Mechanical behaviour and micro-structure of cement-stabilised marine clay with a metakaolin agent

Metakaolin, a fine powder material, has been widely used as an effective additive to produce the high-performance concrete since 1990s, for its high efficiency and relatively low price. However, metakaolin has rarely been attempted in admixtures of cement-stabilised soft clays until presently. This paper focuses on the macro-strength and micro-structure development of cement-stabilized Lianyungang marine clay mixed with metakaolin. The results show that the unconfined compression strengths of cemented soils containing 3% and 5% MK are approximately 2.0-3.0 times of that of materials without MK, that is MK can effectively improve the quality of cemented soils. Additionally, the strength with MK after 7 day's curing periods is approximately 0.87 times of that after 28 day's, while this ratio is 0.58 for the soils lacking MK, which indicates that the cemented soils containing MK show sufficient earlier strength than those lacking MK. Finally, the microstructure analysis reveals that MK mainly changes the pore volume distribution, which ranges between 0.01 μm and 1 μm, and produces more CSH/Aft/CASH bonding and fissures due to the secondary hydration and pozzolanic reactions.