Addressing the constant challenge facing highway agencies and contractors to cost-effectively optimize highway construction operations while improving
Addressing the constant challenge facing highway agencies and contractors to cost-effectively optimize highway construction operations while improving product quality, the Federal Highway Administration (FHWA) offers Û free of charge Û a design tool to efficiently achieve balanced project goals: High PERformance Concrete PAVing (HIPERPAV) II software. Conducting forensic studies of premature pavement distress is another of the software’s possible applications.
When HIPERPAV was first developed in 1996 to predict early-age behavior of jointed plain concrete pavements (JPCP), FHWA’s goal was the creation of a total systems approach to simulate potential problems associated with concrete paving before they occur. The software was designed for use by state and local highway agencies, contractors, suppliers, and members of academia. Enhancements added to HIPERPAV II include prediction models for early-age behavior of continuously reinforced concrete pavements (CRCP) and the effect of early-age behavior factors on long-term JPCP performance.
HIPERPAV II models the impact of specific construction operations, concrete batch proportions, geometric design, concrete properties, and environmental factors on early-age pavement strength and stress development during construction. The combination of these factors, plus traffic loading, affects the pavement’s overall long-term performance. Accordingly, program users must enter data regarding such variables as pavement width, depth, joint spacing, batch proportioning, cement type, and concrete strength. Relevant environmental factors to be indicated include hourly air temperature, relative humidity, wind speed, and cloud coverage for the first 72 hours after concrete placement. Those values can be determined on the basis of a three-day weather forecast or by using a 30-year historical weather database built into the software. Additional variables, such as the concrete modulus of elasticity, coefficient of thermal expansion, ultimate shrinkage, and axial restraint at the base-slab interface, either can be estimated on the basis of material type or entered by the user for a more precise analysis.
After inputting the requested information, a baseline file can be developed in approximately 30 minutes using the essential data. The file thus generated can be copied multiple times for quicker analysis in the future. Well in advance of construction, various concrete batch proportions can be analyzed in view of projected construction scenarios and environmental conditions. On the day before or the day of construction, placement time, concrete and base temperature, curing type and application time, as well as saw-cut scheduling can be established using more accurate geometric, batch, and environmental details.
A recent FHWA survey of HIPERPAV users indicates that most customers find it helpful for approximating the best time to place concrete in undesirable conditions, such as cold or hot weather. In addition, the software reportedly is useful when high proportions of slag cement are required or where paving must be done on an unfamiliar base type. Other software users noted they are deploying the system as a forensic tool to troubleshoot concrete-cracking problems. And, in the academic world, the software enables professors and instructors to illustrate potential paving problems so that they can be avoided in the future.
Since 2006, the Ohio Department of Transportation has required its contractors to use HIPERPAV II on all concrete pavement projects to evaluate early-age cracking potential. Thus, an individual HIPERPAV file must be generated for each scheduled concrete placement to document that early-age cracking will not occur. Files must include information on strategies chosen by the contractor to address all variables that could influence early-age cracking, including weather conditions, changes in concrete temperature, and construction time.
Meanwhile, the Wisconsin Department of Transportation (WisDOT) offers a customized version of the software to potential users statewide. Created by The Transtec Group, Inc., developer of the original HIPERPAV software for FHWA, HIPERPAV-Wisconsin includes data unique to the state as well as local terminology. A customized cement-type selection feature, for example, allows users to choose among various cement types supplied by producers in the area. Since local inputs are preset in the system, HIPERPAV-Wisconsin is expected to save WisDOT engineers and contractors hours of time in planning, evaluation of complex construction scenarios, and optimal selection of construction materials and elements.
Contractors are embracing the software for a wide array of acknowledged benefits. John Romaine of Scruggs Co. in Hahira, Ga., emphasizes that HIPERPAV II plays an important role in improving quality, promoting efficiency, and helping control production steps. Romaine uses the software to determine saw-cut times. Running the system every four hours, especially in harsh weather conditions involving extremely hot or cold temperatures, he determines a suitable window for saw-cutting, thereby producing a quality product that will not crack. Moreover, the software facilitates organizing subcontractors to prevent wasted time on the job. The end results, HIPERPAV II developers affirm, are money saved and increased profits.
The beauty of this for a contractor is simple, says Romaine. It provides peace of mind that [the finished project] will be of high quality, and you won’t have to rip it out and replace it at your own expense, due to cracking that could have been prevented. I would recommend it to any contractor.
More information on HIPERPAV II or a free download of the software is available at www.hiperpav.com. FHWA also offers a one-day workshop on implementing HIPERPAV II. Workshop details can be obtained or scheduling for any state can be completed by contacting FHWA’s Geoffrey Kurgan, 202/366-1335; email: [email protected]; or, Gary Crawford, 202/366-1286; email: [email protected]; or, Angel Correa at the FHWA Resource Center, 404/562-3907; email: [email protected].
This article was adapted from a report that appeared in the October 2007 issue of Focus, published by the U.S. Department of Transportation’s Federal Highway Administration.