Stones in Civil Engineering part 2

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Blasting Procedure 

Boring. Drilling of holes in rock using jumper, manual drilling or machine drilling using pneumatic or mechanical power Charging. Placing of required quantity of explosive charge in the hole at desired location. Quantity depends upon explosive strength, blasting method, number of holes, type and mass of rock

Gunpowder or Dynamite explosive (gms) = Square of length of line of least resistance (m) / 0.008Tamping.

Placing of priming charge, detonation cable (cordite), and sealing off the escape of gases Firing. detonation mechanism (electrical or non-electrical detonators) or fuse ignition Blasting should not be carried out in late evening or early morning. Blasting should be made public with sufficient time allowed to retire to safe distance 200 m radius danger zone should be marked with red flags First aid should be made available Explosive should be handled carefully Cartridges should be handled with rubber gloves Stone Dressing Pitched faced dressed – 2.5 cm edges dressed and made square Hammer dressed, hammer faced, quarry faced or rustic faced – dressed like a brick with 2.5 cm rough edges for use in masonry Rock faced and chisel drafted – chisel draft of 2.5 cm along edges Rough tooled – edges and corners made perfect square and true Punched dressed – rough tooled improved up to 2 mm Fine tooled – fair smooth surface for ashler masonry

Deterioration of Stones


Physical Action. Disintegration, erosion, transportation due to alternate wetting and drying Chemical Action. Decomposition, oxidation and hydration of minerals due to acids formed with rain water Frost. Pierces the pores, freezes, expands and creates cracks Wind. Abrasion due to wind carried dust Temperature Changes. Expansion and contraction affects on minerals of different coefficients of linear expansionVegetable growth. Roots of trees and weeds in cracks and fissures Mutual decay Chemical Agents. Smokes, fumes, acids and acid fumes from atmosphereLichens. Destroy lime stones. Molluses make series of parallel vertical holes Avoiding  Deterioration Initial selection

– use compact, crystalline stones instead of porous material Seasoning – Seasoned stones are less liable to deterioration due to frost and acids Size – it does matter – bigger is more durable than smaller ones Natural bed – placing on natural bed provides greater strength and is detrimental to rain and frost Surface finish – well dressed, smooth finished and polished is more durable Workmanship – all joints filled leaving no cavities in masonry External rendering – pointing or plastering to stop rain penetration Proper maintenance – washing, removing dirt and dust Application of preservatives – eliminate cause of deterioration Cure is better than medicine

Natural Bed of Stones 

It is the plane or bed on which the stone was originally deposited. Natural bed has an important effect on the durability of stone

. Preservation of Stones Stones should be kept dry with blow lamp and applied coat of paraffin, linseed oil,  light paint, etc Stones should be washed with water and steam to remove dirt and salt In industrial towns stones are preserved by application of solution of baryta, Ba(OH)2 to form insoluble barium sulphate Preservative treatment only slows down the decay but does not stop it. All have harmful side effects also Selection of Stones Cost – quarrying and cutting, dressing, transportation charges, etc Fashion & Ornamental value including color, shade, etc specially after prolong usage Durability (usually overlooked and disregarded), resistance to fire and weathering
Heavy engineering works bridges, piers, abutments, break waters, docks, light houses – granite (biotite, hornblende, tourmaline)Buildings facing the sea – granite, fine grained sandstone Buildings in industrial area – granite, compact sandstone Arches – fine grained sandstone Building face work – marble, close grained sand stone Fire resisting structure – compact sand stone Road metal and aggregate for concrete – granite, basalt, quartzite Railway ballast – coarse particles Electrical switch board – slate, marble Artificial Stone- Building material made with cement, sand and natural aggregates of crushed stone for use in place of natural stone Properties Made with white cement, sand and natural aggregates of crushed stone Molded into most intricate forms Cast into any size Reinforced to desired higher strength Desired coloring may be achieved Desired finish may be achieved Concrete block. Cast in molds for steps, window sills, masonry work, etc Ransom stone. Soda silicate plus cement for decorative flooringVictoria stone. Granite pieces immersed in soda silicate for two monthsBituminous stone. Provide noise, wear and dust resistant stone surfacesImperial stone. Crushed granite plus cement, molded, steam curedArtificial marble. Pre-cast or cast-in-situ. Portland gypsum cement and sand. Cast blocks treated with magnesium fluorite, washed, paper wrapped, machine emery ground, polished and finally rubbed with ball of wool moistened with alum waterGarlic stone. Iron slag and cement mixture molded into flag stones, surface drains, etc

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i am a student of civil engineering takes much interest in this field

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