Accelerated Carbonation Of Cement Pastes And Mortars

Sammanfattning

Concrete structures have the largest surface area of all human made structures. Large surface area makes concrete capable to absorb CO2 from environment during its lifetime. It is estimated that concrete during its lifetime can absorb about 15-20% of CO2 which had produced in cement production. In Sweden the CO2 uptake by concrete construction is estimated to 300 000 tons annually. This study aims to investigate the influences of fly ash and ground granulated blast furnace slag on carbonation. Accelerated carbonation with 65% relative humidity and 10% CO2 concentration was utilized to simulate the carbonation in cement pastes and cement mortars. Series of experiments have accomplished by collaborating with RISE and university of Borås. In this study cement pastes crushed into three fractions in order to evaluate the impact of particle size and influence of blended cement in CO2 uptake. Lastly, carbonation depth of mortars after 14 days accelerated carbonation were analyzed. Experimental results show that the increasing CO2 uptake induced by adding mineral admixture such fly ash in cement pastes. In this study cement paste with 30% fly ash replacement and fraction lower than 2 mm exhibit the highest CO2 uptake compared to other cement paste in this study. Moreover, carbonation depth of cement mortar was also increased three times more in mortar with 30% fly ash compared with mortar with 100% Portland cement. Therefore, incorporation of mineral admixture in cement pastes can improve the CO2 uptake and moreover, CO2 uptake can be more efficient if more surface area be involved with CO2 by crushing cement paste into lower 2 mm.