A new performance test for evaluating the ASR potential of job mixtures

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University of New Brunswick


Alkali-silica reaction (ASR) is a problem that plagues many concrete structures worldwide, from dams to residential structures. At the moment, standardized are testing methodologies encounter problems such as leaching of alkalis, extensive testing time, or the inability to test “job-mixtures”. The University of New Brunswick concrete cylinder test (UNBCCT) was developed to overcome such difficulties through the storage of concrete samples in alkali host solutions designed to negate leaching, increase the storage temperature to accelerate the reaction, and the use of job mixture designs. With these modifications, cylinders were cast with various aggregate and cementitious material combinations (100% portland cement, and combinations of cement and SCMs such as fly ash, ground granulated blast furnace slag, and silica fume) to the dimensions of 145 mm in diameter by 285 mm in height. The cylinders were stored in containers (150mm by 300 mm in height) filled with a host solution matching the alkalinity of the concrete pore-solution. The samples were then stored in either 38°C or 60°C to determine if an accelerated version of the test was plausible. The resulting expansion was periodically measured and compared to other test methods such as the concrete prism test (CPT) and long-term exposure blocks. Alkali-leaching occurrence was also investigated through the casting of non-reactive limestone samples. These samples were periodically tested for alkali contents in a profile from the center to the surface. These profiles were generated by dissolving milled powder via hydrochloric acid or water, and measuring alkalis by inductively coupled plasma mass spectrometry (ICP-MS). Testing was also conducted on pore-solution extracted from the concrete and the host solution. The results to date indicate that the storage conditions used in the UNBCCT minimize the reduction or enrichment of alkalis in the test specimen, and that the expansion results compare well with the behavior of long-term exposure blocks. The test appears to have promise as a performance test for “job mixtures”, although further studies are required with a wider range of mixes.