Many public transportation agencies are in the
process of implementing some type of performance specifications for asphalt mix
and concrete. Reasons for doing so include a desire to improve long-term
durability, encourage contractor innovation, better align design requirements
with construction, and to have rational pay adjustments tied to predicted
Ongoing initiatives such as balanced mix
designs for asphalt mixes and performance engineered concrete mixes lend
themselves to a performance specification approach by introducing higher level
test methods that are intended to be more directly related to material
performance than current methods. Introduction of these test methods and mix
design criteria will have a major impact on existing quality assurance
programs. Agencies will need to make informed decisions regarding applicability
of new tests to process control, quality control, and/or acceptance. Lot and
sublot sizes may need to be adjusted to account for test time and complexity. Quantity
of material obtained for testing may need to be increased. Technician training
and certification programs will need to be addressed, as will laboratory
qualification/accreditation programs. Independent assurance procedures will
need to be developed, and the impact on dispute resolution programs must be
assessed. Precision and bias of the newer test methods will need to be
determined, along with appropriate specification limits for various quality
characteristics. New approaches to pay adjustments will need to be developed.
Agencies will benefit from a performance
specification implementation guide for asphalt and concrete. The transition
from current QA practices which often rely on properties such as aggregate
gradation or mixture volumetrics to performance-related criteria will be
challenging, and will introduce new risks for DOTs and contractors.
Understanding the impact on performance-related testing on the core elements of
quality assurance will help this transition to occur in a controlled fashion,
and could help minimize risk to both parties during the implementation process.
There have been
several recent studies related to this subject. NCHRP Synthesis “Performance
Specifications for Asphalt Mixtures” documents the current state of practice
with regards to performance tests used in conjunction with volumetric
properties for asphalt mixtures. One of the suggestions for future research
identified by the authors is “Guidance to agencies and contractors on how to
successfully implement the use of [Performance-Based Specifications] for
asphalt mixtures.” This proposed research would help achieve this goal.
The SHRP2 report “Strategies for Implementing Performance Specifications: Guide for
Executives and Project Managers” provides excellent guidance on high-level
implementation strategies considering organizational, cultural, legal, and
project delivery considerations. It identifies areas for agencies to consider
regarding sampling, testing, and acceptance/payment, but does not drill down to
provide guidance on these issues.
McCarthy, Leslie Myers; Callans, Jonathan;
Quigley, Robert; Scott III, Sidney V.: “Performance Specifications for Asphalt
Mixtures” - Transportation Research Board, NCHRP Synthesis 492, 2016.
Scott III, Sidney;
Konrath, Linda; Ferragut, Ted; Loulakis, Michael C.: “Strategies for
Implementing Performance Specifications: Guide for Executives and Project
Managers” - SHRP2 Report
Scott III, Sidney; Konrath, Linda; Ferragut,
Ted; Anderson, Stuart; Damnjanovic, Ivan; Huber, Gerald; Katsafansa, Jim;
McGhee, Kevin; Sprinkel, Michael; Ozyildirim, Celik; Diefenderfer, Brian;
Merritt, David; Dawood, Dan; Molenaar, Keith; Loulakis, Michael C; White,
David; Schaeffer, Vernon R.: “Performance Specifications for Rapid Highway
Renewal” - Transportation Research Board, SHRP2 Report S2-R07-RR-1, 2014.
Each of the studies
referenced below provide information regarding test methods, quality control
and acceptance procedures, and recommended specifications, but none of them
provide guidance on implementing performance specifications while considering
all the core elements of a quality assurance program.
Smith, D.; Lee, S.B.; Kazmierowski, T.:
“Development of Performance Specifications for Flexible Pavements in Ontario” -
Proceedings of the Sixtieth Annual Conference of the Canadian Technical Asphalt
Grobler, J.; Rebbechi, J.; Denneman, E.:
“National performance-based asphalt specification framework” - Austroads
Project APT1953, 2018.
“Report on Performance-Based Requirements for
Concrete” – American Concrete Institute, 2015.
Task 1 – Literature review.
Task 2 – Provide clear, consistent definition
of terms related to performance specifications.
Task 3 – Identify existing test methods and
mix design procedures that are likely to be included in performance
specifications for asphalt and concrete.
Task 4 – Determine the impact of implementing
these tests and procedures on DOT QA programs, including: technician training
and certification; laboratory accreditation; Lot and sublot sizes; material
sample sizes; turnaround time for test results; cost of testing; applicability
of various tests for design approval, process control, quality control,
acceptance; IA procedures; dispute resolution process.
Task 5 – Develop guidance for agencies to use during
implementation of performance specifications. Include guidance on setting up
pilot projects/shadow specifications, setting appropriate control and
specification limits, and suggest ways to gain buy-in from agency and industry
Task – Publish the final guide as an AASHTO