What Equipment and Test Procedures are Used?

Aggregates

The aggregates used for HFS are generally tested for gradation, abrasion, and polishing. Below are examples of typical test requirements that have been used by various agencies.  Please note that these requirements should not be considered standard practice for HFS, as the requirements vary from agency to agency.

 Test
Procedure
Required Values*
Aggregate Gradation

Sieve Analysis

ASTM C 136

Florida DOT: 95% min. passing No. 6 sieve, 5% max passing No. 16 sieve
Aggregate Abrasion

L.A. Abrasion Test

ASTM C 131

Florida DOT: 10% max.

South Carolina DOT: 20% max.

Accelerated Polishing Test

ASTM E 660

European Standard: EN 1097-8

South Carolina DOT: 75 mm max. (ASTM E660)

UK: PSV >70

 *Note: Florida DOT and South Carolina DOT specifications are developmental specifications and should not be considered standard specifications for HFS.
L.A. Abrasion Machine (Source:Qualitest)

L.A. Abrasion Machine (Source:Qualitest)

Accelerated Polishing Machine (Source: Mastrad)

Accelerated Polishing Machine (Source: Mastrad)

Binder

Binders may be tested for several properties, including tensile strength, pot life, viscosity, and tensile elongation, among others.  Below are examples of test requirements that have been used by various agencies.  Please note that these requirements should not be considered standard practice for HFS, as the requirements vary from agency to agency.

Property
Test Procedure
Requirement*
Ultimate Tensile Strength ASTM D 638

Florida DOT: Minimum 2,800 psi

 Compressive StrengthASTM D 695

Minimum @ 3 hrs - 1,000@ 75 °F

Minimum @ 24 hrs - 5,000 psi@ 75 °F

Florida DOT: 1,600 psi min.

 ElongationASTM D 638 30-70% @ 7 days
 Shore HardnessASTM D 638 Florida DOT: 70 min.
 Abrasion ResistanceASTM D 4060SCDOT: 500 cycles, CS17
 Gel TimeASTM D 2471Florida DOT: 10 minutes min.
 Water AbsorptionASTM D 570Florida DOT: Less than 0.25%
 Viscosity

ASTM D2393

Florida DOT: ISO 2555

7-25 poises

Florida DOT: 3,000 Mpa min.

 Bleed TestFlorida DOT: Swab test visual 7 days @ room temp.Florida DOT: Little trace
 Cure RateFlorida DOT: Thin film @ 75 °FFlorida DOT: 3 hours max.
 Peak Exothermic TemperatureFlorida DOT: ASTM D 2471Florida DOT: 150 °F min.
 Pot LifeASTM C 881 15-45 min. @ 75 °F
 Adhesion

Virginia Test Method 92

ASTM D 4541

Minimum @ 24 hrs - 250 psi @ 75 °F
 *Note: Florida DOT and South Carolina DOT specifications are developmental specifications and should not be considered standard specifications for HFS.

Finished Product 

The finished HFS surface is normally tested for skid resistance and texture depth. However, additional testing can be performed for abrasion of the in-situ product, and tire-pavement noise properties.

Skid Resistance

Skid resistance, as defined by ASTM, is the ability of the pavement surface to prevent the loss of tire traction. Pavement skid resistance is generally quantified using either locked-wheel or fixed slip skid measurement devices which utilize standard tires for the measurements. Other stationary devices are also available for spot measurements of skid resistance. Skid Number (SN) and Skid Resistance Value (SRV) are the most common metrics for quantifying skid resistance.  However, recent efforts to harmonize skid resistance values from different devices have resulted in the development of the International Friction Index (IFI), which provide a means to compare skid resistance valued between devices. Below are some of the types of equipment commonly used for measuring skid resistance:

  • Portable Skid Resistance Tester (a.k.a. British Pendulum Tester) – portable device for spot measurements of SRV.
  • Sideway-Force Coefficient Routine Investigation Machine (SCRIM) – used to determine the Sideway Force Coefficient (SFC).
  • Griptester – continuous measurement device used to measure a GripNumber.
  • Locked-Wheel Trailer – device which uses a full-size test wheel with a standard (smooth or ribbed) tire to measure friction resistance (also produces a SN)
  • Dynamic Friction Tester (DFT) – portable device for spot measurements that calculates surface frictional properties at various speeds.
Pendelum Tester (Source: Munro Group)

Pendulum Tester (Source: Munro Group)

Griptester (Source: Findlay Irvine)

Griptester (Source: Findlay Irvine)

According to the HAPAS Guidelines Document for the Assessment and Certification of High-Friction Surfacing for Highways from the British Board of Agrément, a high friction surface is described as “having a minimum skid resistance value (SRV) of 65 measured using the portable Skid-Resistance Pendulum Tester”.

 Test
Specification
Calculated Value
Pendulum Tester ASTM E 303 SRV, BPN
Sideway-Force Coefficient
Routine Investigation Machine (SCRIM)
In accordance with TRL Report 176: Appendix E
and Road Research Laboratory Road Note 27
 SFC
Griptester ASTM E 1844 (test tire specification) GripNumber
Locked-Wheel Trailer ASTM E 274 SN/FN
Dynamic Friction Tester ASTM E 1911 Dynamic COF

Texture

HFS systems can also be tested for texture depth and/or profile depth, primarily for quantifying macrotexture, using the following tests and equipment.  Specifications for texture depth vary from agency to agency depending on the application.  In general, a minimum mean texture depth (MTD) of 1-1.5 mm is required.

Test
Specification
Type of measurement
Value Reported
 Circular Texture Meter (CTM)ASTM E 2157 Laser Mean Profile Depth
 Sand Patch MethodASTM E 965 Volumetric  Mean Texture Depth
 RobotexISO 13473Laser Mean Profile Depth
Circular Texture Meter (Source: Hanson & Prowell)

Circular Texture Meter (Source: Hanson & Prowell)

Sand Patch Method (Source: Hanson & Prowell)

Sand Patch Method (Source: Hanson & Prowell)

Robotex and Output 3-D Texture Graph

Robotex and Output 3-D Texture Graph

Video of RoboTex in action:

Tire-Pavement Noise

While a reduction in tire-pavement noise is not the primary reason for installing HFS, the macrotexture properties of HFS can help to reduce tire-pavement noise on certain pavement surfaces.

The following table describes types of noise testing commonly used to measure tire-pavement noise.

 Test
Specification
Short Description
Statistical Pass-by Method (SPB)ISO 11819-1Type of wayside testing, where a microphone is located on the side of the roadway in a fixed location. Measures hundreds of individial vehicles.
Close-Proximity (CPX)Draft ISO 11819-2 Fixed microphones are enclosed in a sound-proof trailer and are located near the test tire. 
On-Board Sound Intensity (OBSI)TP 76-08  Fixed microphone located near the tire, measures sound pressure levels as test vehicle is in motion.
Statistical Pass-by (Source: Ulf Sandberg)

Statistical Pass-by (Source: Ulf Sandberg)

Close-proximity (Source: Ulf Sandberg)

Close-proximity (Source: Ulf Sandberg)

OBSI

OBSI