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Describe the concrete mix design concerns when a contractor elects to use a hydraulic pump to...

Describe the concrete mix design concerns when a contractor elects to use a hydraulic pump to place concrete

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Expert Solution

Concrete design concerns are :-

1) cement content : A high cement content greater than or equal to 460 kg/m3 and devoid of any admixture is difficult to pump due to increased friction between concrete and pipeline. Also low cement content in the range of 270 -320 kg/m3 presents difficulty in pumping due to possibility of segregation of concrete mix during pumping. So a proper cement content in range of 350 to 420 kg/m3 is advisable.

2) Maximum nominal size of coarse aggregates is limited to 1/3 and 2/5 of the inside diameter of hose pipe of pump for crushed and rounded aggregates respectively.

3) slump of pumpable concrete should be between 50 mm and 100 mm. Lower slump value have lower lubrication and hence difficulty in pumping and higher slump poses problems of segregation during pumping.

4) In designing the mix the water content of mix should not be increased significantly to improve slump. Rather use of admixtures to increase workability shall be made.

5) The aggregates should be well graded with all sizes present.

Ally Wells answered 1 year ago
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