Concrete and the Carbon Challenge
20 Jan 2016
Guy Thompson explains how The Concrete Centre responds to the challenges and many enquiries about the sustainability performance of concrete and how the industry is committed to a holistic measure of sustainability thus enabling designers and specifiers to produce evermore sustainable solutions.
Since the announcement of the UK government’s 2020 target for reducing carbon emissions, the decision making processes in design and construction have seen some dramatic changes; The Concrete Centre is committed to offering best practice guidance on the use of concrete to help an industry which is striving to exceed its climate change goals.
Carbon Reduction in Manufacture
The 2014 Sustainability Performance report, due to be launched at the Concrete and Masonry Pavilion at Ecobuild 2016, details industry progress in reducing the overall CO2 emissions associated with concrete production. In the seven years since the industry published its first report there has been an 11 per cent improvement in energy efficiency and a 13 per cent reduction in carbon intensity. 2014 data resulted in 76.3 kg of CO2 per tonne of concrete, based on the standardised mix. The target for 2020 is to reduce this figure further to 71.8kg of CO2 per tonne, which equates to an overall 30 per cent reduction from the 1990 baseline.
Concrete is a mix of materials, its CO2 emissions are affected by their production, from processes such as cement manufacture, transportation and a range of other criteria.
The cement sector is a major component of the embodied energy in concrete, and have continued to achieve improvements in energy efficiency. The embodied carbon of cement has been reduced through the use of waste-derived fuels. Some 44% of the fuels the cement industry use are derived from waste or by-products reducing the use of carbon intensive fossil fuels.
The embodied CO2 can be further lowered by the use of cementitious additions derived from other industries. These include fly ash from power stations and ground granulated blast furnace slag (GGBS) from the iron and steel industry. In 2014, 26.2% of all cementitious materials used were by-products; the target set for 2020 is 35%.
Concrete Industry committed to improvement across a holistic range of indicators
The industry has a very clear vision to reduce both embodied CO2 within its own manufacture and operational CO2, through the sustainable use of concrete products in the built environment. In 2008, the UK concrete industry committed to a Sustainability Construction Strategy and a key commitment was to contribute to a low carbon built environment. The strategy also sets targets, for indicators relating to waste reduction, responsible sourcing, water, wellbeing, and biodiversity amongst others.
The original initiative focused more on those aspects that were within the concrete industry’s control – in other words, the cradle-to-factory-gate impacts of production. In 2012, in response to the European Commission’s drive towards greater resource efficiency, the UK concrete industry broadened its strategy to include the impact of the material post production.
Now, this has extended still further with a series of resource efficiency action plans (REAPs), involving close collaboration with stakeholders, contractors and those responsible for projects to the end of service life with the objective to deliver a more holistic approach to measuring and demonstrating whole-life product stewardship.
In 2014, significant progress was made on how to measure and agree targets for water consumption, with the publication of the Mineral Products Association (MPA) Water Policy. The Policy sets out three aims:
- Minimising water consumption
- Prioritising use of the most sustainable water sources
- Protecting the water environment.
Implementation of the Water Policy will improve understanding of the amount of water consumed and demonstrate where measures have been implemented to reduce consumption, ensure the use of the most sustainable water sources and maintain water quality.
Based on this, the Sustainable Concrete Forum is developing specific indicators for the measurement of sustainability performance and target setting, as per the
Concrete Industry Sustainable Construction Strategy 2020 commitment made in 2012.
The role of EPDs and BIM in measuring carbon
The concrete industry is currently investing in generic Environmental Product Declarations (EPDs) and BIM guidance, to help designers harness the sustainability credentials of concrete on a credible basis from the earliest design stage of building and infrastructure projects. The Mineral Products Association published the first of these in 2013, declaring the lifecycle environmental impact of UK-factory produced cement. This has paved the way for the production of generic EPDs for precast concrete products, ready-mixed concrete and mortar, which will provide a sound basis for project environmental or carbon assessments.
The industry is on target to launch these EPDs at Ecobuild, as part of an event in the Concrete and Masonry Pavilion. The precast and ready-mixed concrete sectors are working with Thinkstep (previously PE international) to develop the EPDs.
With regard to BIM, Government legislation for implementation of level 2 for government projects in 2016 has galvanized development and implementation.
For products, the formatting of BIM product data templates (PDT) is key. Each PDT aims to anticipate the information sought by every party – from specification through operations to decommissioning and replacement. When a manufacturer completes a PDT it becomes a Product Data Sheet (PDS) – a ‘digital’ description of the product. It is envisaged that some or all EPD data fields will become part of PDT’s and hence PDS’s - the digital description - will contain environmental impact data.
What should designers do to specify sustainable concrete?
The Concrete Centre provides guidance to enable designers to specify sustainable concrete whilst recognizing that embodied carbon reduction is but a small part of the solution for the provision of sustainable construction when measured over its lifetime, when taking into account energy savings from thermal mass and the climate change protection provided.
Guidance that balances the desire to specify concrete with a low environmental impact, whilst ensuring other performance parameters are optimised, can be summarised as follows:
- Use of cementitious additions (GGBS, fly-ash etc.) can reduce the embodied CO2 (ECO2) of concrete and also influence its visual appearance.
- Do not over-specify strength. Consider the possibility of strength conformity at 56 days rather than the conventional 28 days. This could enable you to increase the amount of cement replacements used.
- Specify responsibly-sourced concrete and reinforcement.
- Permit the use of recycled or secondary aggregates but do not over specify. BS 8500 allows producers to use up to 20% of recycled aggregates in many concretes, they do this when it is available. Recycled aggregates should only be specified when they are locally available, otherwise transportation impacts exceed the intended benefits.
- Admixtures can be used to enhance sustainability credentials and reduce the ECO2 of concrete.
But this guidance is focussed on the material. With concrete there are also a wide range of construction methods that can be more sustainable, based on the decisions of specifiers and contractors:
- Ensure efficient structural design, to avoid over-specification of materials. Post-tensioned concrete or precast slabs with void-formers can all reduce the amount of materials used.
- Re-use of existing concrete structure on site as part of new design proposals.
- The use of concrete’s thermal mass, can reduce the operational energy of buildings, saving considerable carbon emissions across the whole life of the building.
- Use concrete structure as a finish to minimise use of finishing materials and therefore reduce waste in general.
- Design structures for longevity and re-use. Measure performance across the whole-life of a building to make the most sustainable use of resources.
For more information, guidance from The Concrete Centre and product manufacturers will be available from the Concrete and Masonry Pavilion, at Ecobuild 2016. Ecobuild takes place on the 8-10 March at ExCel, London.
The 2014 Concrete Industry Sustainability Performance Report is available to download from www.sustainableconcrete.org.uk