Case Study: Commercializing Carbonated Concrete in Canada
Presented By: Yuri Mytko
Affiliation: Carbicrete Inc
Description: In the Spring of 2020, CarbiCrete launched a pilot project to optimize its patented process to produce cement-free, carbonated CMUs and to integrate the process into an operational environment at scale.
The project involved installing CarbiCrete’s curing system at an existing concrete plant, operated by hardscape manufacturer Patio Drummond, and ratcheting up production to commercial scale over the course of a 36-month period.
CarbiCrete’s technology replaces cement with steel slag, a steel-making by-product, and cures them with carbon dioxide, avoiding the GHG emissions associated with cement production, while permanently sequestering CO2 within the concrete through mineralization.
Over the course of the pilot, Patio Drummond decided that it would turn its entire hardscape operations over to the CarbiCrete process, and in September of 2023, the first CarbiCrete-enabled CMUs became available for sale.
This talk will explore how CarbiCrete took a carbonation technology that had been proven in the lab, implemented it into an operational environment and scaled it to commercial viability.
Mineralization of CO2 in the Production and Use of Cement
Presented By: Craig Hargis
Affiliation: Fortera
Description: Fortera, a leading materials technology company, has developed a patented process to make a reactive polymorph of calcium carbonate, vaterite, at scale. The Fortera Redding ReCarb® Plant when live, Q2 2024, will be the world’s largest industrial CO2 mineralization plant, producing a low CO2 cement.
Fortera’s ReCarb process focuses on vaterite which can be utilized to make blended hydraulic cements or used to make a calcium carbonate cement that cements independently of any hydraulic component. The production of vaterite releases approximately two-thirds less carbon dioxide than the production of Portland cement when fossil fuels are utilized; moreover, since all thermal processes, such as calcination and drying, occur at temperatures below 1000°C, the manufacturing process can be electrified resulting in a net-zero carbon footprint.
Examining the Effect of Carbon-Enriched Fly Ash on the Microstructural Development of Portland-Limestone-Based Cement Mortars
Presented By: Lisa Burris
Affiliation: Ohio State University
Description: Supplementary cementitious materials (SCMs) aid in concrete durability and sustainability by reducing concrete cement content, decreasing concrete’s embodied carbon emissions and simultaneously increasing service life of the concrete structure through the pozzolanic reaction. Now, carbon enrichment of coal fly ash seeks to further increase concrete sustainability efforts. During carbon enrichment, fly ash is ground in a carbon-dioxide-pressurized environment, which promotes calcium carbonate (CaCO3) precipitation onto the fly ash particle. Because fly ash reacts with free lime in cementitious systems to form calcium silicate hydrates, the precipitation of slightly soluble CaCO3 onto the particle may have adverse effects on the particle’s ability to react pozzolanically and aid in the densification of concrete microstructure. Moreover, adding carbon-enriched fly ash with slightly soluble CaCO3 precipitates to a portland limestone cement (PLC) concrete containing higher limestone content and less clinker may change the rate at which the concrete microstructure develops due to a coupled dilution effect. To better understand the severity, if any, of the potential issues posed, carbon-enriched fly ash was characterized. The chemical composition and reactive properties of carbon-enriched fly ash were determined using x-ray fluorescence, x-ray diffraction, the ASTM C1897 R3 Method, isothermal calorimetry, and thermogravimetric analysis. Early microstructural development of PLC mortar specimens with carbon-enriched fly ash was determined using scanning electron microscopy (SEM). Similar chemical compositions were detected and quantified for traditional and carbon-enriched class F fly ashes. The hypothesized dilution effect from carbon-enriched fly ash was not significant in PLC pastes.
Novel Carbon Sink Cementitious Materials Through Binder Carbonation
Presented By: Mehdi Khanzadeh Moradllo
Affiliation: Temple University
Description: The production of concrete materials through binder carbonation (i.e., CO2 mineralization) has the potential to consume approximately one billion tons of CO2 annually. However, the expanded use of these materials depends on addressing their fundamental limitations, namely physical barriers against CO2 transport into the microstructure and the impeding effect of the carbonation product layer and interfacial water chemistry on the reaction kinetics. Therefore, the goal of this presentation is to discuss a novel CO2 curing process to systematically address the key limitations of carbonated concrete materials (CCMs). The resulting CCMs with novel CO2 curing process have better mechanical and durability performance (30-65% improvement compared to control CCMs) and the calcium carbonate precipitation can reach up to 15 times higher compared to control systems (approaching the maximum theoretical degree of carbonation of binder). The outcomes of this study can lead to the design of carbon sink concrete with superior mechanical and durability properties to satisfy/surpass performance requirements for building/infrastructure applications in different geographic regions. This can substantially increase the viability of CCMs for marketing and industrial scale production.
Carbon Uptake in Supplementary Cementitious Materials
Presented By: Prannoy Suraneni
Affiliation: University of Miami
Description: CO2 uptake in a variety of cement-based materials has been studied. Uptake in high Ca-, high Mg- SCMs appears to be promising, but the published data on this topic is limited. Numerous SCMs, pure-phase calcium aluminosilicate glasses, and calcium aluminosilicate glasses doped with Mg, Fe, and alkalis were studied for the CO2 uptake in different experimental conditions. We find that for the majority of systems studied, the CO2 uptake was minimal. Interestingly, this was even true for some high-Ca glasses. Most systems did not show a significant change in reactivity, measured using a modified R3 test, post-uptake. The CO2 uptake in steel slags, recycled mortar fines, and recycled cement paste was significant, ranging from 10 to 30%. The possibility of metal oxides modifying the CO2 uptake behavior is discussed.
Continuous Flow Synthesis of Vaterite Using Recoverable Additives at Ambient (p,T)
Presented By: Jenny Arabit
Affiliation: University of California, Los Angeles
Description: Calcium carbonate (CaCO3), in order of increasing thermodynamic stability exists in the form of amorphous calcium carbonate, and three crystalline polymorphs: vaterite, aragonite, and calcite. Vaterite is of increasing interest as its metastability induced through-solution transformation (eventually) into calcite binds surfaces to each other ensuring cementation. However, the continuous flow synthesis of vaterite using alkaline precursors has remained a challenge. Here, we demonstrate for the first time, the ability to continuously produce vaterite at high selectivity and yield (>80 mass %) using technical alkaline precursors such as hydrated lime (Ca(OH)2) and dilute carbon dioxide (CO2; <25 vol. %) bubbling at ambient pressure and temperature (p,T). Such polymorph selection is promoted using water-miscible agents which are fully recovered and reused – ensuring an irrelevant stoichiometric additive demand – at the conclusion of the synthesis step. This manner of synthesis approach has dramatic implications on the production of low- or carbon-negative carbonate-based cementation materials as a possible substitute for traditional silicate-based Ordinary Portland Cement (OPC).
Carbonation of Recycled Concrete Aggregates and Concrete Slurry Waste and Their Application in Recycling Concrete
Presented By: Frank Winnefeld
Affiliation: Empa
Description: Recycled concrete aggregates (RCA) and concrete slurry waste (CSW) were sourced from a local concrete plant. They were carbonated in the laboratory at ambient conditions using 100% CO2. In case of the RCA, different moisture saturation levels were considered, which is relevant for the real situation at the concrete plant. In parallel, real scale installations to carbonate both materials were implemented at the same local concrete plant. The carbonated materials were used to produce recycling concrete with a lower CO2-footprint than conventional recycling concrete.
About 10-13 kg CO2 per t of dry RCA (0-16 mm) can be sequestered at moisture contents of practical relevance (60-200 % of the aggregate's water absorption). Smaller size fractions, i.e. the 0-4 mm fraction, are able to absorb significantly more CO2 than larger fractions. Carbonation leads to a patchy distribution of decalcified C-S-H on the surface of the RCA particles, which can participate in cement hydration. Thus, on the one hand the carbonated aggregates have a slightly positive impact on compressive strength. On the other hand, concretes with carbonated RCA loose workability more rapid than those with non-carbonated RCA, which can be counteracted using appropriate plasticizing admixtures.
Carbonated CSW can adsorb 120-130 kg CO2 per t of dried material. It shows in blends with Portland cement a rapid early pozzolanic reaction due to the presence of a silica-alumina gel rich in alkalis. Furthermore the formed CaCO3 accelerates the hydration of the Portland cement. Both the dried material and the slurry show a slight improvement of compressive strength when applied in mortar and concrete.
As both carbonated RCA and CSW increase concrete performance, cement content in the recycled concrete can be reduced. Thus, an additional reduction of the CO2 footprint is provided besides the one due to the stored CO2, when the concrete compared to conventional recycling concrete.