Most well-designed concrete mixes are suitable for pumping. Pumpability is affected by aggregate gradation, shape of aggregate particles, relative amounts of fine and coarse aggregate, absorption of aggregate, cement content, and water content. In addition, the pump, pipe and arrangement of lines will greatly affect the success of the operation. Coarse aggregate should not exceed one third the diameter of the smallest opening in the pump or the pipeline. With well rounded aggregate, slightly larger sizes are usable. Sands with a fineness modulus in the range from 2.40 to 3.00 are considered good for pumping. To produce good floor concrete, however, it is preferable to use an aggregate with a fineness modulus towards the higher end of that range. Concrete best for pumping contains about three to five percent air, which can be provided inexpensively by air-entraining admixtures. Water reducing admixtures, pumping aids and finely divided mineral admixtures such as pozzolans also improve pumpability. Mixes for pumping should be tested both laboratory and on the job. The use of a pump for placing floor concrete requires careful planning. The pipeline normally is laid out to deliver concrete first to the most distant part of the floor so that sections of pipe can be removed as the floor finishers work their way back closer to the point of truck delivery. A hydraulic pumping boom may eliminate the need for pipelines. Successful pumping operations are outstanding for floors because of the uniformity with concrete is distributed. Careful manipulation of the end of the hose greatly reduces the work of screeding and initial leveling.