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 ▲]

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 ▲]

Durability of mortar and concretes containing slag with low hydraulic activity

in Cement & Concrete Composites (2012), 34(5), 671677

Granulated blast furnace slag has been widely used as a partial substitute for Portland cement in many applications because of advantages which include cost reduction, reduction in heat evolution and ... [more ▼]

Granulated blast furnace slag has been widely used as a partial substitute for Portland cement in many applications because of advantages which include cost reduction, reduction in heat evolution and improvement of durability properties. However, the effectiveness of slag depends on its hydraulic reactivity. In this paper, the results of an experimental study on the effect of slag with low hydraulicity on the mechanical and durability properties of concrete and the performance of mortar under sulfate attack are discussed. Special attention is given to gas permeability and water absorption of slag concrete. The durability of slag concrete is improved at long term at low Water/Binder ratio. Sulfate resistance of mortar is improved by slag replacement up to 30%. [less ▲]

Characterization of fine aggregates in concrete by different experimental approaches

in Proceedings 13 Int. Congress for Stereology (2011, October)

Being its major component, aggregate can occupy up to three-quarter of the volume of concrete. The structure of aggregate formed in hardened state impacts largely on mechanical and durability properties ... [more ▼]

Being its major component, aggregate can occupy up to three-quarter of the volume of concrete. The structure of aggregate formed in hardened state impacts largely on mechanical and durability properties of concrete. On another hand, physical characteristics of aggregate are primarily assumed to be relevant to granular behavior of aggregate. Therefore, characterization of aggregate is of high relevance to concrete studies. In this study, different types of fine aggregate used in concrete, namely river sand and crushed limestone, are selected for morphological characterization. Traditional sieve analysis and laser diffraction method are employed for separation and size analysis of specimens. Different types of fine aggregate samples with comparable size ranges are then analyzed by two advanced dry (static) and wet (dynamic) image analysers. These new analysers are especially suitable for characterization of fine particles, which is difficult by traditional image analysis equipments. Size and shape characteristics of different fine aggregates will be revealed by different experimental methods. The results on different parameters for shape characterization will be compared and discussed. [less ▲]

Mineralization of bio-based materials: effect on cement-based mix properties

in Bulletin of the Polytechnic Institute of Jassy, Construction. Architecture Section (2011), LIV(LVIII),

The lightweight concrete with bio-based products knows an interesting development in the construction field, especially as thermal insulation panels for walls in buildings. Before identifying and ... [more ▼]

The lightweight concrete with bio-based products knows an interesting development in the construction field, especially as thermal insulation panels for walls in buildings. Before identifying and quantifying the basic physical characteristics of concrete made from wood, miscanthus, hemp or bamboo (acoustic and thermal properties in particular), it is necessary to optimize the composition of the product. It is clear that the final product is not unique and a compromise has to be found between insulation and mechanical properties. The long term stability as well as the reinforcement may be obtained by means of a mineralization process of the natural product: a preparation with a lime and/or cement-based material is necessary to reinforce the cohesion of the bio-based product. Optical and SEM analysis helped to clearly understand the interactions between the bio-based fibrous material and the cementitious materials, the quality of the bond and their effects on the properties of the cement-based concrete products. [less ▲]

Saturation level of the superficial zone of concrete and adhesion of repair systems

in Construction & Building Materials (2011), 25((5)), 2488-2494

Appropriate surface saturation level is essential for the durability of the repaired structure. The repair material is often blamed for ‘‘not sticking’’, although the general source of the trouble lies ... [more ▼]

Appropriate surface saturation level is essential for the durability of the repaired structure. The repair material is often blamed for ‘‘not sticking’’, although the general source of the trouble lies with the substrate surface conditioning. An extensive research project has been undertaken to develop specifications and performance criteria for surface preparation of concrete substrates. A field test was developed to evaluate the optimum moisture conditioning of the substrate concrete prior to application of repair material; this has been calibrated and compared with destructive and non-destructive on three types of concrete and two types of surface preparation. In order to evaluate different saturation levels, concrete samples have been stored in more than 12 modes of conservation. Finally, repair mortars have been applied on concrete substrates and adhesion was measured for different concrete surface saturation levels. Initial Surface Absorption Test (ISAT) can be used as an attractive quantitative test to evaluate saturation level of concrete substrate. Moreover, it is clearly shown that saturation levels higher than 50% and lower than 90% are requested for promoting adhesion of PCC mortars. [less ▲]

The evaluation of the surface free energy of liquids and solids in concrete technology

in Construction & Building Materials (2011), 25

This paper presents initial results from an extensive study on the calculation of the surface free energy of mineral materials. The usefulness of such evaluation is demonstrated through the technological ... [more ▼]

This paper presents initial results from an extensive study on the calculation of the surface free energy of mineral materials. The usefulness of such evaluation is demonstrated through the technological operation of casting and moulding concrete. Surface interactions will firstly act on the dispersion of particles inside the concrete mix and the viscosity of the fresh material; the specific effect of superplasticizers and Modifying Viscosity Agent is presented through the determination of surface free energy properties. The second analysis is dealing with the interactions between mineral and vegetal oils applied on the wooden or steel formwork and fresh concrete. The evaluation of contact angle and interfacial forces help to efficiently select the most appropriate material. [less ▲]

Influence of particle flatness and elongation on size distributions obtained from laser diffraction, static and dynamic image analysis.

in World Congress on Particle Technology (2010, April)

Le béton apparent: influence de l'état du moule sur l'aspect des surfaces

in Benboudjema, Farid (Ed.) Compte-rendu des Journées Scientifiques du (RF)2B (2009)

L’aspect d’un parement en béton (teinte et bullage) dépend entre autres de la surface de coffrage utilisée. L’influence du nombre de réutilisations des coffrages sur la teinte et le bullage de surface a ... [more ▼]

L’aspect d’un parement en béton (teinte et bullage) dépend entre autres de la surface de coffrage utilisée. L’influence du nombre de réutilisations des coffrages sur la teinte et le bullage de surface a été étudiée. Deux séries de moules en bois contreplaqué et OBS ont été usés afin de simuler de 1 à 118 réutilisations pour le contreplaqué et de 2 à 51 réutilisations pour le bois OSB. Les moules ont ensuite été utilisés pour couler des cubes de béton. La première série a été coulée en utilisant une huile végétale et la deuxième une huile minérale. La teinte et le bullage en surface des bétons coulés ont été mesurés et étudiés au travers d’une étude statistique afin de déterminer l’influence de la réutilisation des coffrages sur l’aspect des parements. [less ▲]

Use of concrete road recycled aggregates for Roller Compacted Concrete

in Construction & Building Materials (2009), 24((3)), 390-395

Construction waste management is a quite important economical and environmental deal for our societies. More than 2 million tons demolition and construction wastes are annually produced only in Wallonia ... [more ▼]

Construction waste management is a quite important economical and environmental deal for our societies. More than 2 million tons demolition and construction wastes are annually produced only in Wallonia, Southern Region of Belgium; recycling has clearly to be promoted. Roller Compacted Concrete (RCC) is a special dry concrete made of aggregates, water and low quantity of cement, laid down and compacted like a soil, for the construction of massive structures like dams or large horizontal surfaces like road foundations. The topic of this research is the replacement of natural aggregates by concrete road recycled aggregates in the mix design of concrete. Characteristics of aggregates are of prime importance for the quality of the concrete: Los Angeles, water absorption and specific gravity. It has been observed that RCC with natural and concrete road recycled aggregates are similar for solid compactness, while no major influence of cement content – when around 200 kg - may be detected. However, compressive strength is higher for RCC with natural aggregates. This study clearly shows the opportunity of using concrete road recycled aggregates for RCC in basements. [less ▲]