Relationship between surface characteristics and superficial cohesion of concrete

in Beushausen, H.; Dehn, F.; Alexander, M. G. (Eds.) Concrete Repair, Rehabilitation and Retrofitting (2006)

Existing concrete surfaces have to be prepared before the application of a new layer. Different surface treatments (grinding, sandblasting, shotblasting, hand- and mechanical milling) have been performed ... [more ▼]

Existing concrete surfaces have to be prepared before the application of a new layer. Different surface treatments (grinding, sandblasting, shotblasting, hand- and mechanical milling) have been performed and the quality of the preparation has been established on the base of three main parameters: surface roughness, superficial concrete microcracking and adhesion. Cracks have been systematically observed, in relation with surface treatment by means of Scanning Electron Microscope and Light Microscope. Finally, a repair mortar, with or without bond coat, has been applied on the concrete substrates and adhesion has been measured. Analysis of results clearly show the effect of roughness on adhesion in the case where no bond coat is used, the influence of the surface treatment on the waviness shape of the profile and the presence of microcracks in the near-to-surface layer, which is related to failure type. [less ▲]

Utilisation des fillers dans les bétons

Report (2006)

Utilisation des matières - Problématique 15 : Le cycle de vie des matières – matériaux de construction

Report (2006)

Adhesion of repair systems to concrete: influence of interfacial topography and transport phenomena

in Magazine of Concrete Research (2005), 57(5), 273-282

Eight types of cement slurries were applied to concrete substrates. Surface preparation involved mechanical action - sandblasting and polishing - as well as saturation regulation, both dry and saturated ... [more ▼]

Eight types of cement slurries were applied to concrete substrates. Surface preparation involved mechanical action - sandblasting and polishing - as well as saturation regulation, both dry and saturated surface wet. The adhesion strength for the different combinations was measured by direct tensile tests. Multivariate statistical analysis led to the identification of a major effect of surface saturation on the results. Knowledge of the interfacial behaviour was obtained by the discrimination of the effects of partial interaction between slurry and aggregates and slurry and cement mortar respectively. It clearly showed that a third factor has to be taken into account in the explanation of adhesion, namely the interfacial transition zone between cement paste and aggregates, due to its porosity and anchoring effect. This effect was quantified by topographical observation and image analysis. Penetration of cement slurry was also confirmed by observation with binocular and fluorescent microscopy. [less ▲]

Effect of concrete surface treatment on adhesion in repair systems

in Magazine of Concrete Research (2005), 57(1), 49-60

Existing concrete surfaces need to be roughened to a profile necessary to achieve mechanical interlocking with any repair material. In this study, different surface treatments (e.g. grinding, sandblasting ... [more ▼]

Existing concrete surfaces need to be roughened to a profile necessary to achieve mechanical interlocking with any repair material. In this study, different surface treatments (e.g. grinding, sandblasting, shotblasting, hand- and mechanical milling) were performed and the quality of the preparation established on the basis of three main parameters: surface geometry, superficial concrete microcracking and adhesion. Surface geometry was characterised on the basis of the measurement of surface profile-profilometry-and the analysis of statistical and amplitude parameters calculated from the waviness (lower frequencies) and the roughness (higher frequencies) profiles of the surface. Investigations were also performed to assess the quality of the superficial zone of concrete and cracks were systematically observed in relation to surface treatment where both scanning electron microscopy and light microscopy were used for analysis. Finally, a repair mortar with or without bond coat, was applied to the concrete substrates in order to measure adhesion. Relationships clearly show the effect of roughness on adhesion in the case where no bond coat was used and also the influence of the power of the surface treatment on the waviness shape of the profile and the presence of microcracks in the near-surface layer related to failure type. [less ▲]

Use of municipal solid waste incineration residues in concrete pavement setts

in Proceedings of CONMAT'05 and Midness Symposium (2005)

Valorisation of Municipal Solid Waste Incineration Residues - excluding ashes - is a positive advance in sustainable development : saving natural resources, decrease of wastes volume stored, reduction of ... [more ▼]

Valorisation of Municipal Solid Waste Incineration Residues - excluding ashes - is a positive advance in sustainable development : saving natural resources, decrease of wastes volume stored, reduction of energy consumption. If good conditions of incineration can be ensured and post-combustion treatments are realised, solid residues are in the form of granular materials usable in construction and civil engineering. Application for the fabrication of concrete pavement has been developed. Mechanical and physical performances of municipal solid waste incineration residues let us to replace a part of the granular skeleton and to obtain similar behaviour than for reference granular composition : splitting resistance, water absorption and resistance to abrasion are optimised. Leaching behaviour is also verified in order to avoid detrimental effect on the environment. Example of application is presented in “sleeping policeman” technique and durability of the structure is explained. [less ▲]

Some effects of limestone fillers as a partial substitute for cement in mortar composition

in Banthia, N. (Ed.) Third International Conference on construction materials: performance, innovations and structural implications (2005)

Limestone filler is a raw material that is already used in several applications like paints, bricks, bituminous mixes, … Moreover, and particularly in Belgium, classical additions like fly ashes and blast ... [more ▼]

Limestone filler is a raw material that is already used in several applications like paints, bricks, bituminous mixes, … Moreover, and particularly in Belgium, classical additions like fly ashes and blast furnace slags become rare. There is a need for new additions that could have a positive effect on the properties of the fresh and hardened cementitous composites. Substitution of limestone filler in Portland cement and blast furnace slag cement has been realized between 15 and 30% in mass. In addition to the characterization of the powder itself – specific mass, specific surface and laser granulometry – the problem of the water demand has been analysed: it seems that it remains constant with the substitution rate. Electric conductivity has also been performed in order to study the evolution of the “dormant” period. Tests on hardened mortars concerned the mechanical properties, the evolution of the porosity and the durability. The K factor indicates a higher value and the porosity seems to be better in the case of blast furnace slags cements, partially due to a very low diameter of the slags particles. Oxygen permeability doesn’t seem to be influenced by the filler while capillary absorption increases with substitution rate. Finally, chloride penetration, sulphate resistance and carbonation rate show quite interesting behaviours, leading to the conclusion that this material needs again more investigations in order to define optimum application conditions in cementitous matrixes [less ▲]

Use of Concrete Recycled Aggregates in Roller Compacted Concrete

in Vasquez, E.; Hendricks, Ch F; Hansen, G. (Eds.) Recycled Materials in Building and Structures (2005)

Construction waste management is a quite important economical and environmental deal for our societies. More than 2 million tons are annually produced in Wallonia, South Region of Belgium, and numerous ... [more ▼]

Construction waste management is a quite important economical and environmental deal for our societies. More than 2 million tons are annually produced in Wallonia, South Region of Belgium, and numerous valorisations have been already promoted. Roller Compacted Concrete 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 recycled aggregates in the composition of the concrete. Characteristics of aggregates are of prime importance for the quality of the concrete: Los Angeles, water absorption and specific gravity are measured. Design method, type of hydraulic binder and proportions have to be adapted. Final and long term properties have also been evaluated. [less ▲]

Etude de la consolidation du béton frais sur base de la porosité à l'état durci

in Courard, Luc (Ed.) Compte-rendu des Journées Scinetifiques du (RF)2B (2004)

La consolidation est le terme qui désigne la sédimentation des grains dans les suspensions très denses comme le béton. Le resserrement du squelette granulaire du béton frais entraîne une exsudation d’eau ... [more ▼]

La consolidation est le terme qui désigne la sédimentation des grains dans les suspensions très denses comme le béton. Le resserrement du squelette granulaire du béton frais entraîne une exsudation d’eau qui s’accumule à la surface de l’échantillon, formant la couche d’eau de ressuage. Cette migration de l’eau est à l’origine de nombreux défauts dans le béton qui mettent en péril sa durabilité. Le but de ce travail est de mettre en évidence l’existence d’une relation entre le ressuage et la porosité à l’état durci du béton. [less ▲]

A capillary action test for the investigation of adhesion in repair technology

in Canadian Journal of Civil Engineering (2003), 30(6), 1101-1110

When repair material is laid down on a concrete substrate, the porosity of concrete allows it to penetrate the substrate, increasing the probability of physical interactions, and subsequently increasing ... [more ▼]

When repair material is laid down on a concrete substrate, the porosity of concrete allows it to penetrate the substrate, increasing the probability of physical interactions, and subsequently increasing adhesion. Water absorption by immersion or usual capillary action tests do not provide enough information to understand what happens when contact occurs between the concrete substrate and the cement slurries used as a bonding layer. An adaptation of the capillary action test is presented; this is based on a continuous measurement of mass change of the sample. Major differences according to the type of surface preparation are pointed out: absorption rates as well as mass changes are greater for polished concrete substrates than for sandblasted ones. Centrifuged solutions of cement slurries modified with plasticizers and superplasticizers are used for water replacement in the adapted capillary action test. Results clearly show the influence of these admixtures: the greater the adhesion tension, the greater the wetting of the concrete substrate. Determination of these thermodynamic characteristics and performance of an adapted capillary action test provide a better understanding of the mechanisms of interface creation and promotion of adhesion. [less ▲]