San Francisco : Architect and Engineer, Inc · leaf 396
ally placedin contact with the fresh concrete. Hoses con-nected to this mat lead to a vacuum pumpwhich is used to create a near vacuum underthe mat. The atmospheric pressure then helpsto compact and force the excess water out ofthe concrete. The vacuum process, due to theaddition of atmospheric… … Surface voids disclosed by stoning the surface of a laboratory specimen cast under a slopingwood form. These voids are often hidden by a thin film of cement and fine sand: do not show upwhen forms are stripped in ordinary field operations. SEPTEMBER, 1940
Architecture · Building
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