PIARC INTERNATIONAL WINTER ROAD CONGRESS：Topic 8 – Road Bridges in Winter Conditions

摘要

Many highway bridges in Denmark were constructed during the period from 1960 to 1980. Most of the bridges were built from reinforced concrete, often using aggregate sensitive to alkali-silica reactions (ASR).rnThe use of de-icing salts in Denmark (Area 43.000 km2) is approximately 300.000 ton per year. The average temperature is close to 0℃ in December, January and February thus leading to many days with frost and a heavy usage of de-icing salts.rnThis paper presents cases where reinforced concrete (RC) and post-tensioned bridges have undergone major rehabilitation in order to halt the deterioration primarily caused by de-icing salts. The de-icing salts have a major impact of the durability of a bridge deck due to the following mechanisms:rn1. High chlorides content leads to corrosion of the reinforcement.rn2. The de-icing salts usually consist of NaCl. The Na will provide additional alkali that can speed up ASR if the concrete can develop ASR.rn3. The cracks formed by the ASR will allow additional water ingress that will reinforce the chloride impact and subsequently the deterioration of the structure.rnThis paper will demonstrate how a complete rehabilitation of bridge decks subjected to de-icing salts can be undertaken. The rehabilitation methods can in many cases be combined with strengthening with respect to moment and/or shear capacity in a cost-efficient way.