Article

La méthode du mortier de béton équivalent (MBE)—Un nouvel outil d’aide à la formulation des bétons adjuvantés

Materials and Structures (Impact Factor: 1.39). 04/2012; 33(8):475-482. DOI: 10.1007/BF02480524

ABSTRACT L’article présente une nouvelle méthode d’aide à la formulation des bétons adjuvantés. Elle consiste à concevoir, à partir
d’une composition de béton, un mortier, dit mortier de béton équivalent (MBE), dont les propriétés rhéologiques sont corrélables
à celles du béton. Le but est de diminuer le nombre de gâchées de béton. La démarche de mise au point de la méthode, son champ
d’application et ses limites sont présentés. Le mode opératoire ainsi que le matériel nécessaire sont détaillés. Un exemple
de corrélation entre les propriétés rhéologiques mesurées sur MBE et celles mesurées sur le béton associé est présenté. Parallèlement
aux suivis rhéologiques, des suivis thermiques sur MBE peuvent être effectués. Ils permettent d’anticiper les effects de différents
adjuvants sur le temps de prise du béton. On montre que les décalages observés par suivi thermique traduisent bien les écarts
de résistances aux très courtes échéances. En associant suivis rhéologiques et suivis thermiques, la méthode MBE permet de
sélectionner rapidement parmi différents adjuvants celui qui répond le mieux aux exigences d’efficacité (rapport dosage/coût),
de maintien rhéologique et de délai de décoffrage.
This paper deals with a new method to design concrete containing admixture. Its principle is to design a mortar, deduced from
the concrete composition and called concrete equivalent mortar (CEM), for which the rheological properties display correlation
with those of concrete. The aim is to reduce the amount of concrete batches. This article presents the scientific approach
which has led to this method, its field application and limits. The test procedure and the apparatus are detailed. An example
of correlation between the rheological properties measured on CEM and on the corresponding concrete is presented. After monitoring
fluidity versus time relationship, thermal measurements on CEM were carried out. These measurements allow to anticipate the
effects of different admixtures on the setting time. One shows that the setting delays obtained on CEM are in good agreement
with the difference of compressive strengths measured at early age. With rheological and thermal results, the CEM method permits
to select between numerous admixtures, which is the most likely to fit in with the specifications of effectiveness (proportion/cost
ratio), capacity of keeping the rheological properties over time and delay of formwork removal.

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