THE ALKALI-AGGREGATE REACTION QUANTITATIVE ASPECTS

Analytical quantification of the alkali-aggregate reaction is made difficult by the fact that it involves basically a partial "solubilization" of the silica in the aggregates. This difficulty can be eliminated by thermogravimetry, using the derivative curve, because this makes it possible by cascade to use lime to determine the cement. The excess of "soluble silica" (or even other oxides), which represents the share of the aggregates participating in the reaction, can in this way be determined in nitric acid. A calculation protocol has been developed and validated. The results obtained on structures affected by AAR show that the silica mobilized ranges from 0.2 to 1% of the mass of the concrete, depending on the severity of the phenomenon, and that it is almost always accompanied by alumina and ferric oxide. (A) For the covering abstract see IRRD 871351.