Substitute

I live in an area where limestone quarrying and kilns was a big industry towards the end of the 19th century. I'd wondered how it was done. I watched a PBS Nova episode of Secrets of Lost Empires today, and it told how the ancient Romans did it. If limestone is heated red-hot for long enough, it turns into chunks of light weight, white substance called quicklime. This is mixed with water which makes a chemical reaction (as in portland cement). I think they called this slaked lime, but I'm not certain. To this bubbling white goo they added sand for mortar, or sand and gravel for cement. To waterproof it they liked to add volcanic ash, but since that was rarely available they used crushed clay tiles instead. The red clay in the tiles made their mortar pink. So, when I can't buy a bag of Portland cement anymore, I at least know how to make it.

Offered by Wendy.