Code of Practice for Curing of Cement Concrete Pavements
1983 Edition

For hot conditions, curing should avoid exposure during temperatures above 40°C, especially when combined with low humidity or strong winds. The ponding method involves creating water ponds approximately 1.5 m by 1.5 m with a 5 cm water depth, contained by bunds constructed from cement-sand mortar. Ponds must be maintained for at least 14 days. When water availability is limited or slopes prevent ponding, membrane curing is advised using solid membranes like polyethylene sheets of at least 400 gauge or bituminous waterproof paper, continuing for 28 days. Liquid membranes such as diluted silicones or linseed oil may also be used but are less common. After curing, membranes and bunds are removed, and joints are cleaned thoroughly.

Curing below 4°C requires authorization. When permitted, concrete placement temperature must be at least 10°C (never below 5°C), with surrounding air temperature maintained at 10°C for three days or 5°C for five days via insulation and steam or warm air circulation. Freshly placed concrete should be immediately covered with tarpaulins to minimize temperature shock. Insulating layers consisting of waterproof paper combined with 10 to 30 cm of sawdust or straw are used to protect from cold. No concreting is allowed below -7°C. The total curing period remains a minimum of 28 days, with solid membrane curing prohibited but liquid membranes acceptable if water is scarce.

Approved solid membranes include transparent polyethylene sheets with a minimum thickness of 400 gauge and multi-layered bituminous waterproof papers reinforced with fiber mesh such as cotton, jute, or hessian. Liquid membranes, which are less commonly used in India, encompass diluted silicone wax emulsions (25-50%), linseed oil, resin solutions, and sodium silicate diluted to paint consistency. Liquid membranes must harden within 30 minutes of application and retain at least 90% of mixing water for 72 hours under specified temperature and humidity conditions. Solid membranes are preferred for their availability and efficacy, especially where water is limited or ponding is impractical.

According to IRC 15-1981 referenced in IRC 84, ordinary Portland cement concrete requires a minimum curing period of seven days to ensure sufficient hydration and strength gain. Rapid hardening cement may require only three days. Curing consists of an initial phase immediately after finishing to prevent moisture loss, followed by a final curing stage that maintains appropriate moisture and temperature levels to achieve the desired strength and durability.

For airfield pavements, initial curing involves covering the entire slab surface and edges with wet hessian or burlap mats, overlapping the layers appropriately, and keeping them continuously moist for at least 24 hours until the concrete is walkable. Walking on fresh concrete is prohibited, and wooden bridges are used for placing mats. Final curing may be performed through traditional soil ponding or by creating small water ponds with cement-sand mortar bunds measuring approximately 1.5 m by 1.5 m by 5 cm depth, maintained with 20-30 mm water for at least 14 days. In water-scarce areas, solid membrane curing using polyethylene sheets or bituminous papers is suitable, continuing for up to 28 days. Liquid membranes may be used if available but are less common.