Physiochemical investigation of CO₂ accelerated concrete curing as a greenhouse gas mitigation technology

There is an emerging demand for natural and engineered CO2 sinks to combat the effects of global warming. Carbon capture and storage (CCS) processes are expected to play a predominant role within a broad portfolio of technical innovations to mitigate greenhouse gas (GHG) emissions. A range of CCS methods will be required to provide GHG control technologies for the broad scope of industrial sectors. Within this class of technologies carbon dioxide accelerated concrete curing has the global potential to permanently and safely sequester up to 550 Mt CO2/yr while producing non-reinforced concrete products with improved physical properties and in less time than traditionally cured products. Previous research has exhibited shallow CO 2 penetration depth and modest CO2 uptake in grout and concrete samples despite using severe process conditions such as high pressures, temperatures and long experimental durations. Chemical and microstructural changes during carbonation were investigated to clarify the previously unexplained limitations in CO2 uptake and provide solutions to enhance CO2 storage. Loss of exposed particle surface area was identified as the most significant factor limiting complete carbonation of cement grout samples. The findings were applied to design a bench scale, flow-through carbonation curing reactor that sequestered CO2 at an average of 8.3 wt % of the cured cement with complete depth of penetration. The sequestration results were achieved with ambient temperature (20°C), 40% relative humidity, atmospheric pressure (1 atm), as-captured flue gas CO2 partial pressure (0.20) and low flow (1 Lpm) in less than 60 minutes.