"Wet" set first course of Masonry
"Wet" set first course of Masonry
(OP)
I have been asked by several masonry contractors to "wet" set the first course of hollow unit block for a retaining wall. According to the code we use(2001 Calif. BC), this is not permitted. I get the usual "we do this all the time" response from the contractor. However, what would be the problem of "wet" setting the first course if all the forces can be resolved?






RE: "Wet" set first course of Masonry
RE: "Wet" set first course of Masonry
RE: "Wet" set first course of Masonry
1. The masonry will absorb water from the concrete, reducing the local strength around the base setting of the wall. Mortar is mortar, concrete is concrete. Just because they both are cementitious does not mean they are interchageable. Would you accept concrete as a mortar bed material? Neither would I...
2. I would be very concerned about what has happened to the reinforcing bars in the footing. Have they shifted, lowered down and eliminated their required clear cover, etc, etc, etc. There is just no way of knowing, and that's a problem.
3. I have actually seen a contractor pushing the reinforcing bars into the footing through the hollows in wet-set masonry block. Kind of funny, but not very impressive, and certainly not acceptable.
4. And the number one problem (IMHO): The blocks actually sink slowly into the footing, preventing the concrete from setting up properly and grossly reducing the strength of the footing to wall interface.
I remember there was a list of five things when I was taught to watch for this, but for the life of me #5 escapes me at the moment... I'll post it if I can remember. I think it had to do with trapped air, or perhaps that air entrainment is underirable in a meterial bonding to CMUs. I'll scratch my head a bit for you...
Hope that helps,
Regards,
YS
B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...
RE: "Wet" set first course of Masonry