maxit LWA
LI G H T W E I G H T F I L L F O R C I V I L E N G I N E E R I N G
maxit
LWA
LIGHTWEIGHT FILL FOR CIVIL ENGINEERING
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.
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.
LIGHTWEIGHT INSULATING FILL FOR A WIDE VARIETY OF CIVIL ENGINEERING APPLICATIONS
lightening the loads on bridge abutments
stabilising slopes
reducing earth settlement
lightening the loads against retaining walls
lightening the loads above natural voids or culverts protecting and insulating service pipework
providing efficient drainage
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 and re-used
THE VERSATILE SOLUTION FOR SO MANY CIVIL ENGINEERING APPLICATIONS
maxit
LWA
LIGHTWEIGHT FILL FOR CIVIL ENGINEERING
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 1020mm, but it can also be supplied as 0-32mm material for the benefits of an increased friction angle.
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.
The gradings of both materials fall within the category of Class 1B, uniformly graded granular
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.
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
TRANSPORT AND PLACEMENT
maxit
LWA
LIGHTWEIGHT FILL FOR CIVIL ENGINEERING
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 specific benefits 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 is 100kN/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
LIGHTWEIGHT FILL FOR CIVIL ENGINEERING
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.
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.
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.
1
By lightening the embankment with maxit lightweight aggregate, subsoil strengthening and lengthy settlement periods can be reduced or even avoided altogether.
2
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
3
4
maxit
LWA
LIGHTWEIGHT FILL FOR CIVIL ENGINEERING
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.
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
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
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.
sequence:
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
maxit
LWA
LIGHTWEIGHT FILL FOR CIVIL ENGINEERING
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.
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.
This reduction in weight avoids potential sliding, overturning, slip and tilting or bearing failures and
The ‘pull out’ resistance of LWA also makes it an ideal
enables savings by increasing spacing between
solution for reinforced soil retaining walls. Particularly
buttressing walls and reducing structural dimensions
when constructed over weak sub-soils or voids, this method can cut overall construction costs
The bulk weight of the wall can also be reduced and
considerably.
more cost efficient, attractive materials can be used in place of costly, unattractive structural concrete.
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 subformation 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.
maxit
LWA
LIGHTWEIGHT FILL FOR CIVIL ENGINEERING
1
INCREASING SLOPE STABILITY maxit LWA will also reduce the risk of bearing capacity failure and increase the stability of the side slopes.
PROVIDING EFFICIENT DRAINAGE Efficient drainage of the structural layers of the road build-up can prevent loss of load bearing properties
maxit LWA used as a drainage layer within the road
caused by water and ensure a good load bearing
construction will intercept the percolating water and
capacity throughout the road life.
water rising by capillary action from the subformations and direct the rising water
Using free draining maxit LWA within the road buildup will break the capillary rise of ground water into
With carriageways in cuts that extend below the
the upper construction layers whilst performing as a
natural level of the groundwater, frost damage and
structural material and improving the load bearing
loss of load bearing capacity can also be reduced by
capacity.
forming drain trenches filled with maxit LWA at both sides of the road, along which the water is led away
In sloping terrain and in cuts stretching below the surface of the ground water, streams of groundwater
Used within the carriageway drainage, maxit LWA
can cause localised damage to the road surface and
helps filter and increase microbiological breakdown
reduce the load bearing capacity of the road.
of pollutant runoff from fields and highways.
2
3
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.
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.
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.
maxit
LWA
LIGHTWEIGHT FILL FOR CIVIL ENGINEERING
1
CONSTRUCTING QUAYS 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 number of 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.
2
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.
Table 1. Design parameters for maxit LWA Property
maxit LWA 10-20mm
maxit LWA 0-32mm*
Test method
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
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
3.75
4.5
-
8.35
8.45
-
37
45
Triaxial tests
0
0
Triaxial tests
15-20
25
Large scale oedometer tests
100
150
Large scale oedometer tests
3
Dry loose bulk density (kg/m )
3
Long-term unit weight above water table (kN/m ) 3
Long-term submerged unit weight (kN/m ) Angle of friction, f’ peak (degrees) Cohesion, c’ peak (kN/m2) Constrained modulus provided stress levels below crushing level (MN/m2) Maximum level of effective stress to avoid crushing gains (kN/m2)
*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.
Technical Specification for the use of maxit LWA as a General Fill material Table 2a. Acceptable Earthworks Materials: Classification and Compaction Requirements Material properties required for acceptability Class
General Granular Fill 1D
General material description
Permitted constituents
Typical use
Lightweight expanded clay aggregate (10-20mm)
General fill
maxit LWA EBU 10-20 R or EBU 10-20 RT lightweight expanded clay aggregate
Property
Defined and tested in accordance with
lower
upper
BS 1377: Part 2
Tab 6/2
Tab 6/2
(ii) uniformity coefficient
See note 5
-
2
(iii) moisture content
BS 1377: Part 2
5
20
EN 1097-3
260
300
BS 1377: Part 2
Tab 6/2
Tab 6/2
(ii) uniformity coefficient
See note 5
1.5
10
(iii) moisture content
BS 1377: Part 2
5
20
EN 1097-3
320
350
(i) grading
(Iv) dry loose bulk density General Granular Fill 1E
Lightweight expanded clay aggregate (0-32mm)
General fill
maxit LWA EBU 0-32 RC lightweight expanded clay aggregate
Acceptable limits within
(i) grading
(Iv) dry loose bulk density
Compaction requirements
Layer thickness 1.0m. Compact by not less than 3 passes of a tracked vehicle. Contact pressure not to exceed 50 kN/m2
Layer thickness 1.0m. Compact by not less than 3 passes of a tracked vehicle. Contact pressure not to exceed 80 kN/m2
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
-
TECHNICAL SPECIFICATION DATA Because of the nature of maxit LWA, many of
expanded clay aggregate (0-32mm) and that the
the soil tests given in the Specification for
relevant sections shown here are inserted in Table 6/1
Highway Works are not appropriate. A
of the Specification for the contract.
departure from the Specification should therefore be requested for maxit LWA for use
For structures, it is proposed that the material be
in the situations described here.
classed as Fill to Structures Class 6R, lightweight expanded clay aggregate (10-20mm) and Fill to
For General Fill applications, it is proposed that the
Structures Class 6S, lightweight expanded clay
material be classed as General Granular Fill Class
aggregate (0-32mm) and that the relevant sections
1D, lightweight expanded clay aggregate (10-20mm)
shown here are inserted in Tables 6/1 and 6/2 of the
and General Granular Fill Class 1E, lightweight
Specification for the contract.
Technical Specification for the use of maxit LWA as a Structural Backfill material Table 3a. Acceptable Earthworks Materials: Classification and Compaction Requirements Material properties required for acceptability Class
Selected Granular Fill 6R
Selected Granular Fill 6S
General material description
Typical use
Lightweight expanded clay aggregate (10-20mm)
Permitted constituents
Fill to structures
Lightweight expanded clay aggregate (0-32mm)
Fill to structures
maxit LWA EBU 10-20 R or EBU 10-20 RT lightweight expanded clay aggregate
maxit LWA EBU 0-32 RC lightweight expanded clay aggregate
Property
Defined and tested in accordance with
Acceptable limits within lower
upper
BS 1377: Part 2
Tab 6/2
Tab 6/2
(ii) uniformity coefficient
See note 5
-
2
(iii) moisture content
BS 1377: Part 2
5
20
(Iv) dry loose bulk density
EN 1097-3
260
300
(v) effective angle of internal friction (Ø’) and effective cohesion (C’)
Triaxial tests
Ø’=37° C’=0
-
(vi) permeability
Clause 640
1 x 10-2 m/s
-
BS 1377: Part 2
Tab 6/2
Tab 6/2
(ii) uniformity coefficient
See note 5
1.5
10
(iii) moisture content
BS 1377: Part 2
5
20
(Iv) dry loose bulk density
EN 1097-3
320
350
(v) effective angle of internal friction (Ø’) and effective cohesion (C’)
Triaxial tests
Ø’=45° C’=0
-
(vi) permeability
Clause 640
1 x 10-2 m/s
-
(i) grading
(i) grading
Compaction requirements
Layer thickness 1.0m. Compact by not less than 3 passes of a tracked vehicle or a vibrating plate compactor. Contact pressure not to exceed 50 kN/m2
Layer thickness 1.0m. Compact by not less than 3 passes of a tracked vehicle or a vibrating plate compactor. Contact pressure not to exceed 80 kN/m2
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
-
maxit LWA Ltd The Heath, Runcorn, Cheshire WA7 4QX United Kingdom Tel: +44 (0)1928 515656 Fax: +44 (0)1928 576792 Email: sales@maxit-uk.co.uk
www.maxit-uk.co.uk A maxit Group company
construction is