The weather in Minnesota contrasts sharply with that in Florida, which again differs markedly from that in southern Texas. This is not only in terms of temperature variation from summer to winter, but also in relation to how much and in what form each region’s precipitation falls.
Longstanding concrete specifications have focused on strength, slump, and air content using tools like the slump cone (standardized nearly 100 years ago in 1922 as ASTM C143) and the pressure meter (standardized in 1949 via ASTM C231). These inadequately address the question of what makes concrete pavements “good” under varying environments and also limit innovation. Unfortunately, reactionary measures, often built around previous failures, have tended to introduce unintended consequences. As a result, the Federal Highway Administration (FHWA), state Departments of Transportation (DOT)s: 18 states; and industry: the Ready Mixed Concrete Research & Education Foundation, Portland Cement Association (PCA), Slag Cement Association (SCA), American Concrete Pavement Association (ACPA), and 6 ACPA chapter-state associations, have joined together in a coalition to maximize pavement performance via the Performance Engineered Mixtures (PEM) Program.
Led by the National Concrete Pavement Technology Center (CP Tech Center), this effort aims to do the following:
• Specify the critical properties that make concrete pavements in different locations “good” (therefore, cold-weather-related properties need not be regulated in warm locations and shrinkage is less critical in moist environments)
• Identify tests allowing contractors and agencies to measure each critical property
• Deliver mixtures that reliably meet the needs of particular pavement contexts
The PEM program started with 30 experts from around the country meeting for 4 days, hammering out ultimately six key factors demonstrated to control concrete mixture performance. Since then, the program has focused on identifying tests able to measure each critical property at the key stages of prequalification, quality control, and acceptance. The next-generation Integrated Materials and Construction Practices for Concrete Pavement: A state-of-the-practice manual (IMCP Manual) published by the CP Tech Center in May outlines the resulting suite of tests, as follows:
In addition, the FHWA’s Mobile Concrete Technology Center (MCTC) travels nationwide, giving practitioners hands-on experience with PEM tests and technologies tailored to their specific contexts.
More durable pavements will not only reduce failures, but also save maintenance costs and improve ride. Reducing the risk of construction errors will also reduce costs to contractors and owner agencies. The PEM project is still underway, but owner agencies and contractors are already reporting improved performance through the use of PEM at substantially reduced costs. Find out more about PEM, please talk with CP Tech Center STAFF or other PEM project partners, and go to the CP Tech Center’s page on PEM: https://cptechcenter.org/performance-engineered-mixtures-pem/.
For the ISCP ARTICLE titled “Landmark Reference Manual: ‘Next-Generation Integrated Materials & Construction Practices (IMCP)’”, please go to: https://www.concretepavements.org/2019/06/18/landmark-reference-manual-next-generation-integrated-materials-construction-practices-imcp