Detail specification of lime concrete in roof terracing are as below:-
Detail specification
Material- All materials shall be of standard specifications. Coarse aggregate shall be of well burnt or over burnt brick ballast of 25 mm gauge. It shall be deep cherry red or copper and shall be clean, free from dust, dirt and other foreign matters. It shall be homogeneous in texture and roughly cubical in shape. Ballast which appears porous or shows signs of saltpetre shall not be used. Brick ballast shall be such as to pass through a square mesh of 37.5 cm and not more than 20% shall pass through a mesh of 20cm. any rejected material shall be removed from site of work within 24 hours.
Fine aggregate shall be surkhi, clean free from dust, dirt and foreign matters. Surkhi shall be made from well burnt bricks or brick bats (not overburnt) and shall pass through a screen of 25 meshes per sq cm(144 meshes per sq in).
Lime shall be white fat lime shall be freshly burnt and free from ashes and other foreign matters. Lime shall be slaked at site of work and screened through a sieve of 3 meshes to a cm (8 meshes to an inch).
Proportion- Concrete shall consist of 1 cu m brick ballast, 0.36 cu m of Surkhi and 0.18 cu m white lime (proportion 100 : 36 : 18 by volume).
Mixing- Mixing shall be similar to lime concrete in foundation.
Laying and consolidation- Surface shall be lightly sprinkled with water and then concrete shall be laid slowly and gently (not thrown) in layers so as to have the required slope and specified thickness after complication. The concrete shall then be lightly rammed with 6kg rammer and during preliminary ramming the surface shall then be perfectly levelled by means of trowel, straight edge and sprite level. The concrete with wooden ‘thapis’ and moving forward and backward covering the whole surface. The beating shall continuous for at least 7 days until the concrete is thoroughly compacted and until the ‘thapis’ rebound from the surface when struct on the concrete. Special care shall be taken to consolidate the concrete properly at the junction with the parapet wall and the junctions shall be rounded.
When beating is in progress, the surface of the concrete shall be frequently sprinkled with a mixer of lime molasses and boiled solution of ‘bael’ fruit for water proofing. Beal fruit solution shall be prepared by boiling 2kg of bael fruit in 100-130 lit of water and to this solution after cooling 3.5kg of molasses (gur) and the required quantity of lime shall be mixed.
Finishing- As soon as beating has been completed the mortar that has come to top shall be softened by the addition of lime, “molasses” and “beal fruit” solution and smoothened by rubbing and pressing with a trowel or float to a fine polish. No plaster shall be use on any account for finishing the surface. The finishing surface shall have a minimum slope 1:50 and max slope of 1:36 towards the rain water outlet. For every 40 sq m of roof area, 100 mm dia rainwater pipe shall be provided.
Curing- The concrete shall be kept wet for a fortnight. The wetting should be done by covering with straw or sand and watering frequently by water can or dividing into squares by mud kiaries which shall be kept flooded with water.
Measurement- The measurement shall be taken for the finished work of superficial area in sq m stating the avg thickness. The avg thickness shall be measured correct to 6mm and length and breadth shall be measured correct to 1cm. No deduction in measurement shall be made for opening up to 0.4 sq m and extra payment shall not be made for extra material or labour involved in forming such opening. For opening exceeding 0.4 sq m deduction will be made made in measurement but extra payment shall not be made made for material and labour involved in forming such opening. Rate shall be for the finished work including all tools and plant.
Lime concrete in roof terracing- Detailed Specification
Perfectly copied by M. Chakraborty
ReplyDeleteThanks for the interesting article!Is steel mat not necessary?
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