Sunday, May 8, 2011

Adding super-plasticizers to concrete

Plasticizers and super-plasticizers are sometimes added to concrete mix. Why is this done?

Concrete is a mixture of aggregate (rocks), sand, Portland cement, and water. Water combines with cement to form hydration products, which glue the mix together.

Portland cement has an electrostatic attraction to itself. It tends to stick or clump together when water is added. If cement is not dispersed in the concrete mix, but is stuck together in balls and clumps, then the concrete will be weakened. It is important to evenly disperse the cement for a mix to approach its potential strength.

Plasticizers (often called super-plasticizers) are chemical admixtures which cut the electrostatic attraction in cement . This allows the cement to become more evenly dispersed in the concrete mix, and creates a stronger concrete as a result.

Another significant benefit to using a super-plasticizer is the increased workability of the concrete. The mix doesn’t stick together so much; it is more fluid and liquid, without adding more water (too much water weakens concrete substantially).  Superplasticizers make the work of screeding and floating the poured concrete much easier, without using too much water.

Super-plasticizers are relatively inexpensive, and contribute significantly toward making better concrete.





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  2. Thank you for a down to earth explaination