Sustainability of Well Wall Concrete Exposed to Salts Using Varying Proportions of Metakaolin in Cement Mortar

This research investigated the effect of replacing salt-resistant cement in
oil well casings with varying proportions of Metakaolin, focusing on
compressive strength, flexural strength, and sample density. Ultrasonic
testing was also performed on all samples. Various proportions of
cement, sand, and Metakaolin were prepared, and molds were cast for
testing. Five mixtures were used: the first mixture consisted of saltresistant cement with sand only; the second: cement with 5%
Metakaolin; the third: cement with 10% Metakaolin; the fourth: cement
with 15% Metakaolin; and the final mixture of cement with 20%
Metakaolin. The samples were incubated for 7days, 28days, and 150
days in water only, and a further 150-day period (the first 28days in
water followed by 120days in sulfate chloride solution). The results
showed changes in compressive strength, bulk density, UPV, and
flexural stress. It can be concluded that the optimal Metakaolin content
(10–15%) achieves the best flexural strength performance under all
processing conditions, without any adverse effects from salt exposure.
The study's findings demonstrate the feasibility of using metakaolin in
oil well walls at approximately 10–15% as a partial replacement for
cement, provided that a highly efficient kaolin burning process is
employed to prevent premature loss of concrete strength. Adequate
water curing is essential before the concrete is exposed to saline
environments. This partial replacement helps reduce the environmental
impact of the cement used, while maintaining mechanical properties and
durability, thus achieving a suitable balance between structural
performance and sustainability.