Pozzolans have been used in concrete for centuries, dating back to the Romans who used volcanic ash. Over many centuries, the number of materials that are classified as “pozzolans” has grown to include a variety of materials, both natural and manufactured, and continues to grow. This session aims to provide an overview of emerging pozzolans in the concrete industry. Presentations will be given by researchers and material suppliers with the purpose of informing engineers, contractors, and producers on the impact of these novel materials on the fresh and hardened properties of concrete.
Learning Objectives:
(1) Provide a brief overview of the emerging pozzolans in the concrete industry;
(2) Understand the production methodologies of emerging pozzolans;
(3) Evaluate the properties of pozzolans using new test methods;
(4) Outline the impact of these pozzolans on reducing the carbon footprint of concrete.
This session has been approved by AIA and ICC for 2 PDHs (0.2 CEUs). Please note: You must attend the live session for the entire duration to receive credit. On-demand sessions do not qualify for PDH/CEU credit.
Emerging Approaches for Pozzolans
Presented By: Prannoy Suraneni
Affiliation: University of Miami
Description: It is well-known that concrete production contributes 6-8% of global CO2 emissions. Significantly reducing this amount is critical in the fight against climate change. An introduction to concrete CO2 emissions and traditional ways in which these emissions can be reduced is presented. An emerging approach to reduce the CO2 emissions of concrete is highlighted: novel/manufactured supplementary cementitious materials (SCMs). These include thermal activation, mechanochemical activation, leaching, and CO2 mineralization approaches. Research needs, fundamental and applied, in this research space, are highlighted.
UR2: Ultra-Rapid Reactivity Test for Predicting Pozzolan Performance Within Minutes
Presented By: Nishant Garg
Affiliation: University of Illinois at Urbana-Champaign
Description: Calcined clays are emerging pozzolans suited for meeting the growing demand of SCMs within the cement and concrete industry. However, there is a lack of real-time quality control technology for reactivity assessment during industrial production of calcined clay. We investigated 47 calcined clay samples (natural and commercial), including kaolinite, montmorillonite, and illite-based clays, and developed a novel reactivity test called UR2 that can predict clay reactivity within a few minutes. When compared to the pozzolanic reactivity measured by the R3 test (ASTM C1897), it was found that the results obtained within 5 min were correlated to the 7d cumulative heat release during R3 testing (R2=0.92). Thus, this UR2 method can enable real-time reactivity assessments on the production line and instantaneous adjustments of production conditions. In addition, we will share preliminary results on the extension of UR2 on other SCMs, namely fly ashes and natural pozzolans. Overall, such ultrarapid testing technology can enable the widespread adoption of emerging pozzolans and help in the reduction of the clinker factor.
Transforming Agricultural Residues into High-Performance SCMs through High-Energy Ball Milling
Presented By: Dia Brown
Affiliation: Pennsylvania State University
Description: Despite the abundance of ashed agricultural residues containing up to 90?wt.% silica as potential supplementary cementitious materials (SCMs), high water demand limits their use by compromising fresh-state workability and mechanical performance of concrete – a particular challenge for countries with large agricultural sectors and low production of other industrial SCMs. To address this critical challenge, we have developed innovative processing methods that not only sequester CO2 but also eliminate fresh-state workability issues associated with ash-based SCMs. This presentation will share our latest results on the application of these methods to rice hull ash, demonstrating the production of high-strength concretes reaching 8,000?psi after 28 days at replacement levels of 20?wt.%. These results are benchmarked against improvements achieved from non-CO2 milling processes, highlighting the superior effectiveness of our CO2-assisted method. By enabling the manufacturing of high-performance SCMs from agricultural residues, our findings offer a viable pathway to utilize abundant waste materials in concrete production, addressing environmental and performance challenges globally.
Electrochemical Production of Highly Performant, Consistent Materials
Presented By: Brandon Williams
Affiliation: Sublime Systems
Description: Founded by two MIT battery scientists, Sublime Systems transforms cement and Supplementary Cementitious Material (SCM) manufacturing with an ambient-temperature, electrochemical process using decarbonized electricity to produce ultra-low-carbon cementitious materials. Made from non-carbonate feedstocks like natural minerals or industrial waste, Sublime avoids traditional cement processes and heat emissions, offering an ASTM C1157-compliant cement and engineered SCMs. Sublime currently operates a 250 TPY pilot plant and is currently developing its first commercial facility in Holyoke, MA to produce over 30,000 tons annually. This presentation will cover our technology, testing, and scaling approach for Sublimes Engineered SCMs.
Dehydroxylation Kinetics of Kaolinite and Montmorillonite Clays Examined Using Isoconversional Methods
Presented By: Narayanan Neithalath
Affiliation: Arizona State University
Description: The use of calcined clays as supplementary cementitious materials (SCMs) in concrete is a promising strategy towards decarbonizing the cement and concrete industry. This is especially relevant considering the ever-increasing demand for concrete. Comprehensive understanding of the kinetics of calcination is essential towards maximizing the potential reactivity of clay minerals. In this study, the kinetics of the dehydroxylation of pure kaolinite and montmorillonite are investigated under non-isothermal conditions at constant heating rate. Activation energies ( ) are determined via Friedman differential and advanced Vyazovkin incremental methods for the isoconversional range; these are devoid of computational approximations. Kinetic equations—in the differential form as well as a combination of differential and integral forms are compared against the experimentally determined reaction models to identify the most probable dehydroxylation mechanism for kaolinite and montmorillonite. An order mechanism is established for dehydroxylation of kaolinite, while montmorillonite is noted to undergo dehydroxylation via a single-step reversible diffusion-controlled process. Kinetic triplet—comprising activation energy, reaction model and pre-exponential factor—is used to predict isothermal calcination conditions, which is further verified using analytical techniques. Heat release rates of clay-CH blends from isothermal calorimetry are used within a thermodynamic framework to quantify reactivity of the calcined clays. The study demonstrates a general approach based on isoconversional methods to predict calcination conditions for different clays that can be used in efficient and optimized production of blended cements or SCMs.
Laboratory Evaluation of Natural Pozzolans from Volcanic and Sedimentary Sources
Presented By: Somayeh Nassiri
Affiliation: University of California Davis
Description: Natural pozzolans were used in the construction of large public works projects, such as several dams, in the 1940s and 1950s. Their benefits in mitigating ASR expansion became known through the early works of Thomas Stanton in California. However, natural pozzolans fell out of favor once coal fly ash became known as a cheap and available source of pozzolans with many benefits to concrete performance. Today, with the decline of domestic supplies of coal, fly ash, and slag, natural pozzolans are in the spotlight once again. However, stakeholders across the value chain need to regain familiarity with their properties and performance in concrete. This study sheds light on the inherent differences between coal fly ash and natural pozzolan by providing full laboratory evaluation results for more than 25 tested natural pozzolans from volcanic and sedimentary sources. The effect of heat activation on the sedimentary pozzolans is also discussed.