Multi-Response Optimization of Ultrafine Cement-Based Slurry Using the Taguchi-Grey Relational Analysis Method.

Shuai Zhang,Zhenwang Fan,Weiguo Qiao,Yue Wu,Lei Zhang

doi:10.3390/ma14010117

Shuai Zhang, Zhenwang Fan + Show 3 more

Open Access

https://doi.org/10.3390/ma14010117

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Journal: Materials	Publication Date: Dec 29, 2020
Citations: 10	License type: CC BY 4.0

Affiliation: Shandong University of Science and Technology

Abstract

The grouting technique is an important method in underground engineering that prevents water seepage and reinforces fractured rock mass. In this research, ultrafine cement-based grouting material, including ultrafine cement (UC), ultrafine fly ash (UFA), polycarboxylate superplasticizer (SP), colloidal nanosilica (CNS), sodium sulfate solution (SS) and water, was developed. The flow time, viscosity, bleeding, setting time and uniaxial compressive strength of the UC-based slurry were measured by orthogonal experiments, and the optimal mix proportion of the UC-based slurry was obtained based on the Taguchi-Grey relational analysis method. Microstructure analysis of the UC-based slurry was conducted using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests. The results showed that the Bingham model could provide a satisfactory description of the rheological properties of the UC-based slurry. The addition of CNS and SS could promote the hydration of the UC-based slurry and improve the microstructure of the hardened slurry, thereby increasing the strength of the hardened slurry. The optimum ratio for the UC-based slurry was water/solid (W/S) ratio of 1.0, and the contents of UFA, SP, CNS and SS by mass of UC were 40%, 0.2%, 4% and 4%, respectively.

Highlights

With the increasing shortage of shallow coal resources, the depth of coal mining has been gradually increasing
In terms of the grain size, both the ultrafine cement (UC) and ultrafine fly ash (UFA) can be considered as ‘microfine’ since the grain size value meets the requirements of EN 12715
The orthogonal test results showed that the degree of influence on the properties of UC-based slurries was as follows: W/S ratio > colloidal nanosilica (CNS) content > sulfate solution (SS) content > SP content

Summary

Introduction

With the increasing shortage of shallow coal resources, the depth of coal mining has been gradually increasing. Under the condition of deep high ground stress and high hydraulic pressure, water seeps from the microfractures in the rock mass, resulting in large area water seepage problems in surrounding rock, which seriously affects the safety and stability of the construction, operation and maintenance of tunnels and metros [1,2,3]. In recent years, grouting technique has been widely adopted for the prevention of geological disasters, for example, water leaks, floor heaves and landslides in deep roadways, tunnels, slopes and dams [4]. Ultrafine cement (UC) slurry has been rapidly developed and is widely used to prevent the water seepage problem in underground engineering [6,7,8]

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