Concrete is usually transported by wheelbarrows, carts, cars, or derricks, although other means are frequently used. It is essential, in handling or transporting concrete, that care be taken to prevent the separation of the stone from the mortar. With a wet mixture, there is not so much danger of the stone separating. Owing' to the difference in the time of setting of Portland cement and Natural cement, the former can be conveyed much farther and with less danger of the initial setting taking place before the concrete is deposited. When concrete is mixed by hand, wheelbarrows are generally used to transport the concrete: and they are very often used also for transporting machine-mixed concrete. The wheelbarrows used are of the same type as shown in Fig. 140. About two cubic feet of wet concrete is the average load for a man to handle in a wheelbarrow.

Fig. 144 shows a cart of the Koehring make, for transporting concrete. The capacity of these carts is six cubic feet. One man can push or pull these carts over a plank runway. The runway consists of two planks, each 8 to 10 inches wide, fastened together with 1-inch by 6-inch cross-pieces, and made in sections so that they can be easily handled by two men.

When it is necessary to convey concrete a longer distance than it is economical to do so by wheelbarrows or carts, a dumping car run on a track is often used. Fig. 145 shows a steel car for this purpose. The capacity of these cars is from 10 cubic feet to 40 cubic feet, and the track gauge is from 18 inches to 36 inches. Both end and side dumping cars are made.

If a large amount of concrete is to be deposited near where it is mixed, derricks are frequently used to convey the concrete. A cornbination of car and derrick work is easily made by using flat cars with derrick buckets.

Fig. 143. McKelvey Charging Bucket Discharging Batch into Mixer Operated by Same Power.

Fig. 143. "McKelvey" Charging Bucket Discharging Batch into Mixer Operated by Same Power.