Q.: Would you endorse a concrete sales policy that would use metered scales to stamp the contents of each batch of concrete on the delivery ticket?
A.: We're not sure about all the implications of such a policy but, on the face of it, it sounds like a good one. The advantage would be that both the supplier and the purchaser would have a record of what was put into the concrete. In general, the more information everyone has the better.
The potential problem is that someone might take the record of the batch proportions to be a warranty of how the concrete would perform in service. Those proportions are only one of many factors that determine the concrete's performance. Hence any supplier who does print the batch proportions on the ticket might well want to also include a statement that the proportions, in and of themselves, do not constitute a warranty of concrete performance in the structure.
In the meantime, if you are buying concrete without knowing even what the design proportions are, you might want to follow the practice suggested in the Problem Clinic item, "Mix proportions for the concrete you buy," May 1984 issue, page 521.