Application of CO2 Loaded Ionic Solvent in Concrete
The increase in CO2 emissions, as a major greenhouse gas, has led to increase in average global temperature. At present CO2 levels in the atmosphere are more than 412 ppm and rising. To succeed in limiting the increase in global temperature to 1.5˚ C above pre-industrial levels, CO2 emissions worldwide must be reduced substantially in all sectors of the economy. Carbon capture utilization and storage (CCUS) provides a means of producing low-carbon electricity from fossil fuels and of reducing CO2 emissions from industrial processes such as gas processing, cement and steel making, where other decarbonization options are limited. However, there is urgent need for research and development to deliver even more cost-effective CCUS technologies for the capture, conversion, utilization, transportation, and storage of CO2 (Zhang et al., 2020; Zhu, 2019). Studies on various means of reducing CO2 emission or on the capture, storage and sequestration of emitted CO2 have been conducted to provide mitigation measures for greenhouse-induced temperature increases from a medium-and long-term perspective. Geologic sequestration, among others offered as a substitute for the sequestration of captured CO2, was until recently thought of as the main method of CO2 sequestration.
Although the geologic sequestration method has the capacity to sequester a significant amount of CO2, recent reports of its high cost, little economic added value, and occasionally unfavourable environmental effects indicate a need for a more developed technology. Henceforth, utilizing captured CO2 in a process that yields valuable materials has consequently recently attracted a lot of attention. One of the prime examples is the sequestration of CO2 by mineral carbonation and transformation into an industrially useful product using similar processes. Cement-based substances, such as unhardened cement paste, mortar, concrete, and waste from these cement-based products, can be carbonated in order to absorb CO2 more effectively. Due to their tremendous strength, exceptional durability, and financial advantages, cement and concrete are the most often used construction materials worldwide (Jang et al., 2016). Despite the fact that the cement sector is responsible for 27% of all direct industrial CO2 emissions and 8% of worldwide CO2 emissions, CO2 is still necessary for the curing (carbonation) of concrete and other cement-based materials which is as a result of a reaction between the CO2 and the cement hydrate. (Zhaurova et al., 2021). Among the benefits of carbonation of cement-based material are early strength, reduction in shrinkage, reduction in water permeability and efflorescence in the cement-based material (Monkman & Shao, 2010).The methods under investigation for the utilisation of CO2 in cement-based material include dissolving recovered CO2 in water and adding it to the cement-based material as well as injecting recovered CO2 from exhaust gases into a precast cement-based material in a closed chamber. However, this technology has not been successful in achieving the efficiency of CO2 uptake by cement-based material due to the poor solubility of CO2 in water (Han et al., 2022; Monkman & Shao, 2010). On the other hand, recovering CO2 from exhaust gas and injecting it into a precast cement-based material is seen to have many drawbacks. Despite the equipment cost and energy requirement cost involved in capturing the CO2, precipitation of the calcium carbonate decreases the porosity, inhibiting CO2 diffusivity in the cement-based material (Jang et al., 2016; Monkman & Shao, 2010).
This study seeks to investigate the utilization of CO2 in cement-based material by using a CO2 loaded ionic solvent. In this case, the CO2 captured from industrial exhaust gas is absorbed using a catalyst aided solvent which is being worked on by fellow research students. After the absorption of the CO2, the CO2 rich solvent will then be utilized directly in a cement-based material without desorption to accelerate curing and also improve on the strength and other beneficial properties of the cement-based material. Despite the efficiency and permanent utilization of CO2 by this method as reported in similar work done by (Yu et al., 2019) by using CO2 loaded solvent in CaO rich industrial waste, the cost of desorption column and other ancillary equipment as well as cost of energy requirement for CO2 desorption is also eliminated. For quality assurance of the concrete cured by this method, analysis or tests such as compressive strength, tensile strength, modulus of elasticity, permeability test, density, thaw resistance, resistance to chemicals, resistance to abrasion will be run on the cured concrete. The results of these tests will be compared with that of concrete cured by the conventional method as a benchmark. Moreover, in order to ensure that the captured CO2 is retained in the concrete, CO2 leakage test is also carried out on the cured concrete samples.