EXPERIMENTAL STUDY OF THE BEHAVIOUR OF PRE-PERFORATED POST-REINFORCED BAKED CLAY PANELS OF BEAMS

Abstract

Altogether fifty one large size beams of clay were moulded, compacted, baked, post- reinforced, grouted with cement-sand slurry, cured and tested to study the behaviour of these beams. Different parameters were set in order to check the suitability of these universally available materials of construction, i.e. clay, silt and pit-sand (silica) for low- cost housing without sacrificing durability, the strength and elegance of buildings in the plain areas where the soil is alluvial. Standard materials of construction like hill-sand, coarse aggregate, cement and steel bars are to be transported over large distances for RCC construction. Four Reinforced concrete beams were also cast and tested for the sake of comparison. Preliminary studies were carried out on soil samples collected from twenty five different sites in terms of their physical composition and presence of various salts and other chemicals. Their effect on the strength of baked specimens was also studied. A systematic study was performed experimentally to find the best composition in terms of ratio (clay : pit-sand), the intensity of compression force required for manual moulding and compaction which would impart reasonably good crushing strength to this material (comparable with that of concrete) without compromising on economy. The moisture content was also a parameter of preliminary experimental study to ensure sufficient workability and minimum possible void ratio. The various drying techniques were tried finally to arrive at the best possible system which would not cause cracking. The compressive strength as high as (6100 psi ) 42 N/mm2 has been achieved which can be compared with (3000 psi ) 20 N/mm2 for concrete used in ordinary buildings. The modulus of rupture with a reasonable comparison to ordinary concrete has also been achieved. Flexural behaviour as well as shear strength of beams manufactured from this material were studied for the following cases. 1. Rectangular beams, simply supported subjected to point load at the centre. 2. I-beams, simply supported subjected to point load at the centre. 3. Rectangular beams, supported on plates on both the ends subjected to Uniformly Distributed Load. 4. Rectangular beams, fixed at both the ends subjected to Uniformly Distributed Load 5. Rectangular as well as I-section beams, simply supported with only bottom steel consisting of two bars. 6. Rectangular beams reinforced with four bars two at top and two at bottom, simply supported subjected to Uniformly Distributed Load. 7. Rectangular beams with vertical steel as shear reinforcement, simply supported subjected to Uniformly Distributed Load. 8. Rectangular as well I-section beams subjected to pre-compression to improve the shear strength and simply supported beams subjected to point load at centre and also with Uniformly Distributed Load. 9. Rectangular beams with enhanced compacting force, simply supported as well as plate support on both the ends subjected to point load at centre and also with Uniformly Distributed Load. The beams tested were relatively of large size, 1980 mm (6.5 ft) long, 150 mm (6 inch) thick and 300 mm (12 inch) deep. After shrinkage the final dimensions were determined and the average shrinkage was found, 1868 mm (6.13 ft), 143 mm (0.47 ft) and 286mm (0.94 ft). Several problems were faced and attempts were made to over-come those through various techniques, the details of which are presented in this thesis. The results are encouraging and there is a bright possibility to achieve reasonably good economy if pre-cast panels of this type of materials are produced on mass scale by adopting mechanized system for swift moulding, transportation to the site and erection of the buildings.