Journal
ACS SUSTAINABLE CHEMISTRY & ENGINEERING
Volume 6, Issue 12, Pages 15976-15981Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acssuschemeng.8b03699
Keywords
CO2 Sequestration; Portland cement; Carbonation; Hydration; Compressive strength; Thermogravimetric analysis/derivative thermogravimetric analysis
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Funding
- U.S. Department of Energy, National Energy Technology Laboratory (NETL) [DE-FE0030684]
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An emerging technology of CO2 sequestration in Portland cement (PC) is through accelerated carbonation, where PC is intentionally carbonated at early hydration age and reinitiates long-term hydration upon completion of carbonation. However, the current literature has overlooked a fact that different PC hydration ages prior to carbonation (pre-hydration) could lead to distinct carbonation efficiencies and subsequent hydration behaviors (post-hydration). Here, we examine the effects of length of pre-hydration period on CO, uptake and on the hydration extent and final strength at 28 days. The CO2 and H2O profiles in the carbonated PC were examined with thermogravimetric analysis/derivative thermogravimetric analysis. The pre-hydration path was traced with isothermal calorimetry. Experimental results suggested that extension of pre-hydration decreased CO2 uptake, but enhanced the extent of PC hydration at 28 days. It was found that a pre-hydration beyond the late deceleration period of PC hydration (where heat generation is slowing down) led to a higher hydrate content of cement paste, hence forming a higher compressive strength of mortar compared to the noncarbonated benchmarks at 28 days. The lesser carbonation-induced water loss and the nucleation seeding enabled by calcium carbonate are likely responsible for this effect. The finding reported here should be useful for fine-tuning PC carbonation process for CO2 sequestration in concrete.
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