Hydraulic ram pumps and Sling Pumps

stored in the shade. If the chart shows that both samples are nearly equal, the water of unknownquality can be used for mixing cement plaster.figure 3.33.3 CementCement bonds and hardens in the presence of water. Therefore careful storage is imperative toavoid moisture reaching cement before use. The bags of cement should be stored in a closelypacked pile, no more than ten bags high. The pile should be on a raised platform in a room with littleair circulation. In rooms with open windows and doors, the pile should be covered with plasticsheeting. The same applies if the cement has to be stored outdoors. The platform must be made insuch a way that moisture from the ground cannot affect the cement and the plastic sheeting has tobe tied so that the wind cannot blow it away and rainwater does not affect the cement. As baggedcement ages and absorbs moisture from the air, it becomes lumpy. If lumpy cement is to be used,its proportion should be increased by half and bigger lumps be removed before mixing.3.4 ReinforcementThe cement bond is easily broken by forces which pull it apart—tensile stresses. Thus it isnecessary to use a material like steel inside the concrete or plaster for large water tanks. The weightof the water will stretch the tank walls. Barbed wire or weld mesh is heavy enough to withstand thestress and hold the tank together. (Straight wire can be used in place of barbed wire, but the barbshelp grasp the plaster, and the two twisting wires are stronger than a single wire.) Chicken wirehelps hold the plaster together between the stronger wire.Although the soil helps support the weight of the water, even the ground hemispherical tanks willstretch when full. Hard rocky soils provide better support. Loose or sandy soils should have morereinforcement (barbed wire) in the tanks.Upright water tanks receive most tensile stresses in the bottom third of the wall and in the jointbetween the floor and wall. Extra reinforcement wires in the wall and joint and thickening the plasterat the joint prevent cracking at these points of stress.24