Achieve the required durability and strength
Fresh concrete must be protected whilst in its early life from the detrimental effects of hot sun, dry air, drying winds and frost. In order to achieve the required durability and strength of any concrete, care must be given to curing.
The main reasons for curing are to assist strength development and to improve the durability potential of freshly-placed concrete. In some cases curing also reduces the effects of thermal contraction and the production of satisfactory surface finishes.
Effective curing prevents the evaporation of water from a concrete surface. Curing using applied insulation can also help control damaging internal temperature differentials in large masses of concrete, and to maintain an adequate temperature in the concrete during cold and frosty weather to fully hydrate the cementitious material present.
To ensure that the full benefits of curing are achieved, all involved in concrete production (designers, engineers, operatives) must clearly understand why and how a particular curing process is to be used.
The benefits of proper curing include:
- Increased wear resistance
- Reduction of surface erosion
- Increased frost resistance
- Improved life span
- Optimum strength development
- Reduction in cracking
- Increased resistance to thermal contraction
Duration and effectiveness of curing
Curing periods required by most specifications range from approximately three to seven days, irrespective of weather conditions. Rates of moisture loss from laboratory controlled specimens made with ordinary Portland Cement show that the rate of evaporation decreases rapidly after the first 24 hours and reaches an almost insignificant value within three or four days. The first 24 hours are therefore the most critical.
CP 11013 recommends different curing periods depending on the type of cement used. Four days is recommended for ordinary Portland Cement concrete, and two days when rapid-hardening Portland Cement is used. In adverse conditions, i.e. hot or windy weather, full curing should continue for a minimum of seven days with all Portland Cements.
Slightly longer periods of curing may be necessary when Hanson Regen has been incorporated in the concrete.
Curing of concrete test cubes
The detrimental effects of not curing concrete test cubes cannot be stressed enough. Results obtained from test cubes that HAVE NOT been correctly cured are INVALID and are not wholly representative of the quality of concrete delivered.
Extreme care must be given to correctly curing any test specimen. Failure to do so can cause unjustified concern and the instigation of further costly assessments of compliance.
Hanson concrete can incorporate a proportion of Hanson Regen, (Ground Granulated Blast furnace Slag or 'GGBS'), which is a cement replacement material, helping to produce a product that generates a much lower level of CO2 emissions than ordinary cement.