Carbonation Processing Fly Ash-Portlandite Blends for Conventional and 3D Printed Binder Systems
Presented By: Narayanan Neithalath
Affiliation: Arizona State University
Description: Carbonation of fly ash mortars augmented with portlandite (CH) under ambient conditions to produce sustainable, cement-free binding agents is discussed. Class C and F fly ashes are blended with portlandite and their proportions adjusted to form shape-stable mixtures amenable to be conventionally cast or extruded (or 3D printed). The strength and CO2 uptake strongly depend on the pore moisture saturation, which is adjusted using a low-temperature (50oC), short-time (3 h) treatment before carbonation. High-Ca fly ash blended with 10% CH (by mass) is shown to result in a 7-day compressive strength greater than 35 MPa when carbonated, which is ~40% higher than that of the conventionally cured mixture, while a low-Ca fly ash blended with 30% CH results in a 15 MPa strength, ~300% greater than the conventionally cured mixture. The beneficial effects of low w/p and particle packing in extrudable mixtures towards providing increased strengths and CO2 uptake are also brought out. Overall, this study establishes the applicability (in terms of strength) of portlandite-enriched fly ashes to form binding agents with lower CO2 footprint for several construction applications.
Carbonation Rates – Innovative Assessment Approaches
Presented By: Jason Weiss
Affiliation: Oregon State University
Description: This talk will outline recent experimental methods to assess the carbonation rate. Neutron imaging, thermal analysis and computational tools will be used to discuss the overall approach. Links will be made to historical carbonation observations. Implications will be made for modern concrete. Examples will be presented.
Deep Decarbonization of Concrete via Biomolecule-regulated CO2 Mineralization and Supplementary Cementitious Materials
Presented By: Jialai Wang
Affiliation: University of Alabama
Description: Concrete has the potential to act as a significant CO2 sink through a mineralization process in which CO2 reacts with calcium-rich minerals to form calcium carbonate (CaCO3), ensuring permanent carbon storage. However, the current technologies for CO2 sequestration in concrete are limited by poor diffusivity and reactivity, and existing carbonation methods may compromise the durability of the resulting material. To unlock the full potential of concrete as a CO2 sink, we propose a novel biomolecule-regulated carbonation method (BioCarb). Unlike conventional approaches, the BioCarb method introduces CO2 into concrete before mixing by carbonating a cement slurry that is regulated with biomolecules. These biomolecules play a crucial role in controlling the crystal nucleation, morphology, and phase of the CaCO3, while effectively dispersing the generated nanoparticles. This approach increases the CO2 uptake of the cement slurry by at least an order of magnitude compared to current methods. Multiple interactions between the carbonate and the cement can be triggered by the CaCO3 produced through BioCarb, significantly enhancing the strength of the produced concrete. Importantly, the BioCarb method can be seamlessly combined with widely used supplementary cementitious materials (SCMs), such as fly ash, slag, or silica fume. This integration not only reduces the clinker content in concrete, further lowering its carbon footprint, but also leverages synergies between the metastable CaCO3 and SCMs to improve the hydration process, enhance durability, and optimize overall performance. By coupling advanced carbonation techniques with SCM utilization, the BioCarb method represents a transformative pathway for deep decarbonization of concrete, paving the way for more sustainable construction practices.
Examining Cementation through Carbonation in Calcined Clay/Cellulose Fiber Cementitious Blend
Presented By: Rohitashva Singh
Affiliation: University of Texas Arlington
Description: Substituting cement with a high proportion of low-grade calcined clays reduces the early-age strength development, thereby limiting its applications within the concrete industry. However, upon being subjected to an accelerated CO¬2 curing process, the carbonate (CaCO3) cementation serves as a filler, resulting in a high early-age strength which offsets the loss due to cement dilution. To facilitate the diffusion of carbon dioxide (CO2) within the matrix and to retain the modulus and post-crack tensile strain capacity, cellulose fibers have been introduced. Due to their tubular structures, the fibers have been found to increase the formation of carbonates during early ages, contributing to a further increase in the compressive strength and modulus.
CO2 Mineralization in Fresh Concrete: Mechanisms, Performance, and Global Adoption
Presented By: Yogiraj Sargam
Affiliation: CarbonCure Technologies
Description: Abstract/Description of the presentation: As the cement and concrete industry accelerates efforts toward net-zero emissions by 2050, CO2 mineralization technologies offer a practical and scalable solution. CarbonCure’s technology supports these initiatives and has been licensed to more than 700 ready-mix and precast concrete plants across nearly 30 countries, enabling the production of more than 8 million truckloads of concrete and reducing over 550,000 metric tons of CO2 emissions to date. This presentation will provide a technical and data-backed assessment of the mechanism, performance validation, and global adoption of the technology. The technical overview will cover the scientific mechanisms, supported by experimental data on its effects on physicochemical properties, pore structure, microstructure, and overall concrete performance. The data analysis will present the validation and success of the technology across diverse regions (North America, South America, Europe, Asia, Middle East), industries (precast, ready-mix), mix designs (w/c ratios from 0.30 to 0.70), and binder materials (various cements, SCMs, calcined clays, etc.).
Effect of Amines on Improving Internal Carbonation in CO2 Cured Cement Systems
Presented By: Ali Ghahremaninezhad
Affiliation: University of Miami
Description: This study introduces a novel approach using amine solutions to enhance internal carbonation in CO2 cured cement systems. The CO2 sequestration potential and mechanical properties were assessed using thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), and compressive strength tests. The results demonstrated that carbonated solutions as mixing agents significantly enhanced carbonation. Incorporating 5% and 15% concentrations of MEA and DEA solutions led to improved carbonation due to internal carbonation curing. In terms of mechanical properties, amine solutions at concentrations below 5% maintained compressive strength, while higher concentrations caused strength reduction due to the retardation effects of amines. These findings provide a pathway for developing more efficient carbonation curing methods.