Influencia de la adición de escoria de alto horno en la penetración de los cloruros en el concreto

Debido a que en estructuras de concreto hechas con cemento Portland la penetración del ion cloruro es la principal causa de deterioro por corrosión del refuerzo, el estudio y prevención de los mecanismos que generan corrosión en el concreto son fuentes de constante investigación. En el presente artículo se presentan los resultados de una investigación analítica y experimental sobre la influencia de la adición de la escoria de alto horno en las propiedades que gobiernan los fenómenos de transporte iónico del concreto, especialmente los del ion cloruro. Las relaciones entre los coeficientes de difusión con la resistividad eléctrica, la carga pasada y la resistencia a la compresión, fueron evaluadas para mezclas con diferentes porcentajes de remplazo de escoria. De la misma forma, mediante un modelo computacional y un ensayo de migración eléctrica se obtuvieron los coeficientes intrínsecos de difusión, la porosidad, la capacidad de fijación de cloruros y la concentración química de la solución de poros. Los resultados obtenidos mostraron que la escoria aporta importantes beneficios en la penetración del ion cloruro, obteniéndose un concreto menos vulnerable a la corrosión.Corrosion of steel reinforcement due to chloride penetration is the greatest cause of durability problems in concrete; intense international research has been carried out to understand and avoid this. This paper summarises the results of a theoretical and experimental research programme investigating the influence of blast furnace slag on chloride-related transport properties. The relationship between the apparent chloride diffusion coefficient, electrical resistivity and compressive strength was measured. Chloride, hydroxide, sodium and potassium’s intrinsic diffusion coefficients were obtained by using a computational model and an electrical migration test. The initial hydroxide composition of the pore solution, porosity and chloride binding capacity were also determined from the model. The results showed that blast furnace slag improved chloride penetration resistance, resulting in concrete which was less vulnerable to corrosion

Influencia de la no linealidad de material en las deflexiones inmediatas de vigas de concreto reforzado

Este artículo presenta los resultados analíticos y experimentales de una investigación realizada por el Grupo de Investigación GIES sobre la influencia de la no linealidad de material sobre las deflexiones inmediatas de vigas de concreto reforzado. Bajo condiciones reales y diferentes situaciones de carga fueron ensayadas seis vigas de dicho material. El comportamiento teórico de las vigas fue simulado mediante el modelo no lineal de material del programa comercial de elementos finitos Ansys®. La comparación de los resultados del modelo no lineal de Ansys®, las recomendaciones del código de construcción ACI 318, y los ensayos experimentales, mostraron que el comportamiento estructural de una viga simplemente apoyada está fuertemente influenciado por la no linealidad de material.This paper presents an analytical and experimental research programme’s results regarding material nonlinearity’s influence on reinforced concrete beams’ immediate deflections. Six full-size laboratory beams were tested under different type of loads in the experimental programme. The ANSYS finite element software nonlinear material model was used for simulating the beams’ analytical behaviour. Comparing ANSYS nonlinear material model results, ACI 318 equations and the results of the tests made revealed that a beam’s structural behaviour is strongly influenced by material nonlinearity

Effect of sedimentary and metamorphic aggregate on static modulus of elasticity of high-strength concrete

Taking into account the increasing use of high-strength concrete as a structural material in Colombia, this paper shows the results of research carried out to investigate the effect of different types of coarse aggregate on the static elastic modulus, the compressive strength, the concrete density, and the pulse velocity. To do this, concrete mixes were cast using three different water binder ratios (w/c) (0.36, 0.32, and 0.28). Ordinary Portland cement and pulverized silica fume (SF) were used as cementitiuos materials, while four types of coarse aggregates obtained from different sources near Bogota, Colombia were utilized to prepare the concrete samples. Results were analyzed statistically and these showed that the behavior of all the tests followed a normal frequency distribution. Correlations were found among the mixes. From the experimental data obtained in this study, it was concluded that the equations proposed in standard codes overestimated the modulus of elasticity of high-strength concrete, so empirical equations were obtained in order to predict the elastic modulus of elasticity in high-strength concrete

Elastic response of cross-laminated engineered bamboo panels subjected to in-plane loading

© ICE Publishing: All rights reserved. Novel cross-laminated bamboo panels comprising three and five layers (G-XLam3 and G-XLam5) were tested in compression along the main (0°) and the transverse (90°) directions. Linear variable differential transformer (LVDT) and non-contact three-dimensional digital image correlation (DIC) measuring techniques were used separately to measure deformation in the elastic region, and the elastic moduli, Ep C,0 and Ep C,90, were derived. Mean elastic modulus values obtained using LVDTs exhibited a good match with analytically predicted values. In contrast, the elastic values obtained by the DIC method were considerably higher and presented a considerable scatter of results. For instance, the Ep C,0 for G-XLam3 and G-XLam5 panels were 17·22 and 15·67 GPa, and 14·86 and 12·48 GPa, using the DIC and LVDT methods, respectively. In general, G-XLam panels with a fifth of the cross-sectional thickness and twice the density of analogous cross-laminated timber exhibited an approximately two-fold increase in Ep C,0 and Ep C,90. Overall, this research provides guidelines for the assessment and standardisation of the testing procedures for similar engineered bamboo products using contact and non-contact methods and highlights the potential of using G-XLam panels in stiffness-driven applications and in combination with wood for structural purposes

Modelling chloride penetration in concrete using electrical voltage and current approaches

This paper reports a research programme aimed at giving a better understanding of the phenomena involved in the chloride penetration in cement-based materials. The general approach used was to solve the Nernst-Planck equation numerically for two physical ideal states that define the possible conditions under which chlorides will move through concrete. These conditions are named in this paper as voltage control and current control. For each condition, experiments and simulations were carried out in order to establish the importance of electrical variables such as voltage and current in modelling chloride transport in concrete. The results of experiments and simulations showed that if those electrical variables are included as key parameters in the modelling of chloride penetration through concrete, a better understanding of this complex phenomenon can be obtained