Built to last

This is a cross section of a Roman Road some 1900 years after it was built. The Fosse Way linked Isca Dumnoniorum (Exeter) in the southwest of England and Lindum Colonia (Lincoln) to the northeast, via Lindinis (Ilchester), Aquae Sulis (Bath), Corinium (Cirencester), and Ratae Corieltauvorum (Leicester). Built in the first and second centuries, this cross section excavated in the early 1900s demonstrates the standard road building techniques of the time. The surface ruts show the road was heavily trafficked for an extended period*, and the road was clearly built to last. 

Compared to many modern road construction techniques that seem to need continuous maintenance was the high level of initial investment repaid by well over a millennium of use? The concepts of good substrata, good drainage and a long-lasting wearing course are the same today as in Roman times, so why are we building roads designed to fail? Are the cost horizons too short??

A similar concept is Roman cement. The Roman recipe, a mix of volcanic ash, lime (calcium oxide), seawater and lumps of volcanic rock, held together piers, breakwaters and harbours (as well as structures such as the Pantheon) for centuries. In contrast to modern materials, these ancient structures became stronger over time. 

The chemical processes involved in the cement are known[1], and what we consider corrosion processes can produce extremely beneficial mineral cement and lead to continued resilience over time. The study of Roman cement offers clues for a concrete recipe that does not rely on the high temperatures and carbon dioxide production of modern cement, while providing a blueprint for a durable construction material, particularly for use in marine environments.

Everyone is talking about ESG and we are seeing ‘green buildings’ with bits of timber bolted onto the exterior to get a ‘green star’ – with a life span of 50 years if you are lucky…… 

The 30-year old timber facade at Melbourne Central.

Is it time to start thinking about long term durability and building for 500 to 1000 years with a view to repurposing rather than recycling?

For more on Green Building see: https://mosaicprojects.com.au/PMKI-TPI-005.php#GB

* Note: Despite this photograph proving Roman roads developed cartwheel ruts, there is no support for the common myth that these ruts are linked to the creation of standard guage railways (correlation is not causation!), see: https://mosaicprojects.com.au/Mag_Articles/AA016_The_Origins_of_Standard_Gauge_Railways.pdf

[1] See: Jackson, Marie D., Mulcahy, Sean R., Chen, Heng, Li, Yao, Li, Qinfei, Cappelletti, Piergiulio and Wenk, Hans-Rudolf. “Phillipsite and Al-tobermorite mineral cements produced through low-temperature water-rock reactions in Roman marine concrete” American Mineralogist, vol. 102, no. 7, 2017, pp. 1435-1450. https://doi.org/10.2138/am-2017-5993CCBY