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<p>The best designed Concrete does not segregate during standard operations of placing it. Poorly designed mix segregates even in Std. operations. Mix should be cohesive, with minimum voids & maximum density. Water Cement ratio plays vital role in controlling segregation. No doubt, we all know that increase in W/c ratio directly impacts the strength. The best designed mix represents well graded mix contents to the strength requirement.</p>
Segregation in concrete is commonly thought as separation of some size groups of aggregates from cement mortar in isolated locations with corresponding deficiencies of these materials in other locations. Segregation results in proportions of the laid concrete being in variation to those as designed. Segregation could result from internal factors such as concrete that is not proportioned properly and not mixed adequately, or too workable a mix. It also could result from external factors such as too much vibration improper transportation, placement, or adverse weather conditions. The corresponding increase in proportion of cementpaste in upper areas would tend to make them susceptible to increased shrinkage and formation of cracks. We can avoid happening of segregation by:
1- The concrete mix should be properly designed with optimum quantity of water to make a cohesive mix. Such concrete will not exhibit any tendency for segregation.
2-Field quality control must be maintained while handling, transporting, placing & compacting and finishing concrete.
3-If at any stage segregation is observed, then remixing should be done to make the concrete again homogeneous.
4-Admixtures, such as pozzolanic materials or air entraining agent should be used to avoid segregation. Air entrainment permits a reduction of the mixing water with no loss of slump which increases workability and decreases segregation and bleeding.
5-Concrete should not be allowed to fall from greater heights. It should be placed as near its final position as possible.
Segregaation is the separation of different components of concrete. It can be controlled by adding admixtures, and keeping the mixer revolving during the transportation. Also concrete shouldn't be pored from too much hieght.
Segregation is the seperation of aggregates from the cement matrix. When the concrete is poured freely from a height more than 1 m, the aggregates will be thrown seperately first and the cement matrix will follw them and accumulated at the top.
To avoid segregation:
1. Mix should not be allowed to fall free from heights.
2. remixing at the sites
3. Choosing proper size of aggregates and aggregate to cement ratio.
4. Applying Viscosity Modifying Admixtures which will give cohesiveness to the mix.
Segregation is the separation of the aggregates. Transport in the correct transportation the shortest route possible. Mixing in pan or drum mixer required time. Placing never let the concrete find its way, place it were its required (shute, funnel, trunk) Vibrating first is it a wall, slab, foundation very important to determin the diameter of poker. when vibrating poker fast in slow out to release the air .Mix design cement water ration, slamps and cubes for lab tests to confirm.
Separation of courser part from the entire mass of concrete in plastic state &
seperation of grout from the mix is called segregation in concrete.
poor designs tends to segregate most often and well designed concrete segregates some time as well.
the most common reasons which i have witnessed in my career was segregation in the Bins during loading, load cell errors. excesssive water addition and over dosed superplasticizer.
increase the amount of fine aggregate in mix will reduce the chances of segregation.
To avoid above 1.5mtr height on pouring the concrete , and more water not use in concrete mix.
Field quality control must be maintained while handling, transporting, placing & compacting and finishing concrete.
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