Thanks, that’s great info. I just called my local feed store, and they carry another brand of the same stuff for $5.50 per 40 pound bag. Are you talking about 15 - 18 concrete mixing tubs? I will be using it in cat litter pans and concrete mixing tubs. I usually fill up about 18 or so cat litter pans and around 9 or 10 concrete mixing tubs per week. How many bags do you think I will be using each week? Thanks.