Guillem de Vera

A test method for measuring chloride diffusion coefficients through nonsaturated concrete: Part I. The instantaneous plane source diffusion case

Abstract A test method is proposed for measuring chloride diffusion coefficients through nonsaturated concrete specimens with controlled water contents. The experimental setup used allows one to supply an initial limited amount of Cl − to the tested concrete surface. The procedure consists of submitting the surface of concrete specimens to interaction with the products of combustion of PVC, which contain mainly gaseous hydrogen chloride. This interaction yields a limited Cl − contamination of the concrete surface. After returning the specimens to their controlled humidity exposure conditions, the kinetics of Cl − transport from the surface inwards may be studied. The experimental Cl − concentration profiles determined at selected time intervals have been adjusted to a diffusion model of “instantaneous plane source,” which takes into account the particular initial and boundary conditions of the experimental procedure, for obtaining the corresponding diffusion coefficients.

Analysis of acid-soluble chloride in cement, mortar, and concrete by potentiometric titration without filtration steps

Abstract A potentiometric titration procedure that makes use of Gran’s method for end-point detection has been developed to analyze acid-soluble chloride in cement, mortar, and concrete, eliminating the filtration steps performed in habitual laboratory reference methods. The accuracy and reliability of the proposed analytical technique has been checked against a standard method, such as Volhard’s, by analyzing duplicate samples of cements, mortars, and concretes with varied chloride contents.

Effect of Type of Anodic Arrangements on Efficiency of Electrochemical Chloride Removal from Concrete

Electrochemical techniques can be used to arrest or prevent reinforced concrete corrosion. This article reports on a study that evaluated the effect of the type of anodic arrangement on the efficiency of the technique of electrochemical chloride removal (ECR) applied to reinforced concrete structures. Two different arrangements were tested for maintaining the electrolytic medium in contact with the concrete surface: complete immersion of the system (structure and anode) in water during the electrochemical treatment; and the wrapping of the concrete structure with a sandwich-like anodic system, which consisted of two layers of polypropylene felt embedding the anodic material. Results demonstrate that the efficiency of an ECR treatment applied with a sandwich-like anodic system may be practically equal to that obtained with a liquid electrolyte (immersion) if a good contact between the concrete surface and the polymeric system is ensured. The use of a continuous graphite felt for the sandwich-like anodic system, instead of a discontinuous and more rigid metallic wire mesh anode, makes it easier to achieve the necessary electrical contact. The authors caution that the net influence of carbonation on the efficiency of ECR may vary for different experimental conditions.

Shape Effect of Electrochemical Chloride Extraction in Structural Reinforced Concrete Elements Using a New Cement-Based Anodic System

This article shows the research carried out by the authors focused on how the shape of structural reinforced concrete elements treated with electrochemical chloride extraction can affect the efficiency of this process. Assuming the current use of different anode systems, the present study considers the comparison of results between conventional anodes based on Ti-RuO2 wire mesh and a cement-based anodic system such as a paste of graphite-cement. Reinforced concrete elements of a meter length were molded to serve as laboratory specimens, to closely represent authentic structural supports, with circular and rectangular sections. Results confirm almost equal performances for both types of anode systems when electrochemical chloride extraction is applied to isotropic structural elements. In the case of anisotropic ones, such as rectangular sections with no uniformly distributed rebar, differences in electrical flow density were detected during the treatment. Those differences were more extreme for Ti-RuO2 mesh anode system. This particular shape effect is evidenced by obtaining the efficiencies of electrochemical chloride extraction in different points of specimens.

Influence of Environment on Durability of Fly Ash Cement Mortars

In this study, the durability-related properties of mortars prepared using two types of cement with different contents of fly ash were tested. One of the most important ways of ingress of aggressive substances in cementitious materials is through water. Therefore, to characterize their durability, the capillary suction and the resistance against chloride ingress of the fly ash mortars were studied. The mortars were exposed to four different constant temperatures and relative humidities (RHs) for 365 days. The measured properties of both cement types were affected by the hardening environment. For each environment studied, the durability-related parameters of the fly ash cement mortars studied were quite similar at high hardening ages, independent of their fly ash content. In spite of the different resistance classes of cements used, the durability related properties of both cement types were similar at high hardening ages, regardless of the environment.