In this study involving cementitious matrix composites, the influence of the water/cement (w/c) ratio variation (0.48, 0.60, 0.70 and 0.75) was analyzed in its open pore structure and in the carbonation front advancing. Test specimens were molded in cylindrical dimensions of (5x10) cm and (2x4) cm for each mix proportions, and subjected into accelerated carbonation tests, at controlled exposure conditions. The open porosity of the material was obtained by using a helium pycnometer. A model based on Fick's second law was used to fit an equation to the curve of progress of the carbonation front over time. The results show that the water/cement ratio can highly influence the analyzed properties; the mathematical model used provided an excellent approximation of the advancing carbonation front trend, allowing a good evaluation of the carbonation coefficient (K) associated to each mixture proportioning.
The purpose of this paper is to present the main aspects and results of an experimental study to determine the bond strength between the concrete of a column of an existing structure (old concrete) and the concrete that will be used in its strengthening project (new concrete). For the bond strength tests, a specimen was conceived, called Double Sleeve specimen. The bond strength results obtained from the tests using Double Sleeve specimens, called Double Sleeve Tests, were compared to the results obtained from using the Slant Shear Test. The values for the bond strength between the two concretes, obtained from the Double Sleeve Tests, were either below or above the values obtained from linear regression of the Slant Shear Test results, depending on the sleeve diameter and the ratio of transverse reinforcement used. This fact, enabled concludes that the Double Sleeve Test is the most appropriate test to evaluate the bond strength between concretes of columns strengthened.
The goal is to determine the mechanisms of soil-cement interlocked brick plus wood fibers under compressive loading. For this we used experimental stress analysis techniques. Horizontal deformations (εx) and vertical (εy) of bricks were obtained with extensometers, in the configuration of five rosettes. From the values of these deformations and using the equations of the theory of elasticity, Poisson coefficients were determined and elasticity modules, and calculated the corresponding voltages each escutcheon according to the equations of the State of plane stress. To determine the trajectory of the rupture voltage-loading graphics were made of each rosette. Knowing this trajectory determined the tensions related to the modification of the brick break mechanism. The appearance of a premature cracking or excessive is parameter used to determine the State limit of use of bricks.
Compositions with different pipe segments for constructing structural columns were investigated. In this article there is shown a column type composed of five parallel bamboo bars, connected by screws 16 mm and 13 mm in diameter. Compression tests instrumented with displacement transducers are associated with numerical modeling analysis to describe the column load capacity, from the general criteria of dimensioning. The chosen Bamboos are from the species Phyllostachys pubescens due to its favorable characteristics to produce structures and their common use in China, Brazil and other countries of temperate zones. In this proposal, the load capacity is considerably increased and lateral displacements are insignificant compared to the bamboo tested separately. More usual columns 3 and 4 meters long were modeled and presented the load limits of use for these types of structures. Other dimensions of columns can be calculated by the same system, presenting great design opportunities in the construction of the architecture and built spaces. This article shows a great advantage in using columns with bamboo bars compared to other materials used in the architecture, with guarantee and good indexes of security.
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