Vertical barriers constructed using self-hardening slurries such as cement-bentonite were in use by the early 1970’s and slag-cement-bentonite (slag-CB) slurries were first used in the UK in 1975 (Jefferis, 1997). Since then, a number of studies have been conducted to assess the properties of slag-CB, although the vast majority are laboratory or theoretical studies. In this paper, the authors extract data and observations from recent field applications of slag-CB slurry. The observations from these field studies offer both new insight as well as reinforcement of certain existing understandings of self-hardening slurry walls. Topics addressed include: 1. Long term performance development including strength and hydraulic conductivity 2. Strength variability 3. Relationship between trench sample density and strength. 4. Effect of sample size on strength 5. Effect of sample handling on performance For each topic, potential practical implications associated with the observations are given as well as recommendations for improvement in the standard of practice.