The need to lower carbon emissions to meet Ireland’s climate commitments has intensified the focus on sustainable concrete production.

Ireland’s Climate Action Plan requires that industrial process emissions from cement production be mitigated through the use of 'novel binders' to reduce clinker content. In parallel, there is an ever-increasing need to repurpose waste material as a resource for sustainable development.

The cement and concrete industry have been doing this for several decades, incorporating constituents derived from the waste streams of other industries. The chemical and physical requirements for strong and durable concrete are a constant – it is the sustainable sourcing of the binder chemistry that has become more varied.

Less intimidating

Sourcing lower clinker binders is less of a technical challenge than might be expected. Research has yielded solutions that are technically ready and eagerly awaited by specifiers in the construction industry. Perhaps the phrase 'non-traditional binders' would be less intimidating than 'novel binders' when estimating the scale of innovation required. It would be best of all if we could adopt the phrase 'non-traditional binders' to categorise low technical risk evolutionary solutions, and the phrase 'novel binders' to categorise newly researched formulations that are truly revolutionary for the construction industry.

We are now in a third decade of mainstreaming lower clinker binders in Irish practice. Government policy on mitigating climate change has increased the demand for even lower clinker solutions.

Paradoxically, the pace of the journey has stalled at the very time that it should be accelerating, due to the failure of our national standards body to use its existing framework, as heretofore, to accommodate innovation in Irish concrete practice.

The National Standards Authority of Ireland (NSAI) is currently withholding decision-making on formally submitted low-risk proposals from cement and additions manufacturers. Leaving these proposals in limbo is acting as a market entry barrier and impediment to advancing progress at the rate required under the Climate Action Plan.

The highly conservative existing NSAI framework for innovation in concrete practice is moderated through the NSAI Concrete Standards Consultative Committee (NSAI CSCC), a representative sectoral forum. Regarding previous approvals of non-traditional binders in Ireland (cements and combinations) the following safeguards applied, all of which are still relevant in the approval of future low technical risk binders:

• Primary chemical constituents of the binder had an international track record of satisfactory use in concrete such that the technical risk profile could be categorised as low; and
• Research evidence demonstrated that concrete made with the binder satisfied qualifying criteria in the form of “provisions valid in the place of use”, through performance-based studies of concrete made with the binder against the performance of comparable CEM I or CEM II/A-LL concretes, with or without additions, that were already approved for use in Irish practice; and
• A technical committee of experts assessed the proposal and made recommendations to NSAI CSCC regarding any conditions that should apply in recognising suitability of the binder; and
• A formal process of public comment was conducted by NSAI on any decision to recognise suitability of the binder through amendment of the National Annex of standard IS EN206; and
• A final decision to amend the National Annex was by consensus of CSCC with full stakeholder inclusion, following a review of public comments; and
• Current durability benchmarks are highly conservative, being based on the highest cement content mix in the market for a given concrete strength class as determined in periodic surveys of concrete producers (95% confidence level).

Despite these safeguards in the existing robust framework, there is a move by NSAI CSCC to create a new framework for recognising novel binders. The need for this is understandable for truly novel chemical formulations but is not readily apparent for modest evolutionary proposals that have a low technical risk profile. It would also be useful to create a standing committee of experts to act as the technical committee of evaluators, in place of the current ad-hoc arrangement.

Historically, NSAI CSCC used the Irish Concrete Society Durability Subcommittee as its standing committee of experts but, more recently, a template membership was prescribed. Whatever about a new framework, a matter of greater concern is that NSAI CSCC is being distracted from discharging the day-to-day responsibility of processing decisions on 'recognition of suitability' of the proposals already submitted to them, through the existing framework.

A backlog of proposed low clinker solutions has developed at NSAI CSCC. This is being caused by failure to table the proposals for decision, as opposed to rejection on stated grounds. Manufacturers who have previously used the existing framework are perplexed.

The ‘no decision’ situation is not sustainable when the construction industry is required to urgently meet its responsibilities under the Climate Action Plan. Eventually a clearing house may be required to fast-track approvals, which will not necessarily be any more robust in control of risk than the existing framework, but precious time will be lost.

Proposed novel cementitious product

This article presents a case study of a proposed novel cementitious product, which is currently in the NSAI backlog.

The use of the existing framework is outlined, with reference to the relevant clause in the standard for concrete, and the published NSAI procedures for amending a national annex, which together ensure control of risk.

The failure to progress this proposal to the public comment stage at this time is questioned, when NSAI already has a robust framework in place.

It is argued that delaying a decision which is entirely under national control – three years and counting in the case study – is incompatible with national policy on carbon reduction when control of risk can be engineered to meet that of binders already approved that have given decades of satisfactory service.

The pivotal role of national standards bodies in lowering carbon emissions

Innovation to date in cement and additions as combination binders has resulted from a partnership between academic researchers, industry innovators, and the national standards body. This is reflected in amendments made periodically to the National Annex of the standard IS EN206, 'Concrete – Specification, performance, production and conformity'.

Periodic amendment of the national annex to give 'recognition of suitability' to these materials has been, and remains, a vital step in achieving market acceptance. Hence the pivotal role of the NSAI as a key partner in climate action.

The standard IS EN206 is non-harmonised and, through the national annex, is amendable locally by NSAI. Unlike a harmonised standard, amending a national annex, which is specific to each member state, does not require agreement of all 34 national standards bodies in the European Committee for Standardisation (CEN).

National annexes are dynamic documents updated locally, as and when required, to reflect evolving practice in a region at more frequent intervals than would be possible with a harmonised standard. This places a responsibility on NSAI to respond with agility to proposals from the Irish construction industry, which can accelerate decarbonising the sector.

National annexes are amended by consensus, achieved through ‘standards consultative committees’. The NSAI CSCC acts as the gatekeeper for a number of construction-related standards including the concrete standard IS EN206. This ensures that standards are industry-led documents, facilitated by NSAI, and that technological developments requiring an amendment can be processed in a timely manner.

Requested amendments can be formally submitted by various interested parties but typically come from industry. Examples in the quarter century since the first national annex to IS EN206 was drafted have mainly come from cement and additions suppliers.

The chairman of NSAI CSCC is required to operate in a manner that is independent of sectoral commercial interests and to endeavour to obtain unanimity on decisions, failing which they endeavour to achieve consensus. It is the role of the NSAI to facilitate this process.

Framework for 'recognition of suitability' of lower carbon-intensive solutions in concrete

The process for gaining 'recognition of suitability' for a new cementitious formulation in Irish concrete practice has for decades followed a process that is now formally published as a generic framework to be followed by all NSAI standards consultative committees. Accordingly, requested amendments to the national annex are processed to a procedure summarised in Table 7 of the 'NSAI Standards Development – Reference Manual for NSAI Standards Committee Members – NSAI, ISO and CEN Standards'.

Published standards are best seen as voluntary agreements, by consensus, in a given sector to comply with requirements that ensure fit-for-purpose products. Although innovative formulations could be used on a project-by-project basis, without reference to standards, such workarounds are inefficient and costly.

Manufacturers need the certainty of a regular market for scalable deployment before investing in changes to production. In the case of binders in concrete, that certainty is best provided by 'recognition of suitability' in IS EN206. The importance of granting this recognition through amending a national annex cannot be overstated. The corollary is that delaying or withholding 'recognition of suitability' is effectively a barrier to market access and an impediment to industry’s response to the Climate Action Plan.

Standards are not intended to be inflexible during the lifetime of their application, nor to be an unreasonable barrier to innovation. Thus, standard IS EN206 has a route to innovate the constituents used in concrete and national acceptance of such changes to traditional practice. This is through Clause 5 of the standard, which has been future-proofed by agreement in Europe that its text will remain unchanged in a future revision to the standard, when editorially it is expected to become ‘Clause 6’.

Clause 5 provides a pathway for use of non-traditional constituents in concrete through recognition of 'suitability' – general and specific. General suitability encompasses the basic requirements for a product to be approved for use in standard-compliant concrete, for example essential characteristics and production control.

Specific suitability is achieved for constituents of general suitability by further complying with 'provisions valid in the place of use'. These local provisions primarily relate to durability. This recognises the regional context of variations in locally available materials for concrete and differing exposure conditions across European countries.

Thus, the process for adopting novel binders in Irish concrete practice is a matter of demonstrating compliance with 'provisions valid in the place of use' in accordance with IS EN206 Clause 5, and gaining consensus agreement through the NSAI CSCC to amend the national annex through the published procedure, summarised in Table 7 of the NSAI Reference Manual.

This rigorous nature of this existing framework for 'recognition of suitability' can best be illustrated by the example of a proposal currently in train to incorporate waste container glass in Irish concrete practice.

Case study of ‘recognition of suitability’ of a proposed lower carbon addition in concrete

The case study concerns a ‘win-win’ proposal by Ecocem and REPAK to reduce the carbon intensity of concrete and enhance Ireland’s circular economy. This envisages using recycled container glass as one of two waste streams forming the raw material for a modified slag-based addition in concrete, with a current working title of ‘rcgp-ggbs’. The other waste stream is the traditional granulated blastfurnace slag from the steel industry, which in ground form is used extensively in Irish concrete practice.

The novel product is manufactured by co-grinding recycled container glass and granulated blastfurnace slag to yield the single powder ‘rcgp-ggbs’. Container glass is soda lime glass and is highly siliceous. When ground to a fine powder it undergoes a pozzolanic reaction in moist conditions with calcium hydroxide to produce the calcium silicate hydrates that are the key components of strong and durable concrete.

A proof-of-concept study of the ‘rcgp-ggbs’ proposal was conducted which found that the material conformed to the physical and chemical requirements of the standard for ggbs, IS EN15167-1 and therefore conformity could be evaluated to IS EN15167-2. This brought it into the ‘Clause 5’ route: “….where there is an existing European Standard which does not cover the particular product …. the establishment of suitability may result from…provisions valid in the place of use” (ie, provisions in the national annex to IS EN206).

Following NSAI CSCC custom and practice, now formalised in the NSAI Procedures Manual, the existing framework for amending the national annex in the context of IS EN206 Clause 5 required the following steps to give 'recognition of suitability' to the ‘rcgp-ggbs’ product in Irish practice:

1. Submission of the proposal to NSAI
2. NSAI board notification (but not board approval)
3. Draft amendment recommendations to NSAI CSCC from a ‘Technical Committee’
4. Public comment on proposed amendment and review of comments by NSAI CSCC
5. Approval to NSAI from NSAI CSCC to amend national annex, if consensus agreement
6. Editing of national annex by NSAI to incorporate amendment; NSAI board notification; publication of amended national annex and withdrawal of superseded version.

The proposed rcgp-ggbs product was introduced to NSAI CSCC in October 2022 in a meeting with the proposers and the research team which had established proof-of-concept. This was recorded in the NSAI annual report for 2022, which ensured awareness by the NSAI board.

Step 3 required an evaluation of the proposal by an expert technical committee to identify any constraints that would be recommended in framing amendments to the national annex. The stakeholder representation of the technical committee was prescribed by NSAI, including an academic as chair and also international expert membership.

The expert technical committee submitted its report in September 2023 and presented their findings to NSAI CSCC in November 2023. These were that recognition of suitability of the rcgp-ggbs product in the national annex would be appropriate subject to the following constraints:

• The proportion of rcgp in the rcgp-ggbs product be limited to a maximum of 20% to maintain direct comparability and compliance with the chemical, physical and strength criteria of 100% ggbs powder (EN 15167 Part 1);
• The fineness of the product be such that the maximum particle size was 300 microns to ensure resistance to alkali-silica reaction;
• A limit of 50% rcgp-ggbs be imposed in combination with CEM I or CEM II/A-LL, to assure that concrete setting times and rate of strength gain are similar to current practice;
• A limit of 40% rcgp-ggbs be imposed in combination with CEM I or CEM II/A-LL in the particular case of concrete in Exposure Class XC (carbonation) to assure durability.

The proposal from Ecocem and REPAK already conservatively met the recommendations on percentage of rcgp in the product and the fineness. The recommended inclusion of these constraints in the national annex was to ensure that potential future manufacturers of the product – besides Ecocem as first movers – would be aware of the conditions under which NSAI CSCC approved recognition of suitability in Irish practice.

The proposal was welcomed by NSAI CSCC. Summarising, the chairperson of CSCC recognised and acknowledged the merits of the proposal and the urgency of dealing with the climate crisis.

Somewhat surprisingly at this advanced stage of the framework process he stated that he was of the opinion that the wider CEN technical community should be consulted on the proposal and that it was unlikely that the CSCC of the NSAI would be able to establish suitability without such consultation.

He therefore decided not to table the proposed amendments to the national annex for decision, thus preventing the CSCC from reaching a consensus decision on progressing the proposal to Step 4 of the framework (public comment on proposed amendment). Furthermore, he stated that he would apply this approach (referral to CEN, the 34 nation European Committee for Standardisation) to the assessment of all novel binders or materials that emerge as candidates of potential.

However, it is not clear what role, if any, that CEN would have in this matter of solely national competence – amendment of the Irish national annex of a non-harmonised standard – and no follow-up action was taken by NSAI to refer the proposal to the 'CEN technical community'. Thus, the proposal is stalled in limbo at present.

Apparent reluctance by NSAI to use its existing framework – a cause for concern

The fully researched rcgp-ggbs product proposal remains without a decision in 2026 on progressing it to public comment stage, despite reaching a very advanced stage of the existing NSAI CSCC framework for recognition as long ago as 2023.

The chairperson of NSAI CSCC noted in 2023 that there is growing interest in stronger promotion of performance-based evaluation criteria for novel binders and that this may influence future concrete standards. However, such future developments in European standards do not amount to valid reasons for suspending the operation of NSAI’s traditional partnership with researchers and industry in urgently addressing already requested amendments to a solely national document.

This is especially so when the requested amendments are based on research evidence that is effectively performance-based, as in the case of the rcgp-ggbs proposal which benchmarked its performance in concrete against the performance of approved concrete mixes.

This unfortunate stalling in the evolution of Irish concrete practice coincides with a critical period for cement and concrete enterprises trying to meet sectoral climate targets, not to mention the architects and engineers anxious to meet client requirements for greener solutions.

If the current suspension of NSAI CSCC custom and practice is in anticipation of building a new framework approval process or awaiting the addition of 'Global Warming Potential' classes to future European concrete standards, the resultant delays will in time become an example of ‘perfection being the enemy of good’ in the context of addressing the climate emergency.

Quality improvement in approval processes is always welcome, and a new framework will undoubtedly be essential if revolutionary formulations are developed for novel binders in concrete. However, the proposals coming forward at present in Ireland are evolutionary and of low technical risk. These should be progressed without delay using the existing NSAI CSCC framework to engineer the solutions that are urgently required.

Author: Mark G Richardson, professor emeritus, University College Dublin.