This award is supported under the NSF 18-067, NSF Engineering-UKRI Engineering and Physical Sciences Research Council, funding opportunity. Concrete is the most versatile building material in the United States, used to construct and repair buildings, transportation systems, and energy infrastructure. The development, maintenance, and repair of concrete infrastructure is vital to national growth, prosperity, citizen safety, and welfare. Concrete is a complex, composite material, made of a mixture of mineral aggregates, water, portland cement, and additives that enhance its properties in the initial fluid generated upon mixing and in its final hardened state. Most modern concrete mixtures contain supplementary cementitious materials (SCMs) that partially replace portland cement to improve concrete long-term durability, lower costs, and reduce CO2 emissions associated with concrete production. The most commonly used SCMs are waste-derived, especially residual ashes from coal-fired power plants. However, changes in industrial processes and increasing demand for SCMs are leading to a shortage of high quality, waste-derived SCMs. Natural SCMs, such as calcined clays and volcanic minerals, are a promising alternative to waste-derived SCMs, and their use is rising. Advantages of natural SCMs stem in large part from their chemistry and mineralogy; they are more homogeneous than waste-derived materials, which aids in quality control. Moreover, they also provide economic, environmental, and performance benefits. The use of SCMs, however, also has a downside, i.e., the propensity to increase chemical carbonation reactions between the concrete and atmospheric CO2, which can result in corrosion of steel reinforcement, loss of strength, and cracking. Therefore, it is important to develop a better understanding of the carbonation processes in concrete containing natural SCMs in order to identify materials and mixtures that that impart benefits without sacrificing performance. By combining research expertise and resources between institutions in the United States and the United Kingdom, this project will investigate interactions between concrete containing new and promising sources of natural SCMs and CO2, new methods of testing and damage detection, and new strategies to minimize the impact of the degradation. This research can lead to the production of higher quality, lower environmental-impact concrete. As such, this research can have a broad impact on the lifespan and sustainability of concrete infrastructure, which is critical for infrastructure globally, sustainability, and workforce development. National prosperity depends on a global, sustainable approach to resource utilization and protection. Students working on this project will gain valuable international research experiences.

Considering that the construction field is increasing its use of natural SCMs in concrete, understanding the contribution of natural SCMs toward carbonation degradation will be critical for the viability of this technology. Furthermore, manipulating the composition of the systems to reduce or prevent carbonation is possible, but has not previously been explored. This Response to CO2 Exposure of Concrete with Natural Supplementary Cementitious Materials (RENACEM) project is a joint United States-United Kingdom collaboration among researchers at the University of Texas at Austin, University of Leeds, and University of Sheffield to elucidate the fundamental science controlling the long-term performance of concrete produced with natural SCMs. This project will investigate the chemical interactions between concrete and atmospheric CO2 and its transport to identify meaningful methodologies for their assessment. This will underpin the adoption of new methods for testing carbonation of concrete with natural SCMs and new predictive models. RENACEM comprises five work packages (WPs). WP1 will focus on advanced characterization of natural SCMs and the development of materials with reduced carbonation susceptibility. WP2 will establish the physicochemical mechanisms governing carbonation of natural SCM-based materials, interlinking their mineralogy, phase assemblages, and microstructure with their response to natural and accelerated carbonation. WP3 will investigate in situ monitoring of pH and relative humidity changes upon CO2 exposure of natural SCM-based concrete using advanced fiber optic sensing networks. WP4 will move beyond the state of the art in modeling of carbonation to bring new predictive capabilities for both carbonation rate and extent, including the total extent of CO2 uptake by concrete in service. Finally, WP5 will focus on project management, including risk and progress assessment, and implementation of planned impact activities.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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University of Texas Austin
United States
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