Foundation, Concrete and Earthquake Engineering

Why should Concrete be Remixed after Discharging from Mixer?

Concrete mixing machines are used for both reinforced concrete and mass concrete with some advantages like efficiency and sometimes economical in case of large volume concreting work. There have various mixers with variable efficiency in the concrete industry. In normal concreting work batch mixer is the right choice for concrete technicians. The batch mixer are of different types like pan type and drum type mixer.

Whatever the mixer, the discharging techniques of mixed concrete are important to avoid segregation. We know concrete is a mixer of cementing material and inert materials like coarse and fine aggregates which is to be bonded by the cementing materials like cement or lime in the presence of water with or without application of concrete admixture to render special properties or to ease placement and transportation work of concrete. Of which coarse aggregates, the heavier components of concrete, are supposed to segregate from the relatively lighter mix of cement and sand. When concrete is discharged from mixer, the heavy coarse aggregate falls first and then the matrix of cement and sand comes out resulting a little segregation. In some non-tilting drum concrete mixer have lever operated chute to facilitate the discharge without segregation.
Segregation of coarse aggregate and cement sand matrix after discharge from mixer
But whatever precautions are taken, it is noticed that segregation cannot be avoided. So to have workable and efficient concrete mix, a little remixing is required after discharge of concrete from mixer on the platform upon which mixed concrete are accumulated prior transporting to the placement site.
 Concrete drum mixer with discharge chute

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