Construction of Durable Longitudinal Joints – The Courage to Use Innovations Pays Off

Poorly constructed longitudinal joints will likely lead to joint opening, cracking and ravelling. There are a number of factors that should be considered for cold joint construction that may impact its durability. They include the shape of the unsupported edge, the amount of overlap, the method of raking and compaction of the mix at the joint. However, the best way of avoiding future issues with cold joints is to eliminate them by using hot joints. The City of Hamilton has decided to use innovative paving technology to address the joint quality issues. Wherever possible, the City uses hot joints by specifying echelon paving. When feasible, particularly on major paving projects, the City requires the use of Shuttle Buggy® materials transfer vehicle (MTV) in order to eliminate thermal and gradation segregation. Wherever the use of echelon paving is not practical, the City has started using infrared joint heaters. Quality assurance testing results clearly indicate that the compaction achieved at these joints is the same or very close to the compaction in the middle of the mat. Also, the new warm asphalt technology is now being implemented by the City. Lowering the mix temperature results in reduced aging of asphalt binder, reduced fumes and odours and other environmental benefits. An ongoing study in the City shows that the quality of longitudinal joints in warm asphalt paving is better than in conventional HMA paving; the joints were tight and better compaction and lower permeability can be achieved. The Region of Waterloo has been paving rural projects in echelon also using a Shuttle Buggy® MTV since 2006. To date more than 50 projects have been placed using this method, none of which have required any centreline/longitudinal joint repairs. This paper describes practical aspects of the applied technology and shows photos of construction and the results obtained in the field. The results show that the courage to implement the innovative technology in joint construction pays off and the quality of longitudinal joints is significantly improved. This should reflect in better long term performance of asphalt pavements in the City of Hamilton and the Region of Waterloo.