Hydraulic ram pumps and Sling Pumps

D WATER RESOURCES AND USE: SHIRIMAWater tightness can be improved by using plasters orcoats that contain components which may dissolve inwater and deposit into small cracks. There are alreadyproducts for such purpose like, for example, HEY’D1slurry used in some northern parts of Tanzania. It is usedfor replastering of interior surfaces of tank walls and hasshown good results.Another important reason for plastering both interiorand exterior surfaces is to reduce the danger of rapidshrinkage of mortar joints, especially when one considersthe climatic conditions in Africa which are hot and sometimesdry.Figure 3. Comparison of mean crack widthsto 3 parts sand is recommended. All cross and bed jointsshould be completely filled with mortar and well compacted.It is quite common to find plain bars in use in developingcountries. Whenever deformed bars are available, it ishighly recommended to use them in favour of plain ones.When only plain bars are available, then proper curtailingprocedure should be followed; the bars should be hookedat their ends for adequate anchorage.Laying of concrete blocks should be conducted carefully.All joints must be thoroughly flush and filled withmortar. Reinforcing bars should be fully embedded inmortar (recommended α mis about 0.30). Blocks should bewetted a short while before laying them, to allow a goodbond with mortar and reduce the risk of mortar losing thewater it requires for hydration to dry blocks.Low water/cement ratio for the mortar will reduce thepore content and therefore the carbonation rate althoughit may bring about workability problems. Experiencedmasons are able to judge the proper consistency of mortar.Surface finishingBlockwork surface is normally rough, therefore the interiorside of a blockwork tank requires plastering andscreed, in order to be smooth. The materials used for thepurpose should be inert and nontoxic; they should notform a breeding ground for fungi or other microorganisms.ShadingPotable water should have a comfortable temperature.The practice of covering water tanks by soil, i.e. partialburying, is one way of insulating them in addition to thestructural benefits of reducing ring stresses and thereforecrack widths. Any shading of a water tank from direct sunradiation is a welcome step towards maintaining comfortabletemperature of the stored water.ConclusionWhen properly designed and constructed, reinforcedblockwork tanks may perform well for storage of water indeveloping countries. It is therefore important to provideadequate reinforcement, by choosing suitable diameter ofbars and ensure that they are well anchored in the embeddingmortar. Compaction of mortar, plastering ofblockwork surfaces, and proper design of joints are crucialconsiderations with regard to water tightness.The equations presented in this paper enable the estimationof suitable bar size and reinforcement ratio forparticular crack widths. Further research is required,especially in the area of improving the durability ofreinforced blockwork tanks, since mortar cannot offeradequate protection against the corrosion of reinforcingbars.ReferencesSenyange, K. (1985), ‘Design of Reinforced BlockworkStorage Tanks,’ MSc Thesis, University of Dar es Salaam.Shirima, L.M. (1996), ‘Design of Reinforced BlockworkWater Storage Tanks,’ Dissertation, University of Dortmund.207