In this paper the performance of an Ultra-High Performance Concrete (UHPC) reinforced with different contents of metal fibers is evaluated. This concrete was produced using materials available in Colombia and conventional manufacturing techniques;, ie no high temperatures or pressures in the manufacturing of different specimens were used. This UHPC was tested for uniaxial compressive strength and flexural strength. Furthermore, we evaluated the behavior of different ages cracked joists of different ages, which were subjected to different curing times in order to determine the residual bending strength., was evaluated. It has been observed We observed that the fiber content and adhesion to be generated between them the fibers and the concrete matrix are matters of great importance, in order to ensure no loss of flexural strength, regardless of the age of the cracking.
Rev. ing. constr. [online]. 2014, vol.29, n.3, pp. 220-233. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732014000300001
Construction sector is considered as one of the main sources of environmental pollution in the world. It has massive direct and indirect effects on the environment. Gaza Strip is witnessing widespread construction projects which increase the pressure on the ecosystem and generate various pollutants. Gaza Strip is suffering from weak and deteriorating ecosystems due to limited natural resources, deteriorating economic and political situation, escalating population growth, and lack of awareness of environmental issues. The aim of this paper is to assess the environmental impacts due to construction projects activities in Gaza Strip and propose some suggestions in curbing down these adverse impacts. A total of 50 questionnaires were distributed to professionals working in the construction industry. The environmental impacts are categorized into three safeguard subjects: ecosystems, natural resources and public impacts. The results of this study revealed that dust generation, noise pollution, operations with vegetation removal, and air pollution are the most significant environmental impacts of construction projects. The results also revealed that labors and those who are working in construction sector are the most slices of people exposing every day to health problems such as respiratory problems, liver, cancer, hearing impairment, hypertension, annoyance, sleep disturbance, and other cardiovascular adverse effects. In addition, the public impact was found as the most important category that affects the environment in Gaza Strip. It is recommended to enhance the knowledge and awareness of construction participants with regard to environmental impacts of construction and enact strict laws to attempt curbing down the adverse impacts of construction such as enforcing institutions to conduct environmental impact assessment (EIA) in the early stage of the projects. The results of this study can help decision makers to identify major construction impacts on environment and make environmentally friendly construction plans in the early stages of construction.
Rev. ing. constr. [online]. 2014, vol.29, n.3, pp. 234-254. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732014000300002
In order to produce high performance concrete (HPC), fine Mexican mineral aggregates were characterized using chemical, physical and mineralogical procedures. Used materials included fly-ash, micro silica, silica fume, and coarse, fine and refined ground granulated blast furnace slag (GGBS), which were then dosed with Composite Portland Cement (CPC) in three forms: (1) commercially as-received, (2) as-screened and (3) after being high energy ball milled (HEM), i.e., as-milled. The materials were conditioned with less than 200 mesh (75μm) particles and with submicron particle sizes in order to analyze their contribution to the compressive strength of the paste. After characterizing the raw materials, the experimental parameters for reducing particle sizes by HEM - CPC and GGBS were determined. Milled products and other cementitious materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic absorption analyses. Different materials phases were identified, thus observing a change in the mass percentage of Alite C3S and Belite C2S, which promote the compressive strength of the specimens produced, provided that the CPC has been grounded by HEM for 30 min. Silica fume was proven to the best aggregate, which triggers the compressive strength of the specimens prepared.
Rev. ing. constr. [online]. 2014, vol.29, n.3, pp. 256-269. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732014000300003
Relative humidity is very important for different applications in engineering, including the durability of concrete structures. However, it has been noted that in several cities there are no weather stations with complete time series data. The aim of this paper is to discuss models available in literature to estimate the relative humidity and check its behavior for marine environments. The methodology consisted in comparative analyzes of relative humidity predicted by models and values measured by weather stations for a period of 30 years of data. Two models for 16 different cities of the Brazilian coast were analyzed. For analysis and comparison of these data, the statistical performance of results was evaluated. Among the results, it has been observed through statistical analyzes that one of the models showed better conditions to estimate the relative humidity for marine environments than the other one. However, the need for developing a more appropriate model for this kind of environment has been identified.
Rev. ing. constr. [online]. 2014, vol.29, n.3, pp. 270-282. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732014000300004
This paper evaluates two types of hysteretic passive energy dissipation devices (steel slit plates). These devices are low-cost and easy to build and install. The seismic performance of three structural models were studied with shake table tests: a frame without energy dissipation device and two frames with two types of steel slit plates. The models were instrumented with accelerometers, strain gages and LVDTs, and were subjected to two types of earthquakes signals: a regional earthquake and a near-field ground motion. The results of laboratory tests suggest that the frame with steel slit plates have up to 90% less seismic drift than the frame without rehabilitation. This is because steel slit plates dissipated a large portion of the input energy supplied by earthquakes and the damage to the parent structure was minimized.
Increasing numbers of Taiwan investors are investing in Mainland China foundry industry. This paper examines the existing development, difficulties and risk encountered for Taiwanese foundry industry in Mainland China and Taiwan. Telephone surveys and structured interviews are conducted with 50 foundry companies of 100% response rate. A novel research methodology, spectral analysis, is used for the analysis in identifying dominant factor(s) in the development of Taiwanese and Mainland China foundry industries. From the survey results, it is found that Taiwanese foundry companies tackle a multitude of management issues in both Mainland China and Taiwan; practical strategies must be implemented early to alleviate potential management risks and to promote smooth business operations. Providing enough cash flow and understanding cultural differences between two countries are suggested and encouraged to be concerned for Taiwanese when establishing their business in Mainland China foundry industry.
Rev. ing. constr. [online]. 2014, vol.29, n.3, pp. 299-308. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732014000300006
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