Determining the Most Effective Aggregate Base for Reducing the Expansion and Contraction of Asphalt Pavement
Water drainage is one of the most critical factors when considering what aggregate base (or subgrade) to use for road design. The purpose of this experiment was to determine which of the three materials, sand, gravel, or marble rock, resulted in the smallest average expansion and contraction. The goal of these trials was to determine a aggregate base material suitable for use in climates that experience fluctuations in temperature, thus reducing road repair costs and increasing road safety.
This research focused specifically on the density of each particle size. Based on prior research, it was hypothesized that the marble rock would maintain the smallest average expansion and contraction. Because of its larger, coarser pieces of rock, it is less densely packed in comparison to the other aggregate bases tested. Therefore, water is more thoroughly drained from the pavement surface down to the sand subbase.
To test the hypothesis, the three aggregate bases were separated into one baking tin, with thirty trials in all. Each section of the baking tin simulated road construction; on the bottom was a layer of sand with the aggregate base above, and a layer of asphalt patch was pressed on top of the subgrade. The wetted tins were placed in a freezer for twenty-four hour cycles and were set to thaw for another twenty-four hours for ten consecutive days. The tins were measured from the top of the asphalt to the edge of the tin, and the change in height was found. A descriptive analysis concluded that marble rock resulted in the smallest average change in height, followed by gravel, then sand, supporting the hypothesis that it is the most effective material for water drainage because of larger particle size.
Research Conducted By:
Knicko Mojica
Warren Mott High School
Madeleine Munoz
Warren Mott High School
Warren Consolidated Schools