The ingress of chlorides in concrete under compressive or tensile loads

One common aggressive mechanism acting in reinforced concrete is chloride attack which induces steel corrosion. Although it has mostly been studied and analyzed separately it has been observed that loads acting on concrete may modify the deteriorating effect. In this research the effect that combined attack provokes on concretes made of ordinary Portland cement (OPC), high sulfate-resistance cement (SR) and blast furnace slag (BFS) cement is investigated. Five mixes were made with these materials, 2 of them using a type 52.5 N (OPC) cement, 2 replacing OPC by 50 and 70 % of BFS and 1 made of 52.5 N (SR) cement type. Cubic samples made with all binder types were exposed to a 3% by weight sodium chloride solution while applying a permanent splitting tensile load corresponding to 50 % of their breaking capacity. Prismatic samples (100 x 100 x 400 mm) made of OPC binder were exposed to a 3% by weight sodium chloride solution while maintaining a compressive load equal to 30 % of their maximum capacity. After the exposure time, ground layers were obtained from the samples to determine the chloride ingress into the concrete by means of potentiometric titration. To define chloride transport in concrete an error function solution was applied to Fick’s second law. In terms of their diffusion coefficient and chloride surface concentration in decreasing order of performance were found: the concrete with 70 % replacement by BFS, followed by the concrete with 50 % BFS substitution, then pure OPC concrete and finally the sulfate resistant cement concrete. Load levels of 30 % in compression and 50 % in splitting tensile testing, improved the resistance of concrete to chloride attack

On the quantitative thermogravimetric analysis of calcite content in hydrated cementitious systems

Calcite is a compound that is present in hydrated cementitious materials when carbonation of portlandite occurs or when limestone constituents are used. The quantification of its content in cementitious systems is then frequently necessary. Thermogravimetry (TG) measures the change in mass of a material (as a function of time) over a temperature range using a predetermined heating rate. It can be applied to estimate calcite content in the hydrated cement system, considering the temperature range at which it decomposes and releases carbon dioxide. However, the quantification is not easy because the onset of this decomposition is a function of many variables. The tangential method over the TG signal or the integration method over the derivative TG curve (DTG) are usually used to discount the background over the temperature range at which calcite decomposes. However, consistent underestimation of compounds is frequently described. The reasons for this are unclear and some hypothesis are discussed in this paper. Additionally, experimental quantitative TG of cement paste and aggregate containing calcite and diluted with low contents of analytical calcite are compared with the expected contents, as a calibration method regarding calcite content in the samples is given to improve the reliability of the results

Chloride penetration in concrete under compression or splitting tensile load representing 60-65 per cent of the ultimate load

A critical loading ratio is reached at 50% of concrete ultimate load. Beyond this point the presence of micro cracks exerts a big influence on the chloride transport. For compression the strain distribution in the sample developed micro-cracking system that is more or less homogeneously distributed in the sample. Therefore it is expected the same chloride profile regardless of the position. When combined splitting tensile load and chloride attack are acting on concrete, the main micro-crack system is located on the loading plane. This contributes to regular and alike shaped chloride profiles if they are taken from planes that are kept parallel to the splitting one. Prismatic samples (100 x 100 x 400 mm) made of OPC binder were exposed to a 3% by weight sodium chloride solution while maintaining a loading ratio equal to 60 % of the maximum capacity. Cubic samples (side = 150 mm) made of OPC and 50% BFS had similar chemical exposure while applying a permanent splitting tensile load corresponding to 65 % of their breaking capacity. After the exposure, ground layers were obtained from the samples to determine the total chloride ingress into the concrete by means of potentiometric titration and the effect of the load on the chloride ingress was assessed

Effect of Disorder and Notches on Crack Roughness

We analyze the effect of disorder and notches on crack roughness in two dimensions. Our simulation results based on large system sizes and extensive statistical sampling indicate that the crack surface exhibits a universal local roughness of $\zeta_{loc} = 0.71$ and is independent of the initial notch size and disorder in breaking thresholds. The global roughness exponent scales as $\zeta = 0.87$ and is also independent of material disorder. Furthermore, we note that the statistical distribution of crack profile height fluctuations is also independent of material disorder and is described by a Gaussian distribution, albeit deviations are observed in the tails.Comment: 6 pages, 6 figure

Contribution of the R-Ras2 GTP-binding protein to primary breast tumorigenesis and late-stage metastatic disease

R-Ras2 is a transforming GTPase that shares downstream effectors with Ras subfamily proteins. However, little information exists about the function of this protein in tumorigenesis and its signalling overlap with classical Ras GTPases. Here we show, by combining loss- and gain-of-function studies in breast cancer cells, mammary epithelial cells and mouse models, that endogenous R-Ras2 has a role in both primary breast tumorigenesis and the late metastatic steps of cancer cells in the lung parenchyma. R-Ras2 drives tumorigenesis in a phosphatidylinostiol-3 kinase (PI3K)-dependent and signalling autonomous manner. By contrast, its prometastatic role requires other priming oncogenic signals and the engagement of several downstream elements. R-Ras2 function is required even in cancer cells exhibiting constitutive activation of classical Ras proteins, indicating that these GTPases are not functionally redundant. Our results also suggest that application of long-term R-Ras2 therapies will result in the development of compensatory mechanisms in breast tumoursFil: Larive, Ramon. Universidad de Salamanca; España. University of Montpellier I and II; FranciaFil: Moriggi, Giulia. Universidad de Salamanca; EspañaFil: Menacho Márquez, Mauricio Ariel. Universidad de Salamanca; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; ArgentinaFil: Cañamero, Marta. Centro Nacional de Investigaciones Oncológicas; EspañaFil: de Alava, Enrique. Universidad de Salamanca; España. Hospital Universitario Virgen del Rocío. Sevilla; EspañaFil: Alarcón, Balbino. Centro de Biología Molecular ‘‘Severo Ochoa’. Madrid; EspañaFil: Dosil, Mercedes. Universidad de Salamanca; EspañaFil: Bustelo, Xosé R.. Universidad de Salamanca; Españ

Measuring functional renormalization group fixed-point functions for pinned manifolds

Exact numerical minimization of interface energies is used to test the functional renormalization group (FRG) analysis for interfaces pinned by quenched disorder. The fixed-point function R(u) (the correlator of the coarse-grained disorder) is computed. In dimensions D=d+1, a linear cusp in R''(u) is confirmed for random bond (d=1,2,3), random field (d=0,2,3), and periodic (d=2,3) disorders. The functional shocks that lead to this cusp are seen. Small, but significant, deviations from 1-loop FRG results are compared to 2-loop corrections. The cross-correlation for two copies of disorder is compared with a recent FRG study of chaos.Comment: 4 pages, 4 figure