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Concrete Pavement Technology Update
CPTP Update—New Products and Recent Activities
Products and Reports
Several CPTP reports and related products have been completed recently. These include:
ETG Plans Next Steps
The CPTP Engineering Expert Task Group met on November 6, 2007, in conjunction with a CPTP-sponsored international conference. The group heard updates on CPTP and related projects and discussed priorities for CPTP activities during the coming months. The following action items were identified:
In addition, Bill Farnbach summarized activities at Caltrans related to concrete pavement with a focus on “green” concrete, environmental impact, and long-life pavements.
COMPASS—Concrete Mixture Performance Analysis System Software
With the emphasis on accelerated construction and long-lasting pavements coupled with a wider variety of materials options, concrete mixture optimization has become more challenging than ever. Mixture design requires the consideration of a wide array of aggregate sources, cement sources and types, chemical admixtures, supplementary cementitious materials, and recycled materials. The designer must also consider the interaction of ingredients within the mixture and how a given environment may affect the construction and the long-term performance of the pavement. “What was needed was a mixture optimization tool that could simplify the approach to the mix design and proportioning process based on job-specific conditions,” said Peter Kopac of the Federal Highway Administration’s (FHWA) Office of Infrastructure Research and Development. To meet that need, FHWA developed the new COMPASS software.
The Windows-based system consists of two main parts, a knowledge base (expert system) and four computer modules. The optimization process is illustrated below.
The knowledge base is a compilation of information on concrete properties, testing methods, material characteristics, and material compatibilities with one another and with the environment. The information is interactively accessed, filtered, and logically presented to the user.
Optimization Process Employing a Knowledge Base and Computerization
Four computer modules accept user-defined, job-specific inputs and perform the analysis:
Each module has the ability to be used independently, or the user can perform a comprehensive analysis across modules 1 to 4 building upon each consecutive module’s analysis. The flow for the comprehensive analysis is as follows:
The inputs to the first module are cross-referenced with the information in the knowledge base to help guide the user in selecting the performance criteria and materials to meet those criteria. This information is used to optimize the paving mixture for the environment at the pavement project. Modules 2 to 4 include analytical subroutines to optimize materials proportions based on job-specific criteria. Yet, to simplify and reduce training requirements, a number of input options are fixed.
The COMPASS system has undergone extensive peer review and field application testing, and the draft final report and a user’s manual have been completed and are undergoing FHWA review.
Article prepared by Ken McGhee, CPTP Implementation Team (firstname.lastname@example.org).