Geopolymeric flocculation-solidification of tail slurry of shield tunnelling spoil after sand separation

Abstract

Geopolymeric flocculation-solidification of the tail slurry of shield tunnelling spoil after sand separation was investigated to replace the low-efficient flocculation and filter-pressing method currently adopted on site. The geopolymeric flocculation-solidification agent (GBFS-FS) consisting of flocculation component and geopolymeric solidification component (granulated blast-furnace slag (GBFS) activated by alkali) was prepared and investigated through flocculation-sedimentation test, dewatering model test, unconfined compression test, SEM test, etc. In the flocculation-sedimentation test, the GBFS-FS agent demonstrated the best flocculation effect as compared with other cementitious flocculation-solidification agents. The dewatering model tests revealed that adding the GBFS-FS agent into the slurry can not only dewater the slurry efficiently, but also generate solidified clayey sediments with quickly-increased strength. The solidified clayey sediments with GBFS-FS showed strengths 3.5 times higher than others with cementitious agents at a 28-day curing age. The GBFS-FS agent can also facilitate to make controlled low-strength material (CLSM) using the tail slurry. The fluidity and strength of CLSM with GBFS-FS were distinctly better than those of other groups. SEM test shows that the components of the GBFS-FS agent can interact to avoid large flocs and support each other in strength growth.