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In this paper, the influence of additions of nanosilica (nSi) and microsilica (mSi) on the behav­iour of binary and ternary mixtures in chloride environments is studied. The main objective is to obtain high-performance self-compacting concrete (HPSCC) with a high durability which can meet specific demands in such aggressive environments. Ten blends were manufactured using Portland cement (CEM I 52.5 R) and additions of nSi and mSi in binary and ternary mixtures. The results of three tests frequently used to evaluate resistance to chloride penetration– electrical resistivity, migration and chloride diffusion –were studied and compared. Both binary and ternary mixtures presented significant improvements in chloride resistance, generally in proportion to the total content of the addition. In all the ternary mixtures, high resistivity is obtained, which indicates that such mixtures have a notably low chloride penetrability. Furthermore, these mixtures provided extremely low chloride diffusion coefficients even at small addition ratios. En este artículo se estudia la influencia en el comportamiento frente a cloruros de la adición de nanosílice (nSi) y microsílice (mSi) en mezclas binarias y ternarias. El principal objetivo es obtener un hormigón autocompactante de altas prestaciones con una alta durabilidad frente a estos ambientes agresivos con cloruros. Se prepararon diez dosificaciones usando cemento Portland (CEM I 52.5 R) y adiciones de nSi y mSi en mezclas binarias y ternarias. Se estudiaron y analizaron tres ensayos frecuentemente utilizados para evaluar la resistencia a la penetración de cloruros, resistividad eléctrica, migración y difusión de cloruros. Tanto las mezclas binarias como ternarias presentaron mejoras significativas en la resistencia a cloruros, en general proporcional al contenido de adición. En todas las mezclas ternarias se ha obtenido alta resistividad, indicando una penetrabilidad a cloruros notablemente baja. Estas mezclas proporcionaron un coeficiente de difusión de cloruros extremadamente bajo, incluso para bajos contenidos de adición.

This paper extends the previous work of the authors and deals with the study of fracture of sandwich panels of plasterboard and rock wool under in-plane bending and tensile loading. It presents the results of the experimental campaign focused on the size effect of the tested specimens. To this end, mixed-mode (I and II) fracture tests have been carried out with specimens of three different sizes. The experimental results are compared with the values obtained from the numerical simulation of the test by using a model based on the embedded cohesive crack developed by the authors in previous published works. Comparison of the results shows how the model is able to reproduce the size effect of the specimens in this material from the parameters that characterize fracture behaviour. The aim is to use the cohesive model proposed by the authors to move from laboratory tests to a built panel. Este artículo extiende el trabajo de los autores y aborda el estudio de la fractura en flexión en su plano de paneles de sándwich de yeso laminado y lana de roca. Se presentan los resultados experimentales del estudio del efecto tamaño de fractura en modo mixto (modos I y II) de probetas de tres tamaños. Los resultados experimentales se comparan con los obtenidos de la simulación numérica empleando un modelo de fisura cohesiva embebida presentado por los autores en trabajos previos. El resultado muestra que el modelo reproduce adecuadamente el efecto de tamaño en fractura de los paneles ensayados a partir de los parámetros de caracterización del material. El modelo usado facilita el paso de los resultados de laboratorio al panel construido.

This paper presents the study of plasterboard and rockwool sandwich panels cracking under flexural loading. These panels are usually used to perform interior partition walls and they frequently show cracking pathology due to excessive deflexion of the slabs. There are currently no reliable simulation models and experimental data for the study of this problem. This paper presents the results of an experimental campaign aimed to characterize the fracture behaviour of sandwich panels and their individual components. In addition, the paper presents a cohesive model with embedded crack to simulate the fracture behaviour of the panel. Finally we present the results of tests for mixed mode fracture (tensile / shear) commercial panels and their behaviour is reproduced with the cohesive model proposed, yielding a good fit.

This paper presents a numerical procedure to simulate the cracking process of the brickwork masonry under tensile/shear loading. The model is an extension of the cohesive model prepared by the authors for concrete, and takes into account the anisotropy of the material. The numerical procedure includes two steps: 1) calculation of the crack path with a linear elastic fracture model, 2) after the crack path is obtained, an interface finite element (using the cohesive fracture model) is incorporated into the trajectory. Such a model is then implemented into a commercial code by means of a user subroutine, consequently being contrasted with experimental results. Fracture properties of masonry are independently measured for two directions on the composed masonry, and then input in the numerical model. This numerical procedure accurately predicts the experimental mixed mode fracture records for different orientations of the brick layers on masonry panels.

The compressive strength, flexural strength, porosity and electrical resistivity properties of cement mortars with nano-Fe 2 O 3 and nano-SiO 2 are studied. Amorphous silica is the main component of pozzolanic materials due to its reaction with calcium hydroxide formed from calcium silicate (C 3 S and C 2 S) hydration. The pozzolanic reaction rate is not only proportional to the amount of amorphous silica but also to the surface area available for reaction. Subsequently, fine nano-Fe 2 O 3 and nano-SiO 2 particles in mortars are expected to improve mortar performance. The experimental results showed that the compressive strength of mortars with nano-Fe 2 O 3 and nano-SiO 2 particles were lower than those obtained with the reference mortar at seven and 28 days. It was shown that the nano-particles were not able to enhance mechanical strength on every occasion. The continuous microstructural progress monitored by mercury intrusion porosimetry (MIP) measurements, pore-size distribution (PSD), total porosity and critical pore diameter also confirmed such results.

This article discusses the results of research conducted on the failure behaviour of brick masonry under tensile and shear stress. The study was designed to develop test models and generate experimental results able to provide greater insight into tensile and shear stresses cracking in brick masonry. The results of a campaign conducted with two types of specimens are discussed: 1) double-edge notched specimens under non-symmetrical compression stress, and 2) three point bending specimens under nonsymmetrical loading. Tests were run on specimens of similar size (similarity rate 2) and different bed joint orientation to determine how bed joint orientation affects crack propagation. The tests were conducted on scale models (1/4) of a single wythe, stretcher bond brickwork masonry wall one half foot thick.