How air entrainment concrete is suitable in cold weather?
- Thread starter Shanu
- Start date
Dnyan Deshmukh
Staff member
Concrete do expand and contract due to changes in temperature and goes through a volume change.
IS Codes says any structure should not be made more than 45 meter in length, if it is to be built then expansion joints should be made, else it will break through all floors and show huge cracking everywhere.
During summer / hot weather, concrete and steel bar tries to expan and they need some space outside the structure areas between two continous structures made separate by providing expansion joint generall is of 50mm wide.
Same way during winter / cold weather, concrete and steel bars tries to contract (reduction in volume) and if there is no space left for counter acting on contraction force, concrete may face sever damages.
To allow / companset the effect of contraction, airated concrete is used.
So air bubbles inside in the concrete do really help it to protect its self from cold weather and expansion contraction cycles.
IS Codes says any structure should not be made more than 45 meter in length, if it is to be built then expansion joints should be made, else it will break through all floors and show huge cracking everywhere.
During summer / hot weather, concrete and steel bar tries to expan and they need some space outside the structure areas between two continous structures made separate by providing expansion joint generall is of 50mm wide.
Same way during winter / cold weather, concrete and steel bars tries to contract (reduction in volume) and if there is no space left for counter acting on contraction force, concrete may face sever damages.
To allow / companset the effect of contraction, airated concrete is used.
So air bubbles inside in the concrete do really help it to protect its self from cold weather and expansion contraction cycles.
Karthick P
Senior Member
Modification of pore structure caused by air-entrainment is believed to be responsible for the marked improvement in resistance to frost attack. The hypothesis as to how the airentrainment enhances the resistance of concrete to freezing and thawing is shown in Fig
. It is assumed that the concrete member is wet and quick freezing occurs. The surface is immediately sealed due to the freezing of water at the surface and when freezing continues ice crystals are formed inside the voids. Since the volume of ice is 10% more than that of water, only 90% of water in the voids will turn into ice. The excess of water is forced out through the capillary channels into the adjoining lower air-voids, and the pressure is relieved. Stage No. 3 and 4 show progressive freezing and relief of pressure in the interior of concrete. If sufficient water free voids are available, pressure build up will not occur and the eventual disruption of the concrete will not take place. The reduction in water cement ratio that might be permitted by the use of air entrainment in concrete may also account for the greater resistance to freezing and thawing action.
Reference:Book - M.S Shetty ,Concrete technology
. It is assumed that the concrete member is wet and quick freezing occurs. The surface is immediately sealed due to the freezing of water at the surface and when freezing continues ice crystals are formed inside the voids. Since the volume of ice is 10% more than that of water, only 90% of water in the voids will turn into ice. The excess of water is forced out through the capillary channels into the adjoining lower air-voids, and the pressure is relieved. Stage No. 3 and 4 show progressive freezing and relief of pressure in the interior of concrete. If sufficient water free voids are available, pressure build up will not occur and the eventual disruption of the concrete will not take place. The reduction in water cement ratio that might be permitted by the use of air entrainment in concrete may also account for the greater resistance to freezing and thawing action.Reference:Book - M.S Shetty ,Concrete technology
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