Any historic campus will probably show you the difference. The detail of cement castings from before 1970 are still clear despite exposure. After ~1970 the cement doesn't last as long, it cracks, even the brutalist style minor details are missing. Part of it is because they used sharp sand earlier, but rounded sand came in because it was cheaper. Sharp sand is less oxidized so it is more easily bonded with. It also fits together an makes a more ridged structure inside the cement. Part of it is because at one time, they used a dangerous process of baking limestone at the location when doing construction to make cement. Horrible deadly dust, and terrible stuff to work with but the fresh stuff bonded strongly. It isn't required in order to make strong cement, but their method assured the builders that they had the right mix and the materials were fresh and had not oxidized or gone through moist/dry cycles before arrival.
I am glad this is being recognized, but this has been a problem for a very long time. There are tests that can be made that can assure you of better cement, but that takes time and requires a little bit of training to perform and evaluate. In the late seventies and eighties I was a carpenter working under one of the old time quality builders. When new regulations came in, he often had to us a double structure system since the regulations required a particular way of building, but this old time builder knew what was going to last and be solid. He didn't want any house he built to fail. I think he retired after contractors started insisting on cheaper materials than plywood.
Here it the simple truth about plywood vs the stuff made by sticking fibers of wood together with glue. If either get wet, it could be a real problem, but after particle board gets wet, it won't hold a nail. The very first fiber board was kind of amazing, but it was gone before the stuff got popular. So after fiber board was proven to be amazing and strong, identical stuff replaced it but the glue was cheaper and it didn't hold a candle to the original.
So basic materials have slipped in quality. Combine that with contractors with modern Republican ethics and you got a real mess on you hands.
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