Experimental investigation of the variability of concrete durability properties

One of the main objectives of the APPLET project was to quantify the variability of concrete properties to allow for a probabilistic performance-based approach regarding the service lifetime prediction of concrete structures. The characterization of concrete variability was the subject of an experimental program which included a significant number of tests allowing the characterization of durability indicators or performance tests. Two construction sites were selected from which concrete specimens were periodically taken and tested by the different project partners. The obtained results (mechanical behavior, chloride migration, accelerated carbonation, gas permeability, desorption isotherms, porosity) are discussed and a statistical analysis was performed to characterize these results through appropriate probability density functions

Measurement of CO 2 effective diffusion coefficient of cementitious materials

International audienc

Numerical study of the influence of drying on properties governing the carbonation mechanism of concretes with low clinker content

International audienc

Différentes approches pour la formulation des bétons autoplaçants: Influence sur les caractéristiques rhéologiques et mécaniques

International audienceNo general method is available in France to optimise SCC composition, and therefore design requires a lot of trials in laboratory or in most of cases directly in plant. However more rational approaches can be found in recent publications. The aim of this paper is to compare three of the most recurrent methods. The first one is a very simple mix design: coarse and fine aggregates contents have fixed values, and superplasticizer and water proportions are determined by mortar tests. The second method proposes two criteria to minimise paste volume. The third approach is based on the packing and on several models describing the properties of the fresh SCC. According to the French Standard P18-305, different SCC have been designed, without viscosity agents, by these methods, and their properties at the fresh state have been characterised with tests advised by the AFGC The experimental results provide new solutions for SCC designers in an industrial context. A study of the effect of mix design on harden state properties is provided too.La formulation des bétons autoplaçants se fait, dans la plupart des cas, de manière empirique, alors qu'il existe des approches plus rationnelles. On présente ici une comparaison de trois méthodes de formulation récurrentes dans la littérature. La première est une méthode à la fois forfaitaire, pour le dosage des granulats, et expérimental, pour le dosage en eau et en adjuvant. La deuxième approche propose deux critères pour minimiser le volume de pâte. La troisième approche est basée sur l'optimisation du squelette du béton; il s'agit d'un logiciel compilant un modèle d'empilement granulaire et des modèles rhéologiques. Dans le cadre de la norme P18-305, différents BAP, sans agent de viscosité, ont été formulés avec ces méthodes, puis caractérisés à l'aide des essais préconisés par l'AFGC. Cette étude de faisabilité permet de dresser différents niveaux pour une formulation scientifique des BAP; elle permet également d'envisager de nouvelles possibilités pour le formulateur. Une étude de l'incidence de la formulation sur les propriétés à l'état durci a également été menée par comparaison avec un béton ordinaire

Evaluation of Plastic shrinkage Cracking of self compacting concrete

International audienceThis paper describes an experimental investigation of plastic shrinkage cracking of self-consolidating concrete (SCC). Five SCC mixtures with compressive strengths ranging from 30 to 50 MPa were compared to five ordinary concrete (OC) mixtures. Free and restrained plastic shrinkage tests were performed in drying conditions. Depending on evaporation rate, plastic shrinkage occurs before setting (wind), or before and during setting (no-wind). In the presence of wind, SCC and OC mixtures have almost the same plastic shrinkage. Moreover, restrained shrinkage tests reveal that cracks of SCC tend to be less wide than cracks of OC. Nevertheless, when evaporation rate is low, SCC mixtures exhibit a higher plastic shrinkage than OC mixtures, due to their lack of bleeding. Consequently, SCC could be more vulnerable to shrinkage cracking, especially during setting. Thus, curing is recommended to protect SCC against evaporation at the fresh state

Utilization of sludge from ready-mixed concrete plants as a substitute for limestone fillers

International audienc

A proposed modelling of coupling carbonation-porosity-moisture transfer in concrete based on mass balance equilibrium

International audienc