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OCR for page 44
44
CHAPTER SIX
CONCLUSIONS, GAPS, AND RESEARCH NEEDS
CONCLUSIONS likely influence the success or failure of recycling
projects.
The following conclusions can be drawn from the informa- · Additives and stabilizers need to be selected on the
tion presented in this synthesis. basis of their ability to improve key material and mix
properties or facilitate construction processes.
Project selection:
Quality management program:
· The type, severity, and extent of distresses are used to
identify the most useful in-place recycling method. · Contractor quality control programs include field tech-
· Both the distresses and recycling process will help nician training; validation of mix design properties,
define the depth of the milling to be used. State agen- material properties, and density; and documentation of
cies and contractors use the Asphalt Recycling and application rates.
Reclaiming Association (ARRA)-recommended range · Quality control/quality assurance programs include
of full-depth reclamation (FDR) recycling depths measurements of density, moisture content, recycling
greater than 6 in. The actual depth of recycling is proj- layer depth, verification of material properties, and
ect specific. performance-related mix testing.
· Agencies appear to underutilize FDR on thinner pave-
ments (2 to 4 in.). Specifications:
· Roadway geometry and features need to be considered
during project selection. · Method specifications are commonly used by agencies
· Climate conditions need to be considered during proj- for in-place recycling projects. However, agencies also
ect selection. routinely require the contractor to select additives and
provide mix designs for in-place recycling projects,
Structural design: which suggests that end result or short-term perfor-
mance specifications may be more appropriate types
· Structural design parameters need to be assessed of specifications.
before construction so that the final product meets or · There is no consistent use of in-place recycling terms
exceeds the desired performance. or specification content.
Preconstruction testing: Benefits and barriers:
· The availability or collection of in-place material prop- · Contractor project records can be used to provide
erties information needs to be considered when devel- quantifiable environmental and cost benefits from in-
oping the project design, specifications, and agency place recycling.
estimates of project costs. · Cost savings can be realized when using in-place recy-
· Preconstruction testing is key to designing recycling cling processes.
mixes and identifying areas that may need an alterna- · The magnitude of the savings will be directly related to
tive design. The time needed for this testing as well as the appropriate choice of the surface treatment.
the costs to the project need to be considered in devel- · Limited guidance is available for use in life-cycle
oping cost estimates and project timelines. cost analyses or for the life expectancy of the recycled
roadway.
Materials for in-place recycling projects: · Both agencies and contractors identified the common
most frequently encountered barriers as
· Emulsions historically used in the same environmental Unsuccessful experiences,
conditions may have base asphalts with a wide range Competing industries, and
of performance-graded asphalt properties, which will Lack of specifications.
