Luisa Andreia Gachet Barbosa

Use of expanded clay and silica fume for the improvement of mechanical, physical and thermal performances of structural lightweight concretes

In this study an investigation was carried out for the execution of concretes with high strength, low density and excellent thermal properties, in order to execute energy-efficient constructions. Structural Lightweight Concretes were studied using two different granulometries of expanded clay (C05 and C15), where the coarse aggregate was replaced by 0, 25, 50, 75 and 100%. To promote the maintenance of consistency and resistance, superplasticizer and silica fume were used in the mixtures. Based on the methodology used, the concretes were physically and mechanically characterized, in accordance with current national and international standards. The density of the concretes, in the hardened state, ranged from 1,787 to 2,400 kg/m3 and, for compressive strength, ranged from 26 to 53 MPa at 7 days of age. The thermal conductivity test, using the protected hot plate method, was performed according to EN 12667, where was observed a variation of 0.61 to 1.00 W/mK. Microstructural information of the interfacial transition zone between aggregate and cement matrix were obtained with the purpose of analyzing the relationship with mechanical resistance. The investigation revealed that, with the addition of expanded clay (C05 and C15) and silica fume in the concretes, there was reduction of the density and the mechanical resistance, while the thermal characteristics improved.

Short steel and concrete columns under high temperatures

The growing demand for knowledge about the effect of high temperatures on structures has stimulated increasing research worldwide. This article presents experimental results for short composite steel and concrete columns subjected to high temperatures in ovens with or without an axial compression load, numerically analyzes the temperature distribution in these columns after 30 and 60 minutes and compares them with experimental results. The models consist of concrete-filled tubes of three different thicknesses and two different diameters, and the concrete fill has conventional properties that remained constant for all of the models. The stress-strain behavior of the composite columns was altered after exposure to high temperatures relative to the same columns at room temperature, which was most evident in the 60-minute tests due to the higher temperatures reached. The computational analysis adopted temperature rise curves that were obtained experimentally.

Conventional concrete with addition of recycled rubber tires: Study of the mechanical properties

The world is now pressing for decreasing emissions of greenhouse gases, the reduction and possible revocation of culling and disposal of materials resulting from manufacturing processes that pollute and degrade the environment. Among these problems unused tires has become a major problem for the environment due to years of provisions incorrect. On motion of reuse, recycling and waste disposal, construction has become a major partner of the other production areas to reduce several types of industrial wastes by reusing these materials, the introduction of these materials in construction products civil, replacement of traditional materials and various other ways. Have produced different concrete mixtures without and with different percentages of rubber tires. The results indicate a clear loss of strength both in compression as in tension. Key words: alternative materials, materials and components in construction, materials recycling.