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.

Acknowledgements

Saint-Gobain Weber Portugal S.A.

For supplying the material and for funding the

investigation

15

Eng. Pedro Almeida e LNEC technicians Amélia

Reis and Fernando Rodrigues

THE END

Thank you