This session is seeking to inform stakeholders on an important sustainability topic. It is being co-sponsored by NEU and several ACI committees. It will be of acute interest to the concrete and associated industries. This session will inform ACI and interested stakeholders on progress and work being done by NIST Low Carbon Cements and Concretes Consortium (The Consortium). The purpose of The Consortium is to develop standardized measurement methods in support of low carbon concrete materials and provide consensus based guidance for organizations and individuals seeking to produce and use these materials. This session will deliver updates from the four primary working groups that are taking on these tasks: Performance Specifications, Quantifying Carbonates, Carbon Accounting & Innovative Materials.
Learning Objectives
(1) Discover the technologies and standards that enable lower-carbon concrete mixes and the challenges and opportunities to scaling up these technologies to meet market needs;
(2) Understand the environmental and economic savings gained by shifting to performance-based specifications;
(3) Identify standardized methods to quantify and validate carbon uptake in cement and concrete in the production, construction, use and end-of-life phases of a project’s life cycle;
(4) Learn how researchers evaluate durability of concrete optimized for carbon uptake and sequestration and the standardize test methods used to determine carbonation levels in cement-based products.
Dry-Cast Manufactured Concrete Products – Standards Activity to Promote Low-Carbon Solutions
Presented By: Craig Walloch
Affiliation: Concrete Masonry & Hardscapes Association
Description: Dry-cast manufactured concrete products (MCP), including concrete masonry units (CMU), paving units and slabs, and segmental retaining wall (SRW) units, have a porous interconnected void structure that enhances CO2 penetration. This allows dry-cast MCP to naturally sequester a significant portion of the calcination carbon emissions from cement production. The same porosity makes dry-cast MCP ideal for low-carbon cementitious systems that cure by carbonation rather than hydration. To advance the adoption of low-carbon dry-cast MCP, several initiatives are underway at the NIST Advanced Cements and Concrete Consortium, ASTM, and PCR arenas. These efforts focus on (i) developing guidelines to accurately measure CO2 uptake in hardened concrete, (ii) establishing methods to quantify CO2 in carbonation curing systems, and (iii) creating a performance specification for CMU to enable the use of innovative cementitious systems in structural masonry. This presentation provides an update on these initiatives and their implications for sustainable concrete practices.
Framework for Improved Carbon Uptake Reporting in Environmental Product Declarations of Concrete
Presented By: Pranav Pradeep Kumar
Affiliation: Massachusetts Institute of Technology
Description: Current standards and methodologies often apply generalized assumptions for estimating carbon uptake, overlooking the effects of regional climate, and application-based input. Carbon uptake is known to be sensitive to application-based parameters such as material type and geometry, as well as the changes in the climatic conditions. In this sense, it is important to incorporate this information, and the variability associated with this data. This study introduces a probabilistic context-specific framework that adopts a streamlined approach for capturing the context impacts in carbon uptake estimation. The proposed framework incorporates localized parameters and the associated uncertainties of input data to account for carbon uptake in Environmental Product Declarations (EPDs) which provides a standardized reporting of the life cycle assessments. The framework was implemented on the ready-mix concrete used for Single Family Homes in the United States The results show that the use-phase carbon uptake of single-family homes is equivalent to 20-40% of the calcination emissions. The results underscore the need for context-sensitive adjustments in standardized carbon uptake reporting practices. This research highlights the need for the adoption of a data-driven and adaptable carbon uptake framework to enhance life cycle carbon reporting in concrete EPDs.
Quantifying CO2 Mineralization in Cement-Based Materials: Challenges and Measurement Methods
Presented By: Yogiraj Sargam
Affiliation: CarbonCure Technologies
Description: CO2 mineralization technologies offer a promising approach to reducing the Global Warming Potential (GWP) of cement-based materials. However, accurately quantifying mineralized products (calcium carbonates) remains challenging due to varying CO2 uptake levels, ranging from less than 0.5% to 25-30%. This issue has been highlighted by the working group on 'Quantifying Carbonates' in NIST’s consortium on low carbon cements and concretes.
This presentation will share findings from various laboratory and industrial scale tests performed to determine mineralized products in two different CO2 mineralization systems – (1) a ready-mix system with up to 1% CO2 uptake; and (2) a reclaimed water system with up to 25% CO2 uptake. Qualitative methods (isothermal calorimetry, FTIR, SEM) and quantitative methods (carbon content measurement, TGA, X-ray diffraction) were employed for this purpose. Additional proof-of-concept tests such as ASTM D4373 (based on the pressure of gas evolved due to reaction of carbonates and HCl) and SEM-EDS (EDS analysis to separate various clinker and hydrate phases and quantification of the carbonates) were also assessed for their quantification accuracy. Results indicate that measurement accuracy depends significantly on sample type (paste, mortar, or concrete) and the chosen test method. Among the evaluated methods, infrared cell-based carbon content measurement demonstrated superior consistency and accuracy in CO2 quantification. This presentation aims to stimulate discussion and gather insights from other researchers to improve the quantification of CO2 mineralization in cement-based materials.
NIST Advance Cements and Concretes Consortium Update
Presented By: Nicholas Barbosa
Affiliation: NIST
Description: This presentation provides an update on the NIST Advance Cements and Concretes Consortium activities. The Consortium advances new, high-performance cementation materials through measurement science, standards, and industry collaboration. The talk will highlight recent work from the Measurement Methods and the Enabling Innovative Materials working groups to standardize innovative materials.
Returned Concrete Reclaimer By-product as a Supplementary Cementitious Material – Adoption at Operations Scale
Presented By: Deepika Sundar
Affiliation: Pennsylvania State University
Description: An estimated 20 million yd3 of concrete was returned to ready-mix concrete (RMC) plants last year, about 5% of the annual production of the RMC sector (NRMCA, 2024). To handle this fresh concrete waste, CalPortland has implemented a recycling process in several concrete plants, where returned fresh concrete is processed to reclaim aggregate. However, this process also produces a cement-rich filter cake by-product that is disposed of. As part of this study, the filter cake was processed and then assessed (both raw and carbonated) for use as a supplementary cementitious material, following the upcoming ASTM performance-based specification (WK70466). This presentation will focus on both material qualification as well as the cost-benefit analysis related to the implementation of the technology at the RMC operations scale.