Cementitious products comprise the glue that holds concrete
together. These materials include traditional Portland cement and
other cementitious materials, such as fly ash, ground granulated
blastfurnace slag (GGBS), limestone fines and silica fume. These
materials are either combined at the cement works (to produce a
composite cement) or at the concrete mixer when the concrete is
being produced (the cementitious product is called a combination in
Fly ash and GGBS are the most commonly used of these
materials in the UK. These secondary materials are useful
by-products of other industrial processes, which would potentially
otherwise be sent to landfill.
GGBS is a useful by-product recovered from the blast-furnaces
used in the production of iron. It can be used un-ground as a
coarse aggregate or as a supplementary cementitious material (where
it can replace up to 70% of cement in a concrete mix). Fly ash is a
useful by-product of coal-fired power stations and is
environmentally beneficial. If it were not used in composite
cements or as an addition at the concrete mixer then the material
would be wasted and sent to landfill.
Using GGBS or fly ash in concrete, either as a mixer addition
or through a factory made cement, significantly reduces the overall
greenhouse gas emissions associated with the production of
Concrete credentials: sustainability
||Direct annual CO2 emissons have reduced by nearly
40% since 1990 in absolute terms. The cement industry met the UK's
2010 Climate Change Agreement target four years in advance and is
continuing its commitment to improvement. This compares favourably
with the UK construction industry, which overall recorded an
increase in CO2 of more than 30% over the same
||In 2008, the sector replaced 26.5% of its fuel from
waste-derived material including scrap tyres, pelletised sewage
sludge and meat and bone meal.
||All cement plants and quarries have, or are linked to,
biodiversity action plans.
||The consumption of natural raw materials needed to make
cement has reduced significantly in the last ten years. Between
1998 and 2008, the sector has increased the use of waste-derived
raw materials by over 50%
||The cement sector is a net user of waste. Waste-derived
materials are actively sought as replacements for natural raw
materials and fossil fuels. The sector uses over 1.4 million tonnes
of waste in this way and produces 45,000 tonnes of waste per
||The cement industry has worked hard to reduce its emissions to
air by investing in new technologies. From 1998 to 2008,
significant reductions have been achieved. SOx emissions
have reduced by 75%, dust emissions by 68 per cent and
NOx by 51%
|Health and safety
||The sector has reduced accident rates of its employees by 80%
in the last ten years. The target is to achieve a further 50%
reduction in accident rates by 2015.
Additional cementitious materials
Source: Concrete Credentials: Sustainability, MPA - The
Concrete Centre, 2010
||The use of 50% GGBS can reduce embodied CO2 by
over 40%, compared with a traditional 100 per cent Portland cement
concrete mix. 30% fly ash can reduce embodied CO2 by
over 20% Limestone fines can reduce embodied CO2 by
||The concrete industry recycles by-products from other
industrial processes. GGBS, a by-product of iron production, and
fly ash from electric generating plants can both be used as
additional cementitious material in concrete mixes.
||Every tonne of additional cementitious material used in
concrete mixes saves about 1.4 tonnes of raw materials.
||GGBS and fly ash are by-products of other industries.
These products can be diverted from landfill by being used as
additional cementitious material in concrete mixes. As a proportion
of total cementitious materials used in ready-mixed and precast
concrete, 31.8% is additional cementitious materials.