lightweight fill for civil engineering

8/6/2019 Lightweight Fill for Civil Engineering

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maxit LWA L IGHTWE IGHT F ILL FOR CIV IL ENGINEERING



The process transforms the clay into

various sized lightweight ceramic

granules, which have a hard ceramic

shell and a porous core.

In this form, the material has

excellent insulating properties and is

extremely lightweight with a bulk

density of between 0.28 to 0.33

tonnes per cubic metre.These

granules are also fire resistant, frost

resistant and chemically inert with no

hazardous properties.

maxit LWA was initially developed

in Norway in 1958 to provide

insulation to roads, railways and

ditches across Scandinavia.

It is a lightweight expanded clay,

formed by heating and firing

natural marine clay in a rotary kiln

at temperatures up to 1150

degrees centigrade.

maxit L W AL I G H T W E I G H T F I L L

FOR CIVIL ENGINEERING



ADVANTAGES OF maxit LWA:

• Eliminates costly settlement periods

• Reduces weight on underground voids

• Has superb insulating properties

• Eliminates or reduces expensive load

transfer techniques

• Is free draining

• Allows reduced bulk of retaining structures

• Is installed using the same machinery as

conventional fills

• 1m compaction layers vs 0.25m with

traditional fills

• Not susceptible to oil/diesel spillages

• Surplus can easily be reclaimed andre-used

lightening the loads

above natural voids

or culverts

providing efficient

drainage

protecting and

insulating service

pipework

lightening the

loads against

retaining walls

stabilising slopes

lightening the

loads on bridge

abutments

reducing earth

settlement

LIGHTWEIGHT INSULATING FILL FOR A WIDE VARIETY

OF CIVIL ENGINEERING

APPLICATIONS



THE VERSATILE SOLUTION

FOR SO MANY

CIVIL ENGINEERING

APPLICATIONS





The sheer breadth of its application and

the benefits it can offer as a free draining,

lightweight fill have now become

recognised by civil engineering practices for

highways, rail and marine applications, with

a departure document to the Specification

for Highway works for both Structural and

General Fill now in place and a number of

successful Highways agency and Network Rail

projects completed throughout the UK.

The grading for most geotechnical applications

where light weight is the main criterion is 10-

20mm, but it can also be supplied as 0-32mm

material for the benefits of an increased friction

angle.

The gradings of both materials fall within the

category of Class 1B, uniformly graded granular

material, in Table 6/1 of the Specification for

Highway Works. Finer grades can be made

available where the application calls for filling

directly into water.

It’s a light weight material, with an average

density after compaction of just 300kg/m3 for

10-20mm, that is just a seventh the weight of

sand, gravel or crushed rock and it has a friction

angle of 37° for 10-20mm and 45° for 0-32mm,

providing good stability.

It offers good resistance to moisture retention

allowing installation during wet weather and is

not susceptible to oil or diesel spillages, unlike

polystyrene which, effectively, can melt when in

contact with such spillages.

PRACTICAL ADVANTAGES OF maxit LWA:

• Not damaged by repeated freezing and thawing or by ageing

• Thinner layers required for frost protection

• Reduced digging depths means lower volumes

of material for relocation

• Reduced requirements for imported material

• Reduced transportation

• Reduced residential upheaval• Less disturbance to substrata

• Allows lower structure heights

The practical thermal conductivity of maxit LWA

depends on its intended use. For layers underneath

the drained level, the Thermal conductivity should be

taken as 0.4 W/mK.

Application λp

Inside, dry 0.10 W/mK

Floor against subsoil, drained 0.12 W/mK

In subsoil, drained, unheated 0.15 W/mK

The last value is commonly used when maxit LWA is

employed to protect roads and rail beds against frost.



TRANSPORT

AND

PLACEMENT





Its light weight makes maxit LWA more

economical to transport, typically needing a

fifth of the number of loads required by

traditional heavyweight materials, and this

also has obvious environmental benefits.

It is economical and versatile to place . .

typically tipped into position, spread with a

tracked excavator and compacted by 3 passes of

the same vehicle or it can be pneumatically

blown into position, which offers specificbenefits for some applications especially where

site access is difficult.

It can be installed using machinery already in

use on site for the placement of other

earthworks applications - unlike other

lightweight products that require costly specialist

equipment and installation techniques.

The pellets of maxit LWA are round and find

their position within bulk fill very quickly when

pressure is exerted. For this reason the layers to

achieve adequate compaction are as deep as 1

metre, four times the depth of layer for

traditional fill material making it at least four

times quicker to install.

Once compacted, the modulus of elasticity is

15-20MN/m2 and the maximum level of

effective stress to avoid crushing of grains is100kN/m2. However, protected under a capping

layer such as reinforced concrete, 10-20mm

maxit LWA is able to take weights of 200kN/m2.

Surplus can easily be disposed of - for instance,

if an embankment is for temporary use, the

maxit LWA can easily be reclaimed and re-used

in a number of other locations, unlike other

man made materials.

COST BENEFITS OF maxit LWA:

• Reduced transport costs

• Reduced sitework costs

• Reduced structural costs

• Reduced timescales



REDUCING

SETTLEMENT -

ON SOFT SOILS

AND SUBGRADES





maxit LWA’s ability to reduce settlement

can offer massive benefits, reducing

timescales from years to a few months for

new or extended carriageways or for

embankments and even, in some instances,

eliminate settlement periods altogether.

Construction of embankments over weak and

compressible soil deposits, where the loading of the embankment causes soil consolidation and

settlement, is common.

Depending on the height of the embankment,

the depth of the weak soil deposit and the

consolidation properties of the soil strata, total

settlements can be very deep and problematic

in terms of road evenness, function and

durability of the road construction.

In the most difficult cases, various combinations

of soil strengthening techniques are available,for example, pre-loading, vertical drainage and

deep stabilization with piles - all of which are

time consuming and costly to install.

By lightening the embankment with maxit

lightweight aggregate, subsoil strengthening

and lengthy settlement periods can be reduced

or even avoided altogether.

1. Using maxit LWA on large scale cut and fill

operations and construction on soft soils and

bad ground, can overcome stability problems,

reducing the risk of landslide and deformation.

2. Used in road embankments, maxit LWA exerts

much lower horizontal earth pressures compared

with other backfill materials, helps improve

stability and reduce the need for counterfill.

1 2



REDUCING

SETTLEMENT -

DURING CARRIAGEWAY

WIDENING

1 2 3 4





When newly constructed fills are laid next

to existing fill such as a carriageway

widening or additional rail line, settlement

of the new sub-grade fill often leaves the

new surface lower than the original

existing surface and could pull the existing

surface out of level.

maxit LWA has a bulk density of approximately 15%

of that of general fill materials and will considerably

reduce settlement of the road or rail carriageway,

both immediately and in the long term.

Widening and replacing existing carriageways is also

simplified by using maxit LWA. Here’s a typical

sequence:

1. The lightweight aggregate is installed in

layers adjacent to the existing carriageway and

compacted.

2. Each layer of LWA is encapsulated by

Geotextile to retain and stabilise the material

whilst the new road pavement is constructed

above and the existing pavement excavated

3. The renewed embankment is filled with maxit

LWA adjacent to the new carriageway and

compacted.

4. The new lightweight, insulated carriageway

is completed and ready for traffic.

5 6

5. A road or rail bed widened with maxit LWA is

less prone to level differences caused by

settlement.

6. Excavation and backfill with maxit LWA helps

stabilise the bank.



REDUCING

PRESSURE

ON RETAINING

STRUCTURES





When used against retaining walls, maxit

LWA will reduce the weight acting on the

rear of the structure by at least 75%, in

comparison to traditional fill materials.

This reduction in weight avoids potential sliding,

overturning, slip and tilting or bearing failures and

enables savings by increasing spacing between

buttressing walls and reducing structural dimensions

The bulk weight of the wall can also be reduced and

more cost efficient, attractive materials can be used in

place of costly, unattractive structural concrete.

The use of maxit LWA will also minimise the

differential settlement between piled bridge abutments

and the embankment fill. As it is a free draining

material maxit LWA, can also eliminate the need for

rear wall block drainage.

The ‘pull out’ resistance of LWA also makes it an ideal

solution for reinforced soil retaining walls. Particularly

when constructed over weak sub-soils or voids, this

method can cut overall construction costs

considerably.

1 2

1. maxit LWA backfilled against bridge

abutments reduces loading on the underlying

subgrade, exerts less pressure on adjacent pile

foundations and prevents settlement

irregularities.

2. Backfilled against a retaining or basement

wall, maxit LWA settles less and exerts 75% less

horizontal earth pressure than conventional fill

materials.



REDUCING EARTH

PRESSURE

In areas prone to mining subsidence or where

ground conditions contain natural sub-

formation voids, drainage, culvert or tunnels

and there is a danger of collapse, expensive

techniques such as load transfer are often

considered. However, using maxit LWA can

eliminate these costs and considerably lighten

the load to provide similar benefits to those

when used in weak soil areas.





2 3

INCREASING SLOPE STABILITYmaxit LWA will also reduce the risk of bearing

capacity failure and increase the stability of the side

slopes.

PROVIDING EFFICIENT DRAINAGEEfficient drainage of the structural layers of the road

build-up can prevent loss of load bearing properties

caused by water and ensure a good load bearing

capacity throughout the road life.

Using free draining maxit LWA within the road build-

up will break the capillary rise of ground water into

the upper construction layers whilst performing as a

structural material and improving the load bearing

capacity.

In sloping terrain and in cuts stretching below the

surface of the ground water, streams of groundwater

can cause localised damage to the road surface and

reduce the load bearing capacity of the road.

maxit LWA used as a drainage layer within the road

construction will intercept the percolating water and

water rising by capillary action from the sub-

formations and direct the rising water

With carriageways in cuts that extend below the

natural level of the groundwater, frost damage and

loss of load bearing capacity can also be reduced by

forming drain trenches filled with maxit LWA at both

sides of the road, along which the water is led away

Used within the carriageway drainage, maxit LWA

helps filter and increase microbiological breakdown

of pollutant runoff from fields and highways.

3. In sloping terrain, cuttings and ground which

has high groundwater levels, LWA drainage

trenches and drainage layers can be used to dry

out road and rail structures and keep them free

draining to prevent pore water pressure build

up, slope erosion and provide slope stability.

1. Used in place of general fill, maxit LWA can

be used to strengthen the slope face of an

embankment.

2. Excellent insulating properties make LWA the

ideal filling for road and railway embankments

where frost stability requirements determine

sub-base thickness.

1



PROTECTING

PIPELINES AND

SERVICES

Maintaining levels within any

foul or surface water drainage

system can be difficult when the

drain runs across a soft soil site.

maxit LWA can be used as a

lightweight pipe surround, reducing

the pressure to the underlying soils

and minimizing the likelihood of

irregular settlement.

Surrounding utilities and drainage

carried within bridge beams either

side of the carriageway with maxit

LWA is a lightweight, simple to

install alternative to that of sand

traditionally used to support and

insulate these services.

The added benefit of using the

lightweight round granules of maxit

LWA as a pipe surround is that

there is little danger of any damage

to pipelines during backfilling and

the likelihood of damage from

settlement is also reduced.





CONSTRUCTING QUAYS

2

When constructing quays, the soft ground

conditions often call for the use of lighter

fills to guard against slides or deformation

that can damage structures and a numberof solid berth structures have been built in

recent years using maxit LWA.

It can be used to an advantage in many quay

designs such as sheet pile, sheet pile cell and

caisson structures and is also used as fill

replacement in solid berth structures when

quayside waters are dredged to greater depths.

0-4mm maxit LWA not only has a very low unit

weight, it also has minimal buoyancy, making it

particularly suitable for filling directly into water.

By depositing the aggregate directly into place

from a boat equipped with its own offloading

gear, exceptionally fast progress can be made

with 250-300 cubic metres per hour quite

achievable.

1. The light weight of maxit LWA can

ensure the stability of a quay even when

ground conditions under the sea floor

are poor.

2. maxit LWA has been used to water

depths of 12 metres during quay

construction.

1



Table 1. Design parameters for maxit LWA

Property maxit LWA maxit LWA Test method10-20mm 0-32mm*

Particle density (kg/m3) 750 800 prEN 1097-6

Uniformity Coefficient (D60/D10) 1.2 3.0 EN 933-1 / EN 933-2

D10 (mm) 10 5 EN 933-1 / EN 933-2

Dry loose bulk density (kg/m3) 280 335 EN 1097-3

Volume reduction by compaction (%) 10 10 -

Dry density after compaction (kg/m3) 310 370 -

Typical moisture content as delivered to site (%) 7-15 7-15 EN 1097-5

Long-term moisture content above water table (%) 25 25 EN1097-5

Long-term submerged moisture content (%) 40 40 EN1097-5

Long-term unit weight above water table (kN/m3) 3.75 4.5 -

Long-term submerged unit weight (kN/m3) 8.35 8.45 -

Angle of friction, f’ peak (degrees) 37 45 Triaxial tests

Cohesion, c’ peak (kN/m2) 0 0 Triaxial tests

Constrained modulus provided stress levels below crushing level (MN/m2) 15-20 25 Large scale oedometer tests

Maximum level of effective stress to avoid crushing gains (kN/m2) 100 150 Large scale oedometer tests

Table 2b. Grading Requirements for Acceptable Earthworks Materials

Percentage by mass passing the size shown

Size (mm) BS Series

Class 37.5 28 20 14 10 6.3 5 3.35 2 1.18

1D - 100 90-100 - 0-15 0-5 - - - -

1E 100 - 80-100 - - - 0-15 - 0-5 -

Table 2a. Acceptable Earthworks Materials: Classification and Compaction Requirements

Class

GeneralGranular Fill

1D

Lightweightexpanded clay aggregate(10-20mm)

Generalfill

maxit LWAEBU 10-20 Ror EBU 10-20RT lightweightexpanded clay aggregate

Layer thickness 1.0m.Compact by not lessthan 3 passes of atracked vehicle.Contact pressure notto exceed 50 kN/m2

(i) grading BS 1377: Part 2 Tab 6/2 Tab 6/2

(ii) uniformity See note 5 - 2coefficient

(iii) moisture BS 1377: Part 2 5 20content

(Iv) dry loose EN 1097-3 260 300bulk density

GeneralGranular Fill

1E


Generalfill

maxit LWAEBU 0-32 RClightweightexpanded clay aggregate

Layer thickness 1.0m.Compact by not lessthan 3 passes of atracked vehicle.Contact pressure not

to exceed 80 kN/m2


(ii) uniformity See note 5 1.5 10coefficient



Generalmaterial

description

Typicaluse

Permittedconstituents

Property Defined andtested in

accordance

with

Acceptable limits within

lower upper

Compactionrequirements

Material properties required for acceptability

Technical Specification for the use of maxit LWA as a General Fill material

*Due to increasingly high demand for the lower range of sieved gradings of LWA, minimum order quantities and/or extended delivery periods may apply to this grading of the material.



Table 3a. Acceptable Earthworks Materials: Classification and Compaction Requirements

Class

SelectedGranular Fill

6R


Fill tostructures

maxit LWAEBU 10-20 Ror EBU 10-20RT lightweightexpanded clay aggregate

Layer thickness 1.0m.Compact by not lessthan 3 passes of atracked vehicle or a vibrating platecompactor. Contactpressure not to exceed50 kN/m2


(ii) uniformity See note 5 - 2coefficient



(v) effective Triaxial tests Ø’=37° -angle of internal C’=0friction (Ø’) andeffectivecohesion (C’)

(vi) permeability Clause 640 1 x 10-2 -m/s

SelectedGranular Fill

6S


Fill tostructures

maxit LWAEBU 0-32 RClightweightexpanded clay aggregate

Layer thickness 1.0m.Compact by not lessthan 3 passes of atracked vehicle or a vibrating platecompactor. Contactpressure not to exceed80 kN/m2


(ii) uniformity See note 5 1.5 10coefficient



(v) effective Triaxial tests Ø’=45° -angle of internal C’=0friction (Ø’) and

effectivecohesion (C’)

(vi) permeability Clause 640 1 x 10-2 -m/s

Generalmaterial

description

Typicaluse

Permittedconstituents

Property Defined andtested in

accordance with

Acceptable limits within

lower upper

Compactionrequirements

Material properties required for acceptability

Table 3b. Grading Requirements for Acceptable Earthworks Materials

Percentage by mass passing the size shown

Size (mm) BS Series

Class 37.5 28 20 14 10 6.3 5 3.35 2 1.18

6R - 100 90-100 - 0-15 0-5 - - - -

6S 100 - 80-100 - - - 0-15 - 0-5 -

Because of the nature of maxit LWA, many of

the soil tests given in the Specification for

Highway Works are not appropriate. A

departure from the Specification should

therefore be requested for maxit LWA for use

in the situations described here.

For General Fill applications, it is proposed that the

material be classed as General Granular Fill Class

1D, lightweight expanded clay aggregate (10-20mm)

and General Granular Fill Class 1E, lightweight

expanded clay aggregate (0-32mm) and that the

relevant sections shown here are inserted in Table 6/1

of the Specification for the contract.

For structures, it is proposed that the material be

classed as Fill to Structures Class 6R, lightweight

expanded clay aggregate (10-20mm) and Fill to

Structures Class 6S, lightweight expanded clay

aggregate (0-32mm) and that the relevant sections

shown here are inserted in Tables 6/1 and 6/2 of the

Specification for the contract.

TECHNICAL SPECIFICATION DATA

Technical Specification for the use of maxit LWA as a Structural Backfill material



construction is

maxit LWA Ltd

The Heath, Runcorn,

Cheshire WA7 4QX

United Kingdom

Tel: +44 (0)1928 515656

Fax: +44 (0)1928 576792

Email: [email protected]

www.maxit-uk.co.uk

lightweight fill for civil engineering

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