Title:
Optimized Gel Pat Test for Detection of Alkali-Reactive Aggregates
Author(s):
Victor Lanza and Pilar Alaejos
Publication:
Materials Journal
Volume:
109
Issue:
4
Appears on pages(s):
403-412
Keywords:
aggregate; alkali-aggregate reaction; durability; petrography; scanning electron microscopy.
DOI:
10.14359/51683915
Date:
7/1/2012
Abstract:
In this research, the Standard Gel Pat Test (BS 7943) was optimized to detect the presence of microcrystalline, cryptocrystalline, and highly strained and microcracked quartz in just 3 days. The effectiveness of the standard test was improved by means of raising the storage temperature to 176°F (80°C) to accelerate the chemical reactions and also to cast a “pat” sample with many voids among the aggregate particles to facilitate the accumulation of gels inside. At the end of the third day, if the aggregates are reactive, gels appear on the surface of the pat and into the voids. It is also possible to differentiate between slow and fast reactive aggregates after a visual inspection of gel growth. Finally, reactive particles can be selected and easily removed from the pat specimen for petrographic analysis to find and identify the reactive component of the aggregate.