Evaluation of Ability of Superpave Shear Tester To Differentiate Between Mixtures with Different Aggregate Sizes

1998 ◽  
Vol 1630 (1) ◽  
pp. 69-76 ◽  
Author(s):  
Pedro Romero ◽  
Walaa S. Mogawer
Keyword(s):  
Aggregate Size ◽  
Complete Analysis ◽  
Maximum Aggregate Size ◽  
Air Voids ◽  
Asphalt Cement ◽  
Testing Sequence ◽  
Superpave Gyratory Compactor ◽  
Constant Height ◽  
Direct Measurements ◽  
Shear Tester

A study was conducted to determine whether the results from the Superpave shear tester (SST) could measure the effect of nominal maximum aggregate size on rutting susceptibility of asphalt mixtures without the need of a model. Four mixtures were analyzed using direct measurements from the SST. Two of the mixtures were prepared with AC-5 asphalt cement and nominal maximum aggregate sizes of 19.0 mm and 37.5 mm. The other two were prepared with AC-20 asphalt cement and the same two gradations. The results were analyzed statistically and compared with the performance of the respective mixtures tested by the FHWA Accelerated Loading Facility (ALF). The specimens were compacted to a target air voids of 7 percent using the Superpave gyratory compactor. The testing sequence consisted of performing the simple shear at constant height (SSCH) test followed by the frequency sweep at constant height (FSCH) test at 40°C and 58°C. These temperatures were chosen because they represent, respectively, the highest temperature used in Superpave complete analysis and the target pavement temperature at 20 mm depth used in the ALF tests. After the SSCH and FSCH tests, the repeated shear at constant height (RSCH) test was performed on all samples at 40°C. The ALF provided a significant decrease in rutting susceptibility with increase in aggregate size; however, the SST was unable to separate mixtures with the same binders and the two different nominal maximum aggregate sizes.

Impact of Gyration Reduction and Design Specification Changes on Volumetric Properties of Virginia Dense-Graded Asphalt Mixtures

2018 ◽  
Vol 2672 (28) ◽  
pp. 143-153 ◽  
Author(s):  
Stacey D. Diefenderfer ◽  
Benjamin F. Bowers ◽  
Kevin K. McGhee
Keyword(s):  
Aggregate Size ◽  
Asphalt Mixtures ◽  
Design Parameters ◽  
Maximum Aggregate Size ◽  
Volumetric Properties ◽  
Air Voids ◽  
Asphalt Mix ◽  
Production Value ◽  
Virginia Department ◽  
Air Void

In 2015, the Virginia Department of Transportation (VDOT) proposed changes to their specification for asphalt mix design. The changes incorporated a reduction of design gyrations from 65 to 50; the addition of constraints on the No. 4 (4.75 mm) and No. 30 (600 µm) sieves; and adjustments to the production value for voids filled with asphalt and minimum voids in mineral aggregate. Before these modifications were fully adopted, a study was performed to assess the effect of the changes on mixture properties and laboratory performance. Eleven pairs of asphalt mixtures were evaluated; the pairs consisted of a typical VDOT 65-gyration mixture produced under the specification current at the time and a companion 50-gyration mixture designed and produced in accordance with the proposed specification. Mixtures were evaluated to determine the effect of the design parameters on volumetric properties, gradation, and permeability. The changes had very little effect on volumetric properties or gradation. Permeability effects were mixed, with 9.5 mm nominal maximum aggregate size mixtures requiring greater compaction to meet permeability requirements and 12.5 mm nominal maximum aggregate size mixtures showing improved permeability even at higher air-void contents. For the 50-gyration mixtures, core air voids were reduced, indicating the potential for increased durability attributable to improved densification in the field.

Laboratory Evaluation of Mixture Type on Highly Modified Asphalt Mixtures in Virginia

2018 ◽  
Vol 2672 (28) ◽  
pp. 59-68
Author(s):  
Benjamin F. Bowers
Keyword(s):  
Asphalt Binder ◽  
Aggregate Size ◽  
Asphalt Mixtures ◽  
Laboratory Evaluation ◽  
Maximum Aggregate Size ◽  
Air Voids ◽  
Modified Asphalt ◽  
Modified Asphalt Binder ◽  
Dynamic Modulus Test ◽  
Scb Specimen

The work presented attempts to address reflective cracking of asphalt-surfaced pavements through binder modification with a highly polymer (HP)-modified asphalt binder. Nine asphalt mixtures ranging from fine dense-graded mixtures to stone matrix asphalt (SMA) mixtures were investigated with conventional polymer modified binders and HP binder. The dynamic modulus test, overlay test (OT), and semi-circular bend (SCB) test were used to evaluate the mixtures. In the cracking tests, HP mixtures outperformed the conventionally modified control mixtures for the same mixture type. For HP mixtures, in general, SMA mixtures performed better in the cracking test than dense-graded mixtures. One of the dense-graded mixtures having larger nominal maximum aggregate size (NMAS) performed better than the mixture with a smaller NMAS, whereas the other having a larger NMAS was not significantly different in crack testing. Further, a discussion on the calculation of bulk specific gravity and percent air voids in a cut OT and SCB specimen using saturated surface dry or vacuum sealing methods is presented.

A Measurement Approach for Critical Voids in Mineral Aggregate Based on AC-20

2010 ◽  
Vol 108-111 ◽  
pp. 708-712
Author(s):  
Chen Ning ◽  
Ming Hui Wang
Keyword(s):  
Laboratory Data ◽  
Aggregate Size ◽  
Test System ◽  
Mix Design ◽  
Maximum Aggregate Size ◽  
New Paradigm ◽  
Aggregate Gradation ◽  
Mineral Aggregate ◽  
Superpave Gyratory Compactor ◽  
Object Of Study

The voids in the mineral aggregate (VMA) is considered to be the most important mix design parameter which affects the durability of the asphalt concrete mix. This has traditionally been addressed during mix design by meeting a minimum voids in the mineral aggregate (VMA) requirement, based solely upon the nominal maximum aggregate size without regard to other significant aggregate-related properties. The goal of this study is to determine the validity of the minimum VMA requirement versus nominal maximum aggregate size required in Marshall volumetric mix design. Specimens were compacted using the Superpave Gyratory Compactor (SGC), conventionally tested for bulk and maximum theoretical specific gravities and physically tested using the thiaxial creep test system under a repeated load confined configuration to identify the transition state from sound to unsound. AC-20 was classified in the light of fine, dense and coarse gradation. The AC-20C, AC-20D and AC-20F asphalt mixtures were tested as the object of study. The results clearly demonstrate that the volumetric conditions of an VMA mixture at the stable unstable threshold are influenced by a composite measure of the aggregate size gradation .The currently defined VMA criterion, while significant, is seen to be insufficient by itself to correctly differentiate sound from unsound mixtures. Under current specifications, many otherwise sound mixtures are subject to rejection solely on the basis of failing to meet the VMA requirement. Based on the laboratory data and analysis, a new paradigm to volumetric mix design is proposed that explicitly accounts for aggregate gradation factors.

Analysis of Quality Control and Quality Assurance Data for Superpave Mixes

2000 ◽  
Vol 1712 (1) ◽  
pp. 25-34 ◽  
Author(s):  
Frazier Parker ◽  
M. Shabbir Hossain ◽  
Jiansheng Song
Keyword(s):  
Quality Control ◽  
Quality Assurance ◽  
Aggregate Size ◽  
Mix Design ◽  
Maximum Aggregate Size ◽  
Air Voids ◽  
Density Measurements ◽  
Control Quality ◽  
Asphalt Content ◽  
Mat Density

Asphalt content, voids, and mat density quality control–quality assurance data were collected for selected Marshall and Superpave mixes during 1997 and for selected Superpave mixes during 1998 and 1999. Analyses indicate that the accuracies and variabilities of asphalt content measurements for Marshall and Superpave mixes are comparable. However, analyses also indicate that the accuracies and variabilities of voids and mat density measurements are not comparable. Moreover, variabilities for Superpave mixes are much higher, and measurements for Superpave mixes are more off target than those for Marshall mixes. The effects of gyratory compactor use, mix design range for an equivalent single-axle load, and maximum aggregate size were investigated to explain the observed differences. Although few consistent trends were observed, all these factors seem to affect the variabilities and accuracies of air voids and mat densities of Superpave mixes.

Air Void Characterisation in Porous Asphalt Using X-Ray Computed Tomography

2014 ◽  
Vol 911 ◽  
pp. 443-448 ◽  
Author(s):  
Abdul Hassan Norhidayah ◽  
Mohd Zul Hanif Mahmud ◽  
Putra Jaya Ramadhansyah
Keyword(s):  
Computed Tomography ◽  
Aggregate Size ◽  
Size Composition ◽  
Maximum Aggregate Size ◽  
Aggregate Gradation ◽  
Air Voids ◽  
Porous Asphalt ◽  
X Ray ◽  
Specimen Height ◽  
X Ray Computed

This study presents the characterisation of the air voids distribution for porous asphalt mixtures compacted using gyratory compactor. The distribution of voids content and voids shape within the porous asphalt were characterised for different nominal maximum aggregate size (NMAS) and specimen height. This is to evaluate the effect of different aggregate size composition and lift thickness on the air voids characteristics of the compacted porous asphalt. Two types of gradations were adopted i.e. Grading A (with NMAS=10 mm) and Grading B (with NMAS=14 mm) and they were fabricated for two different heights (50 and 100 mm). The internal structure was captured using X-ray Computed Tomography and image analysis techniques were used to process and analyse the images. It was found that mixture with coarse aggregate gradation produced larger void size with an elongated shape, which indicates voids connectivity within the mixture compared to fine gradation with more circular and smaller void size.For lift thickness, itacts differentlyfor different aggregate gradations. The specimen produced greater voids connectivity when the fine and coarse gradations were compacted at 100 mm and 50 mm respectively. These show that NMAS and lift thickness influence the mobility of the aggregate particles during compaction which affect the voids formation and determine the effectiveness of the compaction.

Superpave® Laboratory Compaction Versus Field Compaction

2003 ◽  
Vol 1832 (1) ◽  
pp. 201-208 ◽  
Author(s):  
Robert L. Peterson ◽  
Kamyar C. Mahboub ◽  
R. Michael Anderson ◽  
Eyad Masad ◽  
Laith Tashman
Keyword(s):  
Mechanical Properties ◽  
Design Process ◽  
Mix Design ◽  
Air Voids ◽  
Superpave Gyratory Compactor ◽  
Asphalt Mix ◽  
Field Compaction ◽  
Shear Tester

Laboratory compaction is an important part of asphalt mix design. For the mix design process to be effective, laboratory compaction must adequately simulate field compaction. In this study mechanical properties measured with the Superpave® shear tester were used to evaluate field compaction and laboratory compaction. The field compaction consisted of three test sections with different compaction patterns. The laboratory compaction used the Superpave gyratory compactor with adjustments to several parameters. Results of this study indicate that current gyratory protocol produces specimens with significantly different mechanical properties than those of field cores produced with the same material and compacted to the same air voids. Results also show that adjustments to certain parameters of the gyratory can produce specimens that better simulate the mechanical properties of pavement cores.

Design and Performance Evaluation of Fine-Graded Permeable Friction Course

2012 ◽  
Vol 2293 (1) ◽  
pp. 48-54
Author(s):  
Cindy Estakhri ◽  
Tom Scullion ◽  
Xiaodi Hu
Keyword(s):  
Water Flow ◽  
Laboratory Testing ◽  
Aggregate Size ◽  
Maximum Aggregate Size ◽  
Void Content ◽  
Rain Event ◽  
Air Voids ◽  
Aggregate Fraction ◽  
Air Temperatures ◽  
And Performance

Permeable friction courses (PFCs) are popular in Texas, where the current specification for PFC (Item 342) has a maximum aggregate size of 1/2 in. and is typically placed in layer thicknesses of 1.5 to 2 in. In this study fine-graded PFCs composed of a single aggregate fraction are proposed for placement at a nominal thickness of 1 in. Initial laboratory testing found that the target air void content for volumetric design would be around 26% air voids, substantially higher than the current PFC designs, which are between 18% and 22% air voids. To minimize the likelihood of failure, extensive laboratory testing was performed to arrive at the proposed design. Tests included Hamburg wheel-track testing, overlay tester cracking, and Cantabro, draindown, and water flow tests. The proposed fine PFC mix was first placed on a test track in Pecos, Texas. Two designs were placed and subjected to limited traffic loadings, field water flow, noise, and skid measurements. These test sections performed well. The next section was placed on a Texas Department of Transportation project in May 2011 and subjected to extremely intense traffic loading conditions on an exit ramp on US-59 in Lufkin. This ramp has a high frequency of wet-weather accidents. In addition to extreme traffic loads, the surface experienced extreme heat (air temperatures approaching 105°F) and heavy localized rain (a 6-in. rain event within a 24-h period). After 3 months the fine PFC is holding up well.

Using Large Linked Field Data Sets to Investigate Density’s Impact on the Performance of Washington State Department of Transportation Asphalt Pavements

2021 ◽  
pp. 036119812110061
Author(s):  
Ryan Howell ◽  
Stephen Muench ◽  
Milad Zokaei Ashtiani ◽  
James Feracor ◽  
Mark Russell ◽  
...  
Keyword(s):  
Aggregate Size ◽  
Large Data ◽  
State Department ◽  
Washington State ◽  
Maximum Aggregate Size ◽  
Test Case ◽  
Data Sets ◽  
Department Of Transportation ◽  
Clear Trend ◽  
Washington State Department

Large data sets of Washington State Department of Transportation (WSDOT) pavement construction and condition data are linked together and used to investigate an implemented change in in-place density to lower specification limit (LSL) from 91% to 92%. This serves as a test case for using such large in-service data sets to create analysis value for a state DOT. Findings include: (1) WSDOT field density has remained relatively steady at 93% for over 20 years; (2) raising the density LSL to 92% will likely result in more contractor effort to achieve higher densities; (3) no clear trend links density with better pavement condition; (4) raising the density LSL will likely result in fewer problematically low densities; and (5) there is no evidence of differing pavement performance based on asphalt content, gradation, or nominal maximum aggregate size.

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