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

Qian Guo,Mingli Wei,Haochen Xue,Guangyin Du,Changhui Gao

doi:10.1155/2019/2527892

Abstract

This paper focuses on the strength development and pore structure evolution of high‐plasticity clay mixtures treated with metakaolin‐ (MK‐) blended ordinary Portland cement (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). The results showed that the MK replacement led to the decrease of unconfined compressive strength of OPC‐treated soil mixture cured for 28 days, but the influence on 7 days strength was negligible. However, the MK addition also enhanced the unconfined compressive strength significantly. The MK addition provided more cementitious products by secondary hydration and pozzolanic reaction, which would give rise to a notable filling effect by turning the large pores (1 to 10 μm) into smaller ones (0.1 to 1 μm). 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 pore structure refinement was reduced. Nevertheless, the presence of MK enhanced the unconfined compressive strength cured for 7 days, due to the high reactivity of MK with CH.

Highlights

Academic Editor: Tayfun Dede is paper focuses on the strength development and pore structure evolution of high-plasticity clay mixtures treated with metakaolin- (MK-) blended ordinary Portland cement (OPC). e unconfined compressive strength of treated soil mixtures is measured to study the effect of MK replacement. e microstructural study is carried out by mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and X-ray diffraction (XRD). e results showed that the MK replacement led to the decrease of unconfined compressive strength of OPC-treated soil mixture cured for 28 days, but the influence on 7 days strength was negligible
Metakaolin (MK) is an aluminosilicate material, obtained by calcining kaolin clay at the temperature of 500– 800°C [4, 5]. It contains high-reactivity silicon and alumina compounds, and the typical mass content of SiO2 and Al2O3 is about 50–55% and 40–45%, respectively [6]. e MK has an acceleration effect on cement hydration and pozzolanic reaction [7, 8], which results in a significant increase of compressive strength by approximately 5–20% MK replacement, and it is utilized for high-performance concretes, mortars, and cement pastes [5,6,7,8,9,10,11]
The MK replacement would result in the reduction of strength at a high clay-water to binder (w/b) ratio [12], which differs with the effect on concretes or cement pastes as mentioned before. erefore, the strength performance and the pore structure evolution of the cement-treated soil mixtures with MK replacement were not well understood, in particular when treating the high-plasticity clay

Summary

Introduction

Academic Editor: Tayfun Dede is paper focuses on the strength development and pore structure evolution of high-plasticity clay mixtures treated with metakaolin- (MK-) blended ordinary Portland cement (OPC). e unconfined compressive strength (fcu) of treated soil mixtures is measured to study the effect of MK replacement. e microstructural study is carried out by mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and X-ray diffraction (XRD). e results showed that the MK replacement led to the decrease of unconfined compressive strength of OPC-treated soil mixture cured for 28 days, but the influence on 7 days strength was negligible. E unconfined compressive strength (fcu) of treated soil mixtures is measured to study the effect of MK replacement. E results showed that the MK replacement led to the decrease of unconfined compressive strength of OPC-treated soil mixture cured for 28 days, but the influence on 7 days strength was negligible.

Results

Conclusion