Curing Of Concrete And Curing Types

This Article Covers Curing Meaning, Curing Of Concrete, Curing Compound, Curing Methods Of Concrete And Curing Process One By One.

Curing Meaning?

Curing of concrete defined as the process of maintaining the moisture and temperature condition of concrete for hydration reaction to the normally so that the concrete develops hardened and properties over time.

Procedures used for promoting the “hydration of cement” which consist of,

  • Control of moisture to and from concrete.
  • Control of temperature.

The object is to keep concrete saturated or nearly saturated as possible, until the originally water-occupied spaces fill up with hydration products,

  • Reduction in porosity.
  • Minimize volume changes in the concrete.

Curing Process

  • The main components which need to be taken care of your heat and time during curing process
  • Curing is the process of preventing the loss of moisture from the concrete which maintaining a satisfactory temperature effect
  • The prevention of moisture loss from the concrete is particularly important if the water cement ratio is low.
  • If the cement has high rate of strain development and if the concrete contains granulated blast furnace and flue Ash then,
  • The curing should also prevent the development of high temperature gradients within the concrete

Curing process is crucial because it affects,

  • Durability.
  • Strength.
  • Water-tightness.
  • Abrasion resistance.
  • Volume stability.
  • Resistance to freezing and thawing.

Curing For Concrete

Concrete Curing Done By Various Methods Let’s See One By One,

Methods/Types Of Curing

  • Water curing / Moist curing (Ponding, sprinkling, wet covering)
  • Sealed / Membrane Surface curing (Plastic sheeting, curing compounds)
  • Heat curing.
  • Special (Mass Concrete, Hot-Weather Concreting, Cold-Weather Concreting)

Moist Curing

  • Surface of the concrete shall kept continuously in Dam or wet condition by covering with the layers of materials like checking Canvas etc.
  • it should kept continuously wet for at least 7 days from the date of placing concrete.
  • In case of ordinary Portland cement at least 10 days. where mineral admixture or blended cement used.
  • The period of curing shall not less than 10 days for concrete exposed to the dry and hot weather condition.
  • In case of concrete where mineral admixture or blended cement used it recommended that above minimum period may extended 14 days.

Membrane Curing

  • Approved curing compounds may used in place of moist curing with the permission of engineer in charge.
  • Search compound shall applied to all exposed surfaces of the concrete as soon as possible after the concrete has set.
  • Impermeable membrane such as polyethylene sheeting covering closely the concrete surface may also used to provide effective barriers against evaporation.
  • For the concrete containing Portland pozzolana cement, Portland slag cement or mineral admixture period of curing may be increased.

Curing Compound (Sealed Curing)

Liquid membranes form impermeable layer on surface, which limits moisture loss waxes, resins, etc.

Benefits- Cost-effective, Lower labor requirement, And Can applied to vertical surfaces.

Drawbacks- Least effective method in preventing moisture loss, Cannot used on surfaces to bonded, And Slightly reduces rate of hydration.

Heat Curing

Development of strength of concrete is a function of not only curing time but also temperature.

When concrete subjected to low temperature, heat curing required in presences of moisture to maintain hydration process.

Types Of Heat Curing,

  • Steam curing at ordinary pressure
  • Steam curing at high pressure
  • Curing by INFRA-RED radiation
  • Electrical Curing
Steam Curing
  • Advantageous where early strength required.
  • Live steam at atmospheric pressure used for enclosed cast in place concrete.
  • High pressure steam in Autoclave used for small units.
  • Application of steam delayed until initial set occurs to allow for some hardening of the concrete.
  • However, a 3-5 hour delay period prior to steaming will achieve maximum early strength.
  • Steam-curing temperatures above 70°C (160°F) should be avoided, they are uneconomical and may result in damage (heat  induced delayed expansion and undue reduction in ultimate strength)
  • Excessive rates of heating and cooling should avoided to prevent damaging volume changes.

Effect Of Temperature

  • Early-age strength of concrete increases with increase in curing temperature.
  • However, there is a decrease in later-age strength.
  • Curing at comparatively low temperatures can result in higher ultimate strength, even though the initial rate of strength development is low.
  • As a rule, the higher the initial temperature of the concrete, the lower its later strength.

Comparison Of Curing Techniques

  • Water curing is better than sealed curing since it protects concrete against self-desiccation (drying) in concretes with low w/c ratio (w/c <  0.4)
  • The efficiency of sealed curing depends on the thickness of the covering and its integrity.
  • Care should exercised in selection of curing technique.

Curing At Ambient Temperature

Parameters affecting curing,

  • W/C ratio
  • Loss of water
  • Internal RH
  • Type of cement
  • Method of curing

Interrupted Curing

  • Interrupted moist curing of young concrete is particularly undesirable.
  • Though re-saturation will resume the interrupted hydration,strength will always be affected.
  • It is not easy to fully re-saturate the concrete except by immersion.
  • Resultant wetting and drying cycles will be harmful.
  • In summer months, interrupted curing might result in thermal length change.

Effect Of Ambient Temperature

  • More the temperature of air and concrete, more rapid will be  the loss of water, leading to drying.
  • Lesser would be the water available for hydration,
  • Thus lesser compressive strength.

Effect Of Relative Humidity

  • Concrete will hydrate even if not fully saturated because of water held in large capillary pore, however drawing water from these reservoirs become slower as the internal RH drops.
  • Difference in hydration and strength gain between concrete sealed against moisture loss and the one continuously moist cured.
  • The level of external relative humidity has the most influence on concrete in its early life.

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