Mixing

June 15, 2017
868 Views

Mixing:

Mixing is the important process in concreting. There are two type of mixing and they are discussed below

  • Hand mixing
  • Machine mixing

Hand mixing:

As the name indicates the mixing process is done only by hands by using human efforts. This type of hand mixing are used only for the small construction work or any repair work. Proper hand mix can be achieved only by years of experience. For achieving the proper hand mixing mix design is calculated using this design the required amount of cement, fine aggregate, coarse aggregate and water are taken.

Process of Hand mixing:

The sand is poured in the water free place in the site. The cement is dumped into the sand. Then the cement and sand are mixed well then the coarse aggregate are poured into the cement-sand mix. Then the cement, sand and coarse aggregate are mixed properly in dry manner. After that the water is poured into the dry mix according to the requirement. Then it is mixed well and now it becomes fresh concrete.

Fig: Hand Mixing

Machine mixing:

As the name indicates the mixing process is done by machine. This type of machine mixing are used for large construction and also for continuous construction process. No experience is required for machine mixing. Mixing is done according to the mix design. In machine mixing there are three type of concrete mixer

  • Twin shaft mixer
  • Vertical axis mixer
  • Drum mixer

Twin shaft mixer:

Twin shaft mixer are used for high intensity mixing in short period. This type of mixer are used for preparing high strength concrete.

Fig: Twin shaft mixer

Vertical axis mixer:

Vertical axis mixer is generally used for pre-stressed concrete and precast concrete. This type of mixer are used only for the small batching. Vertical axis mixer are mostly used for producing the colored concrete. This type mixer are pan mixers.

A small door is present vertically along with the mixer. After mixing the door is opened manually the concrete flows to the bucket or pan kept at bottom front of the mixer. This type of mixers are most commonly used in the laboratory for testing purpose.

Fig: vertical axis mixer

Drum mixer:

          The drum mixer are used for producing more volume of concrete and also for continuous construction process. There are three type drum mixers and they are listed below

  • Tilting mixer
  • Non tilting mixer
  • Reversible mixer

Tilting mixer:

Tilting blenders are typically trailer-mounted or generally compact, little to medium size blenders, utilized either as fundamental solid blending hardware on little locales or as subordinate gear on destinations served by solid plant. The drum has two tomahawks: one around which the drum turns and another that serves to change from stacking and blending position (drum opening up) to releasing position (drum opening down). This position change is done physically by a dump wheel (or handle, in the littler blenders), while drum turn is electric, gas, or diesel controlled. Drums are customarily made of steel, however polyethylene drums for less demanding cleaning are currently advertised. Most blenders are of the side-dump sort, yet end-dump blenders are additionally produced. Material is by and large stacked physically, specifically into the drum. There are bigger size self-stacking units outfitted with a tilting container. In the wake of being filled physically at ground level, the container is tilted up mechanically and dumps the material into the drum. An inherent mechanical drag scoop to encourage total stacking into the container is discretionary in a few models.

Fig: Tilting mixer

The drum is cone like or bowl molded with inner vanes and the release is fast and unsegregated so that these blenders are appropriate for blends of low workability and for those containing bigger size total. The drum hub normally remains at a point of 15 degree from level amid blending.

Non tilting drum:

A non-tilting drum blender is one in which the hub of the blender is constantly even, and release happens by embedding’s a chute into the drum or by turning around the heading of revolution of drum. As a result of moderate rate of release, some isolation may happen. There are two openings, one at each end of the drum: one for bolstering the fixings, the other for releasing the blend.

Fig: Non- tilting mixer

 REVERSIBLE MIXERS:

The reversible drum blender is like the non-tilting blender aside from that a similar opening is utilized to add the constituents and to release the total. The drum on a reversible blender has one flat pivot around which it turns. In blending position, the drum pivots in one course; while for releasing, the revolution is turned around.

Usually self-stacking, reversible blenders are moderate size to extensive size units mounted on a two-or four-wheeled trailer for transportation between locales. The blender is furnished with a tilting container like that incidentally found on a tilting blender, or with a derrick like container that climbs and down on a short slanted arrangement of rails and that dumps the fixings through a base opening into the drum. An implicit mechanical skip to encourage total stacking into the container is discretionary on many models. Most models of this blender sort are furnished with a water tank and meter, and alternatively (the bigger models) with an inherent totals batcher.

Fig: Reversible mixer

 

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