Què és un reductor d'aigua de formigó?

Quan es tracta de formigó, tots sabem que l'aigua és important per crear una barreja viable. Però, sometimes the mix needs to be workable with less water than what is required by a standard concrete mix design in order to meet specifications or for specific project requirements like pouring tall columns. Aquí és on concrete water reducer (also known as plasticizer) can help.

Water reducers are a group of chemicals that are added to concrete mixtures to allow the use of a lower water to cement ratio without adversely affecting strength and finishability. They are used in a wide variety of construction applications including mass concrete, prestressing steel and bridge decks.

Conventional water-reducing admixtures are low-range products that are typically made of lignosulfonates, hydroxycarboxylic acids or carbohydrates. They are usually able to reduce the concrete’s water content by 5 a 10% for a slump range of 3-to-6 inches and must comply with ASTM C494 Type A (additius reductors d'aigua).

High-range water reducing admixtures, també anomenats superplastificants, are able to increase a concrete’s slump from 5-to-8 inches and must meet ASTMC Specification C494 Type F (high-range water reducing admixtures). This group is often used in specialty projects like deep foundations or precast elements where a higher slump is required.

The main way that these admixtures work is through electrostatic repulsion. When concrete mixes come into contact with water, the dissimilar electrical charges on the cement particles attract each other causing them to agglomerate or clump together. Water reducers essentially neutralize these charges so that all the cement particles have the same charge and then repel each other, which allows them to be better dispersed throughout the concrete. This prevents agglomeration and increases the concrete’s flowability or slump.