Guidelines for the Design and Construction of Cement Concrete Pavement for Low-Volume Roads (First Revision)
2014 Edition

The standard recommends a minimum slab thickness of 150 mm. For traffic volumes up to 50 commercial vehicles per day (CVPD), design is based solely on stresses from a 50 kN dual wheel load. For 50 to 150 CVPD, thickness is designed considering combined effects of wheel load and temperature stresses, typically exceeding 150 mm. For 150 to 450 CVPD, the pavement thickness is determined through fatigue analysis accounting for both loading and thermal stresses. These guidelines ensure appropriate pavement thickness corresponding to traffic demands.

Transverse contraction joints should be spaced between 2.5 m and 4.0 m, with 2.5 m spacing optimal for minimizing curling stresses. Joints are typically sawed within 24 hours after casting to a width of 3 to 5 mm and a depth of one-quarter to one-third of the slab thickness. Alternatives include embedding mild steel T-sections or metal/HDPE strips during casting. Construction joints are placed where concreting is interrupted for over 90 minutes or at day’s end, using steel bulkheads for concrete retention. Expansion joints at bridge or culvert abutments have a 20 mm width with dowel bars for load transfer. Proper sealing with bituminous materials per IS 1834 is recommended to maintain joint integrity.

Recommended cements include Ordinary Portland Cement (OPC) 43 Grade, Portland Blast Furnace Slag Cement, Portland Pozzolana Cement (PPC), and OPC 53 Grade blended with fly ash. Sulphate resistant cement is advised when soil sulphate content exceeds 0.5%. PPC is preferred over OPC 43 Grade if costs are comparable due to better durability. Mineral admixtures such as fly ash (Grade I), silica fume, rice husk ash, metakaolin (700–900 m²/kg fineness), and ground granulated blast furnace slag (GGBS) enhance concrete properties and durability. Total cementitious content typically ranges between 360 to 425 kg/m³.

The standard recognizes that temperature gradients in concrete slabs are non-linear, with the surface-to-mid-depth temperature difference being roughly twice that of mid-depth to bottom. This gradient induces curling stresses causing bending moments and tensile stresses, especially at edges and corners. Curling behavior differs between daytime (top warmer, slab curls upward causing tension at the bottom) and nighttime (bottom warmer, slab curls downward causing tension at the top). Stress calculations use Bradbury’s equation assuming a linear gradient, adjusted for non-linear effects by separating linear and bilinear components. The total tensile stress, combining traffic and temperature effects, must not exceed the concrete’s 90-day modulus of rupture to ensure safety.

Full-depth cracks in slabs are unacceptable due to structural concerns. Cracks penetrating deeper than half the slab thickness are also not permissible. Fine, shallow (crazy) cracks are considered acceptable. For cracks less than half the slab thickness, a single crack length must not exceed 750 mm, and the cumulative length of all such cracks within a panel should be below 1250 mm. These limits aim to maintain structural integrity and durability, with preventive measures including proper curing and timely joint sawing to reduce crack formation.