2569
Effect of Grout Bleed Capacity on the Engineering Properties
of Cement Grouted Sands
Effet de la capacité de ressuage de coulis de ciment sur les propriétés mécaniques
des sables injectés
Pantazopoulos I.A., Atmatzidis D.K., Basas V.G., Papageorgopoulou S.K.
Geotechnical Engineering Laboratory, Department of Civil Engineering, University of Patras, Greece
ABSTRACT: Grouts of three different cement types, each at four different cement gradations, with W/C ratios ranging from 0.6 to
3.0 and bleed capacities ranging up to 70% were injected into two different sands. Permeability, unconfined and triaxial compression
and resonant column tests were conducted to investigate the influence of grout bleed capacity on the engineering properties of cement
grouted sands. Cement grouting resulted in (a) permeability coefficient values as low as 10
-8
cm/s, (b) unconfined compressive
strength in the range of 1MPa to 35MPa, (c) cohesion in the range of 100kPa to 1400kPa, (d) improvement of the internal friction
angle by up to 5°, (e) higher shear modulus by up to 25 times and (f) improved damping ratio by up to 10 times. Bleed capacity is an
indicator of sand void volume filled with solidified grout but its degree of correlation with the static and dynamic properties of the
grouted sands ranges from very good to negligible.
RÉSUMÉ : On a injecté des coulis de trois types de ciments différents, chacun avec quatre dosages en ciment différents, avec un
rapport eau/ciment variant de 0.6 à 3.0, et une capacité de ressuage se situant jusqu’à 70% lorsque injectés, dans deux sables
différents. On a effectué des essais de perméabilité, de compression simple et triaxiale et de colonne résonnante pour étudier
l'influence de la capacité de ressuage des coulis sur les propriétés mécaniques des sables injectés. L’injection du ciment a résulté en:
a) des valeurs de coefficients de perméabilité aussi faible que 10
-8
cm/s, b) une compression simple de 1MPa à 35MPa, c) une
cohésion de 100kPa à 1400kPa, d) une augmentation de l’angle de frottement jusqu’à 5°, e) un module de cisaillement jusqu’à 25 fois
plus élevé, f) une augmentation du coefficient d’amortissement jusqu’à 10 fois plus élevé. Le ressuage des coulis est un indicateur du
volume des vides du sable remplis de coulis solidifié mais son degré de corrélation avec les propriétés statiques et dynamiques des
sables cimentés varie de très bonnes à négligeables.
KEYWORDS: cement grout, bleed capacity, permeability, strength, shear modulus, damping ratio
1
INTRODUCTION
Improvement of the mechanical properties and behavior of soils
by permeation grouting using cement suspensions is frequently
required in order to assure the safe construction and operation of
many structures. The grout water-to-cement ratio (W/C) and the
maximum cement grain size (d
max
) are two important
parameters controlling the cement grout bleed capacity and,
consequently, the effectiveness of cement grouts in terms of the
percentage of soil voids volume filled by grouting. Although the
bleed capacity of cement grouts has been frequently quantified,
its correlation with the engineering properties of the grouted
sand has not been investigated so far.
Scope of this presentation is to provide some insights on the
effect of grout bleed capacity on permeability, unconfined
compressive strength, shear strength parameters and dynamic
properties of ordinary and microfine cement grouted sands, in
conjunction with the effect of the grout W/C ratio.
2
MATERIALS AND PROCEDURES
For the purposes of this investigation, a Portland, a Portland-
composite and a pozzolanic cement (CEM I, CEM II/B-M and
CEM IV/B according to Standard EN 197-1) were used. Each
cement was pulverized to produce three additional cements with
nominal maximum grain sizes (d
max
) of 40μm, 20μm and 10μm
and average Blain specific surface values of 567, 720 and
928m
2
/kg, respectively. Cements with d
max
=10μm can be
considered as “microfine” according to Standard EN 12715
(d
95
<20μm and specific surface over 800m
2
/kg). Also, cements
with d
max
=20μm have adequately small characteristic grain sizes
to be considered, marginally, as “microfine”. Typical gradations
of these cements are presented in Figure 1.
All suspensions tested during this investigation were prepared
using potable water since it is considered appropriate for
preparing cement-based suspension grouts. The W/C ratio of the
suspensions was set equal to 0.6, 0.8, 1.0, 2.0 and 3.0 by weight,
in order to test both stable and unstable suspensions in terms of
bleed capacity. A superplasticizer (patented new generation of
admixture based on polycarboxylate chemistry) at a dosage of
1.4 % by weight of dry cement was used to improve grout
properties. All suspensions were prepared using high speed
mixers. As recommended by the superplasticizer producer,
0
10
20
30
40
50
60
70
80
90
100
0.1
1
10
100
Cement grain size (μm)
Finer by weight (%)
10μm
20μm
40μm
100μm
Cement : CEM II/B-M
nominal d
max
Figure 1. Typical cement gradations.
