34 research outputs found
Reinforced Concretes of Tomorrow: Corrosion Behaviour according to Exposure Classes
Reinforced concrete is the most widely used building material but its durability in terms of concrete cover performance and corrosion of steel rebar is still a key point to be studied. To address this topic, within the frame of the national project PERFDUB, two series of eleven reinforced concrete specimens (with metric dimensions) were cast with innovative concrete mixes representative of the French experience, two shapes of rebar and two concrete covers. Then, these specimens were exposed in two natural exposure sites, one in Epernon for carbonation (XC4) and a second one in La Rochelle in the Atlantic Ocean in a tidal zone for chloride ions (XS3m). Their corrosion was carried out using non-destructive testing. In addition, in order to follow the corrosion evolution more accurately in a continuous way, two series of three specimens were casted with embedded sensors and were exposed in two other outdoor sites in Marne-la-Vallée (XC4) and in Eqiom facility (XS3e). The first results of this 20-year project in terms of corrosion of these reinforced concrete specimens obtained with laboratory and field equipment and with monitoring are presented in this paper
Investigating Crack Initiation and Propagation of Concrete in Restrained Shrinkage Circular/Elliptical Ring Test
The restrained ring test, which is recommended by AASHTO and ASTM, has been used for assessing the potential of early-age cracking of concrete and other cement-based materials. Recently, a novel elliptical ring test method has been proposed to replace the circular ring test method for the purpose of shortening ring test duration and observing crack initiation and propagation more conveniently. In order to explore the mechanism of this novel test method, a numerical model is developed to analyze crack initiation and propagation process in restrained concrete rings, in which the effect of concrete shrinkage is simulated by a fictitious temperature drop applied on concrete causing the same strain as that induced by shrinkage. First, an elastic analysis is conducted to obtain the circumferential stress contour of a concrete ring subject to restrained shrinkage. Combined with the fictitious crack model, a fracture mechanics method is introduced to determine crack initiation and propagation, in which crack resistance caused by cohesive force acting on fracture process zone is considered. Finite element analysis is carried out to simulate the evolution of stress intensity factor in
restrained concrete rings subject to circumferential drying. Cracking age and position of a series of
circular/elliptical concrete rings are obtained from numerical analyses which agree reasonably well with
experimental results. It is found that the sudden drop of steel strain observed in the restrained ring test
represents the onset of unstable crack propagation rather than crack initiation. The results given by the
AASHTO/ASTM restrained ring test actually reflects the response of a concrete ring as a structure to
external stimulation, in this case restrained concrete shrinkage.The financial support from the National Natural Science Foundation of China under the grants of NSFC
51478083 & 51421064, Engineering and Physical Sciences Research Council under the grant of EP/I031952/1, and the National Basic Research Program of China (973 Program, Grant No. 2015CB057703) is gratefully acknowledged
Characterization of ready-mixed concrete plants sludge and incorporation into mortars: Origin of pollutants, environmental characterization and impacts on mortars characteristics
International audienc
Reuse of recycled crushed concrete fines as mineral addition in cementitious materials
International audienc
Mix design and carbonation of concrete with high substitution of cement by fly ash
International audienc
Carbonatation de bétons avec forte substitution du ciment Portland par un laitier de haut fourneau
International audienc
Analyse de la cinétique de diffusion du CO2 lors d’un essai de carbonatation accélérée selon la norme XP P 18-458
International audienc
Efficiency of water repellent surface treatment: Experiments on low performance concrete and numerical investigation with pore network model
International audienc
Analysis of the influence of chloride exposure conditions and material properties on the convection zone depth and the corresponding chloride content
International audienc