INVESTIGATION OF POTENTIAL ALKALI-SILICA REACTIVITY OF AGGREGATE SOURCES IN THAILAND

Abstract

Since the first local evidence of alkali-silica reaction (ASR) was reported in Thailand in 2011,
awareness of ASR was raised and the importance of aggregate performance database was recognized, thus an
attempt to set up local aggregate database was initiated. As part of the effort to establish the database, a study
of potential ASR reactivities was carried out involving aggregates from several current industrial sources in
eastern and central Thailand and the results were presented here. Aggregate samples were randomly collected
from various sources and tested by two methods; accelerated mortar-bar test (AMBT) and petrographic
examination. The types of aggregate sampled included limestone, greywacke, and rhyolitic tuff. The AMBT
expansion results indicated that several aggregate types had larger expansion than the threshold of potentially
deleterious ASR behavior as suggested by ASTM C 1260 standard. Furthermore, it was found that samples of
same aggregate type, although apparently had mineralogically similar compositions, had different reactivities,
particularly when sampled from around geological fault zone compared with that taken from the surrounding
area and portions of parent rock were observed to be weathered in this area. Thin section analysis revealed
evidence of ASR gel at the aggregates’ rim, inside the aggregates and in the matrix. These findings suggest
possible future ASR problems in Thailand as well as in neighboring countries where the continuity of
geology pattern is observed.