JNTU B.Tech II BUILDING MATERIAL CONSTRUCTION AND PLANNING Previous Question Paper (March - 2022 - R16)

The Bull's Trench Kiln is a common continuous method of burning bricks. It consists of a trench, either circular or oval in shape, excavated in the ground. The trench is divided into several chambers by temporary partitions. Bricks are stacked in the chambers with fuel (coal dust) distributed throughout the stack. The process involves a moving fire zone that travels around the trench. As the fire moves from one chamber to the next, the bricks in the front are pre-heated by the hot gases, while the bricks behind the fire zone are cooled by incoming air. This continuous operation allows for high efficiency and uniform burning. A sketch would show the trench layout with the fire zone, loading area, and unloading area arranged in a continuous loop, with a central chimney used to create the necessary draft for combustion.

Field tests on stones are conducted to assess their suitability for construction purposes without requiring complex laboratory equipment. Key tests include:

• Appearance and Structure Test: The stone should be uniform in color, free from cracks, cavities, or loose material. A fractured surface should show a uniform, compact, and crystalline texture.
• Hardness Test: A scratch is made on the stone surface using a knife or a sharp tool. If the stone is easily scratched, it is considered soft and unsuitable for heavy structural work.
• Strength Test: A small block of the stone is struck with a hammer. A good building stone should produce a clear, ringing sound and should not break easily. A dull sound indicates the presence of internal defects or weathering.
• Water Absorption Test: A sample is weighed, immersed in water for 24 hours, and weighed again. A good stone should absorb less than 5% of its weight in water.
• Acid Test: A small piece of stone is placed in a solution of hydrochloric acid. If the edges show signs of decomposition or effervescence, it indicates the presence of calcium carbonate, which makes the stone unsuitable for use in polluted or industrial environments.