Abstract Knowledge of alkali concentration in
concrete pore solution is key for long-term eval-
uation of alkali-silica reaction (ASR) expansion.
This study aimed at providing experimental data
on the alkalinity evolution in concrete tested for
ASR in order to determine critical alkalinity
values that stop concrete expansion. The pore
solution was systematically expressed (i.e. ex-
tracted at high pressures) from concrete speci-
mens tested at 38°C over water (Canadian
standard). Alkali concentration showed a
decreasing trend with time, which can be mainly
explained by alkali leaching. After 52 weeks, the
decrease in alkalinity was up to 25% of the ori-
ginal Na
2
O
eq
content in the concrete, contributing
to underestimate long-term expansion of reactive
concrete. Comparisons were also made between
pore solution expressed out of cement paste
specimens and concrete specimens; differences
(from 25% to 43% higher for cement paste)
suggest that results obtained from cement paste
are not suitable for concrete as they tend to
overestimate the concrete pore solution alkalin-
ity. The alkali concentration threshold varied
from one mixture to another (205–335 mmol/l).
Re´sume´ La connaissance de la concentration en
alkalis dans la solution interstitielle du be
´
ton est
un facteur cle
´
pour e
´
valuer le potentiel d’expan-
sion a
`
long terme des structures touche
´
es par
l’alcali-re
´
action. Cette e
´
tude pre
´
sente des donne
´
es
expe
´
rimentales sur l’e
´
volution de l’alcalinite
´
de
be
´
tons teste
´
s pour leur re
´
activite
´
afin de de
´
ter-
miner des valeurs critiques stoppant la re
´
action.
La solution interstitielle a e
´
te
´
extraite sous pres-
sion a
`
partir d’e
´
prouvettes maintenues au-dessus
de l’eau a
`
38°C (norme canadienne). Les analyses
montrent une de
´
croissance de l’alcalinite
´
avec le
temps, ce qui peut e
ˆ
tre explique
´
en grande partie
par le lessivage des alcalis; apre
`
s 52 semaines, la
perte en alcalis atteint jusqu’a
`
25% de la teneur
initiale en Na
2
O
eq
. Ceci contribue a
`
sous-estimer
l’expansion a
`
long terme des be
´
tons re
´
actifs. Des
comparaisons entre la solution extraite de pa
ˆ
tes
de ciment et de be
´
ton ont e
´
galement e
´
te
´
re
´
alise
´
es.
Des diffe
´
rences importantes ont e
´
te
´
note
´
es (25% a
`
40% plus alcalins pour les pa
ˆ
tes), ce qui indique
que les donne
´
es obtenues sur pa
ˆ
te sont difficile-
ment transfe
´
rables aux be
´
tons car elles tendent a
`
surestimer l’alcalinite
´
de ces derniers. La con-
centration seuil varie d’un me
´
lange a
`
l’autre
(205 mmol/l a
`
335 mmol/l).
P. Rivard (&) Æ G. Ballivy
CRIB, De
´
partement de genie civil, Universite
´
de
Sherbrooke, Sherbrooke J1K 2R1, Canada
e-mail: patrice.rivard@Usherbrooke.ca
M. A. Be
´
rube
´
CRIB, Universite
´
Laval, Quebec, Canada
J. P. Ollivier
LMDC, UPS - INSA Toulouse, Toulouse, France
Materials and Structures (2007) 40:909–921
DOI 10.1617/s11527-006-9191-z
ORIGINAL ARTICLE
Decrease of pore solution alkalinity in concrete tested
for alkali-silica reaction
P. Rivard Æ M. A. Be´rube´ Æ J. P. Ollivier Æ
G. Ballivy
Received: 18 October 2005 / Accepted: 18 May 2006 / Published online: 3 October 2006
Ó
RILEM 2006