For AP Chem at my school, I am doing a project on Concrete. Besides go through the chemical formulas for how concrete is made today using Portland cement, I also am hoping to go over the history of the use of concrete starting in 10000 B.C. as well as (maybe) the chemical equations of how Roman concrete and ancient lime mortars were made. As a result, I have a handful of questions about concrete in case anybody knows about them.

  1. Did the Romans widely use concrete out of volcanic ash? I have found a source that made me infer it was mostly only used for large projects like the Colosseum, Pantheon, etc, while the rest of the empire used weak mortar using burned limestone. Simply, I am asking if volcanic ash could be transported hundreds of miles in order to make cement.
  2. When a source says a people used a limestone mortar, I have found that means it hydrates Calcium Oxide, just one of the bonding agents in modern cement. Does anybody know the chemical equation for this reaction? I found that Tricalcium and Dicalcium Silicate (3CaO+SiO2) reacts in modern cement, but limestone only includes CaO and volcanic ash seems to only include SiO2 alongside aluminum and iron. Did the Romans use both to make cement? Is more than just limestone needed to make cement?

I understand this is kind of a chemistry problem, but there are also historical aspects to it. If there is anywhere I could post this that would be more appropiate, that would be nice. Thanks!

Source: reddit post

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