Concrete is a mixture of different sizes of a strong stone, like granite or silicate in a carefully graded mix of sizes from sand sizes upwards. The idea is to

Concrete is a mixture of different sizes of a strong stone, like granite or silicate in a carefully graded mix of sizes from sand sizes upwards. The idea is to get the final block to be 100% stone(impossible) or as close as practical. You then cement this all together (mixing all the while) with powdered cement. Cement is a mixture of C3S: Alite (3CaO·SiO2); C2S: Belite (2CaO·SiO2); C3A: Tricalcium aluminate (3CaO·Al2O3) (historically, and still occasionally, called celite); C4AF: Brownmillerite (4CaO·Al2O3·Fe2O3). This is melted at high temperatures into 'clinker' (when melted it resembles lava from which classic roman cement was made as it collected as a fine volcanic ash). Rock has water of hydration strongly bound into, when melted into clinker the water evaporates = clinker. The clinker is ground to a powder and added to the graded mixture of sand and small rocks and water is added - it is then mixed very throughly and the final water ratio is established. It is then poured into the moulds that hold the cement in the final shape you want when it sets. You vibrate and shake well to get the air bubbles out and then you want for it to cure. As it cures the powdered clinker absorbs water and turns into the fully hydrated final (set) form. It can take months to fully set, but usually after a day it is into the 60-75% area of final strength. This makes heat = big things need active cooling, small stuff not so much. As it cures and very strong matrix of hydrated crystals fills all the space = set or cured concrete. Reinforcing can be any strong material that is not brittle. Usually steel rebar is OK for a dry life structure. For damper areas you can use epoxy coated rebar, then galvanized rebar, then epoxy coated and galvanized rebar. For the next stage stainless steel rebar is the high cost option. Nuclear power stations use SS rebar in some cases. Corrosion. Steel corrodes. Steel = FE,(1 atom) corroded steel = FeO (2 atoms = bigger) if oxygen reaches the steel it will make FeO - these 2 atoms are bigger than the one atom of Fe. This means the FeO will expand with an irrestible force (200 times as strong as concrete). It is this rebar expansion that makes huge cracks = more water in, = bigger cracks etc. FeO is as weak as kleenex as a support member. so as the concret and rebar turn into powder the strngth of the structure vanishes. At some point you get this sort of collapse - all of which was preventable by proper design and maintenance. Punishment? imprison them in the basement of one of their badly made buildings and let them spend their life waiting for the inevitable collapse. Concrete Wiki https://en.wikipedia.org/wiki/Cement https://en.wikipedia.org/wiki/Cement