This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
The concrete work of all footings and exterior foundation walls below grade, will be composed of 1 part Portland cement, 4 parts sand, and 7 parts screened gravel or broken stone. In order to make these proportions efficient, it will be necessary, in mixing and applying the materials, to use great care. The Contractor, under direction of the Architect, will construct a cube about 18 inches square, of the mixture, to show its possibilities when carefully manipulated; this standard will be the one by which the work will be judged, and any portion of the concrete work which falls below this standard will be condemned. The sand and cement must first be thoroughly mixed dry, turning over at least four times, if no machine is employed, so that no uncolored particles of sand can be detected; after which, just enough water is to be added to dampen the mass thoroughly. The aggregate is then to be mixed in, wet.
It will be necessary to place plank forms for all footings and walls; and the concrete is to be placed in such forms, and thoroughly rammed. A smooth surface like a spade is to be forced down, just inside the planking, to force the aggregate back from both faces of the wall until clear mortar will only show. The walls of each portion are to be carried up the full height rapidly, and the planking to be so arranged that it can be removed from any part within two days after the placing of the concrete. Both faces of the wall are to be finished smooth with a trowel, the surface being so compressed as to make it proof against ground moisture.