Three Decades of Studying the Alkali Reactivity of Canadian Aggregates


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Title: Three Decades of Studying the Alkali Reactivity of Canadian Aggregates

Author(s): P. E. Grattan-BelRew and J. E. Gillott

Publication: Special Publication

Volume: 100


Appears on pages(s): 1365-1384

Keywords: aggregates; alkali-aggregate reactions; expansion; limestone; alkali-carbonate reactions; concrete durability; dolomite; petrography; reviews; siliceous aggregates; Materials Research

Date: 4/1/1987

Early studies of concrete durability problems resulting from expansive reactions between certain aggregates and cement alkalies implicated opal and other forms of poorly ordered silica as the reactive component in the aggregate. Later work showed that other types of rocks may expand in alkali and cause concrete durability problems as well. Glassy or poorly crystalline volcanic rocks, dolomitic limestones, greywackes, phyllites, and argillites are now recognized as potentially deleteriously reactive. Standard tests were developed that involve the measurement of length-change of mortar bars, concrete prisms, and rock cylinders held under constant temperature and humidity conditions. Other tests have been used in attempts to gain a better understanding of the expansive mechanisms. Petrographic studies were carried out from an early date; with the introduction of more sophisticated equipment such as the scanning electron microscope, x-ray diffraction, and differential thermal analysis, petrography now plays an increased role in this area of engineering geology.