Strength and Pore Structure Development of High-Plasticity Clay Treated with MK-Blended Cement

Abstract

"This paper focuses on the strength development and pore structure evolution of high-plasticity clay mixtures treated with metakaolin (MK-) blended ordinary Portlandcement(OPC).The unconfined compressive strength(fcu) of treated soil mixtures is measured to study the effect of MK replacement. The microstructural study is carried out by mercury intrusion porosimetry (MIP),scanning electron microscopy(SEM),and X-ray diffraction(XRD).There sults showed that the MK replacementled to the decrease of unconfined compressive strength of OPC-treated soil mixturecured for 28days,but the influence on 7 days strength was negligible. However, the MK addition also enhanced the unconfined compressive strength significantly. The MK addition providedmorecementitiousproductsbysecondaryhydrationandpozzolanicreaction,whichwouldgiverisetoanotablefilling effect by turning the large pores (1 to 10μm) into smaller ones (0.1 to 1μm). However, the MK replacement led to a decrease of cementitious products due to the lack of calcium hydroxide(CH) in soil mixture,and thus the effect on porestructure refinement was reduced. Nevertheless, the presence of MK enhanced the unconfined compressive strength cured for 7days,due tothe high reactivity of MK with CH.