[CurlyDave]

It is possible to use an ordinary twist drill to make a hole in Chinese concrete. They don’t seem to understand that the water/cement ratio is fixed by chemistry. The Chinese also do not test the concrete used in the construction of bridges, dams, and road to verify that it meets specifications. Well, they don’t actually use any sort of specifications for concrete.

Well, in the US we specify concrete, but I have never seen any engineering calculation where the strength of the concrete was actually used. I have seen hundreds of detailed building plans (commercial, residential and industrial) and in every case, calculations are done using only the strength of the steel reinforcement.

Designing for the rebar is a standard practice taught in every engineering school. The reason is that there is so much more area of concrete than rebar that the strength of the concrete is always many times higher than necessary.

[GingisK]

Before I retired I designed and made instruments that tested the strength of concrete. There are ASTM standards for the yield strength of concrete and squishing machines that very samples.

Samples of the pour are taken at bridge and foundation construction sites, and are shipped to labs for testing. New bridges that appear to just sit in disuse and without progress are generally waiting for the concrete to age properly for testing. The concrete company sometimes pours the samples away from the construction site using skim-off of out-bound loads.

It is interesting that the steel is the center of computation. I didn't know that.