|
Stabilized Mud Block Homes in Bangalore Dr. Yogananda Email: yogananda@vsnl.com T he construction practices of today depend heavily on materials like burnt bricks, cement and steel. These materials are not only expensive, but also consume lots of thermal energy and affect the environment. The need for alternatives which save energy while reducing the cost is, hence, very clear. Research with practical application is the key. However, practical applications should not get limited to institutional buildings only. It should reach the common man. Here the support services play a very important role. Consultants may have to give much more time in the beginning and take some important responsibilities in terms of the quality control. Training masons by constantly interacting with them and ensuring continuity in the work will help in improving the technologies and construction techniques in addition to building up a good team of workmen who ultimately become the backbone of the dissemination activity.‘Mrinmayee’, since its inception in 1989, has been trying to play this role in addition to providing the laboratory testing services in the field of Stabilized Mud Block technology (SMB) and alternative roofing systems developed by Prof. K. S. Jagadish and his team at ASTRA, Indian Institute of Science, Bangalore. Today, there are about 150 SMB homes in Bangalore and several in other places too. Most of them are two storied homes with 9 inch thick load bearing walls while a few are designed for taking G + 2. The SMBs (9"x7.5"x4") are produced using a manually operated press ‘Mardini’ and using sandy soils (< 5 mm size; containing non expansive clays) with cement as the stabilizer. Quarry dust is generally added to the soil to achieve the required sand content (~70%). The percentage of cement varies in the range of 5.0 to 8.0 depending on the required wet strength of SMBs (25 to 60 kgs/sq.cms; dry density ~ 1.8 gms/cc). The load bearing walls are constructed using a composite mortar i.e. 1 cement+ 2 soil+ 6 quarry dust. The walls are left exposed outside after pointing and normally receive a water proof coat. Internal walls are selectively left unplastered and painted. Cost savings in the walls are around 25% as compared to burnt brick walls. Special purpose blocks like cornice blocks, decorative corbel blocks and filler blocks can be made using the same press with suitable inserts. Cornice blocks and corbel blocks have been used in the SMB homes in many ways e.g. corbelled openings, arched openings, arched chajjas for windows, roof cornices, parapet walls and railings, etc. These have played an important role in improving the aesthetics of the buildings. Most of the recent buildings have filler slab roofs and floor slabs with SMB filler blocks (15"x9"x3" size). The ceiling is painted without any plastering. The cost reductions are in the range of 15% to 20% as compared to RC slabs. Masonry vaults and domes using SMBs are also incorporated in some of the homes and these alternatives are becoming more and more acceptable among users. A simple new type of moving form work, having two arch shaped templates kept parallel to each other with a distance of 18 to 25cms separating the two, is being used in the construction of vaults. In this system, a portion of the vault is built using the two templates as support. The inner template is then removed and placed in front of the outer template to continue the vault. The vaults are 4" to 6" thick (span: 10' to 16') and rest on the edge beams that are tied properly. Masonry domes are normally done as a segmental sphere with a total angle at the center less than 104 degrees in order to eliminate the possibility of hoop tension in the masonry. The construction of dome is usually simpler and does not need a form work. The domes are about 4.5" thick (span: 10' to 18') and rest on a ring beam. The vaults and domes are constructed with 1:4 cement mortar. The under surface do not need any plastering. The outer surface is finished with either weatherproof tiles or broken glazed tiles. This also helps in better thermal comfort. There are often doubts in the minds of professionals, as well as users about achieving good quality SMBs. Some simple steps, as mentioned below, can help in producing quality SMBs.
|
||||
|
||||