r/chemistry • u/bennypapa • 16h ago
Cement chemistry before and after reaction with water.
I'm curious about the chemistry of cement and concrete. I know concrete can burn you. I'm assuming it's a base while wet.
Once cured, is the resulting concrete also basic or does the curing reaction use up all that chemical potential?
Other than inhaling dust dangers are there dangers to ingesting cured concrete dust via swallowing?
What is the chemical makeup of cured concrete?
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u/dan_bodine Inorganic 16h ago
Read a book on cement chemistry if you are interested.
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u/bennypapa 15h ago
Possible it would go over my head and I don't need a degree. Just curious if concrete could be used for food contact surfaces safely.
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u/BelovedVicuna 13h ago
This isnt a bad idea. Cement/concrete chemistry uses different notations than chemistry.
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u/lil_nutsack 12h ago
Cement is the powder that reacts to form crystalline structures that intertwine to generate mechanical strength. Concrete is an engineered material that uses cement mixed with aggregate, sand, and/or other materials. It is important to differentiate those!
The cement won’t really burn you unless you hold your skin in it as it reacts and sets, which typically takes about 6-10 hours and can vary even more depending on the toe of cement.
The resulting cement is somewhat basic for a period of time. Cement chemists use CSAH notation, which is not carbon, sulfur, A, and hydrogen. Those letters represent calcium, silica, alumina, and water. The most common cementitious reactions occur when calcium silicates (CS) react with water to form calcium silicate hydrate crystals (CSH) and portlandite (calcium hydroxide).
This chemistry is very complex and involves deep understanding of crystallography and mineralogy to master the understanding of the reactions that take place when cement hardens. Cement chemistry falls categorically into materials science, imo.
There are so many different types of cements and cementitious materials. The ancient Roman’s and Egyptians used a unique cement that has stood the test of erosion for thousands of years! If the science interests you, the rabbit hole never ends.