Conditions Affecting Concrete Air Volume

Mastour ReadyMix is a Ready mix Concrete, cement and related construction materials and services company Jeddah Saudi Arabia

Reducing the aggregate size increases the volume of air in concrete. More air entraining admixture is needed when fly ash, pozzolan, slag and silica fume are added to the concrete. High alkali cements entrain more air than low alkali cements. Increasing the mixing water makes more water available to generate air bubbles in the concrete. Algae in water increases air content. Air content increases then decreases as slump increases. Vibrating the concrete decreases air content. Less air is entrained when the carbon black colouring agent is added to the concrete or the concrete curing temperature is high. Proper mixing increases air entrainment. 1-2 percent of air is lost during the transport of  concrete to the job site. At the job site, the air volume remains constant unless long distance pumping or conveying of the concrete occurs. Up to 2.5 percent of the air can be lost by long distance transport.