Dynamic Pavement Deflection Measurements, Progress Report, HR-178, 1977

The Road Rater is a dynamic deflection measuring appa-ratus for flexible base pavements. The basic operating principle of the Road Rater is to impart a dynamic loading and measure the resultant movement of the pavement with velocity sensors. This data, when properly adjusted for temperature by use of a nomograph included in this report, can be used to determine pavement life expectancy and estimate overlay thickness required. Road Rater testing will be conducted in the spring, when pave-ments are in their weakest condition, until seasonal correction factors can be developed. The Road Rater does not have sufficient ram weight to effectively evaluate load carrying capacity of rigid pavements. All rigid pavements react similarly to Road Rater testing and generally deflect from 0.65 to 1.30 mils. Research will be continued to evaluate rigid pavements with the Road Rater, however. The Road Rater has proven to be a reliable, trouble free pavement evaluation machine. The deflection apparatus was originally front-mounted, but was rear-mounted during the winter of 1977-78. Since that time, van handling has greatly improved, and front suspension parts are no longer overstressed due to improper weight distribution. The Road Rater provides a fast, economical, nondestructive test method to evaluate flexible pavements. Road Rater test data can be used to predict pavement life, set priorities for asphaltic concrete resurfacing, and design asphaltic concrete overlays. Temperature and seasonal variations significantly affect Road Rater deflection readings and must be considered. A nomograph included in this report adjusts for temperature, but does not correct for seasonal effect. Road Rater testing will be conducted in the spring until seasonal correction factors can be developed. The Road Rater has not successfully evaluated rigid pavements, but research will continue in this area. 1. Recommendations for continuing Road Rater research, evaluation and application are as follows:A computer program should be established to reduce Road Rater raw data (Range and Sensor reading) to HR-178 Road Rater Dynamic Deflections For Determining Structural Rating Of Flexible Pavements mean deflection (mils) and/or structural rating. This computer printout would be similar to present friction testing printouts, and would greatly reduce Road Rater data reduction manpower needs and costs. 2. Seasonal variation study should continue to develop seasonal correction factors. Seasonal test roads will be studied concurrently with routine testing during 1979 to develop this relationship. All Road Rater testing will be conducted in the spring until the seasonal relationship is established. 3. An asphaltic concrete overlay design method should be established based on Road Rater de-flection readings. The AASHTO Interim Guide for Design of Pavement Structures 1972 will be used as a base document for this study. 4. AASHTO Structural numbers should be compared to Road Rater Structural Ratings during 1979 on asphaltic concrete overlay projects. This analysis will enable us to refine Road Rater evaluation of flexible pavements. Roads will be tested before resurfacing and several months

Thin Bonded Concrete Overlay with Fast Track Concrete, HR-531, Condition and Performance Report, 1987

This report is a supplement to one issued in late summer 1986 which covered construction on U.S. 71, in Buena Vista County Iowa. The work involved rehabilitation of an older 20 feet wide pavement by placing a four inch thick bonded concrete overlay monolithically with two feet of widening on each side. The work was performed on one lane at a time while construction traffic and limited public traffic used the adjacent traffic lane. When work on the first lane was complete traffic was moved onto it and rehabilitation was completed on the second lane. This report covers the condition of the rehabilitated roadway in May 1987 after the first winter. The condition is described by visual observations, core conditions, and various test results including core compressive strength, direct shear tests on cores for bond strength, profilometer results and delamtect test results.

Fast Track and Fast Track II - Cedar Rapids, Iowa, HR-544, Construction Report, 1989

Two lanes of a major four lane arterial street needed to be reconstructed in Cedar Rapids, Iowa. The traffic volumes and difficulty of detouring the traffic necessitated closure for construction be held to an absolute minimum. Closure of the intersections, even for one day, was not politically feasible. Therefore, Fast Track and Fast Track II was specified for the project. Fast Track concrete paving has been used successfully in Iowa since 1986. The mainline portion of the project was specified to be Fast Track and achieved the opening strength of 400 psi in less than twelve hours. The intersections were allowed to be closed between 6 PM and 6 AM. This could occur twice - once to remove the old pavement and place the base and temporary surface and the second time to pave and cure the new concrete. The contractor was able to meet these restrictions. The Fast Track II used in the intersections achieved the opening strength of 350 psi in six to seven hours. Two test sections were selected in the mainline Fast Track and two intersections were chosen to test the Fast Tract II. Both flexural and compression specimens were tested. Pulse velocity tests were conducted on the pavement and test specimens. Maturity curves were developed through monitoring of the temperatures. Correlations were performed between the maturity and pulse velocity and the flexural strengths. The project was successful in establishing the feasibility of construction at night, with no disruption of traffic in the daytime, using fast Track II. Both the Fast Track II pavements were performing well four years after construction.