Natural Hydraulic Lime (NHL) is generally associated with building conservation or as a green, eco-building material. That’s hardly surprising, hydraulic lime goes back as far as the Greeks, Egyptions and Romans. It’s use diminished in Britain in the 19th century as people adopted modern Ordinary Portland Cement (OPC). https://limetecuk.wordpress.com/2017/08/13/hydraulic-lime-practical-advantages/
