IRC :15 -1970 RECOMMENDS FOLLOWING THICKNESS FOR CONCRETE ROAD SLABS

IRC :15-1970 recommends the following thickness of the concrete road slabs. In the case of average 200 number of commercial vehicles,with laden weight over 8 tonnes,both directions anticipated to develop in the next 20 years the thickness of the Concrete road slab may be 15 cm. Over 200 and up to 350 it may be kept 17.5 cm and in case of above 350 commercial vehicles the thickness of the concrete road slab may be kept 20 cm .Very stable subgrade is undisturbed foundation of old roads ,solid rocks ,compact well graded gravel and thickness of the concrete road slab may be kept 10 cm in case of very light traffic intensity. Unstable subgrades are susceptible to non uniform movement and comprise of organic or highly plastic clays or peat and the subgrades formed by the embankments exceeding.1.5 mt in height and those in which the level of water table may rise with in one mt of the foundation. For the Design of rigid pavement, the stability of the subgrade that is uniformity of the subgrade support ,is more important than the thickness of the pavement. If a concrete road fails repair is often very costly, therefore it is advisable to keep a slightly greater thickness of Construction As increase in the slab thickness will result in a percentage increase in Structural strength of about double the percentage increase in the cost of the slab.