I appericiate your effort to educate viewers. You are using British Standard grooving tool and according to BS-1377 Part 2, you should add incremental amount of water between each test. Adding dry soil makes soil puddy to have dry crust, so homogeneous property that we are looking for isn't achieving like the standards suggesting us. There is a lot of nitpicky details in standards' documents to making perfect liquid limit test.
our lab manual instructs: reach a well-mixed soil paste moisture content (by adding water, or by drying) such that you first reach a groove collapse at a blow count between 25 and 35; acquire sample (1); and then: add water and mix thoroughly, successively, to reach blow count ranges of 20 to 25, and 15 to 20, respectively, acquiring samples (2, 3) from each.
I've been looking for better ways of mixing soil for this test in our lab and ran across this video. Very educational but I noted 2 things that hopefully will help students. The water you are using should be distilled or demineralized and also when creating the valley in the Casa Grande I usually hold down the brass bowl to not allow the final second to pull up the bowl and accidently slam on the base. Thanks for making these videos.
at about 13:38 and 14:38, the text should say "decrease" [not increase] moisture content ?; [after the groove in soil collapsed too quickly]; nice video;
