introduction aims objectives - · pdf...

Aims

• The aim of this research is to produce foamed concrete

with/without lightweight aggregate which is suitable for structural

purposes with good insulation and durability properties and to

evaluate its damage behaviour.

Objectives • Produce a range of structural and non-structural foamed

concretes with varying insulation and durability properties.

• Study and understand how microstructure affects the properties

and damage mechanisms of foamed concrete under mechanical

loading.

• Investigate and understand mechanisms of stress-induced

damage (micro and macrocracks) in this type of lightweight

Introduction

• Cellular (aerated) concrete is a lightweight material composed of

cementitious mortar surrounding disconnected bubbles in which

either air is introduced into the mortar mixture or gas is formed

within it.

• Foamed concrete is a versatile material consisting of either

Portland cement paste or cement filler matrix (mortar) with

homogeneous pore structure created by entrapped air voids

roughly 0.1-1.0 mm size. It can be divided into two groups:

physically foamed concrete (by using foaming agents) and

chemically foamed concrete (by adding aluminium powder).

Results • The compressive strength

of foamed concrete (ƒcu) is

affected by such factors as

density, age, cement content,

w/c ratio, s/c ratio, foam

volume, additives and curing. Its

relation with age is shown below.

• Microstructural

Investigation:

On Progress

Study the effect of

in terms of air voids system and

ITZ characteristics on the

mechanical, thermal and fracture

behaviour of foamed concrete.

• Damage Evaluation:

damage study of micro and macro levels will be performed on the

selected mixes by using several techniques classified into

surface observations Digital Image Correlation (DIC) and

Electronic Speckle Pattern Interferometry (ESPI) and internal

observations Acoustic Emission (AE), Scanning Electron

Microscopy (SEM) and X-ray CT system

Foamed Concrete

Cement

Air

Bubbles

Sand

Water

concrete by using several techniques classified into

surface observations, internal observations as

well as standard fracture energy tests.

Foam

Additives

Ordinary

Mixer

Cement Water Binder

Moulding

Curing

Product

Foam

Generator

Foaming Agent

Water

Solution

Compressed

Air

Foam generator used (STONEFOAM-4)

Microstructural characteristics

• Fracture Characterization:

to characterize a fracture of foamed concrete, two fracture

parameters models will be required: fracture toughness (KIc), a

property which characterises the resistance of a material to

crack propagation, and critical crack tip opening displacement

(CTOD) will be adopted.

• By using a scanning electron microscope (SEM) with secondary

electron mode, a few images were captured for three samples

(20×20×10 mm) which were cut from different positions of a cube

specimen. In order to characterize the cracks inside a specimen

exposed to compressive loading, a sequence of 2D images was

captured through the height of the 100mm cube with a slice

thickness of 1 mm using the non-destructive X-ray CT system.

0

5

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30

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0 7 14 21 28

Co

mp

ress

ive

Str

eng

th (

MP

a)

Age (day)

FC1300

FC1600

FCa1600

FCa1600

FCa1800

FCA1600

FCAa1600

Microstructure of two types of

foamed concrete, (Just and

Middendorf, 2009).

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