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When
concrete has been vacuum dewatered, the power floating with
disc is started immediately after the removal of the suction
mat. As, at this stage, the concrete has not yet hardened, an
after-mixing of cement and sand particles takes place, which
essentially increase the wear resistance of a floor. An
improvement of the wear resistance up to 2-3 times can be
achieved through floating and repeated power trowelling.
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A
vacuum treated concrete slab shows no curling because
shrinkage will be lowest on the top part of the slab where the
water/cement ratio is lowest. Therefore, the edges will remain
in the correct position when the concrete hardens.
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The
figure clearly shows that vacuum processing improves
compressive strength and how vacuum affects the top and bottom
part of the slab respectively. Note that already after 7 days,
the compressive strength of vacuum dewatered concrete after 28
days. The final strength values for a vacuum dewatered slab is
on the top surface i.e. the part of the floor that will be
subjected to greater stresses.
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