Curing of Concrete Specimens Containing Metakaolin, Zeolite, and Micro-/Nanobubble Water in Seawater

In marine structures, concrete requires adequate resistance against chloride-ion penetration. As a result, numerous studies have been conducted to enhance the mechanical properties and durability of concrete by incorporating various pozzolans. This research investigated the curing conditions of samples including zeolite and metakaolin mixed with micro-/nanobubble water in artificial seawater and standard conditions. The results indicated that incorporating zeolite and metakaolin mixed with micro-/nanobubble water, cured in artificial seawater conditions, compared to similar samples that were cured in standard conditions, improved the mechanical properties and durability of concrete samples. The 28-day compressive strength of the concrete samples containing 10% metakaolin mixed with 100% micro-/nanobubble water and 10% zeolite blended with 100% micro-/nanobubble water cured in seawater increased by 25.06% and 20.9%, respectively, compared to the control sample cured in standard conditions. The most significant results were obtained with a compound of 10% metakaolin and 10% zeolite with 100% micro-/nanobubble water cured in seawater (MK10Z10NB100CS), which significantly increased the compressive, tensile, and flexural strengths by 11.13, 14, and 9.1%, respectively, compared with the MK10Z10NB100 sample cured in standard conditions. Furthermore, it considerably decreased the 24-hour water absorption and chloride penetration at 90 days--by 27.70 and 82.89%, respectively--compared with the control sample cured in standard conditions. Keywords: curing; metakaolin; micro-/nanobubble; seawater; zeolite.