| |
Some years ago, the cracking of concrete bridge abutments in Peoria, Illinois was shown to be caused by alkali-silica reaction (ASR), with the essential component for this reaction being chert in the sand. Alkali (from the Portland cement) and reactive silica (from the aggregate) can result in an expansive product that causes cracking in concrete under specific temperature and humidity conditions. Chert is a rock composed of microcrystalline quartz (quartz being a mineral composed of silicon and oxygen).
This instance was the first reported of ASR in concrete pavement in Illinois. Subsequent studies were performed on sands from around Illinois, and these studies showed additional instances of deterioration due to ASR. The studies also showed that several sands exhibit excessive expansion in standard laboratory tests, and that chert is a common constituent.
To continue the investigation of ASR issues, ICT has performed research on several specific cases of concrete deterioration. This research has broadly involved microstructural, chemical, and physical testing of concrete and concrete materials. ICT’s research has included investigating pavement expansion and cracking caused by ASR, a much less common reaction that had not previously been implicated in concrete deterioration in Illinois, as well as work to better understand the ASR of chert.
|