Let's continue with the description of the various Roman masonry techniques started in the previous publication of this web A brief description of the main Roman masonry techniques. 1st. Part
Oppus Caementicum. By this name, germ of our word "cement", is known the main contribution of the Roman civilization to the history of architecture: true responsible of the magnificence and longevity that characterize to Roman works. Very similar in its conception to modern concrete, Oppus Caementicum was made using either a wooden formwork or a sort of external walls of ashlar/masonry as a formwork lost, which were filled in both cases with a fairly homogeneous mixture of aggregate -the caementa- and lime mortar. After, this mixture was macerated until its full solidification. Sometimes the aggregate was thrown first, still dry, then mixed with the mortar inside the formwork itself. In any case the Roman layers - this material was placed by layers as in today's world - rarely exceeded one meter in height.
Photo 1.- Cerro de la Muela, Carrascosa del Campo, Cuenca. Oppus Caementicum wall with very marked layers.
Photo 2.- Segóbriga. Saélices, Cuenca. Oppus Caementicum wall in very good condition. 1st century AD.
Once the lower layer had set -photos 1 and 2- the formwork of the upper one was placed, taking advantage of the already raised wall, repeating the procedure in this way until reaching the desired height. The result, if the processes for the elaboration of this technique indicated by experience had been properly respected, was a very resistant, solid material and what is better: suitable for the elaboration of any architectural geometry. Needless to say that this advantage, capital without a doubt, opened the door for the massive use of structures such as arches, domes and vaults, until then of scarce use given its ominous cost, because they had to be necessarily manufactured in carved stone. Besides, this technique provided the possibility of erecting resistant and lasting walls while economic given the relative low cost of its components as well as the high speed of execution that characterized it. All this being said, it seems evident the real revolution that involved the use of this kind of material, whose only drawback lay in the rather coarse aspect that conferred to the final structure, reason because the Oppus Caementicum was often coated with a decorative cladding.