Foamed Concrete.pdf - eab associates

Conspectus 2 0 0 1

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Mr JERZY BASIURSKI

Mr. Jerzy Basiurski, BSc(Honours), MSc, MBA. worked in a scientific

environment for multinational companies in the aluminium and glass

industries. For more than 20 years since then, he has been involved in

construction chemicals. Combining practical skill, experience and

theoretical knowledge, he has given lectures about foamed concrete

and carried out demonstrations in several countries.

Dr DANIEL WELLS

Dr Daniel Wells, BSc(Honours), PhD, obtained his PhD in the field of

Molecular Reaction Dynamics at The University of Manchester. For

the past three years he has been involved in technical marketing

of construction chemicals, in particular of foaming agent, and

has built up an extensive knowledge on foamed concrete.

EAB Associates, England

EAB Associates, England

The Use of Foamed Concrete inConstruction and Civil Engineering

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The Use of FoamedConcrete in Constructionand Civil Engineering

Over the past 15 years or so foamed concrete has become accepted as an

important material for use in the construction industry. Both the amount

of foamed concrete used and the variety of applications that it has been

used for have increased dramatically. For many applications foamed

concrete can provide cost and performance benefits when compared with

traditional building materials.

This paper describes what foamed concrete is and how it is made. The

advantages and technical specifications of foamed concrete are reported.

Applications for which foamed concrete can be used are discussed,

including the use of foamed concrete in building construction, roads,

bridges, void filling, ground stabilisation and land reclamation. Case

studies of foamed concrete usage are described in detail. The case studies

consider the use of foamed concrete for ground stabilisation in Japan,

trench reinstatement in Singapore and an evaluation of foamed concrete

for bridge strengthening in the United Kingdom.

Abstract

...............................................................................................................................................

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I N T R O D U C T I O N

Foamed Concrete is a versatile, lightweight, building material. It can be made with a wide range of densities and

compressive strengths and it is used for a many different applications. In many cases foamed concrete can provide

cost and performance benefits when compared with traditional building materials. This paper describes what foamed

concrete is and provides details of how it is made, what its advantages are and its technical specification. In order to

demonstrate the potential of foamed concrete, three case studies where foamed concrete has been used are discussed.

These case studies illustrate foamed concrete’s superiority over traditional fill materials when used for ground

stabilisation, trench reinstatement and arch masonry bridge strengthening.

W H AT I S F O A M E D C O N C R E T E ?

The most basic definition of foamed concrete is that it

is ‘mortar with air bubbles in it.’ The air content of

foamed concrete may be up to 75% air by volume.

In general terms, foamed concrete can be described as

a lightweight, free flowing material which is ideal for a

wide range of applications. It can have a range of dry

densities, typically from 400 kg/m3 to 1600 kg/m3 and a

range of compressive strengths, 1 MPa to 15 MPa (1).

Foamed Concrete can be placed easily, by pumping if

necessary, and does not require compaction, vibrating

or levelling. It has excellent resistance to water and

frost, and provides a high level of both sound and

thermal insulation. It is very versatile, since it can be

tailored for optimum performance and minimum cost

by choice of a suitable mix design.

The fact that foamed concrete can be made using

different mix designs means that it is not a single

product. With the exception of pre-cast units, foamed

concrete cannot be bought ‘off the shelf’. Foamed

concrete is nearly always made on-site and it is made

using a mix design specifically selected for each

application or job.

Although the material is called foamed concrete, it is

not really concrete at all. Foamed concrete is actually

foamed mortar, where the mortar is made from either

cement and water or sand, cement and water. Foamed

concrete does not contain aggregates.

Foamed Concrete is not the same as conventional

concrete and does not have the same characteristics.

Foamed concrete is much lighter and does not have the

same strength as conventional concrete. For this reason

foamed concrete and conventional concrete are

generally used for different applications, although there

are applications where either may be specified.

Foamed Concrete is not the same as autoclaved aerated

concrete, which is a common building material that is

frequently confused with foamed concrete. Foamed

concrete is a much more versatile material than

autoclaved aerated concrete, the latter being restricted

in its form and where it is made.

A P P L I C AT I O N S O F F O A M E D C O N C R E T E

Foamed concrete is a very versatile material and there

are many different applications for it. Please refer to

Table 1 for typical dry densities and compressive

strengths of foamed concrete for a range of applications.

Foamed Concrete in Building Construction

Roof Insulation Screed

It has long been recognised that lightweight foamed

concrete has excellent thermal insulation properties

which make it an ideal material for roofing insulation.

It is a low density material, and so does not add

significantly to the overall weight of the roof. As well

as providing insulation, foamed concrete is also used

to lay flat roofs to falls. This particular application is

very popular in the Middle East.

Walls

More recently reinforced foamed concrete has been used

to build structural and non-structural walls in houses

and apartments. Whilst it is possible to build walls from

pre-cast foamed concrete elements, foamed concrete


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Conspectus 2 0 0 1The Use of Foamed Concrete inConstruction and Civil Engineering

67

can be used much more efficiently by casting entire

foamed concrete walls in-situ. Foamed concrete walls

are both lightweight and low in cost. Low cost housing

has been built in this way in Africa and The Middle East.

Floors

Solid, cast in-situ floor slabs can be made from foamed

concrete. Also floor levels can be raised and uneven floor

surfaces levelled using foamed concrete. When used in

flooring it is important to cover foamed concrete with

a normal finishing screed or hard floor tiles because

foamed concrete has a low resistance to abrasion and

point impact.

Fire Breaks

Foamed concrete is fire resistant and can be used to

make fire breaks within the under-floor service ducts

of modern buildings or in the space above old style lath

and plaster ceiling in old buildings. Foamed concrete

can also be sprayed onto or poured into shuttering

around structural steelwork for fire protection.

Decorative Panels

In the Czech Republic decorative wall panels are made

out of foamed concrete. These panels are lightweight

and can be used to enhance the appearance of buildings

without adding much extra loading to the structure.

Table 1: Typical Dry Densities and Compressive Strengths of foamed concrete for a range of applications

Roads, Highways and Bridges

Trench Reinstatement

In 1991, following the publication of the Horne report (2)

United Kingdom government legislation (3) specified the

use of foamed concrete for trench reinstatement (this

is the filling of trenches dug in roads when pipes are

laid, or repairs carried out). Traditional methods of filling

trenches in roads, i.e. the use of granular fill materials,

result in settlement and damage to both the road and

the pipes. Trenches that have been reinstated using

foamed concrete have shown no signs of settlement and

have not required any remedial work (4). Table 2 shows

the layer thickness and crushing strength requirements

for foamed concrete that is used for trench

reinstatement in the UK. Other advantages of using

foamed concrete are that it is quick to place, fills hollow

sides, fills under higher services and is easy to re-excavate.

Road and Pavement Sub-Bases

Foamed concrete is lightweight (densities can range

from 400 kg/m3 to 1600 kg/m3), and because of this it

has been used for the construction of the road

foundations for roads built on soft ground. Roads built

using foamed concrete can be constructed in such a

way that by choice of a suitable depth of sub-base they

weigh less, and so do not sink into the soft ground, unlike

Dry Density Rangekg/m3

400 - 6001200 - 1600800 - 16001200 - 1600400 - 1200400 - 1000

10001200

400 - 1000400 - 1650400 - 1600600 - 1000400 - 1600

Application

Roof Insulation ScreedStructural WallsNon-Structural WallsFloor SlabsRaising Floor LevelFire BreaksDecorative PanelsTrench ReinstatementRoad Sub-BaseBridge AbutmentsVoid FillGround StabilisationHarbour Fill

Compressive StrengthRange MPa1.0 - 2.56.5 - 12.03.0 - 10.04.5 - 10.01.0 - 4.51.0 - 3.53.5 - 5.54.5 - 5.51.0 - 3.01.5 - 10.01.0 - 10.02.0 - 5.51.0 - 10.0

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Table 2: Layer Thickness and Crushing Strength Requirements (3, 5)

roads built in the traditional way, using roadstone as

the sub-base. The access roads to Canary Wharf in

London’s Docklands were built on foamed concrete

foundations as are many roads in Holland.

Bridge Abutments

Foamed concrete was used in the construction of a

bridge abutment in Colchester, United Kingdom with

great success (6). With traditional abutments, there is

a lot of sideways pressure against the bridge walls

caused by the materials used, and their compaction.

With foamed concrete, this lateral load is practically

eliminated, so the bridge walls do not have to be as

thick. This in turn means that the bridge foundations

can be made less massive. Huge cost savings can be

achieved by reducing the thickness of the walls, and

the size of the foundations, so the use of foamed

concrete is much cheaper than the use of traditional

materials.

Void Filling

Foamed concrete is a perfect void filling material,

because of its placement characteristics. Foamed

concrete is free flowing, it fills every gap and can be

applied even through small openings. The fact that

foamed concrete is fluid and can be placed through

narrow openings, by gravity or by ordinary concrete

pumps, means that the job can be tackled without too

much disruption at the surface and does not leave any

hidden gaps. When foamed concrete sets and cures it

does not collapse or shrink and it does not impose large

lateral loads. Void filling jobs fall into two categories -

planned and emergency (7).

Planned Void Filling

Typical planned void filling work includes the filling of:

• old underground fuel tanks, which would otherwise

have to be dug out, cut up, hauled away and scrapped,

which is time consuming and potentially dangerous

work;

• redundant sewers, pipelines, culverts and tunnels;

• the gap between the old sewer wall and the new

insert pipe within it (in a sewer re-lining job);

• any large open “hole” to enable the area to be

redeveloped - typical examples of such work include

swimming pools, water reservoirs, surface mine

workings and mine shafts;

• hidden, irregular, unexplored underground voids

which threaten subsidence;

• cavities in structures - service ducts in bridges; cellars

and basements in old buildings;

• voids left behind on old industrial sites.

Emergency Void Filling

Emergency repair work usually arises because something,

usually some structure, starts to show signs of collapsing,

or when a previously unknown underground void comes

to light and is seen to present a risk to whatever is above

or close by. In emergency repair work the foamed

concrete usually provides support as well as filling the

void.

Foamed concrete can be placed quickly and safely so

that the emergency situation can be dealt with without

Layer

Roadbaseand Sub-baseRoadbasealoneSub-baseand/or below

1450 mm

C4Not

allowed150 mm

2450 mm

C4Not

allowed150 mm

C2

3450 mm

C2300 mm

C2150 mm

C2

4450 mm

C2300mm

C2150 mm

C2

Footwayor Cycletrack

N/A

N/A100mm

C2C4 - Minimum 4 MPa crushing strength at 28 days.C2 - Minimum 2 MPa crushing strength at 28 days.

Maximum 14 MPa crushing strength at 28 days.

Road Type


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unnecessary delay. The foamed concrete can either be

left in place as a permanent foundation, or if a different

long term solution is required, because of its cellular

structure, the foamed concrete can easily be re-

excavated.

Foamed concrete was used for emergency void filling

at Heathrow Airport, United Kingdom when a tunnel

collapsed during the construction of a new underground

railway line. A volume of 12,000 m3 of foamed concrete

was placed in 2 weeks in order to stabilise the ground.

In Lublin, Poland, a recently constructed roadway built

over a previously inadequately compacted trench

reinstatement was in danger of collapse when heavy

rains washed away the ground beneath it (7). A large

void was created under the roadway which remained

suspended in mid air over a distance of 30 metres. Using

traditional methods the repair would have taken 3 weeks

to complete, including the dismantling and re-assembly

of the road structure, which consisted of paviors bedded

in mortar. Using foamed concrete the whole job was

completed and the road re-opened in 48 hours. The cost

of the emergency void fill using foamed concrete was

one tenth of what it would have been using traditional

methods.

Ground Work

Ground Stabilisation

As with void filling, ground stabilisation may be either

planned or emergency work. Planned work can involve

using foamed concrete as a foundation for building on

soft ground. The soft ground can be excavated and

replaced by foamed concrete that has a lower density

than the soft ground. When a structure is subsequently

placed on top of the foamed concrete foundation, the

total loading can be matched so that it is similar to

that of the soft ground which was removed. Typical

emergency ground stabilisation work can involve

consolidating embankments following a landslide.

In Gniezno, Poland, the cathedral is situated on a hill.

In 1996 the hill started to slide. The cathedral is built

on a site of national heritage since it is the birth place

of Polish Catholicism. It was of utmost importance that

the cathedral did not collapse. In order to protect the

building the hill had to be stabilised. A layer of soil

2 metres thick was removed and replaced with foamed

concrete of a dry density of 900 kg/m3. The foamed

concrete was poured in stages, forming small terraces.

In total 4,500 m3 of foamed concrete was placed for

this job. This reduced the weight of the hill by

6,000 tons and stopped the landslide.

Land Reclamation and Harbour Fill

Land reclamation is another area where foamed concrete

is finding a use. Foamed concrete has been successfully

used for large harbour fills where it has the advantage

that it does not sink into the soft sub-soil in the way

that traditional materials (usually sand and stones) do.

This means that the site can be redeveloped months or

even years sooner than would otherwise be possible.

A D VA N TA G E S O F F O A M E D C O N C R E T E

Foamed Concrete in its Fluid State

• Non-hazardous

• Large or small amounts can be placed quickly

• Can be easily placed by pouring, or can be pumped

long horizontal or vertical distances

• Free flowing, spreads to fill all voids

• Does not settle, hence requires no compaction

• Does not require vibrating when placed

• Reliable quality control so batches are easy to

reproduce

• Made on site, so mix design can be optimised for site

conditions, if required

Foamed Concrete in its Solid State

• Non-hazardous

• Lightweight, does not impose large loading

• Excellent load spreading characteristics

• Does not impose lateral loads

• Excellent sound and thermal insulation properties

• Excellent fire resistant property

• Low water absorption over time

• Excellent resistance to freeze-thaw

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For the WET method all the ingredients are loaded into

a high speed blade mixer and thoroughly mixed, before

being transferred to the readymix truck. The WET method

gives a better quality slurry.

The mortar slurry is then transported to site, and the

foam is added there, and not at the batching plant.

Some batching plants are reluctant to make mortar

slurries, as they can stick to the insides of the drum,

making them hard to clean. However, this is not a

problem when making foamed concrete for several

reasons:

• more water is used in the slurry making it less

likely to stick

• when the foam is added, the foamed concrete

is very fluid

• the foam itself has a cleaning action.

Making the Foam

Foam for foamed concrete is made from a concentrated

Foaming Agent. Foaming Agents are based on protein

hydrolyzates or synthetic surfactants or both. The foam

is made using a foam generator. In the foam generator

the foaming agent is diluted in water to make a pre-

foaming solution and then the pre-foaming solution is

expanded with air into foam. The foam is stiff, like

shaving foam, with a density in the region of 45 g/litre.

The bubbles are stable and able to resist the physical

and chemical forces imposed during mixing, placing and

hardening of the foamed concrete. Between 75 and 85%

of the bubbles are of 0.3 to 1.5 mm in diameter (8).

There are two methods of making foam and hence two

types of foam generator. The methods used are the DRY

and WET methods. These terms have no relation to the

wet and dry methods that are used for making slurry.

The DRY method is where foam is created by forcing

the pre-foaming solution through a plastic mesh with

compressed air. The foam created using the dry method

is uniform and very stable. Figure 1 is a schematic

diagram that shows how foam is made using the dry

Cost Benefits of Foamed Concrete

• Highly cost effective compared with other methods

• Contains a large amount of air making it inexpensive

• Ingredients readily available

• Enables fast work

• Once placed requires no maintenance

H O W T O M A K E F O A M E D C O N C R E T E

The first step is determine whether there are any

required parameters, such as density and compressive

strength. A theoretical mix design is formulated and

site trials are undertaken. The results from the site trials

are used as a control for making the foamed concrete

that is to be used for the work that is to be carried out.

The next step is to make a cement slurry or a sand-

cement slurry that is appropriate for the mix design.

The second step is to make suitable foam. The foam is

made separately from the slurry. Once the foam has been

made it is blended in to the slurry to make foamed

concrete.

Making the Slurry

The cement used for the slurry is usually Type 1 Portland

Cement although other cements can be used. If sand is

specified in the mix design ideally it should be fine with

2mm maximum size and 60 to 90% passing through a

600 micron sieve (8). Other ingredients such as

Pulverized Fuel Ash (PFA) can also be used. The

water:cement ratio of the slurry is usually between 0.5

and 0.6. If necessary more water can be added to

increased the workability. However it is important not

to use too little water in the slurry since this can cause

water to be drawn out of the foam.

The slurry can be made using a readymix truck mixer.

Firstly, the cement mortar slurry is made at the batching

plant, according to the mix design, by either the DRY or

WET method.

When using the DRY method the ingredients are loaded,

in their correct proportions, by ‘ribbon feeding’, into

the drum of a ready mix truck, where they are mixed

together.


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method. In contrast, the WET method of creating foam,

which is based on the Venturi effect, does not involve

compressed air and does not produce such good quality

foam.

Making Foamed Concrete

It is important to make the slurry first, before making

the foam. Ideally the foam should be generated and

delivered directly into

the mixer of the

readymix truck that

contains the slurry. The

mixer should be rotated

at approximately 10

revolutions per minute.

All of the foam should

be allowed to blend into

the slurry. A sample of

the foamed concrete

should be tested for its

wet density. I f the

density is too low, more

foam can be added.

When making subsequent

batches the amount of foam added can be adjusted.

Figure 2 shows a schematic diagram of foamed concrete

being made and placed on site.

F O A M E D C O N C R E T E - T E C H N I C A LS P E C I F I C AT I O N

Foamed concrete can have a range of dry densities,

typically from 400 kg/m3 to 1600 kg/m3 and a range of

compressive strengths, 1 MPa to 15 MPa. Table 3 shows

typical properties for foamed concrete. In general, the

higher the density of foamed concrete then the higher

its compressive strength will be. However this is not

always true because the mix design used to make the

foamed concrete will also affect the compressive

Figure 1: Making foam from foaming agent, water and compressed air.

Figure 2: A Schematic diagram showing the stages involved whenmaking foamed concrete.

strength. For example, by using a cement only mix design

to make foamed concrete with a dry density of 800 kg/m3

you can achieve a higher compressive strength than if

you make foamed concrete with a dry density of

1000 kg/m3 using a 1:1 sand:cement mix design.

Performance requirements for foamed concrete have

also been published by The American Society for Testing

and Materials (ASTM) (9).

C A S E S T U D I E SLandslide Repair on

Nagano Expressway,

Japan

A section of the Nagano

Expressway in Nagano

Prefecture, Japan, is

built along a hillside. In

order to build the road

an embankment with a

volume of about 6000 m3

w a s p l a c e d . A n

e m b a n k m e n t w a s

constructed using

traditional fill materials. Following the placing of this

embankment there was a landslide 80m long, 50m wide

and 9m deep. The unexpected landslide meant that the

design of the embankment had to be altered. Instead of

using traditional fill materials a lightweight material

needed to be used. Foamed concrete was specified to

re-build the embankment.

Terraces were dug into the subsoil in order to provide a

solid base support for the foamed concrete fill. Drainage

mattresses with impervious sheets on top were placed

on the subsoil to stop water from penetrating into the

foamed concrete. A retaining wall was constructed from

hollow concrete panels. Lightweight foamed concrete

with a density of 650 kg/m3 was poured into the void

Air Compressor

Foaming Agent Water

FoamGenerator

Pre-foamingsolution

Foaming Lance

Foam

Air

Site Mixer

Slurry

Truck Mixer

WORKSITE

Foamed Concretepoured or pumped

Foam isadded to theslurry in thetruck mixerAIR COMPRESSOR

WATERFOAMING AGENT

Lance

FoamGenerator

Concrete Batching Plant

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The trench at NUS was a new trench that contained

new telecommunications cables. The cables were

enclosed in pipes that were encased in dense concrete.

(Normally when foamed concrete is used for trench

reinstatement the pipes are encased in sand. Marker

tape is laid over the top of the sand to give warning of

the position of the pipe in the event that the pipe has

to be re-excavated.) Foamed concrete with a wet density

of 1320 kg/m3 was used to reinstate the trench (Figure 4).

The trench was on a gradient and, although foamed

concrete is fluid, the foamed concrete was placed such

that none flowed out of the trench.

After just 2 hours the foamed concrete had set and was

hard enough to walk on. Once the foamed concrete sets

and has gained a compressive strength of 1 MPa a

wearing course can be laid down. This will be the final

DryDensity

(kg/m3)Dry4006008001000120014001600

7-dayCompressive Strength

(MPa)0.5 - 1.01.0 - 1.51.5 - 2.02.5 - 3.04.5 - 5.56.0 - 8.07.5 - 10.0

ThermalConductivity*

(W/mK)0.100.11

0.17 - 0.230.23 - 0.300.38 - 0.420.50 - 0.550.62 - 0.66

Modulus ofElasticity(kN/mm2)0.8 - 1.01.0 - 1.52.0 - 2.52.5 - 3.03.5 - 4.05.0 - 6.0

10.0 - 12.0

DryingShrinkage

(%)0.30 - 0.350.22 - 0.250.20 - 0.220.18 - 0.150.11 - 0.190.09 - 0.070.07 - 0.06

Figure 4: Foamed concrete being used to fill atrench at the National University of Singapore

Table 3: Typical Properties of Foamed Concrete compiled by the British Cement Association (8)

Figure 3: A cross-section of the Nagano Expressway, Japan.The original design, landslip and the new foamed concrete

design are shown.

New PlanFoamed Concrete 650kg/m3

27m

Original PlanTraditional Materials

Retaining Wall

80m x 50m x 9mLandslip

Wall (8m)

Hillside

A = Road Surface LayerB = Basecourse

A = 0.4mB = 0.3m

between the hillside and the retaining wall. A basecourse

layer of 0.3m thickness was placed on top of the foamed

concrete and a road surface layer of 0.4m thickness was

placed on top of the basecourse. Figure 3 shows a

cross-section of the hillside indicating the original

design, the landslip and the foamed concrete design.

The revised design stopped the landslide movements and

the expressway was opened to traffic in March 1993.

Trench Reinstatement at National University of

Singapore

In 1995 Trench reinstatement work was carried out by

the author at the National University of Singapore (NUS)

as a demonstration to engineers from the Public Works

Department (PWD).

Traditional methods of filling trenches in roads, i.e. the

use of granular fill materials, result in settlement and

damage to both the road and the pipes. Foamed concrete

does not require compaction, it does not settle and will

fill irregular gaps in the trench, even if the trench is

undercut.

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C O N C L U S I O N

Foamed concrete can be described as a lightweight, free flowing material which is ideal for a wide range of applications.

It can have a range of dry densities, typically from 400 kg/m3 to 1600 kg/m3 and a range of compressive strengths,

1 MPa to 15 MPa. Foamed Concrete can be used for a wide range of applications including housing, roads work,

bridges, void filling and ground work. In many cases foamed concrete has cost and performance benefits over

traditional materials. The trench reinstatement case study shows that costs benefits of foamed concrete include ease

of placement and that no maintenance needs to be carried out after placement. The landslip and arch masonry bridge

case studies demonstrate performance benefits of foamed concrete over traditional materials.

wearing course. Since foamed concrete does not settle

there is no need to return to the trench 6 months later

to place the final wearing course as is the case with

traditional fill materials. This minimises disruption to

traffic and saves money since there is less work to be

carried out.

Arch Masonry Bridge Strengthening Evaluation

An evaluation into arch masonry bridge strengthening

was undertaken by the Transport Research Laboratory

in Berkshire, United Kingdom (10). A series of 5m span,

2m wide, three ring brick arches were built and load

tested to failure. After the arches were constructed they

were filled with filling material. One of the arches was

filled with foamed concrete having a wet density of

1000 kg/m3 and a target strength of 1 MPa.

After full curing the bridge was loaded until it failed at

a loading of 1000 kN/m2, which equates to 170 tonnes/m2.

The same test was carried out with a traditional infill

material. The traditional infill material was compacted

to a 5 MPa compressive strength. Despite being

theoretically 5 times stronger with the traditional infill

material , the structure of the bridge fai led at

approximately half the loading that it did with foamed

concrete strengthening the bridge arch. The foamed

concrete transmitted the load much more effectively to

the structural elements of the bridge than the traditional

infill material.

REFERENCES

1. EABASSOC Lightweight Foamed Concrete Handbook, EAB Associates, 1996.

2. Horne, M.R., Review of Public Utilities Street Works Act 1950, London, HMSO, November 1985, 255 pp.

3. Department of Transport, The Scottish Office and The Welsh Office. Highways Authorities and Utilities Committee (HAUC). New Roads andStreetworks Act. Specification for the Reinstatement of Openings in Highways (A Code of Practice). The Stationery Office, London, 1992.

4. Hudson, K.C., Foamed Concrete for Trench Reinstatement, New Zealand Concrete Construction, July 1991, p6-9.

5. Foamed Concrete A Specification for Use in the Reinstatement of Openings in Highways, British Cement Association, 1991.

6. Parker, D., J. New Civil Engineer Concrete Supplement, July 1995, p4.

7. Basiurski, J.R., Foamed Concrete for Void filling, Insulation and Construction, University of Dundee Concrete Technology Unit, Foamed Concrete:Properties, Applications and Potential, Seminar Notes, March 2000, p42.

8. Foamed Concrete Composition and Properties, British Cement Association, 1994.

9. ASTM C 869-91. Standard Specification for Foaming Agents Used in Making Preformed Foam for Cellular Concrete, 1991.

10. Aldridge, D., Foamed Concrete for Highway Bridge Works, University of Dundee Concrete Technology Unit, Foamed Concrete: Properties,Applications and Potential, Seminar Notes, March 2000, p38.

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