Experience with Rubber Asphalt Concrete in Southern Saskatchewan

Manoj Jogi, MSc., P. Eng. Materials Engineer – Southern Region Ministry of Highways and Infrastructure Regina, Saskatchewan

Dennis Klimochko, P. Eng. Senior Surfacing Engineer Ministry of Highways and Infrastructure Regina, Saskatchewan

David Stearns, P. Eng. Preservation Engineer – Southern Region Ministry of Highways and Infrastructure Regina, Saskatchewan

Acknowledgements

Southern Region Construction, Saskatchewan Ministry of Highways and Infrastructure are gratefully acknowledged for their support.

ABSTRACT

Rubber asphalt concrete was used in Saskatchewan for the first time in 2005. This was considered as a very successful project by the Southern Region of Saskatchewan Ministry of Highways and Infrastructure (MHI) in terms of performance. In the following years, MHI constructed a total of 9 projects; in 2007 (3 projects including a thin lift overlay), 2008 (1 project) and 2009 (5 projects) in Southern Saskatchewan with rubberized asphalt. Two of these projects had issues in terms of performance which was attributed to a relatively poor quality construction and few other factors.

This paper describes all these projects in detail, their suitability from climate, aggregate resources, economics and overall performance to date perspective and various lessons learned from them so far. These projects are being continuously monitored to date. In addition to this, the paper describes the impact of construction practices and the resultant density and volumetrics on the performance of the rubber asphalt mat.

RÉSUMÉ

Le béton bitumineux au caoutchouc a été utilisé en Saskatchewan pour la première fois en 2005. Cela a été considéré par la région sud du Ministère des Routes et Infrastructures de la Saskatchewan (MRI) comme un projet très réussi en termes de performance. Au cours des années suivantes, le MRI a construit un total de 9 projets; en 2007 (3 projets incluant un recouvrement en couche mince), en 2008 (1 projet) et en 2009 (5 projets) dans le sud de la Saskatchewan avec des revêtements bitumineux au caoutchouc. Deux de ces projets ont eu des problèmes en termes de performance qui ont été attribués à la pauvre qualité de construction et à quelques autres facteurs.

Cet exposé décrit ces projets en détail, leur pertinence au climat, les ressources de granulats, l’économie et la perspective de performance en général à ce jour ainsi que les diverses leçons apprises de ces projets jusqu’à maintenant. Ces projets sont continuellement suivis jusqu’à ce jour. En outre, cet exposé décrit l’impact des pratiques de construction et la densité résultante ainsi que les volumétries sur la performance de la couche de revêtement bitumineux au caoutchouc.

1.0 INTRODUCTION

1.1 Background

The development of asphalt rubber material for use as joint sealer, patches and membranes began in early 1930’s [1]. A rubber modified asphalt mixture with granulated and graded crumb rubber was developed in Sweden in 1960’s. Charles H. McDonald of the City of Phoenix Arizona worked extensively with asphalt and rubber materials in the 1960s and 1970s and was instrumental in development of the “wet process” (also called the McDonald process) of producing asphalt rubber. In the United States, asphalt rubber usage can be found in the states of California, Arizona, Texas and Florida including various other states and counties that did rubber projects on trial and regular basis. Some Canadian provinces including Alberta have tried asphalt rubber in various forms with mixed results. Rubber asphalt concrete is not extensively used in cold climate regions of Canada. Saskatchewan Ministry of Highways and Infrastructure (MHI) began using rubber concrete since 2005 with first project on Highway 11. The first project had a good success and MHI started using rubber asphalt concrete at other major highways in the subsequent years.

1.2 Advantages of Rubber Asphalt Concrete

The following advantages were kept in mind when making use of rubber asphalt concrete in Saskatchewan after the first project.

 Making use of the recycled scrap tires that otherwise would be landfilled.

 Reduction of pavement-tire noise and better skid resistance.

 Resistance to pavement cracking and better resistance to asphalt oxidation due to blending of rubber with asphalt binder. Further, rubber asphalt concrete has better rut resistance. The ductility of rubber asphalt binder is only 14 to 17 cm as compared to 85 to 100 cm for conventional Asphalt Concrete (AC) binder.

 Reduction in the thickness of AC required for the same amount of traffic and granular thickness based on superior performance of rubber AC.

 Southwest Saskatchewan has gravel predominantly in the cobble form. These cobble stone pits are very well suited for production of rubber asphalt concrete that does not require any natural fines.

 By using cobble stone pits, the haul and other related expenses are minimized.

2.0 MINISTRY PROJECTS

2.1 Overview

Saskatchewan’s first rubber asphalt concrete project was constructed on Highway 11 (CS 11-04) from Findlater to Chamberlain in 2005. This is one of the busiest roads in Saskatchewan. This project was considered as a successful project. Based on the success of this project, more projects were planned to be constructed with rubber asphalt concrete. Figure 1 shows the locations of various rubber asphalt concrete projects in southern Saskatchewan.