2016 Volume 72 Issue 3 Pages 214-233
The causes of deterioration observed in the concrete elements of two removed highway bridges were examined. One is decks taken from a 75-year-old reinforced concrete bridge showing numerous horizontal cracks. The other is an element cut out from the pier of a 47-year-old bridge, of which cracks and spalling along a water leakage from expansion joints were found on the side. The splitting of coarse aggregates was remarkably found along the cracks in both the elements. In each the concrete element, gravel containing reactive aggregates was used, and the several signs of alkali silica reaction (ASR) were recognized. In addition, since the bridges suffered from repeated freezing and thawing cycles and deicing salt used in winter, the effects of frost-induced deterioration were examined. From the results, it was found that the cracks and the necessary conditions for cracking were similar to those as exhibited in the initial symptom of D-cracking shown around joints in concrete pavements, so that the potential causes of the cracks might contain not only the ASR but also the splitting of the coarse aggregates due to the freeze-thaw action.