ACI 304.2R

Abstract

<strong>INTRODUCTION</strong> <br>ACI defines pumped concrete as concrete that is transported through hose or pipe by means of a pump. Pumping concrete through metal pipelines by piston pumps was introduced in the United States in Milwaukee in 1933. This concrete pump used mechanical linkages to operate the pump and usually pumped through pipelines 6 in. or larger in diameter. <br>Many new developments have since been made in the concrete pumping field. These include new and improved pumps, truck-mounted and stationary placing booms, and pipeline and hose that withstand higher pumping pressures. As a result of these innovations, concrete placement by pumps has become one of the most widely used practices of the construction industry. <br>Pumping may be used for most concrete construction, but is especially useful where space for construction equipment is limited. Concrete pumping frees hoists and cranes to deliver the other materials of construction concurrently with concrete placing. Also, other crafts can work unhampered by concrete operations. <br>A steady supply of pumpable concrete is necessary for satisfactory pumping.¹ A pumpable concrete, like conventional concrete, requires good quality control, i.e., uniform, properly graded aggregate, materials uniformly batched and mixed thoroughly^.2 Concrete pumps are available with maximum output capacities ranging from 15 to 250 yd³/hr. <br>Maximum volume output and maximum pressure on the concrete cannot be achieved simultaneously from most concrete pumps because this combination requires too much power. Each foot of vertical rise reduces the horizontal pumping distance about 3 to 4 ft because three to four times more pressure is required per foot of vertical rise than is necessary per foot of horizontal movement. <br>Pumped concrete moves as a cylinder riding on a thin lubricant film of grout or mortar on the inside diameter of the pipeline.^3-5 Before pumping begins, the pipeline interior diameter should be coated with grout. Depending on the nature of material used, this initial pipeline coating mixture may or may not be used in the concrete placement. Once concrete flow through the pipeline is established, the lubrication will be maintained as long as pumping continues with a properly proportioned and consistent mixture.