Fundamental study on quality improvement of cement-based ground improvement using fine bubbles

¹ Department of Architecture and Architectural Engineering, College of Industrial Technology, Nihon University, Chiba, Japan
² Department of Applied Molecular Chemistry, College of Industrial Technology, Nihon University, Chiba, Japan
³ Kanematsu Suntech Corporation, Japan

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

In cement-based ground-improvement methods, the potential difference between soil and cement particles may result in the formation of electrical aggregates, which can hinder the uniform mixing of soil and cement slurry in situ. Consequently, the strength of the improved soil may not be desirable. As a countermeasure, surfactants can be used to prevent aggregate formation by adsorbing onto cement particles to provide steric hindrance and electrical repulsion. However, cost and environmental challenges remain. By contrast, fine bubbles carry negative charges in aqueous solutions and are expected to exhibit effects similar to those of surfactants when mixed with cement slurry. Furthermore, fine bubbles are expected to function similarly to ball bearings. Therefore, this study investigates whether fine bubbles can be used as a substitute for surfactants. First, surface potential measurements confirmed that cement particles with adsorbed fine bubbles exhibited reduced surface potential. Additionally, funnel tests confirmed the improved flowability of the cement slurry. Finally, using a small-scale deep-mixing machine, we confirmed that the mixing resistance of a soil–cement slurry decreased with the addition of fine bubbles. These results indicate that fine bubbles can effectively enhance mixing efficiency and flowability, serving as a viable alternative to surfactants.