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|Title:||Methods for controlling effects of alkali-silica reaction in concrete|
|Authors:||Buck, Alan D.|
|Publisher:||Structures Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Technical report (U.S. Army Engineer Waterways Experiment Station) ; SL-87-6.|
Abstract: This research project concerned methods of minimizing the effects of alkali-silica reaction in concrete. Ten pozzolans were tested to determine how they could most effectively be used to maximize reduction of expansion due to alkali-silica reaction when the pessimum amounts of opal or of reactive glassy igneous rock were used as aggregate with cements of several levels of alkali content, Three of these pozzolans (fly ash AD-505, fly ash AD-509, and natural pozzolan AD-518) were selected for further work and were used at selected levels of cement replacement with pessimum amounts of opal, glassy igneous rock, and an estimated pessimum for chert with each of two high-alkali cements. In general, use of these pozzolans at their optimum levels was an effective procedure as expansions of several tenths of a percent were usually reduced to a few hundredths. It was also found that some fly ashes when us ed at about 30 percent cement replacement level actually caused more expansion, especially with low-alkali cement. This is believed to be due to the additional water-soluble alkali provided by the fly ash to the system. Work was done with different mineral fractions of a reactive granite gneiss plus the whole rock to identify the reactive constituent; it was concluded that the reactivity of the granite gneiss was due to strained quartz as a constituent mineral. Work with combinations of silica fume and calcium hydroxide with water showed the reactivity of the fume and identified a well crystallized calcium silicate (CSH-I) as the reaction product.
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