Year: 2017
Type: dissertation
Abstract: It has been known since the 70s that carbon curing of cement can be beneficial to early strength development.A novel approach has been to add liquid carbon dioxide to industrial batches of concrete, promising increased early strength and disposal of unwanted CO2.In this work, the effect on the first 24 hours of hydration of adding solid carbon dioxide to Portland cement during mixing was investigated.Lab scale batches of cement (w/c = 0.5) were mixed with solid carbon dioxide in doses ranging from 1 % to ~50 % by weight of cement and monitored with isothermal calorimetry, in-situ FTIR and thermogravimetric analysis.Results from isothermal calorimetry show that doses of 2.5 to 10 % CO2 increased the heat of hydration during the first 15 hours, while the highest doses show less effect.Calorimetry suggests that the increased heat is mainly from an acceleration of aluminate hydration.In-situ FTIR shows little effect of CO2-addition on the composition of cement hydrated for 24 hours, and no significant impact on silicate hydration.The most obvious effect shown by FTIR investigation is a large shift in the sulfate region and a crystallization of gypsum during the first 30 minutes of hydration.TGA analysis suggest that the absorption of CO2 added during mixing with cement is small and that calcium hydroxide is mostly unaffected after 24 hours of hydration.Cement samples showed similar mass loss over the temperature intervals assigned to Ca(OH)2 (370-470 °C) and CO2 (530-875 °C), regardless of CO2-addition, suggesting that the cement may be saturated at less than 1 % by weight of cement, at the time of mixing.
Author: Joel André
Language: English
Subfield: Civil and Structural Engineering
Field: Engineering
Domain: Physical Sciences
SDG: Climate action
Open Access status: green
OpenAlex ID: W2727630105