Commodity plastics are being used in many applications due to their low density, high durability, and relatively low cost. Their wide usage and degradable nature create environmental problems. Polyethylene terephthalate (PET) is the one of most used plastics and the second largest contributor to the global plastic waste. The scientific literature suggests a global effort for utilizing PET waste in building materials including concrete, mortars, and cementitious composites, in the form of granules, powder or fibres. This study aims to contribute to the knowledge about the material behavior of Recycled PET Fibre Reinforced Mortars (RPFRMs) by investigating the influence of fibres on some physical and mechanical properties of a cementitious render mortar.
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.
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.
One of the effective vibration control systems used for structures is the semi active tuned mass damper (STMD), which is popular since it is reliable and simple. STMD characteristics in the design for piled foundations are usually obtained by modelling the foundation raft only to incorporate the soil structure interaction (SSI). However, as it proposed in the recent studies the role of SSI and simulation of piled raft in the analyses proved to be very important in the determination of the STMD parameters. Hence, in this study, efficiency of STMD with respect to the control of seismic response of the structure, is studied by considering the soil-pile-structure interaction (SPSI). Nonlinear time history analysis is applied for a three-layered soil profile including pile foundations by using the well-known substructure (spring) model under two different ground motion records. In order to increase the accuracy of the results, soil profile with piles and building structure with STMD are considered all at once in a single model under the action of seismic loading, named as direct method. P-Y curves which are suggested by American Petroleum Institute (API) are used in the spring method for simulating soil-pile-structure interaction. The results showed that, adjusting the STMD characterizations on piled structures without considering the soil-pile-structure interaction may result to ineffective control of the seismic vibration and in the worst case may lead to amplification of the vibration of buildings.
No abstract is provided for this article.
This article presents a factorial modelling, as well as an optimization, of the mix proportion of ultra-high performance concrete (UHPC) in terms of maximising the 28-day strength and minimising CO2 emissions. A full factorial design and desirability function optimization method were performed to find the best UHPC ingredient proportions. To improve the concrete properties, the concrete performance in terms of CO2 emissions and environment effects should be considered. Ultra-high performance with superior properties requires a large amount of cement, steel fibre and an admixture; however, from an environmental perspective, cement and admixtures and steel fibre are the important matter for global warming as cement production corresponds to 5% of all the CO2 emissions around the world. In addition, the 28-day compressive strength is one of the most important properties of concrete and is related to other mechanical properties; therefore, the 28-day compressive strength and carbon oxide emissions were selected as the responses to produce the green UHPC with high performance. The mix design parameters were the cement content (C), the steel fibre amount (F), the superplasticiser (SP), the silica fume amount (SF) and the water to cementitious ratio (W/C). The variables were compared by fine aggregate mass. The optimized ingredient mix designs are valid for the mixes with .18–.32 W/C ratio, .04–.08 steel fibre, .7–1.3 cement, .15–.30 silica fume, and .04–.08 superplasticiser by fine aggregate mass.
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.
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.
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.
The effects of copper tailings as an additive, on some durability properties of cement mixtures were investigated. In each mixture, copper tailings addition levels by mass were 0%, 5% and 10%. Compared to the control samples, copper tailings blended pastes showed superior performance against autoclave expansion while insignificant decreases in sulfate resistance of mortars were observed. Copper tailings increased the water absorption and total permeable voids of concretes slightly. However, the compressive and flexural strengths of blended concretes were higher than those of the control samples. Similarly, improved resistance to acid attack and chloride penetration as the copper tailings content of concretes increased were also observed. Results further showed that the ASTM C 1202 rapid chloride permeability test may not be a valid indicator of chloride migration in mixtures containing conductive copper tailings. These results suggest that copper tailings can potentially enhance the durability properties of cement based materials.
One important issue in compiling siesmic fragility curves is blending and incorporating uncertainties into the model under seismic conditions. Methods used in this regard are either approximate, costly and time-consuming. To address this, the optimized fuzzy method is used. To compile the fragility curve, epistemic and aleatory uncertainties have been incorporated in which model parameters are fuzzy values and FCM-PSO method is used to estimate mean and standard deviation of fragility curve. The FCM-PSO algorithm is trained using scenarios compiled via the IDA method. Results obtained from the full Monte Carlo method were used for verification. The method employed here is advantageous with regard to both accuracy and execution time.
The main objective of this study was to assess and identify general construction faults and to investigate the effects of construction faults on the linear performance levels of reinforced concrete buildings. For doing this, observed two common construction faults (i.e., corrosion and honeycombing) were considered to be used in linear performance analyses. Finite element method was used to model the honeycombing at the column-beam joints. The effects of corrosion on the performance levels were ensured by reducing the cross-sectional area of reinforcement bars and reduced concrete compressive strength as a function of corrosion rate. Thus, two different construction faults on the levels of structural performance were discussed and compared. The results showed that the effects of honeycombing on performance levels of reinforced concrete building with linear performance analyses was more dramatic when it was compared with the results of damage building due to corrosion having a moderate to high corrosion threshold.
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.
