Bradley J. Putman

Evaluation of Rutting Resistance in Warm-Mix Asphalts Containing Moist Aggregate

In recent years, rising energy prices and more stringent environmental regulations have resulted in an interest in warm-mix asphalt (WMA) technologies to decrease the energy consumption and emissions associated with conventional hot-mix asphalt production. In this study, the objective was to conduct a laboratory investigation of rutting resistance in WMA mixtures containing moist aggregates. Rut depth, weight loss, and gyration number of dry and conditioned specimens were measured for all of the mixtures. The experimental design included two aggregate moisture contents (0% and ∼0.5% by weight of the dry mass of the aggregate), two lime contents (1% and 2% lime by weight of dry aggregate), three WMA additives (Aspha-min, Sasobit, and Evotherm), and three aggregate sources. Thirty-six mixtures were prepared, and 216 specimens were tested in this study. Test results indicated that the aggregate source significantly affects the rutting resistance regardless of the WMA additive, lime content, and moisture content. In addition, rut depth of the mixture containing moist aggregate generally satisfies the demand of pavement performance without additional treatment. The mixture with Sasobit additive exhibited the best rutting resistance. The mixtures containing Aspha-min and Evotherm additives generally showed a rut resistance similar to that of the control mixture.

Utilization of Foaming Technology in Warm-Mix-Asphalt Mixtures Containing Moist Aggregates

In this study, the objective was to conduct a laboratory investigation of moisture susceptibility and rutting resistance of warm mix asphalt (WMA) mixtures containing moist aggregates using a foaming technology. Gyration number of various samples, indirect tensile strength (ITS), tensile strength ratio (TSR), rut depths of dry and conditioned specimens, as well as deformation (flow) were measured for all mixtures. The experimental design included two aggregate moisture contents (0% and ~0.5% by weight of the dry mass of the aggregate), two lime contents (1% and 2% lime by weight of dry aggregate), one liquid anti-stripping agent (ASA) and non ASA, three foaming water contents (2, 3, and 4%) with control, and two aggregate sources. A total of 42 mixtures were used and 420 specimens were tested in this study. The test results indicated that the aggregate source significantly affects the ITS and rutting resistance regardless of the foaming water content, ASA, and aggregate moisture content. In addition, the ITS and rut depth of some foamed mixture containing moist aggregate satisfies the demand of pavement performance without additional treatment while some mixture needs a completely dry aggregate or additional treatments. The mixture with various hydrated lime contents exhibited similar rutting and moisture resistance under dry and wet conditions. The liquid ASA used in this study is not recommended to use in foaming WMA mixture with moist aggregates as it is sensitive to moisture.

Influence of Aggregate Gradation on the Performance Properties of Porous Asphalt Mixtures

AbstractThis research investigated the effect of aggregate gradation on the performance of porous asphalt mixtures. Ten aggregate gradations, which represent typical gradations used by 20 different United States highway agencies for open graded friction courses, were compared by evaluating draindown, permeability, Cantabro abrasion loss, indirect tensile strength, and rutting resistance. The results indicated that gradation does influence the performance of porous asphalt mixtures. An increase in the void ratio of the aggregate structure contributes to significant increases in porosity and permeability. Consequently, the indirect tensile strength and durability (as measured by the Cantabro abrasion test) generally decreased as the mixture porosity increased. The 10 mixes showed good moisture resistance characteristics and most of the mixes had no significant difference in tensile strength after the moisture-conditioning procedure. Furthermore, the effects of rutting did not correlate with mixture or aggre...

Effect of Aggregate Size and Gradation on Pervious Concrete Mixtures

The purpose of this research was to determine the effects of aggregate size and gradation on the unit weight, strength, porosity, and permeability of pervious concrete mixtures. The water-cement ratio (w/c) and cement-aggregate ratio (c/a) were kept constant at 0.29 and 0.22, respectively, with a design unit weight of 2002 kg/m 3 (125 lb/ft 3 ). Fifteen different aggregate gradations were tested and categorized according to nominal maximum aggregate sizes (NMASs) of 9.5, 12.5, and 19.0 mm (0.38, 0.49, and 0.75 in.) and had a range of uniformity coefficients C u . The results indicated that as the porosity increased, strength decreased and permeability increased. In general, as the C u of the aggregate increased-that is, the gradation became less uniform or single-sized and more well-graded-the strength also increased, whereas the porosity and permeability decreased. There appeared to be an optimum/pessimum C u range in which the strength of the pervious concrete reached a maximum and the permeability reached a minimum.

Effect of Compaction Temperature on Rutting and Moisture Resistance of Foamed Warm-Mix-Asphalt Mixtures

AbstractA laboratory investigation was carried out to study the effects of various compaction temperatures on moisture susceptibility and rutting resistance of warm-mix-asphalt (WMA) mixtures containing moist aggregates using a foaming technology. The experimental design included two aggregate moisture contents (0 and ∼0.5% by weight of aggregate dry mass), one lime content (1% lime by weight of dry aggregate), two foaming water contents (2 and 3%) with control, and two aggregate sources. The major properties, such as the gyration number of various samples, indirect tensile strength (ITS), tensile strength ratio, rut depths of dry and conditioned specimens, and deformation (flow), were measured for all mixtures. The test results indicated that the aggregate source significantly affected the ITS and rutting resistance regardless of the foaming water content, compaction temperature, and aggregate moisture content. In addition, mixtures from moist aggregate had lower gyration numbers regardless of aggregate ...

Laboratory Evaluation of Warm-Mix Open Graded Friction Course Mixtures

The objective of this study was to evaluate the feasibility of using warm mix asphalt (WMA) technologies to produce quality open graded friction course (OGFC) mixtures. This evaluation was based on the comparison of Evotherm WMA and foamed WMA mixes with traditional hot mix asphalt (HMA) OGFC using three primary criteria: draindown, permeability, and abrasion resistance. The results of the study indicated that fibers could be removed from OGFC mixtures when using the WMA technologies included in this study. This conclusion was based on the performance evaluation of the mixtures, which showed that when the fibers were removed, the permeability of the mix almost doubled. Additionally, the WMA mixtures without fibers met typical aged abrasion loss requirements and the foamed WMA mixtures without fibers performed similarly with regard to aged abrasion resistance to the HMA mixture with fibers, whereas the HMA mix without fibers showed lower resistance to abrasion than the WMA mixtures. The enhanced performance of the mixtures can be attributed to the increased binder film thickness of the WMA mixtures compared to the HMA mixtures without fibers.

Influence of Aggregate Gradation on Clogging Characteristics of Porous Asphalt Mixtures

AbstractThis research investigates the influence of aggregate gradation on the clogging characteristics of porous asphalt mixtures. Ten representative gradations used for open graded friction course (OGFC) applications from across the United States were used in this evaluation. The aggregate gradation was found to be strongly correlated to the macrotexture depth of the porous pavement and the permeability of the mixes both before and after clogging. Utilizing graded sand as the clogging material, it was also found that the operational (or secondary) clogging rate is approximately half of the measured initial clogging rate. Additionally, the operational clogging rate can be estimated from the R15 value for the system, which is the ratio of the D15 of the porous asphalt gradation to the D15 of the clogging material.

Estimation of Pavement and Bridge Damage Costs Caused by Overweight Trucks

This study adopted a damage quantification framework to estimate bridge and pavement damage caused by overweight trucks. The framework was applied to estimate unit overweight truck damage costs for the highway system maintained by the South Carolina Department of Transportation. The analysis revealed that pavement and bridge damage increased significantly when trucks were above legal weight limits. Tradeoffs between the most common overweight truck fee types were estimated to examine their relative efficacy. The study found the axle-based damage cost recovery fee for the additional per trip damage cost above the legal weight limit for an overweight truck loaded up to the maximum overweight limit. The fee varied between

Viscosity prediction of CRM binders using artificial neural network approach

14 and

Effects of Fiber Finish on the Performance of Asphalt Binders and Mastics

165 per trip, depending on the type of overweight truck. The flat damage cost recovery fee was