generation aggregates - rwe02 generation aggregates quality protocol for the production and use of...
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RWE Power International
GENERATION AGGREGATES Providing readily available, cost effective secondary aggregates
1: Aberthaw – supply of FBA and dry and conditioned PFA
3: Tilbury – Supply of stockpiled PFA
2: The Generation Aggregates sales desk and RWE npower head office, Swindon
GENERATION AGGREGATES
Our secondary aggregate PFA can replace primary aggregates, helping to meet environmental targets.
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PROVIDING READILY AVAILABLE, COST EFFECTIVE SECONDARY AGGREGATES 01
Pulverised Fuel Ash, or PFA as it is more commonly known, is a by-product of coal-fired power stations. Along with Furnace Bottom Ash (FBA), which is also produced by burning coal to generate power, PFA is recognised as a safe and versatile construction material.
The properties of PFA make it an ideal, cost-effective
alternative to primary aggregates across a range
of applications, including:
– grouting: filling voids created by old mines or
redundant quarries and improving the bearing
capacity of soils
– engineering fill: for use as a load-bearing fill when
building embankments and road sub-bases, as well
as soil stabilisation
– landscaping: used in large-scale earthworks or the
reclamation of derelict land
– building materials: in the manufacture of building
materials, including concrete, concrete blocks,
cement, tiles and bricks.
With the environmental impacts of obtaining primary
raw materials becoming less and less acceptable, PFA
helps to reduce the demand for virgin aggregates and
assists businesses in meeting their recycling targets and
reducing their carbon footprint.
About us
RWE Power International coordinates the sales and
distribution of ash from RWE npower’s coal-fired power
stations in Southern England and South Wales, ensuring
that PFA is readily available to our customers. As part
of the RWE group, we can call upon the capabilities and
resources of one of Europe’s largest utility companies.
With the expertise that comes from over 80 years
of producing and utilising PFA in the UK, we have
an outstanding knowledge of the material and its
use in different industrial applications.
Technical support
With our engineers and scientists specialising in ash and
environmental issues, RWE Power International is able to
offer an exceptional level of technical advice, supporting
the sale and use of power station ash products.
We can offer extensive knowledge covering the
geotechnical, physical and chemical analysis of PFA.
Our technical support includes:
– monitoring ash quality in accordance with the Quality
Protocol (please refer to the following page) to ensure
its suitability
– advising on the standards relevant to the use of ash
across different applications
– providing product certificates for all our ash products
– providing technical data to enable you to assess the
suitability of ash in your particular application
– advising on best practice for use in your application.
Our quality system is accredited to ISO 9001. For more
information, or if you would like an ash sample to trial for
your particular application, please contact us.
ABOUT PULVERISED FUEL ASH
02 GENERATION AGGREGATES
QUALITY PROTOCOL FOR THE PRODUCTION AND USE OF PFA
RWE Power International and RWE npower’s coal fired power stations supply ash products in line with the WRAP Quality Protocol specifically for bound and grouting applications.
Quality Protocol compliant PFA is produced to meet
the requirements of a relevant product standard or
client specification for a given application and is
therefore regarded as a product and not as a waste.
Benefits
The Quality Protocol will bring the following benefits:
– makes it easier for you to use PFA in projects or processes
without the need for waste management controls
– provides you with the confidence that the ash
product you receive conforms either to a known
relevant product standard or your own specification
and is suitable for a given application
– provides suppliers, customers and regulators with the
assurance that ash products are produced and used
in a manner that protects and brings overall benefits
to the environment.
We provide product certification to accompany all
our commercial supply documentation.
We are always interested in developing new uses
for PFA and are happy to work together on the
creation of client specifications where standards are
yet to be developed.
Our responsibility
We are committed to acting responsibly, so advise
you to use all of our products in accordance with best
practice and in a manner that does not cause harm
to the environment or human health. Please contact
us for more information on best practice.
RWE Power International now supplies ash based
products in accordance with the Quality Protocol
for the following applications:
PFA based products – Bound and grout applications
We manufacture lightweight aggregate filler products
according to BS EN13055 parts 1 and 2 suitable for
use in the following applications:
– hydraulically bound mixtures, for example, to form
pavement layers by stabilisation with lime or cement
– bitumen bound mixtures, for example, to form road
base layers and surfacing
– concrete and other bound building products, for
example, as a lightweight filler aggregate in blocks
– grout, for example, geotechnical grouting of caverns
or redundant mine workings.
PFA based products – Unbound applications
We manufacture a lightweight aggregate filler product
according to BS EN 13055-2 and in accordance with
the Specification for Highway Works (SHW) 600 series
for the following applications:
– engineering fill and landscaping, for example,
embankment construction or raising of levels.
PROVIDING READILY AVAILABLE, COST EFFECTIVE SECONDARY AGGREGATES 03
MAKING YOUR PROJECTS GREENER
Government and industry is working collectively through the “Green Construction Board” (GCB) to drive forward actions set out in the Low Carbon Construction Action Plan. The target is to achieve an 80% reduction in greenhouse gas emissions in the built environment vs 1990 levels by 2050.
See how Generation Aggregates and
our ash products can make your project
more sustainable and help ensure that
the construction sector secures
continued growth whilst using green
goods and services:
ACT ON WASTESelling ash products from coal-fired
electricity ensures beneficial utilisation
of large quantities, avoiding landfill.
PFA can also be used to stabilise poor
or contaminated soils on your projects,
eliminating the need for costly disposal.
ACT ON WATERPFA absorbs water and is therefore not
easily saturated, so where it is used as
engineering fill, it allows construction work
to continue in bad weather, keeping your
projects on track.
ACT ON CARBONPFA is lower in density than other virgin
aggregates and soils so requires less
vehicle movements (approx. 25%) to
transport the same amount of material. The
replacement of Portland cement with PFA
also reduces the greenhouse gas signature
of concrete by lowering emissions of CO2.
ACT ON MATERIALSOur ash products are certified to the
UK Quality Ash Associations (UKQAA)
Responsible Sourcing Certification scheme.
Ash products as opposed to virgin
aggregates can be used across a range
of construction and building applications.
They offer a low cost alternative with low
environmental impact whilst maintaining
performance and improving the resource
efficiency of your projects.
ACT ON BIODIVERSITYPFA can be covered by or blended in with
topsoil to support a full range of
biodiversity and boron tolerant vegetation.
Where landscaped and left uncovered, PFA
gradually becomes colonized by plant and
animal species. This gives rise to biodiverse
habitats, particularly plants that thrive in
the alkaline conditions of PFA such as
Orchids and Marsh Helleborine. These in
turn attract many insects including
butterflies and bees, and birds such as
Skylarks and Sand Martins.
PFA is typically used as an engineering fill material behind bridge abutments and in the building of embankments and bypasses or as part of any major civil engineering project where an extensive amount of imported fill is required.
The superior benefits of PFA as a fill material come
from its lower density when compared to soils.
PFA has a density of 1.5Mg/m3 compared to around
2Mg/m3 for soils. These benefits include:
Reduced settlement in poor underlying soils. There is
also minimal long-term measurable settlement within
the fill material after placement and full compaction.
It is lightweight leading to savings in materials and
haulage costs. For example, there is approximately
a 25% reduction in lorry movements.
Increased stability as its self-supporting properties
provide stable conditions for shallow trenches and
other excavations.
Other significant benefits include immediate and
increasing strength. For example, field tests on
existing embankments have demonstrated the
positive strength gain and long term stability of PFA.
In addition, PFA will absorb water and therefore is not
easily saturated, allowing construction work
to continue in bad weather conditions.
To suit specific project requirements, RWE Power
International can supply two types of PFA for use
as engineering fill:
Conditioned ash taken directly from silos to which
water has been added. This assists with the delivery
and subsequent compaction on site.
Stockpiled ash previously conditioned ash which has
been placed temporarily on a stockpile before delivery
to site.
We have supplied PFA for use in many successful
engineering fill projects, including the widening of the
M25 motorway, see opposite.
PFA FOR ENGINEERING FILL
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RWE Power International supplied over 88,000 tonnes of PFA to the M25 widening project in Essex for various construction applications, proving what a successful and versatile construction material it is.
CASE STUDY 1PFA PROVIDES A SUSTAINABLE SOLUTION TO THE M25 WIDENING SCHEME
The M25 widening project (Junctions 27 to 30) is
currently being carried out by Skanska Balfour Beatty
Joint Venture for Connect Plus, working on behalf
of the Highways Agency, as part of the Design, Build,
Finance and Operation contract for the M25.
This is one of a number of major improvement
schemes on the M25, which was originally completed
in 1986 with the use of over one million tonnes of PFA.
RWE Power International secured a contract in 2009 to
supply conditioned PFA for the project. Material was
supplied from RWE npower’s Tilbury Power Station in
Essex for the first phase of works between Junctions
27 and 28. Approximately 88,000 tonnes of
conditioned PFA was used as a general fill to
widen the existing motorway embankments and
as fill behind some of the retaining wall solutions.
At its peak, up to 3,250 tonnes of PFA were being
delivered per day, with RWE Power International
coordinating up to 175 daily lorry deliveries.
PFA being used as fill to widen the existing M25 embankments PFA being compacted on site
PFA FOR GROUTING
Grouting is the injection, under pressure, of suspensions for structural purposes. This is often undertaken to improve the geotechnical properties of soils and rocks and allow for the future development of the land.
Cheaper and easier to use than sand cement grouts,
PFA grouts normally consist of PFA, Portland cement
and water. They bring the environmental benefit
of a reduced need for primary aggregates and high
cement contents, meaning cost savings for customers,
improved durability and reduced CO2 emissions.
The self-hardening properties of PFA also allow for
the production of low strength grouts containing
only PFA and water.
PFA grouts can:
– reduce the permeability of the ground
– increase the shearing resistance and subsequent
strength and durability of the ground
– fill inaccessible voids.
The benefits of PFA grouts include:
Reduced bleeding
A low rate of bleeding (typically less than 1%)
that improves the stability of grout suspensions.
Increased yield
Compared to cement, using PFA produces higher
volumes per unit weight. Typically it takes 0.7 to
1.0 tonnes of PFA to produce a cubic metre of grout,
compared to 1.6 tonnes of a primary aggregate
such as sand to produce the same. The need for
less materials and transportation reduces costs.
Ease of use
Grouts containing PFA are more easily pumped
and require less water than those without. It is also
possible to delay the setting of PFA mixtures for
up to four hours, so they remain pliable for longer.
These improved flow properties mean PFA grouts
can be pumped longer distances and through small
diameter pipe work.
Using PFA in cementitious grouts results in a more
durable composition. PFA can replace the use
of sand as a filter, improving flow properties and
penetration (without limiting the size of cracks
or fissures to be injected).
Increased strength
The slower rate of strength development but longer
term final strength of PFA/cement grouts can offer
economic benefits.
Increased resistance to chemical attack
PFA improves the sulphate resistance of grouts,
leading to reduced volume requirements and
less disruption.
We have supplied PFA for use in many successful
grouting projects, including a ground stabilisation
project in South Wales, see opposite.
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RWE Power International provided PFA from RWE’s Aberthaw Power Station for a grouting project to facilitate the construction of a new 7km bypass close to Pontypridd, South Wales.
CASE STUDY 2PFA PROVIDES COST AND USABILITY ADVANTAGES OVER PRIMARY AGGREGATES IN GROUND STABILISATION FOR THE CONSTRUCTION OF A BYPASS
Ground stabilisation specialist, Forkers Ltd, was
employed by the main project contractor, to
undertake shallow mineworkings treatment at
four points along the route. These locations were
considered to pose a threat to the future stability
of the road if left untreated and in fact, prior to
grouting, the area was deemed unsuitable for
development and construction, due to the unstable
nature of the ground.
Therefore, ground stabilisation in the area was
essential and this phase of the project commenced
in September 2008. During this period, probe drilling
was used to locate mineshafts and subsequently,
Forkers drilled 1,920 holes into 59,530 metres
of mine workings, injecting almost 7,000 tonnes
of PFA grout.
To complete this work, up to eight rotary percussive
water flush drilling rigs were used at up to three
areas concurrently, to ensure the earthworks and
road construction programme could proceed at the
required rate.
PFA rather than sand grout was selected in this case,
due to the compressive strength achieved when
mixed with cement. The mix also conformed to the
flow and bleed characteristics specified for the job,
whereas the use of sand would have required the
use of more water and increased costs and logistical
difficulties. Furthermore, the flow properties of the
PFA grout allowed it to be pumped further,
which made site logistics easier to manage for the
project contractor.
From an environmental perspective, the use of PFA
rather than sand reduced the need for ongoing
quarrying, whilst the density of sand is considerably
greater than PFA, which would have required more
material to produce the same volume of grout; the
lower density and cost per tonne of PFA considerably
reduced the cost of the grout mix in comparison
with sand.
The ground stabilisation phase of the project
was completed, on time and within budget, in
January 2009.
PFA is ideal for reclaiming areas of land by providing
subsoil fill.
With the growing importance of planning consent
conditions requiring landscape treatment, PFA can
be the answer to a range of land related problems.
The benefits of PFA in landscaping include:
– it is of known properties and consistency
– it is sterile and free from weeds
– it can be used as a soil forming material.
PFA can be used under topsoil, blended with topsoil
or with treatment it can support vegetation itself.
It is usual to cover PFA with topsoil to allow growth
of plants. However, if there is insufficient good quality
topsoil then PFA can be blended into the available
material to provide adequate cover.
If PFA is not covered it will weather over time and
plants will naturally colonise the surface. This starts
with mosses and, in time, grasses and will ultimately
result in trees such as willow, birch and alder.
However, it is usual to establish growth soon after
placing the PFA to eliminate erosion and dust
blow. This can be done by ripping the surface and
hydroseeding the area. Rye grasses and clovers can
be established on PFA relatively easily, provided
there is sufficient nutrient applied.
It is important when planning to grow plants
on unweathered PFA to select those that are
tolerant to boron, an essential plant nutrient,
and saline conditions.
We have supplied PFA for use in many successful
landscaping projects, including the creation
of the Twenty Ten golf course for the Ryder Cup
at Celtic Manor, see opposite.
PFA FOR LANDSCAPING
As well as having many uses in industry and civil engineering projects, PFA can also be used for landscaping.
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RWE Power International supplied over 150,000 tonnes of PFA from Aberthaw Power Station, to help Celtic Manor Resort prepare for the 2010 Ryder Cup.
CASE STUDY 3PFA REDUCES CO2 EMISSIONS AND ENVIRONMENTAL IMPACT IN THE CREATION OF A GOLF COURSE
In order to host one of the world’s most popular
sporting events, a number of significant improvements
were required at Celtic Manor. These included the
construction of a new club house, an extensive
television compound and practice ground, plus
improvements to the championship golf course to
enable it to meet the needs of the world’s top golfers,
media and thousands of expected visitors.
PFA was used to raise up parts of the course that will
eventually form the television compound, driving
range and practice area. This initial phase of
development, involving 100,000 tonnes of PFA, was
so successful that an additional 50,000 tonnes of PFA
was requested to complete the work.
James Norvill at GD Environmental, the contractors
responsible for the improvements at Celtic Manor,
said: “This has been a great project to be involved
in and it has been extremely successful. Ash is the
perfect product for the job, both from an
environmental and construction perspective.”
PFA being compacted to raise levels at the Celtic Manor resort The completed works
PFA IN BUILDING MATERIALS
PFA can be utilised in the manufacture of a wide range of building materials, including cement, concrete and ceramic products such as tiles and bricks and also in aerated and non-aerated blocks.
Concrete
PFA can be used in ready-mixed concrete, concrete
blocks and other concrete products, primarily as
a replacement for cement.
The use of PFA in concrete improves long-term
strength, durability and finish, whilst reducing
thermal cracking, segregation, bleeding and
permeability. The replacement of Portland cement
with PFA reduces the greenhouse gas signature
of concrete by lowering the emission of CO2.
Cement
The UK cement industry consumes nearly 20 million
tonnes of raw materials annually. However, not all of
these ingredients need to be primary raw materials.
PFA can be used in the production of cement
as a replacement for raw materials like clay or
shale. It can also be used to supplement cement
clinker, producing more cement per tonne of
quarried material.
Ceramic products
The properties of PFA make it an excellent raw
material replacement in the manufacture of ceramic
based products, such as bricks.
Aside from reducing the need to use primary
raw materials, utilising PFA can improve the finish
of ceramic products, as well as reducing drying
shrinkage and providing additional strength.
Aerated blocks
PFA can be used as an alternative for ground sand
in the manufacture of Autoclaved Aerated Concrete
Blocks (sometimes known as Aircrete or AAC Blocks).
The use of PFA in aerated block manufacture results
in an increased durability and high insulation values,
making the blocks suitable for the construction of
building foundations.
RWE Power International supplies PFA to some of
the UK’s largest manufacturers of building materials
including H+H UK Limited.
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RWE Power International offers a full service to customers from supply of aggregate to technical expertise, after sales advice and guidance through the process.
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322/10/13
RWE Power International
Generation Aggregates Electron Windmill Hill Business Park Whitehill Way Swindon Wiltshire SN5 6PB
T +44(0)800 731 2865 F +44(0)1793 892421 E [email protected] I www.generationaggregates.com
Registered office: RWE Npower plc Windmill Hill Business Park Whitehill Way Swindon Wiltshire SN5 6PB
Registered in England and Wales no. 3892782