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Co2 Sequestration in Portland Cement-Based Materials and Foams.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Co2 Sequestration in Portland Cement-Based Materials and Foams./
作者:	Valverde, Francisco Wladimir Jativa.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2021,
面頁冊數:	90 p.
附註:	Source: Dissertations Abstracts International, Volume: 83-05, Section: B.
Contained By:	Dissertations Abstracts International83-05B.
標題:	Mechanical properties. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28747802
ISBN:	9798494450753

Co2 Sequestration in Portland Cement-Based Materials and Foams.
Valverde, Francisco Wladimir Jativa.

Co2 Sequestration in Portland Cement-Based Materials and Foams. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 90 p.

Source: Dissertations Abstracts International, Volume: 83-05, Section: B.

Thesis (Ph.D.)--North Carolina State University, 2021.

This item must not be sold to any third party vendors.

In the present thesis, three subjects have been studied. The first study investigates the potential of CO2 sequestration as CaCO3 in cement-based materials by intermixing CO2 gas directly with freshly mixed cement paste at atmospheric pressure. In the second study, the feasibility of generating foamed cement grout with CO2 gas instead of N2 gas is investigated. The third, and final study focuses on how Calcium-Silicate-Hydrates (CSH) interact with magnesium sulfate solutions at different concentrations, and explores its micromechanical implications using nanoindentation testing.Cement is the largest manufactured product on earth by mass and it is the second most used substance in the world after water. Cement production releases approximately 0.85 tonnes of CO2 per tonne of cement manufactured and is currently accountable for nearly 8% of all global carbon emissions. Reducing or offsetting CO2 emissions generated by cement production without compromising the durability of cement-based materials is the primary challenge faced by the construction industry today. Significant efforts have been made to reduce CO2 emissions in cement-based materials over the past decades. In the present thesis, a unique method is proposed where CO2 gas is directly intermixed with freshly mixed cement paste made with different waterto cement (w/c) ratios to reduce Ca(OH)2 and increase CaCO3 contenings for the first study indicate: (i) CO2 Intermixints.The findings for the first study indicate: (i) CO2 Intermixing with cement paste reduces Ca(OH)2 and increases the CaCO3 contents when compared to N2 intermixed and control (no-gas intermixed) specimens; (ii) Void size distributions and saturated hydraulic conductivity of CO2 intermixed specimens remained similar to control specimens, while N2 intermixed specimens showed an increase in void volume fraction; (iii) The mechanical properties (dynamic modulus and compressive strength) of CO2 intermixed specimens are increased when compared to N2 intermixed specimens and are similar to control (no-gas) intermixed specimens; (vi) CO2 intermixing increases the water content of specimens product of the reaction between Ca(OH)2 and CO2 and, (v) CO2 intermixing has the potential to offset CO2 emissions coming from cement manufacturing between 2.6% to 4.3%.In the second study, CO2 foamed cement grout (CFC-g) was explored as an alternative to traditionally made N2 foamed cement grout (NFC-g) to sequester CO2 in the form of CaCO3 and reduce Ca(OH)2 contents in specimens. Results indicate: (i) CFC-g contains less Ca(OH)2 and more CaCO3 when compared to NFC-g; (ii) While keeping analogous densities, the void size distribution in NFC-g is broader (larger amount of bigger voids) compared to CFC-g; (iii) The mechanical properties (dynamic modulus and compressive strength) of CFC-g are increased when compared to NFC-g; and (iv) An 11% CO2 sequestration efficiency was determined for CFC-g.With regards to the third study, the deterioration of cement-based structures due to sulfate attack has been a widely studied topic in cement science. Magnesium sulfate (MgSO4) is a common salt in natural waters and is often in contact with concrete structures. The physically unstable component, Ca(OH)2, is known to react with MgSO4 producing Mg(OH)2 -Brucite- and CaSO4 -Gypsum-. As for the stable component, Calcium-Silicate-Hydrates (C-S-H), different chemical responses may occur depending on concentration. Despite the vast amount of research performed on this subject, the fundamental reaction mechanism of C-S-H when exposed to different MgSO4 concentrations has not been studied quantitatively from a micromechanical standpoint. The findings for the third study are as follows: (i) At lower and moderate concentrations (2-4 g/l) an increase in elastic modulus is observed on C-S-H specimens (the formation of brucite and gypsum crystals contribute to the overall magnitude of the elastic modulus of the specimen) and (ii) At high concentrations (10-20 g/l) a significant reduction of elastic modulus is detected due to C-S-H decalcification.

ISBN: 9798494450753Subjects--Topical Terms:

3549505
Mechanical properties.

Co2 Sequestration in Portland Cement-Based Materials and Foams.
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500 $a Advisor: Borden, Roy;Gabr, Mohammed.
502 $a Thesis (Ph.D.)--North Carolina State University, 2021.
506 $a This item must not be sold to any third party vendors.
520 $a In the present thesis, three subjects have been studied. The first study investigates the potential of CO2 sequestration as CaCO3 in cement-based materials by intermixing CO2 gas directly with freshly mixed cement paste at atmospheric pressure. In the second study, the feasibility of generating foamed cement grout with CO2 gas instead of N2 gas is investigated. The third, and final study focuses on how Calcium-Silicate-Hydrates (CSH) interact with magnesium sulfate solutions at different concentrations, and explores its micromechanical implications using nanoindentation testing.Cement is the largest manufactured product on earth by mass and it is the second most used substance in the world after water. Cement production releases approximately 0.85 tonnes of CO2 per tonne of cement manufactured and is currently accountable for nearly 8% of all global carbon emissions. Reducing or offsetting CO2 emissions generated by cement production without compromising the durability of cement-based materials is the primary challenge faced by the construction industry today. Significant efforts have been made to reduce CO2 emissions in cement-based materials over the past decades. In the present thesis, a unique method is proposed where CO2 gas is directly intermixed with freshly mixed cement paste made with different waterto cement (w/c) ratios to reduce Ca(OH)2 and increase CaCO3 contenings for the first study indicate: (i) CO2 Intermixints.The findings for the first study indicate: (i) CO2 Intermixing with cement paste reduces Ca(OH)2 and increases the CaCO3 contents when compared to N2 intermixed and control (no-gas intermixed) specimens; (ii) Void size distributions and saturated hydraulic conductivity of CO2 intermixed specimens remained similar to control specimens, while N2 intermixed specimens showed an increase in void volume fraction; (iii) The mechanical properties (dynamic modulus and compressive strength) of CO2 intermixed specimens are increased when compared to N2 intermixed specimens and are similar to control (no-gas) intermixed specimens; (vi) CO2 intermixing increases the water content of specimens product of the reaction between Ca(OH)2 and CO2 and, (v) CO2 intermixing has the potential to offset CO2 emissions coming from cement manufacturing between 2.6% to 4.3%.In the second study, CO2 foamed cement grout (CFC-g) was explored as an alternative to traditionally made N2 foamed cement grout (NFC-g) to sequester CO2 in the form of CaCO3 and reduce Ca(OH)2 contents in specimens. Results indicate: (i) CFC-g contains less Ca(OH)2 and more CaCO3 when compared to NFC-g; (ii) While keeping analogous densities, the void size distribution in NFC-g is broader (larger amount of bigger voids) compared to CFC-g; (iii) The mechanical properties (dynamic modulus and compressive strength) of CFC-g are increased when compared to NFC-g; and (iv) An 11% CO2 sequestration efficiency was determined for CFC-g.With regards to the third study, the deterioration of cement-based structures due to sulfate attack has been a widely studied topic in cement science. Magnesium sulfate (MgSO4) is a common salt in natural waters and is often in contact with concrete structures. The physically unstable component, Ca(OH)2, is known to react with MgSO4 producing Mg(OH)2 -Brucite- and CaSO4 -Gypsum-. As for the stable component, Calcium-Silicate-Hydrates (C-S-H), different chemical responses may occur depending on concentration. Despite the vast amount of research performed on this subject, the fundamental reaction mechanism of C-S-H when exposed to different MgSO4 concentrations has not been studied quantitatively from a micromechanical standpoint. The findings for the third study are as follows: (i) At lower and moderate concentrations (2-4 g/l) an increase in elastic modulus is observed on C-S-H specimens (the formation of brucite and gypsum crystals contribute to the overall magnitude of the elastic modulus of the specimen) and (ii) At high concentrations (10-20 g/l) a significant reduction of elastic modulus is detected due to C-S-H decalcification.
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