WHAT ARE THE PROPERTIES OF AIR ENTRAINED CONCRETE?

AIR ENTRAINED CONCRETE

A major advance in concrete technology in recent years is that the introduction of small disconnected air bubbles into concrete called air entrainment. Air entrained concrete results from using either an air-entraining cement or an air-entraining admixture during mixing.
 Adding entrained air to concrete provides important benefits in both plastics and hardened concrete, like resistance to freezing and thawing during a saturated environment. Air entrapped in non-air-entrained concrete fills relatively large voids that aren't uniformly distributed throughout the combination. 

                Air entrained concrete

PROPERTIES
 The following are properties of air-entrained concrete: 
1. WORKABILITY 
The improved workability of air-entrained concrete greatly reduces water and sand requirements, particularly in lean mixes and in mixes containing angular and poorly graded aggregates. additionally, the disconnected air bubbles reduce segregation and bleeding of plastic concrete.
 2. FREEZE-THAW DURABILITY 
The expansion of water because it freezes in concrete can create enough pressure to rupture the concrete. However, entrained air bubbles function reservoirs for the expanded water, thereby relieving expansion pressure and preventing concrete damage. 
3. DE-ICERS RESISTANCE 
Because entrained air prevents scaling caused by de-icing chemicals used for snow and ice removal, air-entrained concrete is suggested for all applications where the concrete contacts de-icing chemicals.
 4. Sulfate RESISTANCE 
Entrained air improves concrete’s resistance to sulfate. Concrete made with a coffee W/C ratio, entrained air, and cement having low tricalcium-aluminate content are that the most immune to sulfate attack. 
5. STRENGTH 
The voids to cement ratio basically determine air-entrained concrete strength. For this ratio, voids are defined because of the total volume of water plus air (both entrained and entrapped). When the air content remains constant, the strength varies inversely with the W/C ratio. because of the air content increases, you'll generally maintain a given strength by holding the voids to the cement ratio constant. to try to do this, reduce the quantity of blending water, increase the quantity of cement, or both. Any strength reduction that accompanies air entrainment is minimized because air-entrained concrete has lower W/C ratios than non-air-entrained concrete having an equivalent slump. However, it's sometimes difficult to achieve high strength with air-entrained concrete, like when slumps remain constant while the concrete’s temperature rises when using certain aggregates. 
6. ABRASION RESISTANCE 
Air-entrained concrete has about an equivalent abrasion resistance as that of non-air-entrained concrete of equivalent compressive strength. Abrasion resistance increases because of the compressive strength increases. 
7. WATER TIGHTNESS
 Air-entrained concrete is more watertight than non-air-entrained concrete since entrained air prevents interconnected capillary channels from forming. Therefore, use air-entrained concrete where water tightness may be a requirement.

Er.SP.ASWINPALANIAPPAN., M.E.,(Strut/.,)

Structural Engineer

Madras Terrace Architectural Works

www.civilbaselife.blogspot.in