The filter bags will allow the smaller material to penetrate into the weave and cause the blinding. To validate this I recomend that you look at the PSD and solids density upstream of the float process (the slurry you were feeding) and compare that to the PSD and solids density down streram (the slurry you are now feeding).
I have a question of all you experienced structural (foundation) and geotechnical engineers. For the project on which I am currently working, there are two grades of PCC (plain cement concrete) specified for blinding mats underneath all foundations. One is called M10 (requiring 10MPa cube...
Agree that blinding concrete (or what I call a mudmat) is a good idea many times for ease in setting formwork and steel, to prevent damage of the founding soil in case of rain or just construction (workmen) damage. You could use a good crushed stone layer as well . . .
The flocculation occurs in the bed, however, your problem is the flocc forming too soon, forming large flocc and collecting on the media surface and blinding it. You want to be looking for a steady almost linear headloss buildup on the filter indicating deep penetration into the bed rather than any sudden increases in headloss indicating blinding.
Hi comrades :) Designing a retaining wall. Structural layering from top to bottom: the cast-in-place retaining wall base > blinding (weak concrete thin layer or geotextile) if necessary > crushed rock pad 0,5 m mainly to avoid capillary effect, but have to be compacted properly to provide good...
Blinding is doing a different job to cover. It's simply there to provide a decent working surface nothing else. Cover implies protection for reinforcement, which blinding might seem to provide, but given there'll be a cold joint between the blinding and the structural concrete waiting to allow moisture to get in I wouldn't rely on it in any way.