CNRS Materials and Construction Durability Laboratory

Toulouse, France

CNRS Materials and Construction Durability Laboratory

Toulouse, France

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Maillard P.,Center Technique Of Materiaux Naturels Of Construction Ctmnc | Aubert J.E.,CNRS Materials and Construction Durability Laboratory
Construction and Building Materials | Year: 2014

The study focuses on the thermal and hydric properties of extruded earth bricks. The thermal conductivity and water vapour permeability tests highlight anisotropic behaviour of the bricks depending on the extrusion direction during the production process. The results confirm that the extrusion process has a major influence on the orientation of clay layers and has an impact on the hygrothermal properties. © 2014 Elsevier Ltd. All rights reserved.


Khan I.,CNRS Materials and Construction Durability Laboratory | Francois R.,CNRS Materials and Construction Durability Laboratory | Castel A.,University of New South Wales
Cement and Concrete Research | Year: 2014

This paper studies the evolution of reinforcement corrosion in comparison to corrosion crack width in a highly corroded reinforced concrete beam. Cracking and corrosion maps of the beam were drawn and steel reinforcement was recovered from the beam to observe the corrosion pattern and to measure the loss of mass of steel reinforcement. Maximum steel cross-section loss of the main reinforcement and average steel cross-section loss between stirrups were plotted against the crack width. The experimental results were compared with existing models proposed by Rodriguez et al., Vidal et al. and Zhang et al. Time prediction models for a given opening threshold are also compared to experimental results. Steel cross-section loss for stirrups was also measured and was plotted against the crack width. It was observed that steel cross-section loss in the stirrups had no relationship with the crack width of longitudinal corrosion cracks. © 2013 Elsevier Ltd.


Bejan A.,Duke University | Lorente S.,CNRS Materials and Construction Durability Laboratory
International Journal of Heat and Mass Transfer | Year: 2012

Here we show that the main features of citations history (S-shaped curve, increasing h index, decreasing m quotient) are predictable with the constructal law of how an idea flows over a populated territory. It flows in two ways: fast and long, as "convection" along established channels of researchers interested in the idea, and slow and short, sideways from channels, by "diffusion" to new users. The first regime accounts for the rising portion of the S curve, and the second for the slow-down. Tree-shaped established channels spread the idea faster than single channels over the same area. The complexity of the design of fast channels increases in time due to the evolution of communications technologies. © 2011 Published by Elsevier Ltd. © 2011 Elsevier Ltd. All rights reserved.


Bejan A.,Duke University | Lorente S.,CNRS Materials and Construction Durability Laboratory
Physics of Life Reviews | Year: 2011

The constructal law accounts for the universal phenomenon of generation and evolution of design (configuration, shape, structure, pattern, rhythm). This phenomenon is observed across the board, in animate, inanimate and human systems. The constructal law states the time direction of the evolutionary design phenomenon. It defines the concept of design evolution in physics. Along with the first and second law, the constructal law elevates thermodynamics to a science of systems with configuration. In this article we review the more recent work of our group, with emphasis on the advances made with the constructal law in the natural sciences. Highlighted are the oneness of animate and inanimate designs, the origin of finite-size organs on animals and vehicles, the flow of stresses as the generator of design in solid structures (skeletons, vegetation), the universality and rigidity of hierarchy in all flow systems, and the global design of human flows. Noteworthy is the tapestry of distributed energy systems, which balances nodes of production with networks of distribution on the landscape, and serves as key to energy sustainability and empowerment. At the global level, the constructal law accounts for the geography and design of human movement, wealth and communications. © 2011 Elsevier B.V..


Bejan A.,Duke University | Lorente S.,CNRS Materials and Construction Durability Laboratory
Journal of Applied Physics | Year: 2013

This is a review of the theoretical and applied progress made based on the Constructal law of design and evolution in nature, with emphasis on the last decade. The Constructal law is the law of physics that accounts for the natural tendency of all flow systems (animate and inanimate) to change into configurations that offer progressively greater flow access over time. The progress made with the Constructal law covers the broadest range of science, from heat and fluid flow and geophysics, to animal design, technology evolution, and social organization (economics, government). This review presents the state of this fast growing field, and draws attention to newly opened directions for original research. The Constructal law places the concepts of life, design, and evolution in physics. © 2013 American Institute of Physics.


Zhang R.,Northeastern University China | Castel A.,CNRS Materials and Construction Durability Laboratory | Francois R.,CNRS Materials and Construction Durability Laboratory
Cement and Concrete Research | Year: 2010

This paper deals with the evolution of the corrosion pattern based on two beams corroded by 14 years (beam B1CL1) and 23 years (beam B2CL1) of conservation in a chloride environment. The experimental results indicate that, at the cracking initiation stage and the first stage of cracking propagation, localized corrosion due to chloride ingress is the predominant corrosion pattern and pitting corrosion is the main factor that influences the cracking process. As corrosion cracking increases, general corrosion develops rapidly and gradually becomes predominant in the second stage of cracking propagation. A comparison between existing models and experimental results illustrates that, although Vidal et al.'s model can better predict the reinforcement corrosion of beam B1CL1 under localized corrosion, it cannot predict the corrosion of beam B2CL1 under general corrosion. Also, Rodriguez's model, derived from the general corrosion due to electrically accelerated corrosion experiments, cannot match natural chloride corrosion irrespective of whether corrosion is localized or general. Thus, for natural general corrosion in the second stage of cracking propagation, a new model based on the parameter of average steel cross-section loss is put forward to predict steel corrosion from corrosion cracking. © 2009 Elsevier Ltd. All rights reserved.


Dang V.H.,CNRS Materials and Construction Durability Laboratory | Francois R.,CNRS Materials and Construction Durability Laboratory
Engineering Structures | Year: 2013

The structural performance of a 27-year-old corroded beam was investigated. The cross-sectional area loss, load-carrying capacity, mid-span deflection and force-elongation of some of the corroded reinforcing steel bars were measured. It was found that the mechanical performance after 27. years of heavy corrosion was reduced in terms of both ultimate load and ductility but that ductility would be potentially the biggest problem for the requalification of corroded reinforced concrete members according to the prescriptions of standards. The experimental results revealed a more brittle failure mode of the corroded RC beam in comparison with the ductile failure mode of a control beam of the same age. This was linked to the change in mechanical properties of corroded steel bars in comparison with non-corroded bars. © 2012 Elsevier Ltd.


Zhu W.,CNRS Materials and Construction Durability Laboratory | Francois R.,CNRS Materials and Construction Durability Laboratory
Construction and Building Materials | Year: 2014

This paper presents the reinforcement corrosion process and the results of experiments on a highly corroded beam subjected to a chloride environment for 26 years so as to assess the residual performance of long-term-corrosion-damaged beams. A cracking map was drawn for the corroded beam, which was then tested by a three-point loading system until failure, as was a control beam of the same age. Force displacement curves were recorded for both beams. The corrosion distribution and loss of diameter of the steel bars were studied for the reinforcement. Tension tests of the tensile bars were carried out, and stress strain curves of the tension experiments were also plotted. From the results, it appears that corrosion has a significant impact on the reinforcing bar behavior, and on the load-bearing capacity, stiffness and deflection of the beam. © 2013 Elsevier B.V. All rights reserved.


Bertron A.,CNRS Materials and Construction Durability Laboratory
Materials and Structures/Materiaux et Constructions | Year: 2014

Building materials can be exposed to microorganisms (mainly bacteria, fungi and algae) in almost every aqueous medium or damp environment, water being the indispensable condition for life development. The activity of microorganisms can be responsible for mineralogical, chemical and microstructural damage to the material (biodeterioration). Deleterious effects can also concern the aesthetics of a building (proliferation of colored biological stains on façades and roofs) or the quality of indoor air (presence of microorganisms in damp buildings). However, microorganisms can also have positive effects (healing of materials) and their action is explored through the development of bio-based protective systems intended for building materials. In all cases, understanding interactions between building materials and microorganisms is an indispensable step toward the development of more sustainable, better quality, safer structures in many environments. This paper presents two examples where the action of microorganisms has—or is likely to have—strong impact on the durability and safety of concrete structures. The first example concerns the biodeterioration of concrete in agricultural and agro-food environments. The second example is that of the abiotic and biotic reactivity of nitrates in repository of intermediate-level long-lived nuclear wastes. The paper presents the approaches used to explore and understand the phenomenology of bio-geo-chemical interactions in these complex environments. These studies notably comprise the development of test methods and experimental pilots to enable these explorations to be carried out. Current shortcomings in the scientific literature and in the standardization environment are also highlighted. © 2014, The Author(s).


Francois R.,CNRS Materials and Construction Durability Laboratory | Khan I.,CNRS Materials and Construction Durability Laboratory | Dang V.H.,CNRS Materials and Construction Durability Laboratory
Materials and Structures/Materiaux et Constructions | Year: 2013

This paper deals with the impact of corrosion on the mechanical properties of steel in reinforced concrete. Steel bars were extracted from a 27-year-old corroded reinforced concrete beam that had been exposed to a chloride environment. Bars with different degrees of corrosion and with different corrosion pit depths were tested in tension. A comparison was made between nominal and true stress for corroded and control steel specimens. It was noted that the degree of corrosion strongly affected the mechanical properties of the steel, particularly the ultimate stress and strain. Interestingly, the true yield strength of all the corroded steel bars remained almost constant while their true ultimate strength was considerably increased. A reduction of the ultimate elongation appeared to be the major effect of corrosion and affected the compliance with standards. © 2012 RILEM.

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