Figure 4. Cumulative risk profiles for savings ($/yd2) resulting from the use of Alternate A vs Alternate B

Figure 6. Cumulative risk profiles for savings resulting from the use of asphalt rubber -
Maricopa County, AZ

 

  1. 2) Maricopa County. The results are the same as for Phoenix including the comparisons of alternates A vs C (high and low traffic).
  2. 3) California Counties and Cities. Only two applications did not exceed 50%, E vs F for San Diego County and K vs L for Mission Viejo.

Again, it must be stressed that all of the results presented are based on the input collected from the interviews. Different outcomes would result if the estimated lives or costs were changed.

Guidelines for use
Asphalt rubber is cost effective for most of the scenarios presented in this paper. LCCA should be used to evaluate alternate maintenance and rehabilitation strategies to answer the following questions:

  1. 1) Where to use asphalt rubber? Can asphalt rubber be used on the existing pavement types (HMA, PCC) and in the environmental conditions present at the site? Based on the results of this study, the use of asphalt rubber products is a cost effective solution in most of the scenarios evaluated.
  2. 2) What asphalt rubber products to use? Both AR hot-mix and/or chip seals proved to be cost effective for the intended applications. Allowing a thickness reduction increases the cost effectiveness of asphalt rubber hot-mix applications.
  3. 3) When to use asphalt rubber? Historically, AR was often used on only the poorest pavements. The results of this study suggest they can be used for all pavement conditions but are primarily most cost effective when reflection cracking is expected (8).
  4. 4) What is the user cost impact? Is it significantly different between the scenarios investigated? The differences in user costs between the conventional and AR alternates was not great. This is likely due to the fact that the user costs employed were related to low to medium volume traffic conditions. For high volume urban facilities, the differences in user costs would likely be greater.

It should be emphasized that asphalt rubber binders will not be cost effective unless the thickness of the layer is reduced or extended life is achieved.