Specifications for unbound granular base materials vary among transportation agencies based on
the availability of materials, climatic conditions, and function. Specifications aim to provide
durable materials that meet design requirements and achieve the target design life. This paper
compares Manitoba Infrastructure and Transportation (MIT) specifications for unbound granular
base materials with the specifications developed by selected Canadian provinces and
neighbouring States. This work is part of a research project to evaluate the effect of base material
gradation on performance and, if required, update current MIT specifications for unbound
granular base materials. The comparison showed that MIT specifications allow a higher
percentage of fines (particles passing sieve No. 200). MIT’s maximum particle size (19 mm) is
generally smaller than the maximum particle size in other specifications (25 to 37.5 mm).
The effect of the base material gradation and fines content on the stiffness and stability is being
evaluated in the laboratory. Results of laboratory tests will be used to update current
specifications, if required, and develop performance-based parameters for pavement design using
the Mechanistic-Empirical Pavement Design Guide (MEPDG).
