A pozzolanic based methodology to reinforce Portland cement used for CO2 storage sites

Carbon Capture and Sequestration (CCS) technique is an effective strategy developed in the past decade to reduce the amount of CO2 emission in the atmosphere. Integrity of storage sites plays an important role in the success of a CCS project once CO2 is injected in a suitable geological formation such as depleted hydrocarbon reservoirs. However, the interactions of supercritical CO2 with the cement in the presence of brine may degrade the cement in the injection intervals, causing seepage of CO2 to surface or subsurface resources. In this study, efforts are made to show the application of agricultural wastes and nanomaterials as potential pozzolanic additives which can improve the performance of the cement once exposed to CO2. Palm Oil Fuel Ash (POFA) and Rice Husk Ash (RHA) as agricultural wastes together with Nano Silica (NS) were used in this study. Two series of tests, known as pre-carbonation and post-carbonation, were conducted and comparison was made between the agricultural and nanosilica cement composites. The results obtained indicated that the cement with 5 wt% POFA and 0.5 wt% NS can provide the highest compressive strength after 24 h of curing. The viscosity of the cement composites with NS and RHA also increased with the increase of the replacement level. A series of carbonation tests was done for 40 days and it was found that almost all of the cement samples provide a better performance than the neat cement in the CCS sites, although the best result was obtained by the samples with 0.5 wt% NS and 0.75 wt% NS given the interactions that may take place faster in the nanoscale.