Road map to the future: A new generation of concrete pavements is coming of age, thanks in part to an innovative, long-term CPTP plan for research and technology

Public Roads, July-August, 2002 by Theodore R. Ferragut, Dale Harrington, Marcia Brink

Envisioning what we want concrete pavements to look like in the next 20, 50, or 100 years and developing a long-term research plan to make the vision a reality will require the industry to examine itself closely--and perhaps even redefine itself.

How can we narrow the gap between the design life expectancy and the actual life of concrete pavements?

Why is concrete consistently perceived as the more expensive alternative?

Can concrete compete as a reliable, cost-effective, short-term paving alternative?

Can concrete be a 100-year pavement?

Can we construct concrete pavements that meet lighter operational demands and tough budget restrictions?

Can new technologies or processes make today's marginal mix materials, such as low-grade aggregates, tomorrow's useful materials?

These and other questions are guiding a national project to develop a far-reaching road map to tomorrow's concrete pavements. Under the Transportation Equity Act for the 21st Century (TEA-21), Congress authorized the Federal Highway Administration (FHWA) to undertake a significant research program to improve the performance of concrete pavements. A Long-Term Plan for Concrete Pavement Research and Technology is being developed through the Concrete Pavement Technology Program (CPTP).The CPTP selected an Iowa State University-led team of program planners, university researchers, engineering consultants, and practitioners from industry and public agencies to create the plan.

Why Another Research Plan?

In recent years several groups have conducted or sponsored pivotal research programs that continue to have significant impact on the concrete paving community. Consider, for example, the possible ramifications of ultra-high-performance concrete pavement, currently being evaluated at FHWA's Turner-Fairbank Highway Research Center in McLean, VA. This steel fiber-reinforced product typically displays twice the compressive strength of high-performance concretes now used in the United States.

The Transportation Research Board, American Concrete Pavement Association, American Association of State Highway Transportation officials, and FHWA's Long-Term Pavement Performance Program also have conducted research that will lay the foundation for CPTP's new long-term research plan.

Nevertheless, the CPTP plan will be unlike any other. Broad in scope and vision, it will guide investigations into innovative technologies, processes, and systems that result in superior concrete paving solutions for 21st century needs and budgets.

Desirable Pavement Characteristics

The long-term research plan will be the product of extensive input from stakeholder representatives from Federal, State, and local agencies; contractors, suppliers, and consultants; professional associations; and academia, particularly those conducting applied research. At regional workshops, these stakeholders are helping to envision concrete pavements of the future and identify their desirable characteristics.

The value of the long-term research plan will depend on the vision and practicality of stakeholders' input regarding desirable characteristics, and the integrity and thoroughness with which the team identifies and prioritizes needed research.

Many characteristics identified to date are easy to agree on: (1) stable, long-lived joints; (2) quiet, safe, comfortable ride; (3) low permeability; (4) initial designs that consider future rehabilitation; (5) high reliability (predictable performance); and (6) environmental friendliness.

Other pavement characteristics are generating more discussion. One nontraditional characteristic is the level(s) of service future concrete pavements could or should provide. Do we want a menu of cost-effective, reliable concrete pavements--"mixes of fixes"--that serve a variety of needs and design lives? Only research can tell us if such a menu is feasible. But, first, stakeholders must decide if mixes of fixes are part of their vision for the next generation of concrete pavements.

Performance-Based Research

The planning team is convinced that desirable characteristics to improve pavement performance and more accurately predict the length of a pavement's life can become cost-effective realities only if they are developed through a performance-based process. Such a process is cyclical, based on identifying and measuring performance criteria, or performance predictors, for various elements of a paving system.

In a performance-based process, pavement designs, mixes, and construction and maintenance practices are developed and applied. Performance is measured during and after mixing and construction to determine to what extent optimums were missed and adjustments are needed. Additional research is conducted to further improve designs, mixes, and construction and maintenance practices.

This research cycle of trial, error, improvement, and early discovery and rehabilitation of performance problems results in performance-based pavements, concrete pavements that are not over-or under-built. Such a cycle requires reliable, accurate performance-based measurement and prediction tools to ensure that the best materials are used, reduce initial costs, improve pavement reliability, reduce eventual maintenance and repair costs, and provide for future rehabilitation of the pavement (through its use as a subbase, for example).