Evaluation of Maturity and Pulse Velocity Measurements for PCC Traffic Opening Decisions, HR-380, 1998

Concrete paving is often at a disadvantage in terms of pavement type selection due to the time of curing required prior to opening the pavement to traffic. The State of Iowa has been able to reduce traffic delay constraints through material selection and construction methods to date. Methods for monitoring concrete strength gain and quality have not changed since the first concrete pavements were constructed in Iowa. In 1995, Lee County and the Iowa DOT cooperated in a research project, HR-380, to construct a 7.1 mile (11. 43 km) project to evaluate the use of maturity and pulse velocity nondestructive testing (NDT) methods in the estimation of concrete strength gain. The research identified the pros and cons of each method and suggested an instructional memorandum to utilize maturity measurements to meet traffic delay demands. Maturity was used to reduce the traffic delay opening time from 5-7 days to less than 2 days through the implementation of maturity measurements and special traffic control measures. Recommendations on the development of the maturity curve for each project and the location and monitoring of the maturity thermocouples are included. Examples of equipment that could easily be used by project personnel to estimate the concrete strength using the maturity methods is described.

Strength Development of Concrete Based on Maturity and Pulse Velocity, MLR-95-03, 1995

The effect of curing temperature, in the range of 4.4 to 22.8 degrees C (40 to 73 degrees F), on strength development was studied based on the maturity and pulse velocity measurements in this report. The strength-maturity relationships for various mixes using a Type I cement and using a Type IP cement, respectively, were experimentally developed. The similar curves for early age strength development of both the patching concrete, using a Type I cement with the addition of calcium chloride, and the fast track concrete, using a Type III cement and fly ash, have also been proposed. For the temperature ranges studied, the strength development of concrete can be determined using a pulse velocity measurement, but only for early ages up to 24 hours. These obtained relationships can be used to determine when a pavement can be opened to traffic. The amount of fly ash substitution, up to 30%, did not have a significant influence on the strength-maturity relationship.

Bond Development in Concrete Overlays, August 1995

Data collection to determine the rate of bond strength development between concrete overlays and existing pavements and the evaluation of nondestructive testing methods for determining concrete strength were the objectives of this study. Maturity meters and pulse velocity meters were employed to determine the rate of flexural strength gain and determine the time for opening of newly constructed pavements to traffic. Maturity measurements appear to provide a less destructive method of testing. Pulse velocity measurements do require care in the preparation of the test wells and operator care in testing. Both devices functioned well under adverse weather and construction conditions and can reduce construction traffic delay decisions. Deflection testing and strain gaging indicate differences in the reaction of the overlay and existing pavement under grouting versus nongrouted sections. Grouting did enhance the rate of bond development with Type I11 cement out performing the Type I1 grout section. Type I11 and Type I1 cement grouts enhanced resistance to cracking in uniformly supported pavements where joints are prepared prior to overlays achieving target flexural strengths. Torsional and direct shear testing provide additional ways of measuring bond development at different cure times. Detailed data analysis will be utilized by TRANSTEC, Inc. to develop a bonded overlay construction guidelines report.

Fast Track and Fast Track II Cedar Rapids, Iowa, HR-544, 1993

Two lanes of a major four-lane arterial street in Cedar Rapids, Iowa, needed reconstruction. Because of the traffic volume and the detour problem, closure of the intersections, even for 1 day was not feasible. Use of Fast Track concrete paving on the mainline portion of the project permitted achievement of the opening strength of 400 psi in less than 12 hr. Fast Track II, used for the intersections, achieved the opening strength of 350 psi in 6 to 7 hr. Flexural and compression specimens of two sections each in the Fast Track and Fast Track II sections were subjected to pulse velocity tests. Maturity curves were developed by monitoring the temperatures. Correlations were performed between the pulse velocity and flexural strength and between the maturity and flexural strength. The project established the feasibility of using Fast Track II to construct portland cement concrete pavement at night and opening the roadway to traffic the next day.

Comparison of Setting Time Measured Using Ultrasonic Wave Propagation with Saw-Cutting Times on Pavements, TR-675, 2015

At present, there is little fundamental guidance available to assist contractors in choosing when to schedule saw cuts on joints. To conduct pavement finishing and sawing activities effectively, however, contractors need to know when a concrete mixture is going to reach initial set, or when the sawing window will open. Previous research investigated the use of the ultrasonic pulse velocity (UPV) method to predict the saw-cutting window for early entry sawing. The results indicated that the method has the potential to provide effective guidance to contractors as to when to conduct early entry sawing. The aim of this project was to conduct similar work to observe the correlation between initial setting and conventional sawing time. Sixteen construction sites were visited in Minnesota and Missouri over a two-year period. At each site, initial set was determined using a p-wave propagation technique with a commercial device. Calorimetric data were collected using a commercial semi-adiabatic device at a majority of the sites. Concrete samples were collected in front of the paver and tested using both methods with equipment that was set up next to the pavement during paving. The data collected revealed that the UPV method looks promising for early entry and conventional sawing in the field, both early entry and conventional sawing times can be predicted for the range of mixtures tested.

Interlaboratory Study to Determine the Precision of the MIT Scan T2 for PCC Pavement Thickness, MLR 14-01, 2015

The MIT Scan T2 device has been implemented in Iowa as a new method for determining PCC pavement thickness compliance. The T2 device utilizes a magnetic pulse induction technology to measure the distance from a sensor to a metal target. The objective of this project was to conduct an interlaboratory study (ASTM C802) to determine the precision of the test.Fifteen MIT Scan T2 gauges and fifteen operators performed testing on three reference platforms and nine pavement locations of varying thicknesses. The testing was conducted on October 29, 2014 at two sites near Ames, Iowa. Usable data was obtained from every operator at all locations.

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.