Lime Sludge Mortar

Abstract

O. Introduction The Central Building Research Institute Roorkee (U.P.) India has developed a lime sludge mortar made from by-products of sugar mills, paper mills and rice mills. Basically this type of mortar is made from lime sludge (sugar - and paper mills) and rice husk (rice mills). Because of its potential advantages also for Kenya the HRDU has investigated the availability of the basic materialso This preliminary investigations showed that limesludge is not available as a waste material, while rice husk is available in abundance in some locations. 1. The preparation of lime sludge mortar. The two basic materials for the production of the mortar are rice husk and waste lime sludge (1) (2). Rice husk should be Cine or in crushed state. Therefore husk obtained from small rice producers ca~ be directly used. Rice husk coming from rice mills, producing rice in the full shell form, should be passed through a huller or grinding machine before use. The other ingredient, lime sludge, should be in dry and powdery form. This lime sludge is a waste product of sugar industries and paper mills, depending upon the production process adopted in these industries. Waste lime sludge and rice husk are dry mixed together roughly in equal amounts by weight. A required amount of water is added to the dry mix for making manually balls/cakes. These balls/cakes are put out in the open for drying before burning. It should be noted that the balls/cakes possess sufficient strength and do not disintegrate during handling or firing. The dried balls/cakes are next fired in the open on a grating base of a clamp or in trench. Rice husk not only acts as integral fuel but also provides tn situ silica for the lime produced during firing. The fired material obtained is a soft powder. The finer the material is, the greater its reactiv~ty like other hydraulic binders. The bulk density is 700 kg/m on griding. '. - 2 - 2. Availability or production wastes in Kenya. Sugar mills A number of sugar mills were informed about the above process but it turned out that there is no waste of lime sludge nor of sugar cane (3). Limesludge is a by-product from the carbonation process, which is not adopted in Kenya. The Kenyan factories have adopted the 'sulphitation process'. The sludge from this process does yield a filter cake (equivalent of sludge) which has a high wax content. The filter cake is used as bulk manure in sugar cane plantations. Sugarcane arter processing is called bagasse and is burned in the boiler furnaces to generate steam. At times there is a surplus of bagasse but this quantity is small and irregular. Pap~r mills The paper mills in Kenya hayc- Ll .Li.emr-e bu r-n Lug plant..f'o r' recirculating lime. As :suchthere is no residual lime sludge. Timber waste is used as fuel in the bark boilers and therefore not available for other purposes (3). Rice mills According to the National Irrigation Board most of the rice is milled by Mwea Mills Ltd., at Nwea. Rice husk is not used for other purposes and is therefore available in abundance. Some individuals collect rice husk, free of charge, but the remaining quantities are still abundant (3). 3. Conclusions lhe small survey showed thai lime sludge is not available from small scale industries. On a larger scale hydrate lime is produced at Koru by the Homa Lime Company Ltd., at a price of' K.Shs.523/55 per tonne ex-factory. (Prices March 1980). For small scale production of lime mortar this lime is too expensive. Lime sludge mortal' can therefore not be produced on a small scale in Kenya. However because rice husk is available in abundance, further investigations have to be carried out whether this husk can be used for the production of cheap building materials. There are some limitations: Presently there is little information available about other wastes from the agricultural industry or other industries in Kenya. Experiences in other countries (ref. 2) have shown that some of these wastes are very good components for building materials of high qualitYA - 3 - Therefore it would be desireable to carry out a more in-depth survey, preferably allover Kenya into the availability of wastes. Some of these wastes, together with other materials, can be very suitable for the production of building materials, either on a small scale or on a large scaleo - 4 References. 1. Central Building Research Institute Cementitious Binder from waste lime rice husk; Technical Note No. 750 India, 197 • 2. Mohan, Dinesh and Verma, Narendra, Construction materials and technology for building industry in rural India; Engineering World p. 21 - 24. 3. Communications in 1980 with the following industries in Kenya: Pan-African Papermills (EnA.)Ltd., Webuye. Chemelil Sugar Company Ltd., Muhoronio East African Sugar Industries Ltd., Muhoroni. South Nyanza Sugar Co. Ltd., Awendon Mumias Sugar Co. Lld., Mumias. National Irrigation Board, Nairobi.