DESIGN CONSIDERATIONS REQUIRED FOR LONGITUDINAL AND TRANSVERSE STEEL REINFORCEMENT ,COMPUTED BY THE CODE FOR SPECIFICATIONS AND USED FOR THE CONCRETE PAVEMENT AT WEAK PLACES IN THE SUBGRADE.

REINFORCEMENT IN CONCRETE ROAD SLABS:-- The normal form of rigid (concrete) pavement is without reinforcement.Because of its rigidity and beam -action it distributes the wheel load over a greater area of the subgrade than to the flexible pavement over the same thickness but it doesn't adjust itself to minor settlements that may occur beneath it . Reinforcement is not usually necessary where the slab is laid over the firm and we'll consolidated foundation. Reinforcement helps to carry over any weak places inthe subgrade, and is usually provided under heavy loads only . Reinforcement does not materially increase the load carrying capacity of a properly supported concrete slab but it does increase the resistance of the concrete to cracking and controls any cracking that may occur by preventing the cracks from opening further Where the slabs are provided with Proper joints and are well supported , the Reinforcement has little function. Reinforcement may therefore be used only on doubtful subgrades .If the subgrade is weak ,the reinforcement must be laid in the bottom and about 5 cm above the bottom line of the concrete, but if the subsoil is unreliable as regards it's settlement and temperature stresses are expected a double layer of the reinforcement should be provided. Reinforcement should be equal in both the layers .Slabs 15 cm thick or less need be provided only with one layer of the reinforcement. There is no evidence to show that better performance is obtained with a double layer of the reinforcement than with a single layer (of the same total weight) .The use of two layers of reinforcement impedes Construction, especially where the concrete is being spread and compacted by power propelled machines. The amount of reinforcement per each layer is about 3kg /sq mt for moderate traffic and about 5 kg /sq mt for heavily trafficked roads ,with the greater proportion placed in the longitudinal direction.Reinforcement for concrete pavement is most often of the bar mat type or the welded fabric type. The amount of longitudinal and transverse steel required per metre length of slab can be computed by the following Design parameters :- As= LfW / 2S Where As is area of steel in sq cm required per metre width or length of slab , L is length of slab between joints , f is coefficient of friction ,W is weight of slab per sq metre and S is working stress in the reinforcing steel in kg/ sq cm .