Field studies of fly ash concrete structures containing reactive aggregates

The paper presents the, findings, from field studies of fly ash concrete structures containing reactive (alkali-silica) aggregates. Data is presented from a number of hydraulic structures in Wales and Ontario constructed using geologically similar greywacke-argillite aggregates. All the structures without ash showed evidence of damage due to ASR: indeed reaction with this aggregate has led to replacement of structures in both areas. Reaction may occur at alkali levels significantly below 3 kg/m3 Na2Oe, and has been, found in a structure with a measured [available] alkali content of less than 25 kg/m3 Na20e, However; the, fly ash concrete structures are in excellent condition after more than 25 years service despite having higher alkali contents than many of the damaged structures; the Lower Notch Dam was actually constructed using a high alkali cement (> 1·0% Na20e). Microstructural and pore solution analysis showed that much of the alkali in the fly ash concrete was [bound] in the CSII and not available ...