Opus Caementicium

;

Mortars and concrete are the fundamental components of much of the construction industry in the UK. For everyday definition purposes, a concrete is a cementitious material containing aggregates with dimensions greater than 5 m m, whereas a mortar is a cementitious material containing aggregates with dimensions less than 5 m m. The term mortar comes from the Latin mortarium, the name given to the trough in which the material was mixed, as in mortar and pestle.

In fact, the Romans had a rudimentary but highly effective concrete made of a volcanic ash sourced from Pozzuoli on the slopes of Mt. Vesuvius and slaked lime , hence the term Pozzolanic cement. Cement technology goes back even further, to the Ancient Greeks and Mesopotamian civilisations preceding them, but it was the Romans that developed concretes sufficiently to construct concrete – filled walls, known as opus caementicium, cementitious terracotta flooring, opus signinum and even used their concretes in building the Pantheon, which still stands today, a testament to their skills.

The Pantheon

However, it was the patenting of Portland Cement by Leeds-based Joseph Aspdin in 1824 that led to the development of the reliable, high – strength concretes and mortars that are used throughout the world today. Named Portland Cement because of its similarity in appearance to the highly – admired building stone from Portland Bill in Dorset, it is manufactured by heating a slurry of limestone or chalk with clay in a kiln, and grinding the resultant clinker to a fine powder and adding gypsum.