Recent Observations on Self-Hardening Slurries in Slurry Trenching

Self-hardening slurries such as cement-bentonite and slag-cement-bentonite have been increasingly used in the installation of subsurface vertical barriers since the 1970s. In this paper, the authors build on previously reported lessons learned from the use of self-hardening slurries in vertical barriers to highlight recent developments and observations related to the applicability, specifications, installation, and testing of self-hardening slurry trenches. These lessons are based on direct observations from recent field applications. Lessons from this recent field experience offer new insight and reinforce existing knowledge. Topics addressed include the switch from type I/II Portland cement to type IL Portland cement, observations from field sampling and testing including coring and in situ permeability testing, comparison of strength and hydraulic conductivity results from mix design samples, wet-grab samples and core samples, discussion of changes in recent specifications, and updates on constructability considerations.