Background to the Study

Key Messages

• Over the past two decades an increasing number of companies have emerged with a focus on developing innovative materials that utilise CO2 to lower the carbon emissions intensity of construction products.
• Climate change is an extremely important priority throughout the building materials industry, with CO2 intensity or other measures being increasingly common to be part of tendering processes and shareholder pressure to decarbonise an important factor. However, safety and testing is seen as vital to maintain high standards.
• Developing confidence in new materials is likely to be achieved by using them first in non- safety critical operations (e.g. retaining walls).
• Knowledge sharing across industries and countries is important, particularly as the main growth area will be in emerging nations rather than developed countries.
• Support in terms of legislation and tax credits is important from governments to deploy new materials, cases where this is happening include New York and New Jersey.
• Performance based standards are preferable but take longer to develop and it is a challenge to include every possible combination of materials in a performance-based standard. A transition to performance-based specifications will require the development of rapid and reliable (appropriate) performance test methods. Some test methods need to be altered for new materials.
• Effort, time and funding is required to speed up the currently slow drift from mainly prescriptive to performance-based standards that are needed. The work of experts on both the RILEM (International Union of Laboratories and Experts in Construction Materials, Systems and Structures) and BSI (British Standards Institution) Flex committees to develop performance- based standards for novel cements is an example of ongoing work in this area.
• Comparing specifications for cements or concrete between international standards is difficult because cement types are defined using different criteria either using end-use requirements or composition.
• Within the same overarching standard there are large differences in values between countries, because they can set limits on specific properties when specifying the same material property (e.g. compressive strength) for a material exposed to a particular set of conditions.
• The number of potential new supplementary cementitious materials (SCM) is much larger than those currently permitted in existing standards. The need for consensus for new SCMs to enter the standard may hinder the adoption and exploration of locally available materials, which is important considering resources of traditional SCMs like coal fly ash have declining availability.
• The aggregate market is estimated to currently be 46Gt per year. Recycled aggregates and those produced as industrial by products, including those utilising CO2 in production are becoming prevalent.
• Other ways to use CO2 in the production of building products include:
  • Accelerated CO2 curing of concrete,
  • Use of alternative cement chemistry produced using CO2.
• Some material such as carbonated concrete slurry waste can act in a complex manner within cement, allowing reduction of the total amount of cement clinker. There is a large potential resource of concrete slurry waste and it could be profitably used.
• There is a significant potential market for carbonatable materials, but lifecycle emissions and commercial factors could potentially reduce CO2 savings and the total market available.
• An analysis of the CO2 capture potential of industrial by-products from five industrial sectors found that up to 0.56 Gt of CO2 emissions could be captured by 3.6 Gt of carbonatable materials each year using CO2 mineralisation
• Emissions reductions for the substitution of other materials could save between 0.01 and 0.49 kgCO2 - eq per kg material substituted. The greatest reduction occurs with the use of carbonated lightweight aggregate,
• It is strongly suggested that “low carbon” terminology be significantly better classified in the production of building products.

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