Determination of the Existence and/or Extent of Alkali-Silica Reaction in MDOTStructures

摘要

Alkali-silica reaction (ASR) is a deleterious chemical reaction in concretebetween active silica constituents of the aggregate and potassium and sodium alkalis in the concrete. Most of these alkalies are usually from the cement. Until recently alkali-silica reaction was not considered a significant problem for concrete roads and bridges in Maine. However, during the last few years crack growth in the surface of the portland cement concrete pavement on I-95 between Gardiner and Topsham and map cracking in the substructures of several Maine bridges has increased concern about the existence and extent of ASR in Maine leading to the present study. The objectives of the study were to: Make a preliminary determination of the extent and severity of ASR in the concrete structures of Maine's highway system; Determine what corrective actions, if any, may be feasible for existing structures; Suggest cost effective preventive actions for reducing ASR damage to future MDOT concrete structures. Approximately 38 test samples were taken from 25 bridges from South Portland to near Fort Kent. Thirty five additional bridges not known to have map cracking were also visited and inspected. Four cores were obtained from the concrete pavement on I-95.