Historical texts reported that #Romans used slaked lime to make #concrete, and mixed the lime with water before adding it to other ingredients, such as volcanic ash.

Chemical analysis of the dry, pre-mixed piles found in the Pompeii workshop shows that the ancient concreters were, in fact, using a hot mixing method involving quicklime, or calcium oxide.

https://www.newscientist.com/article/2507648-pompeii-building-site-reveals-how-the-romans-made-concrete/ #globalmuseum