Preparation of a Synthetic Geopolymer Cement Utilizing Saudi Arabian Volcanic Ash for a Sustainable Development: Method, Preparation and Applications

Abstract

Abstract The global production of cement is the third largest source of CO2 emissions into the environment, which comes from the decomposition of carbonates. Geopolymer cements can reduce CO2 emissions by 64-80% compared to conventional Ordinary Portland Cement (OPC). In other words, OPC produces around 900 kg of CO2 for every 1000 kg of cement production. Whereas, geo-polymer cements emits zero CO2 emissions while production. In addition, Geo-polymer cements can be prepared utilizing waste materials such as fly ash. In Saudi Arabia, we have enough volcanic ash to sustain the development of this ecofriendly cement. Moreover, geopolymer cements have demonstrated promising mechanical properties in comparison to OPCs. We successfully developed a novel geopolymer cement utilizing a Saudi Arabian volcanic ash for primary cementing applications for the Oil and Gas industry that can replace OPCs completely. This novel cement was prepared by activating the volcanic ash particles with an alkali solution to undergo a geopolymerization reaction. The objective of this paper is to prepare a geopolymer cement with excellent strength and to discuss the synthesis of this cement based on the chemical composition of the volcanic ash (VA). Also, to investigate the effect of the type and concertation of the activating solution on the final geopolymer mechanical properties as well as to detail lab testing. The volcanic ash particles were activated by a mixture of NaOH, sodium silicate and water to develop a geopolymer cement. In this study, we prepared four different activating solutions by varying the alkali concertation based on the VA chemical composition. The effect of these variations on the setting time and compressive strength of the final geopolymer VA-based cement were investigated. This was done to develop a cement with excellent strength and controlled setting to assure a right cement placement. In addition, the chemical conditions were evaluated to simulate a variety of downhole conditions to prove the effectiveness of this novel geopolymer composition as a cement for primary cementing applications. The lab testing includes thickening time measurement, compressive strength, and a chemical analysis of the volcanic ash. Test results indicate that the resulting compressive strength and thickening time are strongly affected by the alkali concentration and the addition amounts of the activating solution. Based on this study, we were able to prepare a geopolymer cement with good rheology, setting time and compressive strength for primary cementing application.