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Achieving the Cement and Concrete Industry net zero goal by 2050 relies significantly in carbon capture as represented in Figure 1. Many of these technologies are not readily available today, and those that exist may not be scalable, or lack efficiency. A scalable carbon removal solution, for direct source emissions capture using photo bio reactors is presented as an innovative solution to reach the net zero goal.

The capture and utilization of carbon dioxide (CO2) is emerging as a potential research area, which offers the advantage of mitigating climate change and generating economically viable products. For CO2 sequestration in cement-based composites, a number of nanomaterials are being investigated, including graphene, graphene oxide, nano-titania, carbon nanotubes, and graphene nanoplates. Graphene-based nanomaterials have been extensively employed to modify cement matrix due to their exceptional surface area, high strength, and modulus. The enhanced adsorption capacity and affordability of these materials are making them a viable alternative for the removal of ambient CO2. In our study, we found that the CO2 absorption capability of cement composites was increased by 30% when very modest amounts of graphene oxide nanosheets (about 0.05 to 0.1%) were added. GO-reinforced concrete offers the ability to store CO2 while maintaining structural integrity in comparison to conventional cement-based materials.

Chitin is the second most abundant biopolymer after cellulose and is found in many species, including crustaceans. The nanofiber structure of chitin in shrimp shell waste was extracted in this study by mechanical and chemical methods, producing chitin nanofibers (ChNF) and nanocrystals (ChNC), respectively. Their surface functional group, size, morphology, and zeta potential were characterized. Testing of a range of dosages in mortar showed that ChNF (0.05%wt) with a larger aspect ratio than ChNC resulted in the greatest improved flexural strength and fracture energy by 24% and 28 percent. In addition, elastic modulus increased by up to 91% and 43% with ChNC and ChNF. With their anionic surface charges, both chitin nanomaterials induced electrostatic interactions with cement particles and caused a delay in setting time and increased the viscosity of the fresh cement slurry. Findings so far indicate chitin is a viable biomass source for powerful structural nanofibers to strengthen cementitious materials and reduce cement demand in concrete.

As the supply of conventional supplementary cementitious materials (SCMs) continues to fall behind concrete industry’s demand, new sources must be identified and evaluated to allow production of high-quality and durable concrete. This session reports on the latest research related to the use of harvested fly ash (HFA) and ground bottom ash (GBA) as concrete SCMs. The presentations will include studies on the chemical and physical characteristics of these ashes, their pozzolanic reactivity, and their performance in concrete in terms of their impact on fresh, mechanical, and durability properties of concrete mixtures. The audience will become familiar with this potentially valuable new SCM source.

Understanding chloride penetrability and corrosion performance is one of the key issues hindering the advancement and continued adoption of belitic calcium sulfoaluminate (BCSA) cements and composites. There has been little work to address the suitability of existing standardized test methods or the correct interpretation of test results for these materials. In this work, we use a wide variety of electrical (rapid chloride penetrability, surface resistivity, and bulk resistivity) and diffusion-based (ponding, bulk diffusion, non-steady-state migration) test methods to measure the chloride penetrability of a range of BCSA and portland cement concretes. Results suggest that there is a need to recalibrate chloride penetrability classifications based on electrical test methods to better align with ground truth results from diffusion-based tests. Furthermore, there is a need to recalibrate the chloride concentration threshold for color change with silver nitrate indicator, which is a critical factor in interpreting the results of the non-steady-state migration test. Finally, we applied the ASTM G109 corrosion test to the same concrete mixtures. Results indicate corrosion of rebars in BCSA concretes at early ages, but further analyses show this to be a function of the test conditions rather than a shortcoming of the material. The ASTM G109 testing age is not consistent with the time period required for steel passivation in BCSA systems.

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