Reduction of ASR-expansion using powders ground from various sources
of reactive aggregates
, Patrice Rivard
, Francis Labrecque
Université de Toulouse, UPS, INSA, LMDC (Laboratoire Matériaux et Durabilité des Constructions), 135, Avenue de Rangueil, F-31 077 Toulouse cedex 4, France
Département de Génie Civil, Université de Sherbrooke, Sherbrooke, Canada J1K 2R1
Received 8 January 2009
Received in revised form 22 April 2009
Accepted 26 April 2009
Available online 5 May 2009
Reactive aggregate powder
Supplementary cementing materials (SCM)
This study assesses the potential of ground reactive aggregates to reduce or suppress expansion associ-
ated with ASR. Particular attention is paid to ﬁne admixtures (<80
m) added to mortars, which contain
the reactive aggregates from which the ﬁnes were ground. Many varieties of aggregate (quarried and nat-
ural, igneous, metamorphic and sedimentary rocks) from different geological settings were subjected to
an autoclave test. The replacement of 10–20% of the sand by reactive aggregate powder (RAP) of different
surface areas from 11 different reactive aggregates led to the reduction of ASR-expansion by up to 78%
compared with control mortars. Increasing the amount of ﬁnes led to better performance. No clear rela-
tionship was observed between the reactivity degree of the aggregates and the efﬁciency of their ground
powder to reduce expansion. A general trend was found regarding the ﬁneness of ground aggregates:
ﬁner particles were more effective in reducing expansion. The reduction of the expansion due to RAP
is discussed in terms of parameters affecting its efﬁciency and of the mechanisms responsible for the
Ó 2009 Elsevier Ltd. All rights reserved.
Aggregates cannot be considered as totally inert in concrete.
Under certain conditions, some siliceous minerals can react, lead-
ing to swelling and early deterioration of concrete structures. This
deleterious reaction, observed worldwide, is known as the alkali–
silica reaction (ASR). It occurs when the reactive silica phase in
an aggregate particle is attacked and dissolved by the alkali
hydroxides in the concrete pore solution. A reactive product, silica
gel, is formed and swells in the presence of water. In this respect,
ASR will develop only if the following conditions are found:
sufﬁcient amount of alkalis in concrete pore solution;
sufﬁcient moisture level in concrete;
reactive aggregate (coarse or ﬁne).
In order to limit ASR-expansion, or even to suppress it, engi-
neers must act on one or more of the above factors. Numerous pa-
pers have been published regarding the mitigation of ASR with
supplementary cementing materials (SCM). It is well-known that
SCM, particularly silica fume, metakaolin, low-calcium ﬂy ash,
ground glass, high-calcium ﬂy ash and blast furnace slag (these last
two at higher dosages), are effective against ASR [1–7]. The reduc-
tion of expansion stems from the low permeability of concrete
incorporating SCM and a combination of one or more factors such
as the alkali dilution effect due to the reduced cement content, the
reduction in the pH of the pore solution due to pozzolanic reaction,
and a change in the composition of C–S–H which allows more alka-
lis to be trapped in the C–S–H structure. Lithium solution also ap-
pears to be effective in several cases [8,9].
Limiting the moisture level in concrete may appear viable when
the affected elements are relatively small (e.g. bridge pier, retain-
ing wall) and when there is no permanent or large water supply.
Usually, it is achieved with the application of a seal on the surface
of the affected element . In the case of hydraulic structures,
such as dams and locks, this measure is ineffective.
Regarding the aggregate reactivity, various tests have been de-
signed and implemented over the past decades to assess the degree
of reactivity of rocks in concrete and most of them are efﬁcient.
Therefore, aggregates can now be used in concrete without worry-
ing about the further expansion of the structures. However, for
economic or technical reasons, the use of innocuous aggregates is
not always possible . In addition, SCM or lithium may not be
available or would represent excessive costs.
An alternative may be the use of reactive aggregates in combi-
nation with powders ground from the same aggregate. A few
authors have already reported results on this approach [11–15]
but the technique has remained limited to only a small number
of aggregates. This study aims to assess the potential of reactive
aggregate powders (RAP) to reduce or suppress the expansion
associated with ASR. The objective of this paper is to assess
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* Corresponding author.
E-mail address: firstname.lastname@example.org (M. Cyr).
Cement & Concrete Composites 31 (2009) 438–446
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