Concrete Plastic
Plasticizers are concrete products for public facilities Readymix. They are widely used throughout the world and yet they are number 1 adjuvant / Additive as far as it concerns global consumption.
Other names used in this class of additives are:
– Normal water reducer
– Water reduction additives / adjuvants
– Etc normal Plasticizers
Plasticizers are mainly based on lignosulfonates. Lignosulphonates or sulfonated lignins are – products of the paper industry, recovery of liquid pulp.
Lignosulfonates are usually modified with special polymers to control the main air intake and configuration time, or improve or adjust other parameters.
Other chemicals used are hydroxy salts.
Plasticizers are considered reductions of giving water to the region of 10%. A little more or a little less.
The usual dose is from 0.25 to 0.8% by weight of cement.
Example: a mixture of 350 kg of concrete can accept cement/m3 a certain amount of plasticizer from 0.25 x 350/100 and 0.8×350/100 kg/m3 or 0.875 to 2.8 kg / m 3.
Doses are more frequent in the range of 0.3-0.4% by weight of cement.
For each separate project, the testing of products should be saved in the search for a combination optimal.
How does PLASTICIZERS?
Cement particles tend to flocculate and the role of water, reduction of plasticizers is to induce deflocculation.
This is achieved by adsorption active ingredients in the cement particles. Thus, they neutralize the surface charges on its surface, and cement flakes disintegrate.
For example, water that has been locked in cement flocs is published and used to reduce the viscosity of the mixture.
WHY ARE plasticizers used?
Plasticizers are used for the following reasons:
1. To reduce the moisture content of concrete on + / – 10%. That they obtain dispersion and virtually no deterioration of the crisis.
The reduction of water will increase in assets.
2. To increase depression / viability without changing the O / C. This facilitate the establishment of concrete.
3. To reach a compromise between the above.
4. To achieve savings in the composition of mixtures, reducing the cement content without compromising end strength.
DELAY
Most water reducers / plasticisers have a delayed effect on the setting time of concrete. This is more pronounced when:
– The rates are higher than those recommended by overdose ()
– The temperatures are lower
– The summary contains polysaccharides.
Overdose
Overdose will lead to developmental delays.
In severe overdose cases – double the amount or more – new adjustment measures should be taken to prevent excessive drying of the concrete surface.
CONCRETE RESISTANCE
When plasticizers are used as water reducers, an increase of about 7-10% of the compressive strength 28 days can be expected.
Typically, the initial resistance, depend on the reduction of water.
Reduce / CONSISTENCY
The ability of concrete to flow is called the coherence and Sag is a measure of consistency. If the ratio E / C remains unchanged, the addition of a plasticizer will increase the concrete consistency and depression.
To slow the loss of fall, the initial coherence must be increased.
AIR DRIVE
Water reduction based on lignosulfonates plasticizers tend to induce some air drag on a contract with hydroxy salts.
GENERAL RESISTANCE
The W / C reduces the durability of concrete is generally higher.
Chris Strogili
Civ Eng – MBA – DIPM
http://maconwaterproofing.blogspot.com
About the Author:
Civil engineer with postgraduate studies in MBA and Marketing
Article Source: ArticlesBase.com – Concrete admixtures/additives:water reducers
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