Ruggedness Testing of the Dynamic Shear Rheometer and the Bending Beam Rheometer Test Procedures

Ruggedness testing of the bending beam rheometer (BBR) and the dynamic shear rheometer (DSR) was performed. Four laboratories participated in this effort. Three materials were used for BBR ruggedness testing and four materials were used for DSR ruggedness testing. Measurement of the creep stiffness and m-value at 60 s with the BBR was found to be fairly repeatable. Of the factors studied, the mold used for casting the beams had a significant effect. Different beam thickness by the two molding techniques was found to be a factor that caused this variation. Other unknown factor(s) also seemed to contribute to this effect. The test temperature also had a significant effect and should be controlled to +/-0.1 deg C. Measurement of the complex shear modulus (G*) and the phase angle (delta) with the DSR was very repeatable. The measurement of G* with 8-mm parallel plates had more variation than the measurement of G* with 25-mm parallel plates. The measurement of delta with both 8-mm and 25-mm plates had lesser variation than the G* measurement. Test temperature was the primary factor that affected the test results for both 8-mm and 25-mm parallel plates, requiring +/-0.1 deg C control. For G* measurements with 8-mm parallel plates, it seemed to make a difference whether asphalt was directly applied to the plates or if it was transferred in the form of a pellet. This effect can probably be accounted for by different thermal history imparted to the pellet. Inconclusive, but definite, effects were observed due to overhang in the case of the 8-mm parallel plates

Pavement Testing Facility -- Phase 1 Final Report

The Pavement Testing Facility (PTF) is a permanent, outdoor, full-scale pavement testing laboratory located at the Federal Highway Administration's (FHWA) Turner-Fairbank Highway Research Center in McLean, Virginia. The purpose of this facility is to quantify the performance of test pavements trafficked under accelerated loading. The facility consists of several instrumented test pavements and the Accelerated Loading Facility (ALF) testing machine. Formal operation of the facility began in October 1986. This report summarizes the work performed during the first phase of research, October 1986 to April 1989. The report includes a discussion of the construction and instrumentation of the PTF test pavements. It describes the operation of the ALF testing machine, and the data collection procedures used at the PTF. The report also summarizes the environmental, and pavement response and performance data collected during the first phase of research. Finally, an analysis of the accelerated pavement testing data was conducted to assess the strengths and weaknesses of accelerated testing with the ALF machine

Evaluation of the Supplemental Procedure of the Maximum Specific Gravity Test for Bituminous Paving Mixtures

The objective of this study was to investigate the effects of performing the supplemental procedure of AASHTO T 209 (or ASTM D 2041) on the percent air voids, the effective aggregate specific gravity, and the maximum specific gravity of a bituminous paving mixture, using both thoroughly coated aggregates and partially coated aggregates. The supplemental procedure should correct the test data for water absorbed into the aggregate during the test. Although the supplemental procedure can be used when designing mixtures, it is most often used for determining the maximum specific gravities of moisture damaged pavement samples, or cores or specimens where sawing has exposed a significant amount of aggregate. The majority of aggregates used in this study had water absorptions below 2.5% and thus were not highly absorptive. It is recommended that the supplemental procedure not be peformed on laboratory mixtures or pavement cores having aggregates with water absorptions below 2.5%. When testing any mixture prepared in the laboratory during the mixture design process, the procedure for determining the maximum specific gravity should only be performed on well coated mixtures so that the supplemental procedure does not have to be used. For highly absorptive aggregates, it is recommended that the test only be performed at high binder contents which provide thick coatings. Only binder contents close to or slightly above the optimal binder content should be used. The maximum specific gravities for the lower binder contents can be calculated using the effective specific gravity of the aggregate. For laboratory mixtures containing highly absorptive aggregates, the supplemental procedure may indicate whether the coating is sufficient

Evaluation of Procedures Used to Predict Moisture Damage in Asphalt Mixtures: Executive Summary

Procedures for evaluating the moisture susceptibility of asphalt mixtures were compared by performing them on mixtures having a known history of susceptibility. Data included the retained ratios, visual stripping, mechanical values (tensile strength, stability, etc.), saturation, and swell. The most promising procedures appeared to be the NCHRP 246 and NCHRP 274. Moisture susceptibility was not effectively predicted by the 1-Minute Boiling Water, 10-Minute Boiling Water, Immersion-Compression, Marshall-Immersion, and Dynamic Tumbling procedures. The NCHRP 246 procedure (often referred to as the Lottman procedure) contained two parts: one for short-term pavement performance, and one for long-term pavement performance. The short-term part was not found to be useful with regards to predicting performance. An 80-percent pass/fail criterion was chosen for both tensile strength ratios in the NCHRP 246 and NCHRP 274 procedures, and 70 percent for the M sub r test. Ten percent or greater visual stripping generally indicated unacceptable damage in all procedures performed on compacted mixtures. The data indicated that a freezing period, or higher air void levels, can be beneficial for evaluating moisture susceptibility. The degree of saturation was found to be important in that sufficient water must enter a specimen; however, saturation was not found to be the dominant factor affecting moisture damage. The effects of saturation were masked by other mechanisms such as the type of mechanical test, air void levels, and freezing. There was no conclusive evidence that high saturations or oversaturation due to vacuum conditioning adversely affected the test results

Time-to-Corrosion of Reinforcing Steel in Concrete Slabs, Volume VI: Calcium Nitrite Admixture

Eighteen relatively large reinforced concrete slabs were fabricated in 1980 using calcium nitrite admixture with black (uncoated) steel. Their performance is compared with uncoated steel in concrete without admixtures. The slabs were placed in two lifts: the bottom lift consisted of a bottom mat of reinforcing steel in chloride-free concrete, and a top lift consisting of the top mat rebars in concrete contaminated with various quantities of sodium chloride. All the electrical connections between the reinforcing mats were made exterior to the slabs so that the corrosion current flow could be measured. After curing, the slabs were mounted above ground and exposed to the environment of the Washington, D.C., Northern Virginia area. They were periodically subjected to additional chloride exposure while being monitored for the initial 1-year period. Findings of the study indicate that the calcium nitrite can be effective in reducing rate of corrosion for black reinforcing steel embedded in salt-contaminated concrete up to a chloride/nitrite ratio of 0.9

Performance Evaluation of Sulfur-Extended Asphalt Pavements - Laboratory Evaluation

In 1987 the Federal Highway Administration (FHWA) completed a field study to compare the performance of sulfur-extended asphalt (SEA) pavements to conventional asphalt contra 1 (AC) pavements. A representative set of pavements was chosen to provide a comprehensive evaluation of the effects of sulfur on pavement performance. The primary conclusion was that there was no difference in overall performance between the SEA and AC sections. This field study is documented in FHWA Report DP54-0l, Federal Highway Administration, Washington DC, 1987. It is entitled "Performance Evaluation of Sulfur-Extended Asphalt Pavements - Field Survey and Assessment." The laboratory study documented in the accompanying report complements the field study. Cores were obtained from many of the pavements and tested (1) to verify that the SEA and AC sections were similar in thickness and mixture composition, except for sulfur content, (2) to predict whether the pavement performances of the SEA and AC sections will remain similar, and (3) to investigate individual pavements where the performances of the two sections were not equal. In genera 1, the laboratory test results supported the results of the field study. Overall, sulfur did not increase or decrease most test properties, and often it had no effect on a given test property of a mixture. Sulfur did decrease the resistance to moisture susceptibility in the laboratory. There were also minor trends\ub7 indicating that with some mixtures, sulfur may reduce the susceptibility to rutting and increased the susceptibility to fatigue cracking. This report also presents the results of several tasks where SEA binders and mixtures prepared in the laboratory were evaluated

Moisture Damage in Asphalt Mixtures - A State-of-the-Art Report

This state-of-the-art report is on the moisture susceptibility of asphalt mixtures used in highway pavements. It addresses the known causes of moisture damage, methods for controlling damage such as antistripping additives, and moisture damage tests. Several current research studies are also given in the report. Moisture damage in asphalt mixtures is a complex mechanism which is not well understood and has many interacting factors. This report is mainly concerned with dense-graded hot asphalt mixtures as most of the literature discusses these types of mixtures. Some information on chip seals and emulsion mixtures is also included. One of the intents of this report is to indicate where data is lacking so that research can be performed in these areas. State-of-the-art reports often give the impression that more is known than is really known. More knowledge is needed in all areas dealing with moisture damage in asphalt pavements. How to develop moisture damage tests so that they relate to pavement performance needs to be addressed

Tunneling Technology for Future Highways

This report gives an overview of research conducted for FCP Project 5B, Tunneling Technology for Future Highways. That project was aimed at research including state-of-the-art tunneling techniques unknown in the United States although accepted by other countries, and more experimental tunneling techniques not yet generally accepted. Specific research studies dealt with cut-and-cover tunnels, site investigation, earth movements, environmental criteria, and supporting activities (research conferences, information exchange, etc.). The report summarized research on: cost, classical ground control techniques, slurry walls, tie backs, anchors and grouting for cut-and-cover tunnels; planning of site investigations, direct mechanical measurement (pressuremeters, cone penetrometers, vanes, piezometers) of soil properties, and indirect measurement by sensing techniques (aerial photography, acoustic, seismic, and electromagnetic systems); prediction and control of ground movements including phenomenological study and development of lining techniques; guidelines for the environment including air movement and pollution, tunnel lighting, traffic operation, driver behavior, safety and fire hazards

Comparison of Laboratory Testing Methods for Bridge Coatings

This study was performed to investigate the effect of combining a freeze cycle, an ultraviolet/condensation cycle (QUV), and a salt-fog plus pollutant/dry cycle (Prohesion) in an accelerated laboratory weathering test on the performance of coating systems for steel bridges. The test results were compared with those obtained from the salt-fog test, the Prohesion test, and natural marine exposure. The coating systems selected were water-based systems of acrylic, acrylic epoxy, inorganic zinc alkali silicate, vinyl, and zinc-rich epoxy, and solvent-based systems of calcium sulfonate/alkyd, high-solid epoxy, zinc-rich polyurethanes, epoxy mastic, epoxy urethane mastic, and low-VOC epoxy. All of these coating systems contained volatile organic compound (VOC) content less than 340 g/L. Evaluation parameters for coating performance included coating film thickness, coating gloss, hardness, adhesion strength, blistering, rust, and creepages at scribe. The failure modes of these coatings are discussed and the coating performances are compared. Low-VOC solvent-based zinc-rich polyurethane/polyurethane/polyurethane coating systems outperformed the rest of the coatings tested. The epoxy mastic system and the epoxy urethane mastic system developed serious undercuttings at the scribe. The waterborne acrylic system and the waterborne acrylic epoxy system did not protect steel effectively and they blistered rapidly at the scribe. Zinc-rich primers were highly resistant against corrosion without developing any undercutting on steel, but their water-based topcoats exhibited extensive delamination due to the poor adhesion to the zinc primers. Waterborne vinyl blistered badly in all the laboratory tests, but performed fairly well after 28 months of outdoor exposure. The test results obtained in this study were also analyzed by a statistical variance method to determine the difference among the test methods, and coating systems. The cyclic freeze/QUV/Prohesion test results were found to generate a much more promising performance trend when compared to the natural marine exposure results than did the Prohesion test alone. However, salt-log test results exhibited large deviations from those of the natural marine exposure, indicating that salt-fog testing is not a reliable predictor of field performance of coatings

Changes Occurring in Asphalt in Drum Dryer and Batch (Pug Mill) Mixing Operations

Staff StudyThis is part of NCP Study No. 2E1A4082.The study was designed (1) to discover whether steam distillation of asphalt takes place in a drum dryer mixer, (2) to compare changes induced by various laboratory conditioning (aging) techniques versus those occurring in drum dryer mixers, and (3) to identify possible differences in asphalts subjected to drum dryer mixing versus batch (pug mill) mixing. Fifty-five virgin asphalts were subjected to various laboratory conditioning experiments including thin film oven exposure (TFO), rolling thin film oven exposure (RTFO), (small) steam distillation (SSD), forced air distillation (FAD), and rolling forced air distillation (RFAD). Various physical and chemical properties of these conditioned samples were measured. These properties were compared with those of the residues recovered from drum dryer operations for each asphalt. By comparing the laboratory conditioned residues to the recovered residues from the drum dryer operation, similarities of the variously exposed asphalts to asphalt recovered from drum dryer mixers were ascertained. This demonstrated that steam distillation does not take place in drum dryer mixers. Eight matched asphalt pairs, one used in a drum dryer mix and one in a batch (pug mill) mix, were identified among 24 virgin asphalts from Georgia by statistically comparing various physical, thermal, compositional, and molecular size properties of the virgin asphalts. Asphalts were then recovered from the mixes in which each of the eight drum dryer - batch (pug mill) asphalt pairs were used. The recovered asphalts were analysed, and the results show the asphalt residues extracted from drum dryer operations to be slightly harder than those extracted from batch operations