solutions.

Abstract: The purpose of this study is to investigate the influence of the cement/sand (c/s) ratio on the behavior of cement mortar. The used c/s ratios in this study were 1:0, 1:0.45, and 1:0.83. The findings of this study showed that increasing the sand content reduces the compressive strength of the mortar mixture by 41.5 and 28.2% for the c/s ratios of 1:0.45, and 1:0.83, compared to the plain cement mortar (c/s: 1:0). The increase in sand content requires more water content to increase the workability and strength of the mixtures. However, the flexural strength slightly increased compared to the control mortar. In addition, to enhance sustainability, the cement was replaced with two waste industrial materials namely, micro silica (MS) and fume treatment plant (FTP) dust by 20% of cement weight. The modified mixtures (c/s: 1:0) also showed reduced strength at the testing age. The compressive strength of the modified mixtures was reduced by 50% and 19% for the FTP and MS-modified mixtures, respectively. On the other hand, the flexural strength was reduced by 19.1 and 30.2% for the FTP and MS-modified mixtures. This reduction can help achieve certain strength requirements by lowering the cement content in cement concrete mixtures.

Abstract: The effect of zinc stannate and synergy between zinc stannate with ammonium polyphosphate in polypropylene matrix is studied. The zinc stannate nanoparticles were synthesized by surfactant assisted low temperature precipitation method, and further surface modified with tetraethyl-orthosilicate at room temperature. Zinc stannate (ZS) and ammonium polyphosphate (APP) were incorporated in polypropylene matrix (1, 5 and 10 % by wt.). PP nanocomposites were analysed for flexural strength, tensile strength, linear burning rate, smoke density and LOI test. Morphology of nano particles and composites were analysed by FESEM. Mechanical analysis of PP nanocomposites demonstrates that, the modified ZS-TEOS performed better than unmodified ZS. Smoke density profiles suggest that the APP could slightly generate more smoke in PP with ZS and ZS-TEOS. Linear burning rate test results indicates that the APP with ZS and ZS-TEOS provide stability to PP for resisting flame spread.

Abstract: The need of removing the mechanical damage and the stress introduced during the thinning step of device process flow is challenging for manufacturing of high quality SiC-based devices. In this respect we have identified two different back finishing approaches, based on material removal and material rearrangement. The first one includes dry polishing (DP) and chemical mechanical polishing (CMP); the second one includes bulk and laser annealing. Systematical investigation on wafer warpage, sample morphology and die mechanical reliability have been conducted and comparison between the two approaches has been done. The CMP and DP processes can remove the damage produced by back grinding, recovering wafer warpage and resulting in a smoother surface. Bulk thermal annealing has provided better roughness levels and has been successful in stress relief, although the wafer permanence at high temperature is not compliant with the device process flow. Under laser annealing process, the surface features keep almost unchanged as well as warpage level. Despite being not effective in stress relief, from a mechanical point of view, the laser annealing process, does not impact die reliability, representing a suitable back finishing process especially in the optic of its use in backside ohmic contact formation.