ABSTRACT

Extensive use of traditional materials or construction such as cement and aggregate, in Reinforced Cement (RCC) construction may result in the rapid depletion of natural resources. These materials are costly and are to be transported at the Site, Where they are not available locally. It is the need of time to decipher the material of construction that can be sustainably used as replacement of RCC. Clay is indigenous, low cost and environmentally friendly material of construction. It is being used for thousands of years in the form of unbaked and baked clay bricks for the construction of buildings. To achieve the dream of low cost houses, the idea is to use baked clay in the form of reinforced pre-cast panels of beams, columns, slabs and footings in those areas where traditional material for construction is not available. This study investigates the possibility of use of reinforced baked clay (RBC) beams as replacement of RCC beams. Studies reveal that mechanical properties of clay can be improved by compaction at the time of casting. For this purpose, a mechanized system for casting and compacting of clay beams was designed and fabricated. These clay beams were dried, baked, and reinforced. Before using these reinforced baked clay beams as structural member, it is necessary to investigate the structural behaviour of these RBC beams in terms of flexural strength under short-term and long-term as well as impact loading. In ease of short and long term loading the size Of RBC beam specimen used was 150x300x1880 mm. All of these beams were singly reinforced with two 12.7 mm diameter steel bars, without shear reinforcement. The reinforcing bars were welded to anchoring plates at both ends of the beams.
Results of this experimental study showed that the compressive strength of the cubes cut from the baked clay beams increased with increasing rate of intensity of compaction at the time of casting. Reinforced baked clay beams tested in short term loading showed pure flexural mode of failure without any signs of shear failure. These RBC beams were tested up to failure to determine ultimate load caring capacity. In long loading these RBC beams were loaded at 30%.40% and 500/0 of ultimate load carrying capacity, Averagely all the RBC beams subjected to long-term sustained loads showed first crack at about 30% of ultimate load carrying capacity. All the cracks developed and stabili7Æd during first hundred days of loading. The deflection increased with decreasing rate and the increase in deflection diminished after first hundred days of loading in all the RBC' beams.
In case of impact loading, the size of the beams was 150x150x500 mm. The beams were doubly reinforced in pairs with three ratios of reinforcement of 0.27%, 1.090/0 and 1.71%. Compressive strength of baked clay used in each pair of beams was 20 N/mm2, and 30 N/mm respectively. Drop height of the hammer used was 930 mm and the weight of hammer was equal to the weight of specimen tested. The results showed that mode of failure in RBC beams subjected to impact loading mainly depend upon the compressive strength of the baked clay. The beams having higher compressive strength, failed locally on application of about three times more number of blows as compared to the beams having less compressive strength which showed general mode of failure. This study shows that the mechanized system developed for casting and compacting of clay beams is efficient to expel added water up to the extent of optimum moisture content, by compaction through compression. This study also reveals that the RBC beams discussed do not require any shear reinforcement.