Geopolymer as well cement and its mechanical behaviour with curing temperature

Abstract

Carbon capture and storage (CCS) technique is found as a best solution to reduce the emission of CO2 to the atmosphere. In this technique, the CO2 emitted from large industries is captured, and pressurized, and finally injected into deep underground reservoirs. In a geological sequestration project, integrity of injection well play an important role. It means the well cement is a key factor that affects the well integrity. In typical injection wells, Ordinary Portland cement (OPC) based cement is used as well cement and it has been found that it undergoes degradation in CO2 rich environment. Geopolymer can be a good alternative to existing OPC based well cement as it has been found that geopolymer possess high strength and durability compared to OPC. Geopolymer is a binder produced through the process called geopolymerization of alumino- silicate materials and alkaline activators. In the sequestration wells, well cement is exposed to different curing temperatures with a geothermal gradient of 30°C/km. Therefore, it is important to study the mechanical behaviour of well cement with curing temperatures expected deep under the ground. Therefore, this research aims to study geopolymer as well cement and its mechanical behaviour at different curing temperatures (25, 40, 50, 60, 70, 80 °C). In addition, effect of ageing on the mechanical behaviour was also studied. The OPC samples were tested for the comparison of results with geopolymer. The results showed that the optimal curing temperature for higher strength of geopolymer and OPC are 60 °C and 50 °C respectively. Geopolymer possess highest strength at elevated temperatures whereas OPC possess higher strength at ambient temperatures. Moreover, at elevated temperature curing, geopolymer develops ultimate strength within short curing period and it does not gain significant strength with further ageing.