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S/EN/17. An investigation into the causes, effects and subsequent steps required to inhibit the alkali silica reaction in concrete

WORDS:

1800

DATE:

2003

PRICE:

19.99 GBP

The alkali silica reaction that so often occurs in concrete is a heterogeneous chemical reaction between the alkaline content of the cement and/or water and whatever siliceous aggregates are in the overall mix. Conditions not only require silica and high alkalinity present, but also hydroxyl ions. Hydroxyl ions penetrate the surface of the aggregate and in doing so free silicon molecules by breaking silica ? oxygen bonds. The aggregates with high siliceous content will, when placed in an alkaline solution of around 0.60 % or above, and in the presence of water and hydroxyl ions form into a gel like substance. Due to the influx of negative hydroxyl ions, positive sodium, potassium and calcium ions also join the site to maintain electro neutrality. This report investigates this phenomenon and gives methods of prevention, examples are given.

KEYWORDS: en, investigation, causes, effects, subsequent, steps, required, inhibit, alkali, silica, reaction, concrete,