Vacuum Dewatered Concrete
It has been repeatedly emphasized that the adoption of a lower water-cement ratio yields improving the quality of concrete, but satisfactory workability is essential to the need to put concrete.
One solution to this problem is the use of a superplasticizer and the other solution is to incorporate vacuum dehydration of the concrete.
Lastly around the ten-year vacuum dehydration technique is widely used in factory construction floors.
Techniques for DCM Devo construction have been adopted in a big way motors in Delhi, whirlpool factory construction near Pune, Tata Cummins in Jamshedpur, Fiat Ltd., etc. on hundreds of other factory floors.
The process is equipment-based. It needs formwork in the form of channels, internal vibrators, double Beam Screed Board Vibrator, Bull Float, Filter Pads, Full width for Vacuum pump, Disk Floater and Power Trowel.
First, concrete with relatively high w / c to facilitate complete contraction with needle vibrator is poured.
The concrete is then further compressed through a double beam screed vibrator. It does surface smooth.
The filter mat is placed and it is pressed on all four sides and effectively sealed. In about 30 minutes, the vacuum pump is started, which absorbs the unwanted water, from concrete, which can be called “water of viability” and is disposed of.
The vacuum pump is run for about 20 to 30 minutes depending upon the thickness of the concrete floor. Vacuum dewatered concrete becomes stiff and walkable.
The top surface may undergo a depression of about 3 %, with a loss of about 20% of original water. Then the concrete is skim floated and further power trawled and finished. Often surface hardeners are used in conjunction with the dewatering process.
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After vacuum dewatering, it gives the ideal condition for the application of surface hardeners in powder form. With the combined effect of Vacuum dehydrated concrete becoming hard and mobile, a very good abrasion-resistant factory floor may be constructed.
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The application of disc float and power trowelling may act like revibrating of concrete to eliminate or segment the continuous capillaries or channels formed in the suction of water.
As the effective w/c is comparatively lower at the top surface, the quality of concrete concerning strength and abrasion resistance will be better.
Also read: Lightweight concrete
Fig shows the result of the test carried out at the Cement and Concrete Institute, Stockholm, Sweeden, which is the supplier of vacuum dewatering equipment by the trade name “Tre mix”.