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Show Roman Use of Concrete. M The IloinnuH' discoveries In concrete H mixing mude It possible for them to H mnko prodigious strides In engineer- H Ing nnd architecture. At the foot of H Vesuvius were linmenso deposits of M reddish sand or volcanic nsli called H pozzuohtnn, which, when added to llmo M mortar, made hydraulic cement. This H gnvo to the Itonians n concrete of H extraordinary strength and pormnn- M ence, which hnrdened tinder water ns H well as In tho air, and became the H basis of their cntlro system of building. H |