Bleeding is also termed as water gain in concrete. The water leakage in concrete is a serious issue and it happens because of low specific gravity of water. The leakage water is preserved at the top surface of concrete. Bleeding is generally happened in poor proportioned, inappropriately mix and extremely wet concrete. In low depth members like slab and road pavement, surplus bleeding arises throughout scorching weather concreting.
It also happens that along with water some quantity of cement also emerges out of concrete to the surface. The development of cement paste is recognized as laitance. Laitance makes feeble surface over consolidated concrete member below and shrinks bond concerning new and concrete. It is occurred while casting of column starters over the slab. Laitance should be taken out by chipping of the skinny paste prior to initiate next layer of concrete.
Water emerging from the top throughout bleeding, creates continuous channels within the concrete. Concrete turns to be leaky because of these continuous channels.
How to get rid of bleeding in concrete?
- Applying air entraining agents.
- Employing delicately segregated pozzolanic materials.
- By means of accurately proportion, and identical assimilation of concrete.
How to obtain the percentage of bleeding in concrete
Take the container having fairly accurate 10 lit capability and containing inner diameter of 250 mm and height about 280 mm. Load the container with brand new concrete in five layers (50 mm depth). Each layer must be tamped with tamping rod.
Work out the weight of concrete sample.
weight of concrete = (weight of container filled with concrete – weight of empty container.
Getting the total water content in 1 m3 of concrete (apply mix design data), quantity of water in container is estimated.
The container is positioned on level surface with any vibration and wrap it by lid (keep temperature approx 27 degree +/- 2 degree). Water amassed at the top throughout bleeding is drained by pipette at 10 mins intermission for the first 40 mins and 30 mins subsequently unless and until bleeding controlled.
Collect the water drained through pipette in jar and compute the volume.
% of bleeding = (volume of drawn water / volume of water in concrete sample) X 100
Ref. : www.constructionblog.org
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Published By
Rajib Dey
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