Determination of Moisture Diffusivity During Drying of Mortar Cement: Experimental and Modeling Study

in International Journal of Energy Engineering (2013), 3(1), 1-6

The aim of this study is the experimental characterization of the behaviour of a mortar during convective drying. We focalise on mortar that has a rate water-cement of 0.5. The drying tests are developed ... [more ▼]

The aim of this study is the experimental characterization of the behaviour of a mortar during convective drying. We focalise on mortar that has a rate water-cement of 0.5. The drying tests are developed in a micro-convective dryer that can use samples weighing from 0 to 8g. The advantage of these experiments is to reproduce the natural conditions that can be found during the treatment of the mortar-atmosphere problems. The response of the drying curve or the drying kinetic depends on the applied drying conditions. So, the temperature of the air varies from 60°C to 130°C, the velocity of the air is changed from 2 m.s-1 to 5 m. s-1and the relative humidity is kept less than 1.7%. The comparison between the experimental results and the proposed analytical solutions of the equation of diffusion represented by Fick’s law, applied for a finite shape, allows determination of the values of the diffusion coefficient. It has a value of 1.71×10-10 m2.s-1 at 60°C, 13.69×10-10 m2.s-1 at 90°C and 16.27×10-10 m2.s-1 at 130°C. Calculation of the activation energy and the D0 constant are also possible. [less ▲]

Eco-efficacité et éco-efficience: un nouveau paradigme en construction(s)

Conference (2012, November 20)

Spécificités des dégradations dans les bétons du patrimoine

in Conservation et restauration des bétons du patrimoine moderniste (2012, November 09)

Detection of thin layers into concrete with static and CMP measurements

in 2012 14th International Conference on Ground Penetrating Radar (GPR) (2012, June)

Most concrete bridge decks contain a thin waterproofing layer, whose complex GPR signature can affect the detection of disorders or delaminations into the slab. In this study, we characterized the ... [more ▼]

Most concrete bridge decks contain a thin waterproofing layer, whose complex GPR signature can affect the detection of disorders or delaminations into the slab. In this study, we characterized the detection limits of our 2.3 GHz antenna for the detection of thin layers, with static and CMP measurements. In this last configuration, we showed that the radiation pattern and the reflection coefficient estimation are key parameters to use the inversion of the amplitude versus offset (AVO) curves for the estimation of the layer parameters. The theoretical results were compared to the results of FDTD simulations, performed with GprMax2D, and to laboratory measurements, performed on concrete slabs or sand containing thin layers. [less ▲]

Quels critères de choix pour les matériaux de demain?

Scientific conference (2012, May 09)

Effet de l'empilement et de la forme des additions dans les propriétés des liants à matrice cimentaire

in Georgin, Jean-François (Ed.) Compte-rendu des Journées Scientifiques du (RF)2B (2012)

Cement blending with mineral admixtures, especially with by-product or waste product powder, can effectively reduce consumption of cement and promote the ecology. Recently, an innovative concept was ... [more ▼]

Cement blending with mineral admixtures, especially with by-product or waste product powder, can effectively reduce consumption of cement and promote the ecology. Recently, an innovative concept was proposed to replace of “coarse” cement grains by the inert fillers for sustainable cement in the low w/c concrete cement. As a basic mechanism, particle packing plays an important role in such replacement or blending. In the first part of study, the paper discusses the particle packing aspect of cement grains, limestone filler (LF) and LF blended cement. The new developed wet packing method and a dry packing method are proposed for the evaluation purpose. Particle size distributions (PSDs) and particle shape of different powders are firstly characterized by an advanced image analysis system. The paper presents results of packing tests with the influences of PSD, particle shape, cement type, vibration, mixing, superplasticizer (SP), blending proportions, etc. The advantages and limitations of two packing methods are also discussed in this paper. [less ▲]

Supplementary Cementitious Materials for Concrete: Characterization Needs

in Proceedings of the XXI International Materials Research (2012)

A wide variety of materials are currently used as supplementary cementitious materials (SCMs) for concrete, including natural materials and byproducts from various industries. Historically, natural SCMs ... [more ▼]

A wide variety of materials are currently used as supplementary cementitious materials (SCMs) for concrete, including natural materials and byproducts from various industries. Historically, natural SCMs, mostly derived from volcanic deposits, were common in concrete. In recent years, the dominant SCMs have been industrial by-products such as fly ash, ground granulated blast furnace slag (GGBFS), and silica fume. There is currently a resurgence of research into historic and natural SCMs, as well as other alternative SCMs for many reasons. The primary benefits of SCM use in improvement of long-term mechanical performance, durability, and sustainability are widely accepted, so local demand for these materials can exceed supply. This paper describes some of the SCMs that are attracting attention in the global research community and the properties and characteristics of these materials that affect their performance. Special attention is paid to the importance and demands of material characterization. Many SCMs do not necessarily lend themselves to characterization methods used in standardized test methods, which sometimes fail to describe the properties that are most important in predicting reactivity. [less ▲]

Topography evaluation methods for concrete substrates: parametric study

in Alexander, Mark (Ed.) Concrete Repair, Rehabilitation and Retrofitting III (2012)

Research projects performed at the University of Liege, Laval University and the Warsaw University of Technology have pointed out the importance of taking care about the surface roughness of concrete ... [more ▼]

Research projects performed at the University of Liege, Laval University and the Warsaw University of Technology have pointed out the importance of taking care about the surface roughness of concrete substrate with regards to the adhesion of repair materials. This paper wants to make a State-of-Art on this specific problem: surfometry methods, interface analysis, adhesion measurements, …etc are presented, interpreted and compared. Surfology, which is a more wide concept, contributes to understand what will make the contact effective or not, and allow interactions of variable intensities between the materials. Different scales of observation – micro to macro - are needed to exactly represent what happens when materials are put into contact. [less ▲]

Comparison of Destructive Methods to Appraise the Mechanical Integrity of a Concrete Surface

in Concrete Repair Bulletin (2012), 25(4), 22-30

Depending on the technique being used, the concrete removal operation prior to repair can be harmful to the residual concrete skin left on the structure. Whenever a tight bond between the repair and the ... [more ▼]

Depending on the technique being used, the concrete removal operation prior to repair can be harmful to the residual concrete skin left on the structure. Whenever a tight bond between the repair and the old concrete is required, the soundness of the prepared surface should thus be assessed. Although this is widely recognized, there is no standard method intended to characterize the integrity of a concrete substrate after concrete removal. This paper presents the results of an investigation intended to assess and compare quantitatively different test methods, namely the Schmidt rebound hammer, the pull-out test and the pull-off test, to evaluate superficial mechanical integrity of a substrate after concrete removal operations. Although it does not yield a precise evaluation of compressive strength, the Schmidt rebound hammer test is recognized as a useful tool for performing quick surveys to assess concrete uniformity. The pull-off test is very well correlated with the splitting-tensile test, but it is not suited for vertical and overhead surfaces. The Capo pull-out test has limited interest for surface preparation, as it is applicable to flat surfaces only. Conversely, the accelerated pull-out test showed interesting potential as a simple and relatively rapid means for assessing the mechanical integrity of a concrete surface prior to repair for any type of concrete surface. More work is definitely required to refine the procedures and develop performance criteria. Nevertheless, it appears from the results generated in this study that the combination Schmidt hammer / pull-off test could fill the needs for the evaluation of horizontal surfaces after concrete removal, while the combination Schmidt hammer / accelerated pull-out test could be used effectively on vertical and overhead surfaces. [less ▲]

Effet de l’empilement et de la forme des additions sur les propriétés des liants à matrice cimentaire

in Georgin, Jean-François (Ed.) Recueil des communications des journées scientifiques du (RF)²B (2012)

Mélanger le ciment avec des additions minérales, en particulier avec des sous-produits industriels, permet de réduire efficacement la consommation de ciment et de réduire son impact environnemental ... [more ▼]

Mélanger le ciment avec des additions minérales, en particulier avec des sous-produits industriels, permet de réduire efficacement la consommation de ciment et de réduire son impact environnemental. Récemment, un concept novateur a été proposé en vue de remplacer les plus gros grains de ciment par les charges inertes, en vue du développement d’un ciment durable. En tant que mécanisme de base, l’empilement des particules joue un rôle important dans le remplacement ou le mélange. Dans la première partie de l'étude, l’empilement des grains de ciment, de filler calcaire (LF) et de ciment mélangé est abordé. Une nouvelle méthode, basée sur l’empilement en phase humide, est comparée à une méthode d'empilement à sec. La distribution de taille des particules (PSD) et la forme des particules des différentes poudres sont caractérisées sur base d’un système d'analyse d'image avancée. Le document présente les résultats des tests d’empilement avec l’influence du paramètre PSD, de la forme des particules, du type de ciment, de l’énergie de vibration, du mélange et du superplastifiant (Sp). Les avantages et les limites des deux méthodes sont également discutés. [less ▲]