Improvement of the Brittleness and Drying shrinkage in Very High Strength Concrete Incorporating Micro Metakaolin

Concrete commonly displays substantial brittleness and drying shrinkage, which have a detrimental influence on its performance and durability, especially in combinations with high quantities of cementitious elements, such as extremely high strength concrete. This type of concrete frequently encounters these issues due to its strong compressive strength and comparatively low split tensile strength. Consequently, micro MK was used to relieve brittleness and drying shrinkage in concrete. Five mixes were tested using micro metakaolin as a partial cement replacement at 0%, 3.5%, 4%, 4.5%, and 5% in very-high-strength concrete mixes using the wet mixing method. Additionally, each mix's compressive strength, split tensile strength, drying shrinkage, water absorption, and ultrasonic pulse velocity were all examined. The results showed that incorporating 4% micro metakaolin into very-high-strength concrete reduced the brittleness index to 9.101, while drying shrinkage and water absorption were reduced by 18.6% and 19.04%, respectively, due to a reduction in both the quantity and size of pores within the concrete matrix caused by micro-sized metakaolin. Incorporating 4% micro metakaolin increased pulse velocity, reaching a high of 7.493 mm/µs due to shorter distances between micro voids in the concrete matrix.