Authors

Lindsay Duran

Publication Date

2015

Abstract

The low durability and low resistance of ordinary Portland cement led to an investigation into the viability of geopolymer cement as an alternative to well cement for soil improvement in saline environments and well cement in offshore drilling and carbon sequestration projects. This thesis presents the results of a laboratory investigation into the effect of immediate saline water curing on the strength, composition, and microstructure of geopolymer cement. The experimental program began with preliminary work in designing adequate geopolymer cement and developing a curing environment that simulates offshore or underground conditions and facilitates immediate curing of cement specimens. Pure geopolymer cement with a Si/Al ratio of 1.78 was synthesized from an admixture of Class C fly ash and metakaolin and immediately cured in saline water of 0, 15, and 35 ppt concentrations. After 28 days of water curing, the specimens were removed from their curing environments and characterized for strength, composition, and microstructure. Class G well cement specimens were simultaneously cured under similar conditions and analyzed as a source of comparison. Results indicatethat the strength of the geopolymer cement increases with increasing salinity, while the Class G cement exhibits opposite behavior. Mineralogical compositional analysis (X-ray diffraction) demonstrates the formation of a geopolymer through alkali activation of amorphous silica and alumina. Chemical compositional analyses (pH, X-ray fluorescence) revealed an increased rate of chemical exchange between the cement slurry and curing water occurred with decreasing salinity for both cement types. The microstructural characterization was carried out using scanning electron microscopy and energy dispersive X-ray spectroscopy. The geopolymer cements possessed nanoporosity and observed reacted product that was independent of curing salinity. All of the findings suggest that geopolymer cement derived from an admixture of metakaolin and Class C fly ash would be a viable alternative to ordinary Portland cement in well cementing applications.

Share

COinS