FIELD STUDY OF REPAIR METHODS FOR TRANSVERSAL CRACKS

摘要

Transversal thermal cracks are a difficult problem on Finnish roads. Those cracks occur especially on minor roads but also the heavily used roads suffer from transversal thermal cracks. Traditionally hot bitumen has served as a repair method. Unfortunately it has happened very often, that transversal cracks occur exactly on the same place during the following spring. Even if a whole new asphalt layer has been laid on the road, there have been as many cracks after maybe just two years. In July 2000 a field test was performed. On the main road 1 altogether 49 transversal cracks were repaired by eight different methods and the location of every crack was determined carefully. Four of the methods were based on fibre grids and the other four were more traditional methods. After the repair work a new SMA layer was laid on the road. The following spring 2001 the test area was examined. The main result: not even one of the cracks repaired with grids had occurred again. Traditional methods had not been as successful; some cracks were already visible. After two winters in spring 2002 the difference with grids and traditional methods was even bigger. Then it seemed as if there is a difference also whether the grid has been laid straight on heated remixed surface or on a "milled box". The spring 2003 showed the final order of the tested repair methods. It seems that the best method to prevent transversal cracks is to lay a grid on a "milled box".