CMMI-EPSRC RENACEM: Response to CO2 exposure of concrete with natural supplementary cementitious materials

Lead Research Organisation: University of Leeds
Department Name: Civil Engineering

Abstract

Concrete can traditionally be thought of a mixture of mineral aggregates, water, and Portland cement. However, modern concrete mixtures are much more complex, also containing chemical admixtures and supplementary cementitious materials (SCMs) to enhance properties in the fluid and hardened states. SCMs are widely used in the US, UK and internationally to replace a portion of the Portland cement, improving concrete long term durability, reducing cost, and reducing CO2 emissions associated with concrete production.

The most commonly used SCMs are waste-derived, including coal combustion ashes and blast furnace slags from iron-making. However, changes in industrial processes (e.g. co-firing of coal with biomass, use of renewable energy, structural changes in the global iron industry) and increasing demand for SCMs are leading to a shortage of high quality, conventional SCMs. The use of widely-available natural SCMs, such as calcined clays and volcanic minerals, is rising dramatically, as their chemistry and mineralogy are more homogeneous, aiding in quality control compared to waste-derived SCMs. Standardization is advancing in the US and the UK to enable broader use of these materials, but the fundamental science of their use needs further investigation.

Natural SCMs, like waste-derived ones, generally have positive impacts on concrete durability, cost, and environmental footprint. However, one concern with all SCMs is that they often increase the vulnerability of concrete to carbonation. Carbonation occurs when CO2 enters the material, chemically reacting and reducing pH, leading to corrosion of steel reinforcement as well as changes in the integrity of the cementitious matrix. In concretes with natural SCMs, the mechanisms governing carbonation and related degradation are largely unknown. Considering that the field is pushing toward use of increasing volumes of natural SCM use in concrete (so-called LC3 systems), understanding the contribution of natural SCMs toward carbonation degradation is critical for future proof this technology. Furthermore, it is possible that manipulating the composition of the systems to reduce or prevent carbonation is possible, but has not previously been explored.

RENACEM is a joint US-UK collaboration between leading infrastructure materials researchers to elucidate the fundamental science explaining the long-term performance of concretes produced with natural SCMs. We will understand the chemical interactions between concretes and atmospheric CO2, and its transport, to identify meaningful methodologies to be used for their assessment. This will underpin the adoption of new methods for testing carbonation of concretes with natural SCMs and prediction models.

Planned Impact

The costs associated with degradation of infrastructure, in the US and the UK, are vast; in both nations roughly 50% of the annual infrastructure budget is allocated to maintenance, repair and replacement. With the projected new infrastructure spending by 2025 ($1000B in the US; £480B in the UK), it is imperative to improve and predict the resilience of construction materials. A critical threat to concrete is CO2, which is now present in the atmosphere at record concentrations. Increasing presence of CO2 in the environment makes concrete structures more vulnerable to degradation due to carbonation; this problem is coupled with the increase in use of concrete mixtures that contain high-volume SCMs that are even more vulnerable.

The research proposed in this program has potential broad societal impact, reducing the monetary costs associated with infrastructure and building repair and reducing the risk of life-threatening failures due to deterioration and collapse of structures. The research programme establishes a strong and unique international network for research on cement-based materials encompassing materials characterization, design and synthesis, property development, accelerated degradation testing, innovative sensing, and thermodynamic and kinetic modelling. This diverse and multifaceted approach, bringing together experts from three universities in two countries, also builds upon existing collaborative relationships the researchers have with universities around the world on similar topics. For example, Prof. Juenger and Katz have collaborative relationships with researchers in Chile, Mexico, and Brazil already. The UK researchers have strong collaborations across the EU, Brazil, China, Colombia, and Australia, while the connection of team members to RILEM activities brings truly global reach. Strengthening the global research network facilitates solutions with broad, global impacts and improves the likelihood of acceptance of new materials and methodologies by standardization agencies, including those influential bodies (ACI, ASTM, BSI and others) for which the PIs and co-PIs are senior committee members. The industrial partnerships also established with this project also contribute to this effort.

Strengthening the global research network also provides an educational opportunity for students that broadens their research experience and improves their competitiveness in the global job market. The students and postdoctoral researchers involved in this research will learn how to work with a cross-institutional team of researchers, giving them valuable skills they can apply in today's increasingly global workplace. Further, the students will be able to learn from and participate in programmes available at the three applying universities that enhance education.

Publications

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Description The RENACEM project is a joint collaboration between academics from the USA and the UK, along with industry partners aiming to determine the effects of CO2 exposure in the performance of concretes produced with locally available natural cement replacements known as supplementary cementitious materials (SCMs). During the first year of this project strong industry link have been developed in USA, including with the Natural Pozzolan Association, Imerys, Christy Co., Kirkland Mining Co., and US Minerals, who have provided clay materials to study, as well as information about the geological sources of such clays. This is the first study that collectively examines both calcined clays and volcanic mineral SCMs that cover a broad geographic and mineralogical range. A primary interest in studying natural SCMs is to examine those that have low purity and are undesirable for other industries (i.e. paper and cosmetics). The materials sourced and characterized for this study are "impure" for a range of reasons, including mixed clay minerals and different crystalline impurities. The work will impact the field by providing better understanding of how these impurities affect performance of concretes produced with them.
Exploitation Route There is an urgent need, particularly in the UK, to find locally available resources that can be used for production of low-carbon cement concretes, as part of the construction industry strategy to reduce the carbon emissions linked to this sector. The outcomes of this projects is allowing to identify the suitability of using 'impure' clay resources and soils as potential cement replacements for production of more environmentally friendly concretes. Recent creation of BS standards enable the use of such materials in concrete production, however, local calcined clays are not commercially available to fulfil the potential market that is opening up, as blast furnace slag and fly ashes availability rapidly reduces. Such standards for the specific use of calcined clays do not exist in the US (the ASTM C311 included natural pozzolans), and we are hoping that the outcomes from this project and the transatlantic experience serves as foundation to promote standardisation of such materials in the US. But this project goes beyond just sourcing and utilising these materials. A truly sustainable materials needs to be durable, and climate change, particularly the increased CO2 concentrations in the air can threaten the service life of these novel low-carbon cements, hence, understanding how carbonation can impact the properties of these materials will enable us to select mitigation strategies (e.g. use of mineral additives) to increase the durability performance against CO2, while optimising the carbon capture potential of these new generation of cements. The modelling tools to be developed in this study also open new opportunity for optimisation of cementitious materials selection at the design stage for sustainability and longevity.
Sectors Construction,Education,Environment,Transport,Other

 
Description Collaboration with EMPA (Switzerland) and Oregon State University (USA) to advance modelling capabilities 
Organisation Empa - Swiss Federal Laboratories for Materials Science and Technology
Country Switzerland 
Sector Academic/University 
PI Contribution One of the key planned activities of RENACEM is the development of modelling tools for the prediction of carbonation performance of concretes produced with natural SCMs. As part of this efforts we have partnered with Prof. Barbara Lothenbach (EMPA) and Prof. Burkan Isgor (Oregon State University) to develop a training plan for the PGRs and postdoc researchers linked to RENACEM, so they can gain the necessary skills for the creation and implementation of thermodynamic modelling and multi-physics modelling for developing novel modelling tools for evaluation of the materials currently studied and to be developed from this research.
Collaborator Contribution Prof. Lothenbach is world-leading in thermodynamic modelling of cementitious materials, and a long-lasting collaborator of both the UK-PI and the US-PI, and Prof. Isgor has developed some of the most sophisticated modelling tools to combine chemistry and transport properties phenomena taking place in cementitious systems exposed to different environment. Prof. Isgor collaborated closely with the USA team of this project, and the UK team has benefited greatly from this new interaction.
Impact This collaboration started in mid-2020 in an effort to adapting the activities of RENACEM to the impact of the COVID pandemic, particularly reduced laboratory access in all the partner Universities, hence no outcomes and results beyond ongoing training has taken place.
Start Year 2020
 
Description Collaboration with EMPA (Switzerland) and Oregon State University (USA) to advance modelling capabilities 
Organisation Oregon State University
Country United States 
Sector Academic/University 
PI Contribution One of the key planned activities of RENACEM is the development of modelling tools for the prediction of carbonation performance of concretes produced with natural SCMs. As part of this efforts we have partnered with Prof. Barbara Lothenbach (EMPA) and Prof. Burkan Isgor (Oregon State University) to develop a training plan for the PGRs and postdoc researchers linked to RENACEM, so they can gain the necessary skills for the creation and implementation of thermodynamic modelling and multi-physics modelling for developing novel modelling tools for evaluation of the materials currently studied and to be developed from this research.
Collaborator Contribution Prof. Lothenbach is world-leading in thermodynamic modelling of cementitious materials, and a long-lasting collaborator of both the UK-PI and the US-PI, and Prof. Isgor has developed some of the most sophisticated modelling tools to combine chemistry and transport properties phenomena taking place in cementitious systems exposed to different environment. Prof. Isgor collaborated closely with the USA team of this project, and the UK team has benefited greatly from this new interaction.
Impact This collaboration started in mid-2020 in an effort to adapting the activities of RENACEM to the impact of the COVID pandemic, particularly reduced laboratory access in all the partner Universities, hence no outcomes and results beyond ongoing training has taken place.
Start Year 2020
 
Description American Concrete Institute (ACI) Student Chapter booth at the Girl Day STEM Festival 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Undergraduate students
Results and Impact The PhD researcher based at U. Texas at Austing, Katelyn O'Quinn, assisted in the organization and preparation of activities for the American Concrete Institute (ACI) Student Chapter booth at the Girl Day STEM Festival at the University of Texas at Austin. This event introduces thousands of students to different types of engineering and sciences through demonstrations and hands-on activities put on by a variety of university clubs. Katelyn prepared concrete disks for a demonstration on the effects of reinforcement within concrete and small concrete figures for the students to take home. At the event, Katelyn helped with assigning and training for the stations at the booth and explained to students what concrete is and why it is important.
Year(s) Of Engagement Activity 2020
 
Description Conference presentation - Reactivity of low-grade kaolinitic calcined clays as supplementary cementitious materials 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact This presentation was delivered in the RILEM Week 2020 and IOM3 Cement and Concrete Science Conference, by the PhD researcher of RENACEM based at U. Texas at Austin, showcasing some of the preliminary results of chemical reactivity of clay sources from the USA and the UK.
Year(s) Of Engagement Activity 2020
 
Description RILEM TC 281- CCC - Carbonation of concrete with supplementary cementitious materials 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The UK-PI of RENACEM in co-chair of this international RILEM technical committee (TC) leading international efforts in understanding carbonation mechanisms leading to degradation of concrete structures, and interlinks between concretes produced with high volumes of SCMs and their carbonation response. Members of the UK team are actively participating in the activities of this international committee, when a critical review on carbonation of concretes with SCMs was completed. This document awarded the Materials & Structures journal Outstanding paper award, and enable the identification of research needs for validation of the standardised testing methodologies currently applicable for the assessment of carbonation resistance of SCM-containing materials. At present an Interlaboratory Test is being performed across 10 different laboratories and two additional discussion publications are being prepared to critically evaluate the suitability of existing accelerated methods to evaluate carbonation performance of concretes. It is expected that the activities of this committee lead to the revision of a RILEM recommendation for carbonation resistance testing.
Year(s) Of Engagement Activity 2020,2021
URL https://www.rilem.net/groupe/281-ccc-carbonation-of-concrete-with-supplementary-cementitious-materia...
 
Description RILEM TC 282-CCL - Calcined clays as supplementary cementitious materials 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The RENACEM teams from USA and UK are active members of this international technical committee (TC) which is leading international efforts in developing the fundamental understanding needed for the widespread uptake of calcined clays as cement replacements. The RENACEM members are participating in three working groups (WGs), focused in technical aspects of clay characteristics, calcination processes and properties of concretes produced with these materials. WGs meet once every 6 weeks, with attendance of 10-20 members per meeting. TC meetings are attended by members of all WGs (>60 members) where technical questions are asked, it is discussed about white papers currently being prepared, and future activities from this TC are planned. The topic of this TC is of great interest for the construction sector, as evident from their active participation in the conversations and activities.
Year(s) Of Engagement Activity 2020,2021
URL https://www.rilem.net/groupe/282-ccl-calcined-clays-as-supplementary-cementitious-materials-374