. Economic Papers. give the mortar a desirable smoothness. The ingredients of concrete are carefully measured before comes in measured packages. Sand, stone and gravel are usuallymeasured in wheelbarrows or in a bottomless box similar to Fig. 10,p. 33. An ordinary wheelbarrow load is about 2 cubic feet. When possible a concrete mixer should be used, as the resulting con-crete is much more uniform. However, for small jobs, hand mixing isgenerally cheaper and more convenient. In hand mixing the amount mixed at one time should not ordinarilyexceed one cubic yard. A batch requiring 3
. Economic Papers. give the mortar a desirable smoothness. The ingredients of concrete are carefully measured before comes in measured packages. Sand, stone and gravel are usuallymeasured in wheelbarrows or in a bottomless box similar to Fig. 10,p. 33. An ordinary wheelbarrow load is about 2 cubic feet. When possible a concrete mixer should be used, as the resulting con-crete is much more uniform. However, for small jobs, hand mixing isgenerally cheaper and more convenient. In hand mixing the amount mixed at one time should not ordinarilyexceed one cubic yard. A batch requiring 3 or 4 bags of cement isconvenient. Six turnings are usually necessary to secure a thorough mixture,three of these being dry and cement and the other three beingwet with the stone added. A turn consists in lifting the mass with ashovel and depositing it in another place with a spreading pointed, short-handled shovels should always be used for mixingconcrete. COUNTRY ROADS IN NORTH CAROLINA 33. Fig. 10.—Measuring box for a batch of 1:2:4 concrete containing four bagsof cement. Fill level full of stone; half full of sand. Concrete should be mixed wet, especially if much reinforcing steel i»used. Wet mixed concrete will slowly flatten out when piled up. Plentyof water should be used in mixing, but it should not be dashed is well to use a definite number of pails of water for each batch. Agood running board should always be provided for wheeling material tothe mixing board. A good mixing board is 8x12 feet in size, the floorbeing laid so that shoveling will be along the grain of the wood. Placing: The concrete is generally wheeled in barrows to the 2xl2 running board on a gentle incline should always be providedwhen possible. If the walls are high and thin buckets are sometimesused to convey the concrete, but this should be avoided. It is sometimes-convenient to use a trough or chute or to shovel directly from the mixingboard into the forms.
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