Papers by Keyword: Hardened Properties

Abstract: The issue of waste accumulation exists around the world, particularly in the densely populated regions. These waste materials not biodegradable in nature, so it is left as stocks or dumped illegally. The burning millions of tons of waste tires creates great risk. To prevent the hazardous effect of produced chemical gases (CO₂) through combustion processes, many research attempts to use huge amounts of rubber waste in concrete mixes. In this paper, properties that are both fresh and hardened of self-consolidating concrete with different sizes of waste tires rubber and micro steel fibers were investigated. The various sizes of waste tires rubber were utilized in place of coarse and fine aggregates, limestone (Al-Gubra) and silica fume after obtaining a rubber size close to the size of each material that has been replaced. Coarse and fine aggregates were replaced with chip and crumb rubbers (20% and 10% by weight). Al-Gubra and silica fume were replaced with ground and finely ground rubbers (50%, 25%, and 12% by weight). The experimental results showed that the fresh properties of self-consolidating concrete had been adversely affected by incorporating micro steel fibers and scrap tires rubber, but remained within the European Federation of National Trade Association Representing Concrete (EFNARC). The results of tests also showed that the mechanical properties decrease when used rubbers as aggregates. However, the results demonstrated that the compressive as well as splitting tensile strength of specimens increased by replacing lime stone dust and silica fume with rubbers. The increases were (12.2-28.0) % and (11.6-41.9) % for compressive strength and splitting tensile strength, respectively.

Abstract: This paper investigates both fresh and hardened properties of concrete produced with different particle sizes of coarse aggregate (CA). The CAs with the maximum sizes (D_max) of 25 mm, 19 mm, 15 mm, 12.5 mm, and 9.5 mm were used to produce concrete samples with a water-to-binder ratio of 0.4. The workability, fresh unit weight, compressive strength, and ultrasonic pulse velocity (UPV) of the concrete were tested. Additionally, some concrete samples were fully immersed in 5% sodium sulfate solution in order to assess the performance of the concrete under sulfate attack condition. The experimental results show that the workability of fresh concrete increased with increasing the particle size of CA used, while the particle size of CA insignificantly affected to the unit weight of fresh concrete mixtures. The concrete mixture produced with D_max of 12.5 mm obtained the highest compressive strength and UPV values in comparison with those of other mixtures. This study also found that the compressive strength values of concrete samples that fully immersed in sulfate solution reduced about 15% as compared with those of the concrete samples cured in lime-saturated water. All of the concrete samples prepared for this investigation exhibited good durability performance with ultrasonic pulse velocity values of above 4300 m/s. Test results also indicated that the concrete properties can be enhanced if the CA sizes were appropriately selected.

Abstract: The use of strain-hardening cement composite (SHCC), which exhibits metal-like deformation behavior and has ability to restrict crack opening, as a retrofit material for seismic retrofitting of existing infrastructures, has been the subject of high expectations. In this work, Three SHCC mixtures including different chemical or mineral admixtures were prepared and evaluated based on the mechanical properties, such as flow, sprayability, compressive and uniaxial tensile performances. All SHCC mixtures were reinforced with polyvinyl alcohol (PVA) fibers at volume fraction of 2.2%. Mechanical properties of each SHCC mixture were measured and evaluated after mixing, pumping, and shotcreting. Experimental results indicated that the compressive strength and elastic modulus of three SHCC mixtures increased almost linearly according to shotcreting procedure from mixer to nozzle. And the uniaxial tensile of SHCC mixture (SHCC-AE) with AE agent was superior to the other SHCC mixtures (SHCC-MC and-N).

Abstract: Palm oil fuel ash is considered as an agro-waste material in Malaysia. Various investigations have been conducted on the use of palm oil fuel ash as a supplementary cementing material for concrete. In the present study, palm oil fuel ash was used as a partial replacement of normal portland cement to produce high-strength self-consolidating concrete. In total, twenty (20) self-consolidating concrete mixes were prepared by varying water to binder ratio, palm oil fuel ash content, and high-range water reducer dosage. Palm oil fuel ash was used by replacing 0–30% of normal portland cement by weight at the water to binder ratios ranging from 0.25 to 0.40. The compressive, splitting tensile and flexural strengths, modulus of elasticity, ultrasonic pulse velocity, and porosity of various self-consolidating concrete mixes were investigated. However, the correlations between the hardened properties of concrete were emphasized in this study. The experimental findings revealed that strong correlations exist between different hardened properties of high-strength self-consolidating concrete.