Strength and micro-mechanism of MK-blended alkaline cement treated high plasticity clay

Abstract This paper focuses on the strength behavior and micro-mechanisms of treated high plasticity clay-mixtures with Metakaolin- (MK-) blended alkaline cement. The MK-blended alkaline cement was prepared by the alkaline activation of Ordinary Portland Cement (OPC) and MK blends, while the MK-based geopolymer and MK-blended cement were also prepared for comparison purpose. The results show that the unconfined compressive strength (UCS) of the clay treated by MK-blended alkaline cement increases with MK replacement at ranges of 30%. Meanwhile, the pore structure was significantly improved in terms of large pores transferring to the smaller size. The increase of MK replacement from 10% to 20% leads to the increase of UCS of the MK-blended alkaline cement treated clay mixture (L/S = 53.8%, 3.2 M) by 21.8%, and increase of pores ranging from 0.01 to 0.1 μm by 47.5% along with the decrease of pores ranging from 0.1 to 1 μm by 28.1%. This attributes to the notable bonding and filling effect by the coexistence of cementitious gels such as (N,C)-A-S-H and C-A-S-H gels, which differ to the hydration products from traditional OPC hydration. More significantly, the treated clay mixture with 60% MK replacement has the potential to reduce large portion of OPC, due to its appreciable strength of approximately 31.0% increase over the OPC treated clay-mixture.