Overview
ABSTRACT
While the reactivity of surfaces of concrete directly influences its aesthetics and durability, new surface functionalizations intended to widen the field of use of concrete are emerging by using the reactivity of certain loads.
The aim of this article is to explain how the surface reactivity of concrete can be related to its chemical composition and to interactions with its environment. Many examples related to the presence of ions in solution, the formwork conditions, the use of particular charges in the mixture and the application of protective coatings are detailed in this article.
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Matthieu HORGNIES: Doctor, HDR - Research associate - LafargeHolcim Innovation Center (Saint Quentin-Fallavier, France)
INTRODUCTION
The reactivity of concrete surfaces is a complex subject that can be defined by the interactions at the interface between the microstructure of a hydraulic binder-based material and the external environment, the latter of which can consist of various gases (CO 2 , NO 2 ), liquid water (more or less loaded with salts), stripping products (or residues) and even micro-organisms (molds, algae...).
The aim of this article is to describe the variability of possible reactions between the concrete surface and its immediate environment, whether during hydration and hardening, or carbonation and ageing. Various examples will be presented to explain the type of reaction taking place at the surface, with the interactions detailed in this article separated into three groups:
those resulting from reactions with liquid water or ions present in solution: hydration phenomena at an early age, efflorescence formation after formwork stripping, leaching and decalcification following recurrent exposure to water, acid attack, interactions with sulfates and penetration of chloride ions ;
those resulting from interactions with formwork components, such as moulds and stripping agents: influences of stripping oils, contamination and functionalization with certain moulds, portlandite growth favoured by certain surfactants ;
those resulting from interactions with the environment: carbonation in the presence of CO 2 , depollution of certain irritating or toxic gases, growth of micro-organisms.
Finally, the last chapter will describe the functionalities provided by the various types of protective coatings potentially applicable on concrete, and their implications with regard to the interactions previously described.
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KEYWORDS
surface | degradation | functionalization | Shuttering | concrete | reactivity
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Corrosion - Aging
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Reactivity of concrete surfaces
Bibliography
- (1) - VERNET (C.), LUKASIK (J.), PRAT (E.) - Nanostructure, porosity, permeability, and diffusivity of Ultra high performance concretes (UHPC). – - Proceedings of the International Symposium on High Performance Concrete and Reactive Powder Concrete, Edited by AITCIN (P.C.) and DELAGRAVE (Y.), p. 17 (1998).
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Standards and norms
- ISO Acoustique : méthode de calcul du niveau d'isotonie. - ISO 532 1975 ISO - 1975
- AFNOR Tests for fresh concrete – Part 5: Impact table spread test - NF EN 12350-5 AFNOR - 2005
- AFNOR Clay roof tiles for discontinuous laying – Determining physical characteristics – Part 1: Impermeability test - NF EN 539-1 AFNOR - 2006
- ISO Fine ceramics (advanced ceramics, advanced technical ceramics) – Test method...
Patents
Concrete element having a superhydrophobic surface WO2011095744.
Use of a concrete-based element for the treatment of gases and volatile compounds EP2488279, WO2011045509.
Concrete article comprising a surface with low open porosity EP2603471, WO2012020012.
Cement-based paving blocks for photocatalytic paving for the abatement of urban pollutants EP1601626....
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CABOT Corporation
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http://www.techni-moulage.com/entreprise.moulage.drome.shtml
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