The AFREM method for the mix-design of high performance concrete

Abstract

The article presents the results of work by the AFREM/HPC group on the formulation of high-performance concretes. This is an updating of LCPC's grout method. The goal is a methodology making it possible, for a given binder (or mixture of binders), to determine the saturation doses of a certain number of superplasticizers and compare them in terms of their effectiveness and the duration of the rheological behaviour they impart. The innovations with respect to the old method are the following: i) the starting concrete can vary over a broader range, ii) part of the sand is added in the grout, iii) mixing and measurement are better codified, and iv) the method of determining the saturation proportion is objective. The method has successfully passed tests of repeatability and reproducibility (between the six member laboratories of the group). Ri~SUMi~ L'article pr&ente le r&ultat du travail du groupe AFREM/BHP sur la formulation des b~tons h hautes performances. Il s' agit d' une remise a jour de la m~thode des coulis du LCPC. Le but en est de fournir une m&hodologie permettant, pour un liant (ou m~lange de liants) donnS, de d&erminer les doses de saturation d'un certain hombre de superplast~'ants, de comparer leurs efficacit& respectives et leur propension h con)&er un comportement rh&logique stable dans le temps. Les nouveaut& introduites, par rapport l'ancienne m&hode, sont les suivantes : i) b~ton initial pouvant varier clans une plus large gamme, ii) introduction d'une partie du sable clans le coulis, iii) malaxage et mesure mieux codifi&, iv) m~thode objective de d~termination de la dose de saturation. La m~thode a fait l'objet d'essais de r~p~tabilit8 et de reproductibilit~ (entre les six laboratoires membres du groupe) satisfaisants.

Revisão: conceitos de dispersão e empacotamento de partículas para a produção de concretos especiais aplicados na construção civil

“…Para a visualização da influência dos aditivos sobre a hidratação do cimento, um esquema representando Figura 1: Exemplos de métodos utilizados para a determinação do ponto de saturação do aditivo superplastificante. A: método apresentado por Aïtcin [7]; B: método AFREM [28]. Obs.…”

“…A: method presented by Aïtcin [7]; B: the AFREM method [28]. Deve-se atentar principalmente para as etapas em que o superplastificante influencia o processo de hidratação, ou seja, os estágios I, II e III apresentados na Fig.…”

Analytical method for determining the saturation point of superplasticizers in cement pastes using the Marsh cone

“…cement, shape and dimension of fines, w/c ratio, type of SP, compatibility between cement and SP, as well as the temperature and humidity of the materials and the environment [4][5][6][7][8]. In the SP literature, it can be seen that there is an optimum dosage of SP for each kind of composition, and for many times, there are differences from those ones purposed by the manufacturer [9,10].…”

“…Moreover, from these tests, information about the cement incompatibility, mineral additions, and other chemical additives, quality and efficiency of SP can be collected [9][10][11][12]. The test methods used for obtaining the SP dosages are those that are based on rheological properties by the rheometer [13,14], from the flow curves using the Marsh cone [3,4,6,7,11,12], and from spreading tests by mini-slump [4,5,15]. Due to the simplicity of apparatus and procedures, Marsh cone test of the pastes and mortar has become a widely used method.…”

Influência da incorporação de ar em concreto autoadensável para paredes de concreto moldadas no local

“…escoamento de cada pasta de classe C25 com 0%, 10% e 20% de f/c era muito curto e difícil de se medir com precisão. Dessa maneira, os resultados obtidos ficaram imprecisos, não sendo possível obter o teor ótimo de superplastificante a partir do método AFREM, proposto porDE LARRARD et al (1997). Como solução, adotou-se um valor de sp/c igual a 0,20% para os referidos teores de fíler.…”