<
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Electricity generation from coal-fired power plants represents 25% of total carbon dioxide (CO<
sub>
2<
/sub>
) emissions from the United States (1.4 billion tons of CO<
sub>
2<
/sub>
emitted in 2015). In view of upcoming legislation that seeks to limit CO<
sub>
2<
/sub>
emissions, in support of climate change goals, it is anticipated that such emissions will be (financially) penalized. This is of great consequence to emissions intensive sectors such as coal-fired power generation which are expected to be substantially burdened by such penalties. Carbon capture and storage (CCS) has been proposed as a solution to mitigate anthropogenic CO<
sub>
2<
/sub>
emissions. However, CCS is not always a viable solution, for: (i) reasons of cost which is estimated to range from $10-to-$150 per ton of CO<
sub>
2<
/sub>
, (ii) the permanence (or lack thereof) of the sequestration solution, and/or, (iii) the lack of suitable geological features in the local vicinity where CCS can be favorably achieved. This is further complicated by increasing levels of anthropogenic CO<
sub>
2<
/sub>
emissions which render CCS a limited term solution. To address issues of accumulating atmospheric CO<
sub>
2<
/sub>
emissions, pragmatically, it is necessary to identify routes for the large-scale utilization of CO<
sub>
2<
/sub>
as a precursor in beneficial products and processes
while simultaneously yielding a CCS solution of permanence. A promising approach of this nature involves upcycling (i.e., beneficially utilizing a waste or by-product such as CO<
sub>
2<
/sub>
) by mineralizing stable carbonate compounds which show cementitious (bonding) character (e.g., CaCO<
sub>
3<
/sub>
, calcium carbonate polymorphs). But an important challenge in this regard is to rapidly source light metal cations, and to accomplish material processing that enables CO<
sub>
2<
/sub>
-uptake (mineralization) without generating additional CO<
sub>
2<
/sub>
emissions. <
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<
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To simultaneously address the challenges noted above, upcycled concrete, a transformative, CO<
sub>
2<
/sub>
- negative construction material is proposed as a complete technology solution for CO<
sub>
2<
/sub>
and industrial waste upcycling. This is accomplished as follows. First, light metals required for CO<
sub>
2<
/sub>
mineralization are sourced from historical reservoirs (i.e., landfills) which contain crystallized iron/steel slags rich in Ca and Mg. The Ca (and Mg) present in the slags is leached, and then following controlled concentration of the leachant, used to precipitate portlandite (Ca(OH)<
sub>
2<
/sub>
)
a potent sink for CO<
sub>
2<
/sub>
. The portlandite thus produced, and leached slag granules are recombined with fine and coarse mineral aggregates, and fly ash sourced from historical reservoirs (i.e., landfills, and ash ponds), water and rheology modifiers to form a slurry that is suited for shape stabilization, i.e., by extrusion, as beams, columns, slabs. The stabilized structural sections are then contacted with flue gas borne CO<
sub>
2<
/sub>
within a reactor, wherein CaCO<
sub>
3<
/sub>
forms, locking-in the CO<
sub>
2<
/sub>
, while also ensuring cementation. The composition of upcycled concrete can be altered to ensure: (a) a specific extent of CO<
sub>
2<
/sub>
uptake (e.g., 0.3 g of CO<
sub>
2<
/sub>
/g of solid reactants), and (b) target mechanical properties. Original data indicate that such a pathway for CO<
sub>
2<
/sub>
mineralization, and cementation endows mechanical properties (e.g., flexural strengths ? 7 MPa) that are equivalent, if not superior to traditional ordinary Portland cement (OPC) based concrete
a key requirement to substitute OPC-based concrete as a construction material. Importantly, upcycled concrete is designed to offer functionality, utility and cost-structures that are similar to OPC-based concrete
to reduce both end-user and market inertia to the uptake, and diffusion of a novel, CO<
sub>
2<
/sub>
-negative substitute for OPC-based concrete. <
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<
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The first activity in the project was to create the Project Management Plan including inputs provided by DOE/NETL. During Budget Period 1, the Recipient obtained critical data on the reaction kinetics of slag leaching, portlandite production and carbonation processes. These data helped establish appropriate process conditions and strategies that maximize CO<
sub>
2<
/sub>
uptake, industrial waste utilization, and waste heat reuse. The carbonation characteristics of relevant coal-derived fly ash and leached slag granules, as well as the process conditions for carbonation of the upcycled concrete mortar were delivered as a compiled dataset at the conclusion of the budget period. During Budget Period 2, the Recipient developed an optimal shape stabilization process for upcycled concrete production and assessed the product?s mechanical performance. The Recipient also delivered a detailed design for a laboratory-scale, integrated upcycled concrete production system that was constructed and tested during Budget Period 3. These efforts supported the development of a conceptual scaled-up process design and the completion of the required technical and economic feasibility study, market assessment, lifecycle analysis, and technology gap analysis.<
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