Basic Research on Improvement of Construction Sludge

Tsutomu Watanabe*, Kazuhito Komiya* and Eiji Shimizu*
* Department of Civil Engineering, Chiba Institute of Technology
+ Correspondence should be addressed to Tsutomu Watanabe:
(2-17-1, Tsudanuma Narashino-city, Chiba 275-0016 Japan)

Abstract
This paper studies the effective recycling of the construction sludge which arises during the construction of slurry type shields and earth pressure balance type shields.
With shield tunnels being frequently constructed, the quantity of the construction sludge has become remarkably copious. Processing of construction sludge by shield tunnelling is serious environmental problem.
In this study, a super absorbent polymer was added to the sludge in order to reduce the degree of fluidity. The stabilizer was mixed with the sludge to improve the strength of the sludge. The improved efficiency satisfied the second level standard which Ministry of Construction determined for the reuse soil; 0.5%~0.7% addition of the super absorbent polymer and the stabilizer 13%~18% mixture for the mass of the construction sludge.
The investigation was conducted to estimate the change in strength of improved sludge for a period greater than one year. It was found that improved long-term stability could be achieved in the modified sludge.

Key words: construction sludge, super absorbent polymer, strength, long-term stability, shield tunnel