Hydraulic ram pumps and Sling Pumps

half-width of the wall is sufficient as slab seating. Again, the seating must be plastered and twolayers of plastic foil must be put under the slab. There must be 15 mm of softboard strippingbetween the wall and the fresh concrete to prevent the expanding slab from pushing the half-stonewall which acts as a permanent shutter. This material should be removed a few hours after finishingthe concreting and the open space should be cleared. Although this method is not as good as thefirst method described, it will serve the purpose if it is properly implemented. If the slab still pushesthe half-stone course, it is easy to remove the entire course and, by doing this, the problem ofvisibility of movement is eliminated It must be stressed that the seating for the slab on half the wall issufficient, but the lintel must be seated on the whole width of the wall.Waterproof plaster should be handled with special care according to standards described in Chapter3. Waterproof plaster consists of three coats, each applied to the previous coat while still fresh.Keeping the plaster fresh is often a major problem in hot, arid climates, but this can be done bycovering the fresh plaster and by splashing it with water before applying the next coat. Plastic sheetsmake the best covers.First Coat:Before plastering, make sure the wall is moist. Make sure there are as many labourers on site asrequired for the job, and organize the work in such a way that the mixing, delivery and application ofthe plaster can be accomplished in a continuous fashion. Remember even a large tank must becompletely coated in one operation. This is best done by having two teams of plasterers working atthe same time, but starting opposite each other, -working anti-clockwise towards the other team'sstarting point. Figure 6.6 shows two plasterers working in the same direction: one on the floor andthe other on a scaffold. The plasterer on the floor starts plastering an area larger than the areacovered by the scaffold. The scaffold is then moved to the wall and the second plasterer startsplastering the upper wall, while the first plasterer continues on the lower part of the wall. Thereshould be no joint between the two working areas or at the meeting point. This might require extracuring of the meeting point until the coat of plaster is closed.67figure 6.6The first coat of mortar should be composed of three parts river sand and one part cement, asdescribed in Chapter 3. The river sand must be passed through a screen sieve not exceeding 3 mm.If a 3-mm sieve is not available, the sand used in the first coat can consist of the same core size asused in the second coat. The first coat should be a minimum of 10 mm thick and