The rapid increase in population and the consequent increased construction activities are causing significant damage to the environment on account of the removal of fertile top soil for brick manufacture, mining and quarrying activities, unscrupulous extraction of precious sand and silt from the river bids, indiscriminate lumbering and the use of the scarce forest resources. Further, the production processes for conventional (traditional) building materials are also energy intensive besides contributing to global warning due to the emission of green house gases.
Hence, there is an urgent need to cut-down the usage of traditional building materials. Fortunately, new building materials have been developed by the institutes and bodies involved in building materials research and development. They include laboratories of Council for Scientific and Industrial Research (CSIR), Central Building Research Institute (CBRI), Roorkee, Structural Engineering Research Centre (SERC), Chennai, ASTRA,
The alternative building materials which are popular in
1. Stabilized Mud Blocks
2. Concrete Blocks
3. Ferro-Cement
1. Stabilized Mud Blocks
Traditionally mud has been intensively used for building construction in
i) loss of strength on saturation, and
ii) erosion due to rain impact, necessitating frequent repairs and maintenance.
Hence, eliminating the drawbacks of pure mud construction necessitates the use of stabilization techniques. Stabilization of a soil means, modifying the characteristics of soil such that the modified soil has the desired properties for specific work. Soil mixed with cement could be compacted at optimum moisture in to a high density block using a machine. Such a block can be termed as ‘Stabilized Mud Block’ (SMB). The soil used for making mud blocks should have low clay content (10 to 15%) and high sand and silt content (60 to 70%). The cement content in the stabilized soil will be at least 5% by weight.
The stabilized mud blocks are characterized by moderate compressive strength (5.5 N/mm2), low thermal conductivity, high water absorption, high fire resistance and good sound absorption. SBMs are extensively used in low cost building constructions. Fly ash, iron-ore tailing, and red mud (from Aluminium plants) can be used for SMB production thereby eliminating environmental problems associates with disposal of such waste products.
2. Concrete Blocks
The concrete blocks used in the masonry are of two types
i) Solid Concrete Block
ii) Hollow Concrete Block
i) Solid Concrete Block
They are manufactured to meet the requirement of building blocks in towns and cities. They are longer compared to bricks and are of size 400 mm x 200 mm x 150 mm.
To reduce the weight of solid blocks, no-fine concrete is used. No-fine concrete is the one in which fine aggregate is not used, but smaller size aggregates, say 12 mm size round aggregates are used. Solid blocks are used for construction load bearing walls.
ii) Hallow Concrete Block
They are made from cement aggregate mix of 1 : 6 proportion in sizes of 390 mm x 190 mm x 300 mm, 390 mm x 190 mm x 200 mm and 390 mm x 190 mm x 100 mm. Aggregates used are 60% fine sand and 40% course aggregate (6 to 12 mm).
Hollow concrete blocks possess core-void area greater than 25% of gross area. The minimum compressive strength of such blocks will be 3 N/mm2. They are used for the construction of non load bearing walls, partition walls and compound walls.
3. Ferro-Cement
Ferro cement implies cement mortar of cement sand ratio 1 : 2 or 1 : 3 reinforced with multiple layers of steel fibres. The reinforcement is usually made of wire mesh which is usually made of 0.8 to 1.0 mm dia steel wires at 5 mm to 50 mm spacing. The skeletal steel may be placed 300 mm apart to serve as a spacer rod to the mesh reinforcement. The thickness of ferro-cement is kept between 10 to 40 mm, with a clear cover of 2 mm for the reinforcement. The special feature of the ferro-cement is the absence of form-work during construction.
Ferro-cement is suitable for low-cost roofing, pre-cast units, man-hole covers etc. It can be used for the construction of domes, vaults, shells, grid surfaces and folded plates. It is a good substitute for timber. It can be used for making furniture, doors and window frames, shutters and partitions. It can also be used for making water tanks, boats and silos.
Summary:
The demand for traditional building materials is increasing due to increase in construction activities. It is difficult to meet the demand with out environmental degradation and over-exploitation of natural resources. Hence, a lot of research is being carried out in
Stabilised mud blocks are produced by compacting soil stabilised with ordinary portaland cement in a mud block making machine. Concrete blocks are produced in the factors and transported to the site for masonry works. Ferro-cement is fast becoming an alternative to wood and is used various purposes.
