CONTRIBUTION FOR THE STRUCTURAL
CHARACTERIZATION OF THE PARTICLES
OF LIGHT EXPANDED CLAY AGGREGATES
1
Rafaela CardosoInstituto Superior Técnico, ICIST
Emanuel Maranha das NevesInstituto Superior Técnico, ICIST
Laura Caldeira
Laboratório Nacional de Engenharia Civil
12º Congresso Nacional de Geotecnia – Guimarães, 28 de Abril de 2010
Índice
1. Introduction
2. Study of single particles
3. Study of aggregates of particles
2
3. Study of aggregates of particles
4. Conclusions
1. Introducion
An experimental study was performed in LNEC where
the structure of a particle of light expanded clay
aggregate (LECA) was investigated .
3
P = η Dλλλλ
η = 38,9 e λ = 1,68 (HR ≈ 60%)
η = 8,30 e λ = 2,20 (HR ≈ 100%)
1. Introducion
4
Veiga Pinto (1983)
Weathered Greywacke(Veiga Pinto, 1983)
Liquid water
Rock poreAir flow (RH%)
Vapour diffusion
Liquid water
Rock poreAir flow (RH%)
Vapour diffusion
1. Introducion
5
Rockfill voidRockfill void
Pore with
access from
the exterior
Isolated
pore
Expanded
clay
• Mercury intrusion porosimetry
0.14
0.16
0.18
Com recobrimento
Sem recobrimento
2. Study of single particles
Pore with access from
the exterior
Isolated pore
Void between particles
Expanded clay
Acc
umul
ated
dis
trib
utio
n
with exterior cover
without exterior cover
6
0
0.02
0.04
0.06
0.08
0.1
0.12
1 10 100 1000 10000 100000 1000000
Diameter of the pores (nm)
Acc
umul
ated
dis
trib
utio
n
2. Study of single particles
• Water retention curve
2 particles with the exterior cover 2 particles without the
exterior cover
Dave=18mm
7
1- Drying: Saturated particles (vacuum followed by water injection)
2- Wetting: Particles dry in laboratory environment
2 particles with the exterior cover
2 particles without the exterior cover
Precision: 4 decimal places
2. Study of single particles
8
Suction measurement equipment (0,8MPa to
180MPa)
0.1
1.0
10.0
100.0
1000.0
Suc
ção
(MP
a)
com revestimento - secagem
com revestimento - molhagem
sem revestimento - secagem
sem revestimento - molhagem
Sem revestimento
Com revest.
No exterior cover
With cover
with cover - wetting
with cover - drying
without cover - wetting
without cover - dryingS
uctio
n (M
Pa)
9
Na secagem, a água fica retida por capilaridade:
Secagem mais difícil
Secagem mais fácil
Na molhagemNa molhagem
Na molhagem, o ar fica preso no interior dos vazios
Na molhagem, o ar fica preso no interior dos vazios
On drying, the
water is retained
by capillarity
On wetting, the air is
retained in the pores
difficult easy
0.0
0.1
0 50 100 150 200
teor em água, w (%)Water content, w (%)
HR=50%(laboratory environment)
HR=75%
• Crushing tests
2. Study of single particles
10
HR=85% HR=100%(saturation using vacuum)
D=16mm
HR=50% (dry)
HR=75%
log
(P)
x102
(kP
a)
2. Study of single particles
11
HR=85%
HR=100% (fully saturated)
log (D) (cm)
log
(P)
x10
HR (%) η λ50 (dry) 11.3 0.675 10.3 0.687 9.4 0.8100 (saturated) 6.5 1.3
P = η D λ
3. Study of aggregates
Vertical stress (kPa)
Ver
tical
dis
plac
emen
t (m
m)
γγγγ= 2.92kN/m 3
diameters
between 10 mm
and 20 mm
• Oedometric tests
DrySubmerged
12
Ver
tical
dis
plac
emen
t (m
m)
4. Conclusions
The results of MIP tests and the water retention curves explain the
influence of the exterior cover on the answer to changes in
relative humidy (RH).
Crushing tests of particles for differents RH show some
sensitiveness to water.
13
The oedometric tests performed on dry and submerged aggregates
did not presented relevant differences. This may be because of the
low stresses applied and also because the particles are difficult to
be wetted.
4. Conclusions
Long term deformations due to climate (mainly wetting caused by rain)
are not expected in embankments built with these materials, since
breakage measured by particles crushing was not significantly
increased with water presence.
14
If these results are confirmed, the material can also be used in the
construction of drainage systems as its grading size distribution and
other mechanical characteristics are not expected to be much
affected by the presence of water.