97 publications from this institution
This paper provides the result of experimental and statistical modeling study on modulus of elasticity of Ultra High Performance Asphalt Concrete Pavement consisting different level of silica fume, superplastisizer, steel fiber, cement, and water binder ratio. Number of experiments designed by using design of experiment (DOE) in two levels, results modeled by using analysis of variance (ANOVA), and monitored using response surface methodology. This study clearly revealed the effect of each variable and their interactions on modulus of elasticity of Ultra High Performance Asphalt Concrete Pavement. This study is valid for the mixes of UHPC with 0.18–0.32 water binder ratio, 0.04–0.08 steel fibre, 0.7–1.3 cement, 0.15–0.30 silica fume, and 0.04–0.08 superplasticiser by aggregate mass.
Con el fin de confirmar la utilización de una fibra de acero para reforzar un hormigón, se puso en práctica un método consistente en un test de resistencia al impacto, sencillo, práctico y económico. Los resultados obtenidos indicaron que existe una relación logarítmica entre la tenacidad a flexión (E^..^.) y la energía (Ej) de impacto para estos hormigones. En la realización de este estudio se tuvieron en cuenta tres factores diferentes en lo concerniente a las fibras, con extremo en forma de gancho, con relación longitud/diámetro (mm/mm): 30/0,50:60/0,80y 50/0,60. Las fibras se añadieron al cemento en cuatro porcentajes en volumen diferentes: 0,5, 1,0, 1,5 y 2,0 %. A la vista de los resultados obtenidos, puede decirse que las fibras mejoran, tanto la resistencia al impacto, como la flexión en el hormigón, habiéndose establecido, asimismo, una buena correlación entre la energía de resistencia a flexión y la energía de impacto.
Naturally concrete shrinks when it is subjected to a drying environment. If this shrinkage is restrained, tensile stresses develop and concrete may crack. Plastic shrinkage cracks are especially harmful on slabs. One of the methods to reduce the adverse effects of shrinkage cracking of concrete is by reinforcing concrete with short randomly distributed fibers. The main objective of this study was to investigate the effect of fiber volume and aspect ratio of hooked steel fibers on plastic shrinkage cracking behavior together with some other properties of concrete. In this research two different compressive strength levels namely 56 and 73 MPa were studied. Concretes were produced by adding steel fibers of 3 different volumes of 3 different aspect ratios. From this research study, it is observed that steel fibers can significantly reduce plastic shrinkage cracking behavior of concretes. On the other hand, it was observed that these steel fibers can adversely affect some other properties of concrete during fresh and hardened states.
This paper presents the results of an investigation on the effect of Portland cement replaced by fly ash or granulated blast-furnace slag on the concrete strength at different curing temperatures. Also, it presents the coefficients in the relationship of strength-time-curing temperature for the tested concretes as suggested by Carino and Brooks and Al-Kaisi. Compressive strength results are analysed according to the hyperbolic strength-age function by introducing a power index n. The regression analysis is done considering different n and t0 (final setting time) values.
No abstract is provided for this article.
This paper aims to model the effect of density in 7, 14, 28 days on compressive strength of Ultra High Performance Concrete (UHPC) in same compaction and curing conditions by Design of Experiments (DOE) methodology using vary range of 5 variables: Silica fume (SF), Steel Fiber, Cement 42.5, Superplasticizer (SP), and water cemetiotious ratio (w/c).The results shows the significance effect of density on compressive strength of UHPC in different days, The models are valid for the mixes made with 1.0 sand, 0.15-0.30 silica fume amount, 0.70-1.30 cement amount, 0.10- 0.20 steel fiber, 0.04- 0.08 superplasticizer (all values are by sand by weight mass) and 0.18- 0.32 water cementitious ratio.
In recent years, extensive research has focused on investigating rubberized concrete as a structural material due to its enhanced properties, including increased ductility, improved energy dissipation, and higher damping ratios. Additionally, rubberized concrete contributes to sustainable development by recycling non-biodegradable waste and reducing the use of natural aggregates in concrete mixtures. However, its performance in retrofitting existing structures remains unclear and requires thorough investigation before it can be widely implemented in construction activities. The main objective of this research is to evaluate the seismic performance of reinforced concrete buildings strengthened with rubberized concrete jackets under severe earthquake excitations. To achieve this, laboratory tests were conducted to assess the properties of high-performance, self-compacting rubberized concrete mixes with various rubber content levels. Additionally, finite element models of reinforced concrete retrofitted with these mixes were analyzed using nonlinear response history analysis to compare their performance against control models. The results of this experimental work indicate a significant reduction in the mechanical properties of rubberized concrete. However, there is a considerable improvement in the damping ratio, which enhances the energy dissipation capacity of the structures. This improvement contributes to an increase in damping energy and a reduction in hysteretic energy, suggesting that rubberized concrete jackets can enhance the seismic resilience of reinforced concrete buildings.
The aim of this paper is to investigate the effect of quartz powder (Qp), quartz sand (Qs), and different water curing temperature on mechanical properties including 7, 14, 28-day compressive strength and 28-day splitting tensile strength of Ultra High Performance Concrete and also finding the correlation between these variables on mechanical properties of UHPC. The response surface methodology was monitored to show the influences of variables and their interactions on mechanical properties of UHPC, then, mathematical models in terms of coded variables were established by ANOVA. The offered models are valid for the variables between: quartz powder 0 to 20% of cement substitution by cement weight, quartz sand 0 to 50% of aggregate substitution by crushed limestone weight, and water curing temperature 25 to 95oC.
In this study, concrete specimens, having different shapes and sizes have been studied for two different strength levels cured in air and in water. Compressive strength test was performed on cubic and cylindrical samples, having various sizes. The analyses of this investigation were focused on conversion factors for compressive strengths of different samples. Conversion factors of different specimens against cross sectional area of the same specimens were also plotted and regression analyses were done. It was found that according to the results of analyses, the best fit curves, tend to have different trends at different curing conditions.
The corrosion of reinforcement is a major concern for the structural integrity and durability of reinforced concrete (RC) structures. In order to investigate the effect of reinforcement corrosion on bearing capacity and changes in the collapse mechanism, an experimental study on two identical square columns with a section size of 200 × 200 mm were designed, one column was kept sound and the other one was corroded by applying accelerated corrosion process. The two columns were tested under a constant axial compression and reversed cyclic torsional loading with variable drift amplitudes. In order to calibrate accelerated corrosion process for the columns, the results of preliminary corrosion tests, applied to bare steel bars and later on reinforced concrete beams with a section size of 600 × 150 × 150 mm, were used. The results of the experiment on columns showed that the reinforcement corrosion in concrete structures can cause reduction of the strength and ductility up to 20.54% and 11.34% respectively, and also alters the failure modes from bending failure to a shear-bending mode. This could be a significant concern, particularly for buildings in earthquake-prone areas.
This paper reports the results of research investigating the impact of copper tailings on some durability properties of cement pastes, mortars and concretes. Four mixtures incorporating copper tailings at 0% to 15% cement substitution levels by mass were used. Minor reductions in sulfate resistance of mortars and improved performance against autoclave expansion of pastes were observed in mixtures containing copper tailings. Despite increased water absorption and total permeable voids in concrete samples containing copper tailings, sample compressive and tensile strengths comparable to those of the control specimens were obtained. Resistance to acid attack and chloride penetration improved as the copper tailings content of mixtures increased. Moreover, chloride penetration depths obtained from immersion tests suggest that because the rapid chloride permeability test is an indicator of sample conductivity rather than chloride permeability, it may not be appropriate for evaluating mixtures with high-conductivity copper tailings. The high conductivity of concretes containing copper tailings could potentially be utilised in the de-icing of roadways and electromagnetic shielding of electrical and electronic devices.
