Did they actually have cement in the Middle Ages? That’s another common question that guests have asked at the Ozark Medieval Fortress. The short answer is: Yes. Of course, it didn’t have all the additives and hardeners like today. The Romans (remember that pre-dates the Medieval) were engineer-types and experimented. They knew from the Ancients that you cook sand and get glass. They improved on the Greek cooking of iron ore and ended up with good weapons. They also realized that if you cook limestone, you get lime and if you mix lime, water and common sand you get the grandfather of cement: Roman cementorium. That is what is used at the Ozark Medieval Fortress.
What is satisfying for me is that the old cement can be better than the modern cement. Cementorium takes literally hundreds of years to dry-cure and breathes because it is so gritty or fibrous. You can touch it and feel the difference. The reason it is better is that even without “control joints”, it doesn’t crack from expansion and contraction. Think about it: if you built a 5-foot thick wall as long as those in the Castle using modern cement without rubber spacers, it would crack like crazy. The Medieval castles, even with their solid, incredibly thick continuous walls have not cracked. Well, not because of the cementorium anyway.