Abstract: Cast-in-place concrete piles constructed using the slurry wall protection process often consume large quantities of bentonite slurry. The used slurry has a greatly reduced montmorillonite mineral content and is mixed with a large number of clay and sand particles to form a waste slurry with deteriorated performance. Most of the waste slurries were disposed of for transportation, which not only caused environmental pollution, but also wasted the montmorillonite minerals. In this study, the waste mud samples from two pile foundation construction sites in Shenzhen area were taken separately, and some additives (e.g. calcium bentonite,Na₂CO₃, CMC, etc.) were mixed into the slurry samples to carry out the experimental study of “mud modification”. It was found that a single admixture in the waste slurry cannot achieve the purpose of slurry modification, only according to the characteristics of the additives mixed with different additives to effectively realize the slurry modification; and in the study to improve the performance of the effective slurry required to be mixed with calcium bentonite, Na₂CO₃ and CMC additives in the optimal ratio of 0.1% Na₂CO₃, 0.1% CMC, and 2.5% Bentonite. The waste slurry was recycled for pile foundation construction after the performance improvement, and the results of the later excavation of grouted piles showed that it was significantly more effective than the waste slurry without improved performance. This is of great significance for the recycling of waste slurry in the field of pile foundation construction.

Key words: Engineering Piles, Waste Slurry, Slurry Performance Improvement, Additives, Proportioning Test