Multi-technique investigation of metakaolin and slag blended portland cement pastes: Fid-Bau Portal

Multi-technique investigation of metakaolin and slag blended portland cement pastes

Shanahan, Natallia / Markandeya, Ananya / Elnihum, Ahmed / Stetsko, Yuri P. / Zayed, A.

AbstractIncreasing incorporation of metakaolin (MK) into field concrete mixtures necessitates careful study of the portland cement/MK hydrating systems. While a number of studies have been conducted on MK blends with cement, the current knowledge on its effect on hydration products and paste microstructure remains incomplete. This study evaluated the effect of MK on the nature of hydration products through X-ray diffraction, while the effect on microstructure was assessed by measuring porosity with nitrogen adsorption and determining nanoindentation modulus as well as volume fractions of CSH with varying packing densities. The 10MK paste hydrated for 7days was compared to the plain ordinary portland cement (OPC) paste as well as to paste containing 52% slag (52SL). No significant effect was observed on the nature of hydration products with MK or SL addition. However, nitrogen-accessible porosity increased with MK and SL addition, the increase being larger with SL. The average indentation modulus for hydration products decreased with addition of MK and SL which corresponded to increasing nitrogen accessible pores.

Highlights•Addition of 10% MK or 52% SL did not significantly change the nature of hydration products identified by x-ray diffraction.•N2 adsorption indicated an increase in LGP volume with addition of 10% MK and 52% SL.•Nanoindentation showed an increase in C-S-H porosity for 10MK and 52SL in agreement with N2 adsorption.