3. Curing
Curing is the process of maintaining concrete moisture and temperature after casting to facilitate optimal cement hydration. Proper curing is vital for compressive strength development, especially in early ages.
Inadequate curing results in rapid moisture loss, hindered hydration, increased porosity, early cracking, and low strength.
Curing methods include:
- Wet curing: Regular surface watering or covering with wet burlap or geotextile—ideal for slabs, pavements, or open surfaces.
- Ponding: Suitable for flat horizontal elements, like bridge decks, by creating shallow water pools.
- Curing compound: Liquid chemicals sprayed on the surface forming a thin film to prevent moisture loss—ideal for large or hard-to-access areas.
- Plastic sheeting or tarpaulins: Protect surfaces from wind and sunlight that can accelerate evaporation.
Minimum curing duration for normal concrete is 7 days, extended to 14 or more for high-strength concrete or hot/dry climates. Research shows that lack of curing can reduce potential compressive strength by up to 40%. In contrast, proper curing improves not only strength but also resistance to water penetration, chemical attacks, and temperature fluctuations.
Key factors in curing:
- Weather conditions: Hot, dry, or windy climates demand more intensive curing.
- Curing start time: Should begin as soon as the concrete sets and surface water has evaporated.
- Curing duration: Longer moist curing yields higher final strength.
Here we continue with the discussion on the Condition of Test Specimen Factor on the next page.