iHemp issue #15 May 2021 Fibre Construction | Page 25

Ancient Bridge made from Hemp , still stands after 1500 years

The Hempen bridge has withstood Viking conquests , multiple world wars , natural disasters and has stood as a sanctuary and landmark for centuries .

The oldest structure in Saint Céneri le Gérei dating back to the Merovingians is the old stone bridge crossing the Sarthe river . The fact that it has survived antiquity is a miracle , the secret to how it survived is shocking .

A stone and mortar bridge crossing the river point was constructed by the Merovingians who ruled the area around 500 AD . Upon closer inspection the secret to its longevity is discovered … Hemp !
The bridges ancient stonework has been held in place for centuries using mortar made from hemp . With a mixture of more than 10 % hemp , the hemp mortar has held the bridge together longer than any other structure in the village , not to mention that it is also the only structure that has had to withstand the rivers punishing current .
The hemp mortar ’ s immortality comes from its ability to breath . Typical mortar cracks and chips to pieces as the mortar expands and contracts with typical temperature and moisture influxes . Hemp has the amazing ability to absorb moisture , allowing the mortar to take in and release the excess water when conditions allow . These abilities have allowed the bridge to survive as other structures turn to rubble . q
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