Strength development of aplite-based geopolymer cements

Abstract

The purpose of this work is to investigate and develop aplite-based geopolymer as an alternative material for Portland cement. This was done by conducting a series of experiments using an Ultrasonic Cement Analysis (UCA) on different recipes. In order to get the desired results, the recipes were modified after each experiment. When the final recipe was found, several Uniaxial Compressive Strength (UCS) tests were conducted to verify the obtained results from the UCA.

The reason for wanting to develop this geopolymeric material, is to find an alternative to Portland cement for plug and abandonment operations. Portland cement is the most common sealant used for Plugging and Abandonment (P&A) operations. However, when it comes to high temperatures and corrosive environments it has its weaknesses. So if geopolymers are more resistant in these cases, and may be produced cheaper and do less impact on the environment, then this would be a good development for the industry.

After series of experiments the results suggested that a high silica/aluminum ratio was needed to develop strength. The increase of concentration of the alkali solution also improved the strength. However, a too high content of NaOH gave poor results, and might be explained by excess Na+ ions that weakened the geopolymer framework. After modifying the recipe and removing metakaolin a recipe was developed that achieved a compressive strength of 4200 psi in the UCA, and 5700 psi by UCS tests. The results suggest that an elevated curing temperature and pressure increases the compressive strength of the mentioned geopolymer. They also indicate that a higher Solid – Liquid Ratio (SLR) will reduce the time for the slurry to set. All the experimental work was done at the University of Stavanger in the well cement lab, and the concrete lab.