Terry Dossey

Considerations for high-performance concrete paving: Recommendations from 20 years of field experience in Texas

Presented are recommendations for high-performance concrete paving (HPCP) practice drawn from 20 years of design and monitoring of the performance of continuously reinforced concrete (CRC) pavements in Texas. Performance indicators used were crack spacing distribution, crack width, crack randomness, delamination spalling, and vertical distribution of tensile strength. Variables studied were aggregate type, aggregate blending, placement season, placement time of day, placement above 32°C (90°F), use of crack initiators, use of skewed transverse steel, evaporation rate, percent steel reinforcement, and steel bar diameter. The variables studied are ranked in the order they affected performance, to identify which are significant and can be controlled in the design and construction phases. The focus is on the most recent experimental pavements designed and built specifically to study HPCP in Texas—85 CRC test sections built at eight locations between 1986 and 1995 in the greater Houston area. Each project consisted of 8 to 22 experimental sections of slightly different design. These sections were closely controlled and monitored during construction, and periodic condition surveys continue to be conducted. The recommendations offered are especially useful under adverse conditions, such as hot weather placement of portland cement concrete using high thermal coefficient aggregates, or paving during periods of high surface evaporation. Critical temperatures and evaporation rates are specified; using weather stations, maturity meters, or other devices that indicate in situ temperatures and evaporation rates, dangerous conditions may be identified in time to take corrective measures and thus ensure adequate performance.

Distress Prediction Models for Rigid Pavements for Texas Pavement Management Information System

The development of distress prediction models for nonoverlaid portland cement concrete (rigid) pavements in Texas for the Texas Department of Transportations pavement management information system is described. The regression models presented quantitatively predict distress level versus pavement age and are based on pavement condition data maintained by the Center for Transportation Research at The University of Texas at Austin. Models are available for the following distress types in continuously reinforced concrete pavement (CRCP): punchouts, portland cement concrete patches, asphalt patches, serviceability loss as measured by loss of ride score, transverse crack spacing, and crack spalling. Preliminary models are available for the following distresses in jointed concrete pavement and jointed reinforced concrete pavement: patches, corner breaks, faulted joints and cracks, spalled joints and cracks, transverse crack spacing, and slabs with longitudinal cracks. A sigmoidal regression equation was used fo...

Development of Jointed Concrete Pavement Database for State of Texas

A jointed concrete pavement database was developed as part of a pavement information management system for Texas. Topics discussed include the identification of variables, a statewide selection of pavement projects using an experimental factorial design, and the collection of performance information through a visual condition survey. A preliminary distress index for jointed pavements is also presented. In this analysis, the distress variables collected in the field are reduced to a single performance value and related statistically to the various design variables of the pavement projects investigated.

Controlling early-age cracking in continuously reinforced concrete pavement: Observations from 12 years of monitoring experimental test sections in Houston, texas

Presented are findings drawn from 12 years of monitoring and analyzing thermal cracking in experimental continuously reinforced concrete (CRC) pavements placed in and around Houston, Texas. Between 1986 and 1995, 85 CRC test sections were built at eight locations (projects) in the greater Houston area. Each project consists of between 8 and 22 experimental sections of slightly different design. These sections were closely controlled and monitored during construction, and periodic condition surveys continue to be conducted. Adjacent placement of the experimental sections in each project minimized the effect of uncontrolled variables such as traffic and climate. The purpose of the study was to evaluate new design elements and construction considerations intended to control earlyage thermal cracking and cracking-related distress caused by coarse aggregate with a high thermal coefficient of expansion. Experimental factors considered include coarse aggregate type, percentage of steel reinforcement, bar size, double or single mat steel, paving time, and paving season. Findings from the study show significant differences in performance between low and high thermal coefficient aggregates, along with some effective methods to minimize them as well as some attempts that were not as successful. Aggregate type and placement season were found to be the most significant factors affecting PCC performance, whereas day or night placement, steel percentage, bar size, and skewed placement proved less significant.

Case Study of Overlay Performance on Rigid Pavement in Bowie County, Texas

A case study of flexible overlay performance on an old rigid pavement is presented. This special study was devised in cooperation with the Pavement Section of the Design Division of the Texas Department of Transportation to take advantage of a unique opportunity to study overlay effectiveness. Condition survey, roughness measurements, and deflection basins were taken before and after the removal of an old flexible overlay and after the construction of a new asphalt overlay. Subsequent analysis of the data shows that although the overlay restores the ride quality of a rigid pavement and eliminates dynamic loading caused by swelling subgrades, it can only slow, not reverse, fatigue in the underlying pavement structure.

Early Age Performance of Continuously Reinforced Concrete Pavement with Different Types of Aggregate

The effect of coarse aggregate on pavement performance has been attributed to the volume of aggregate used in pavement construction. The different patterns of crack development for limestone (LS) and siliceous river gravel (SRG) are a typical example of aggregate-induced variable performance in continuously reinforced concrete pavement (CRCP). An attempt was made to find a reasonable solution for pavements with SRG. As a way to solve the performance problem observed from the SRG pavement, a blended aggregates mixture was suggested. Laboratory and field tests were performed to check the feasibility of their application in pavements. From the laboratory test, a 50:50 blending ratio was suggested after considering the effect on tensile strength and thermal coefficient of expansion. Field test sections were also constructed to verify previous performance observations for the two aggregates and to provide performance data for new variables such as blended aggregates and special curing methods. Unexpectedly, the blended mixture did not improve the performance of SRG pavement; rather it experienced worse cracking than SRG alone. A controlled experiment with additional field test sections is needed to verify or disprove this finding. The only definitive finding was that selection of aggregate in the concrete pavement is a vital consideration for the design of the pavement. The CRCP8 analytical program reasonably predicted crack spacing for both SRG and LS pavements, predicting mean crack spacing of 0.99 m (3.25 ft) for SRG and 1.98 m (6.41 ft) for the limestone. These values are somewhat below the actual spacing observed at 100 days. Data collected after the first winter period will be required to calibrate the program.

Benefits of continuous deflection profile analysis: a case study of runway 17R-35L at Dallas/Fort Worth International Airport using the rolling dynamic deflectometer

A research project was undertaken by the The University of Texas at Austins Center for Transportation Research to assess the condition and remaining life of a large section of Runway (RW) 17R-35L and taxiway L at Dallas/Fort Worth International Airport. Concrete fatigue was determined from fatigue testing of RW core samples and from deflection data obtained from an experimental testing device called the Rolling Dynamic Deflectometer (RDD). The RDD is a truck-mounted device that measures continuous deflection profiles of pavements. The RDD appears to be a very promising device for use in pavement performance analysis. The RDD gives much more comprehensive deflection data than devices currently in use such as the Falling Weight Deflectometer and the Dynaflect and the data collection procedure is quicker and more efficient. Additionally, continuous deflection profiles provide more ways of assessing the in-place structural adequacy of pavements. For this research, RDD data from one section approximately 305 m (1000 ft.) was selected to illustrate several possible ways to analyze the data. Due to the large amount of data collected by sampling every 152 mm (6 in.) on a runway over a mile in length, a program called RDD3 was developed to perform the analysis. Results of this analysis are presented here.