Utilisation de l'absorption d'eau des bétons comme critères de leur durabilité—Application aux bétons de granulats recyclés

Abstract

RI~SUMI~ A 13 S T R A C TLes granulats issus du recyclage des produits de d4molition s'inscrivent dans le cadre des mat~riaux locaux de substitution, mais leur valorisation dans les b&ons hydrauliques est actuellement frein& par le fait qu'ils sont consid&& comme (~ granulats hors normes >>. On les suspecte ainsi d'avoir des cons4quences ndfastes sur la durabilit~ des b&ons.Les ph~nom~nes de transport, dont l'absorption d'eau par capillarit& s'avhrent &re primordiaux vis ~ vis de la durabilit8 des b&ons ~ base de granulats recycl& compte tenu de leur rapport eau totale/ciment ~lev& Uinfluence de la composition de ce genre de b&on et de leur cure sur le processus d'absorption d'eau a 4t6 4tudi4e : l'absorption initiale, repr&entative de la dimension des gros capillaires, et l'absorptivit4, repr&entative du volume des capillaires fins ont 4t~ mesur&s.Les b&ons de granulats recycl& absorbent une quan-tit4 d'eau plus importante que les b&ons naturels de contr61e. Ils sont donc plus vuln&ables ~ diverses agressions. Malgrd tout, selon les seuils propos& dans la littG rature, ils peuvent 6tre qualifi& de qualit4 (~ moyenne >~. Uemploi de b&ons ~ base de sable naturel et de gravillon recycl~ (b&on mixte) peut ~galement &re envisag~ dans des conditions d'agressivit4 moyenne.Aggregates produced by the recycling of building wastes could be used as local substitute materials in construction, but their benefit to hydraulic concrete has not been fully exploited due to the fact that they are not "standard". They are indeed suspected of having a very bad influence on the durability of concrete.As a matter of fact, transfer phenomena, including the absorption of water by capillarity, play an essential role in the durability of recycled aggregate concrete (RAC in short) considering their high total water/cement ratio. The influence of the RAC composition and the curing conditions on the water absorption process has been studied: the initial absorption, representing the size of large capillaries and the absorptivity, representing the volume of the fine capillaries, have been measured.The RAC absorb a more important quantity of water than natural concretes do. They are therefore more vulnerable to various aggressions. Despite this fact, according to standard thresholds given in the literature, their quality can aptly be described as "average". River sand and coarse recycled aggregate concrete that we call "mixed concrete" can also be considered for usage in average aggressive conditions. iiiiiiiiiiiiiiil ~

Durability Parameters of Reinforced Recycled Aggregate Concrete: Case Study

“…In some investigations [10,24], similar values and trends of porosity were found as a function of RCA amount in concrete. In other works [27,31,32], it was found that in concrete with RFA, the amount of water absorbed (implicit porosity) increases.…”

Chloride migration in structural lightweight aggregate concrete produced with different binders

“…Several authors have tested the transport properties of concrete to indirectly characterize its durability [35][36][37][38][39][40][41][42]. Air permeability, electrical resistivity [43] and capillary absorption tests [38,44] are usually regarded as the most appropriate for evaluating concrete durability.…”

Caracterização de agregados de resíduos de construção e demolição reciclados e a influência de suas características no comportamento de concretos.

“…Na Espanha, um estudo analisou os agregados graúdos obtidos a partir de 15 A porosidade, que é uma propriedade que está intimamente relacionada com as propriedades físicas dos agregados, pode ser um critério mais interessante, por influenciar a resistência mecânica e durabilidade dos concretos (CALLISTER, 2000;MEHTA;MONTEIRO, 1994;LIMBACHIA et al, 2000;WIRQUIN et al, 2000).…”