International Standards and Testing for Novel Carbonaceous Building Materials

Publication Overview

Over 4 billion tonnes of cement are produced each year, equating to approximately 8% of global anthropogenic CO2 emissions, and this industry will continue to grow with the expansion of the built environment at a time that emissions need to be reduced. The utilisation or reduction of CO2 within cement, concrete and building materials could be a valuable way to contribute to emissions reductions in the sector , but there are several barriers, including the current state of standards, regulations and policies. This study will provide useful information for the technical and research community, the CCUS industry, the construction industry, and policymakers, providing an unbiased and non-prescriptive evaluation of international standards and testing relevant to novel carbonaceous building materials to address some of those barriers. The market potential for CO2 utilisation processes in the construction industry is also investigated, and the methods for certifying and measuring embodied carbon content of carbonated building materials is evaluated and the challenges therein.

Publication Summary

• 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.