Title: Alkali-Silica Reaction as Cause of Distress in Concrete Pavements Made from Purported Alkali-Carbonate Reaction Aggregate
Author(s): Mengesha A. Beyene and Richard C. Meininger
Publication: Materials Journal
Appears on pages(s): 67-82
Keywords: alkali-carbonate reaction (ACR); alkali-silica reaction (ASR); cryptocrystalline quartz; dedolomitization; microcrystalline quartz; polarized light microscopy (PLM); scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS)
The mechanism of alkali-carbonate reaction (ACR) is still controversial. ACR distress in concrete has been described as an increase in volume caused by the crystallization of brucite following dedolomitization. In this study, the cause of concrete distress in reported ACR-damaged concrete pavements was investigated, and it was determined that alkali-silica reaction (ASR) was the cause of the damage. Optical microscopy and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) analyses identified ASR gel extending from reactive aggregates into the paste, X-ray elemental mapping confirmed the composition of the gel, and EDS determined the amount of each element in the ASR gel spectra. Silica in the form of cryptocrystalline-microcrystalline quartz was found in the matrix of reactive aggregates and was the source of reactive silica. The test results confirmed that ASR caused the damage to the primary concrete pavements and present the first case ever reported in the United States in which ASR is the main cause of concrete damage in concrete made from carbonate aggregate exhibiting a classic texture and composition cited for ACR.