Roman concrete strength investigated

[guy]

The mystery of  the strength of Roman concrete is being unraveled. Investigators looked at the unusual strength of the concrete used for the tomb of the noblewoman Caecilia Metella. 

This is a scientific article that is written for those of us with no engineering background:

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“One of these structures [still standing, exhibiting remarkable durability despite conditions that would devastate modern concrete] is the large cylindrical tomb of first-century noblewoman Caecilia Metella. New research shows that the quality of the concrete of her tomb may exceed that of her male contemporaries' monuments because of the volcanic aggregate the builders chose and the unusual chemical interactions with rain and groundwater with that aggregate over two millennia.”

The tomb is an example of the refined technologies of concrete construction in late Republican Rome that contain no cement. The technologies were described by the architect Vitruvius during the period when the tomb of Caecilia Metella was under construction. Building thick walls of coarse brick or volcanic rock aggregate bound with mortar made with hydrated lime and volcanic tephra (porous fragments of glass and crystals from explosive eruptions), would result in structures that "over a long passage of time do not fall into ruins."

”What the ancient Romans couldn't have known, though, is how crystals of the mineral leucite, which is rich in potassium, in the volcanic tephra aggregate would dissolve over time to beneficially remodel and reorganize the cohesion of the concrete. “

“But the tephra the Romans used for the Caecilia Metella mortar was more abundant in potassium-rich leucite. Centuries of rainwater and groundwater percolating through the tomb's walls dissolved the leucite and released the potassium into the mortar. In modern concrete, such a flood of potassium would create expansive gels that would cause microcracking and eventual spalling and deterioration of the structure“

 

 

https://www.sciencedaily.com/releases/2021/10/211008134107.htm

Here is a recent post on the unusual strength of Roman concrete:

 

 

Edited February 2 by guy