CONCRETE DESIGN

True to its name of the “Great Northern CONCRETE Toboggan Race”, it is specified that any running surface of the toboggan in contact with the ground must be constructed out of concrete. This adds complexity to the design and overall construction of the toboggan for the team but creates a great opportunity to push creativity and explore the limits of various concrete mixtures.

As the competition has evolved over the years, a larger emphasis has been placed on creating thinner and lighter skis (commonly referred to as runners) to enhance the toboggan’s performance down the hill. The runner’s concrete mix can contain many different aggregates, each of which produces varying qualities in the cured structure. There are major constraints that the concrete design must adhere to, which include:

• -50% of the cementitious materials in the composition must be Portland cement

• The design must meet a compressive strength established by the organizing committee of the competition (typically >20 MPa)

• The only permissible surface additive to the runners can be ski wax.

This leaves much of the design of the concrete running surface open to interpretation, including reinforcement techniques, mounting mechanisms to the superstructure, and the overall geometry the runners will take. At the competition, the ideal mix is deemed to be the one that features the highest strength/weight ratio and achieves this in a creative way. Aspects of creativity are rewarded in the judgment of the concrete mixture design, theme incorporation, and reinforcement structure and materials. All mixtures and runners are poured in-house at the team’s shop, and the development of these mixtures expands the team’s knowledge and provides hands-on experience when joining the GNCTR team at Guelph.

The team has an internal goal of sustainability in all aspects of the design and fabrication of the runners.