Service Life and Early Age Durability Enhancement due to Combined Metakaolin and Nanosilica in Mortars for Marine Applications

Abstract

The addition of a range of micro- and nano-particles to high-performance concrete has been the focus of recent research. At present, studies are mainly aimed at designing customised mortars, providing them with specific properties for each application. Improving the durability of mortars is one of the main objectives in such research, as a result of increasing environmental concern. The research presented herein analyses the synergistic effect of nanosilica and metakaolin as additives on the service life of cement-based mortars subject to aggressive environments (i.e., chloride exposure) at early ages. The effects of the additives on the durability properties of submerged samples after two and three days of curing were analysed. Tests were conducted on several different properties: resistivity, porosity, mechanical properties, chloride diffusion, and service life. It is observed that metakaolin and nanosilica exhibit a synergistic effect as additives, which is related to porosity refinement and chloride ion binding capacity, which contributes to enhanced resistance against chloride penetration from very early ages.

Matrix Optimization of Ultra High Performance Concrete for Improving Strength and Durability

“…Pozzolanic materials, such as metakaolin, silica fume and nano silica are used as partial substitution of cement in mixing designs and are responsible for microstructure densification, porosity reduction and accelerating the clinker hydration process [20][21][22][23], resulting in improved concrete performance. The UHPC matrix densifies due to two types of phenomena: the pozzolanic reaction of these materials with calcium hydroxide, and the associated filler effect that is associated with the packaging density [24][25][26].…”