Performance evaluation of steam cured HPC pipe piles produced with metakaolin based mineral additives.

Highlights • The effect of MK based materials on the steam cured high performance concrete is investigated. • The XRD and TG analysis were applied to quantify the content of CH and AFt after curing. • The MK based admixtures remarkably refines the ITZ and optimize the pore structure of concrete after heat treatment. Abstract High performance pipe piles are widely used in precast industry. In order to improve the production efficiency and performances of the products, steam curing and mineral admixtures are usually applied. This paper evaluates the performances of HPC pipe piles produced with metakaolin-based admixtures. Quantitative phase composition analysis shows that the addition of 10 wt% metakaolin reduces the portlandite content by up to 57.1%, while increases the content of ettringite to some extent. The addition of metakaolin or metakaolin-slag/limestone blends improves the mechanical properties, especially the hybrid usage of metakaolin and limestone filler. Pore structure and microscope analyze confirm the remarkably-refined pore characteristics caused by the addition of metakaolin-based admixtures, in which case the gel pores accounts up to 85% of the total pores. Those remarkably improved properties caused by the addition of metakaolin-based admixtures indicate a promising future for their applications in producing high performance pipe piles with further modified properties. [ABSTRACT FROM AUTHOR]