Cross-section of the Roman road (belonging to the so-called via munita) located in Rome. It is dated to the 4th century BCE.
Via munita was a kind of Roman road, covered and made of stones or polygonal lava blocks. The construction of the road began with determining its width by digging two ditches called sulci . The native soil was removed from such a trough until it encountered a rock, i.e. at a considerable depth. The next step was to lay a layer of sand, which was compacted and profiled. 1 or 2 layers of flat stones were laid on the prepared substrate, they were covered with cement mortar or silted with clay. Instead of mortar, volcanic ash (puzolana) was also used. This formed the lower road layer, statumen, 20-30 cm thick, sometimes reaching 0.5 m. Statumen was framed with curbs weighing from 10, 15 kg to 50 kg, it was intended to strengthen the edges of the road. The next layer called rudus or ruderatio, 20-30 cm thick, consisted of crushed sandstone, crushed brick or crushed stone. They were beaten with carefully forged wood rammers. All this was poured with a mortar with a ratio of crushed brick and calcium – 3: 1.
Then the foundation was laid, the first layer of which was nucleus, i.e. cement with fine stone chips, slag, clay and sand. The whole formed a layer of impermeable, sealed fine-grained concrete. The approximate composition of this half-meter layer was 3 parts crushed brick and 2 parts calcium.
The upper layer, summum dorsum, was made of gravel with a grain size of up to 6 cm, called gloren stratata or polygonal stone tiles, silicea stratata .
The profiled and carefully levelled surface, parimentum, was laid with 5 cm thick stone slabs with a fall of 1:60 and an area of 30 to 100 cm.
The total thickness of the Roman road ranged from 1 m to 1.5 m with different thickness variants of individual layers. In later times the roads were lined with stone slabs.