Testing Overview
- Testing Facilities: University of Toledo, Norwich University, Marquette University
- Test Period: February 2012 – September 2018
- Panel Type: SR3 hexagonal laminated tempered glass panels (26"×30")
- Standards: ASTM testing methodologies and DOT specifications
Traction and Skid Resistance Testing
Test Methodology
Testing conducted on February 24, 2012 at the University of Toledo, Department of Engineering Technology using the British Pendulum Test per ASTM E303-93(2008). Six panel configurations were tested with different surface textures, including longitudinal grooves, transverse grooves, and glass chip textures.
Test Results
| Sample Configuration | British Pendulum Number (BPN) | Skid Number (SN) | DOT Minimum SN | Result |
|---|---|---|---|---|
| Sample 1 - Longitudinal Grooves | 55.8 | 38.41 | 35.00 | PASS |
| Sample 1 - Transverse Grooves | 74.6 | 54.62 | 35.00 | PASS |
| Sample 2 - Longitudinal Grooves | 56.6 | 39.10 | 35.00 | PASS |
| Sample 2 - Transverse Grooves | 71.4 | 51.86 | 35.00 | PASS |
| Sample 3 - Glass Chips | 70.0 | 50.65 | 35.00 | PASS |
| Sample 4 | 57.0 | 39.62 | 35.00 | PASS |
| Sample 5 - Glass Chips | 70.0 | 50.31 | 35.00 | PASS |
| Sample 6 | 51.8 | 34.96 | 35.00 | ACCEPTABLE |
Note: Conversion formula used: SN = 0.862(BPN) - 9.69. All tests performed with water applied to surface per ASTM E303-93(2008) standards.
Structural Load Testing
Test Methodology
Testing conducted on July 6, 2012 by Edwin Schmeckpeper, P.E. using Norwich University's Instron 250,000 lb capacity universal test machine. Tests evaluated internal support structures for laminated glass panels under various loading configurations simulating vehicular wheel loads.
Load Test Results - 6×30" Glass Strips
| Specimen ID | Load Location | Internal Support Structure | Maximum Load | Design Load (Safety Factor 4.0) |
|---|---|---|---|---|
| 9715-10 | Center | 3.5" Concrete (f'c = 2500 psi) | 20,500 lbs | 4,600 lbs |
| 9715-7 | End | 7/8" Brown Decking | 27,000 lbs | 6,000 lbs |
| 9715-1 | Center | 2" Grey + 7/8" Brown Decking | 20,100 lbs | 4,500 lbs |
| 9715-6 | End | 2.625" Brown Decking | 33,600 lbs | 7,600 lbs |
Load Test Results - 26×30" Hexagonal Panels
| Panel ID | Load Location | Internal Support Structure | Maximum Load | Design Load (Safety Factor 4.0) |
|---|---|---|---|---|
| 9715-13 | Center | 7/8" Thick Brown Decking | 47,400 lbs | 10,700 lbs |
| 9715-15 | Edge | 7/8" Thick Brown Decking | 41,000 lbs | 9,200 lbs |
| 9715-16 | Corner | 7/8" Thick Brown Decking | 36,000 lbs | 8,100 lbs |
| 9715-17 | Center | 2" Grey + 7/8" Brown Decking | 29,200 lbs | 6,600 lbs |
| 9715-18 | Center | 4" PVC Sheeting | 37,400 lbs | 8,400 lbs |
- All panels exceeded required load capacity for vehicular traffic (typical 9,000 lb wheel load)
- Average modulus of elasticity: Eglass = 10,400,000 psi
- Laminated design provides redundancy - lower glass layer remained intact even after upper layer fracture
- Multiple support structure materials tested successfully, including recycled materials
Impact Resistance Testing
Test Methodology
Testing conducted on October 14, 2012 at Norwich University using ball drop tests based on GANA (Glass Association of North America) standards. Steel balls (1-7/8" diameter, 0.922 lb) were dropped from increasing heights to simulate dropped tools and objects.
Test Results
| Target Location | Test Result | Maximum Drop Height | Impact Energy |
|---|---|---|---|
| Center of Panel | No failure at maximum test height | 10.0 feet | 9.2 ft-lbs |
| Edge of Panel | Upper layer fractured | 8.4 feet | 7.7 ft-lbs |
Performance Characteristics:
- No cracking observed for drop heights less than 4.0 feet on center-loaded specimens
- Minor surface cracks (3/8" diameter) at 9.6 feet drop height did not propagate
- Impact resistance comparable to dropping a 14" lug wrench from waist height
- Tempered glass fracture pattern matched standard specifications
- Lower glass panel remained completely intact even after upper panel fracture
Moisture Conditioning and Duration Testing
Test Methodology
Testing conducted between July 17, 2017 and August 29, 2017 at Marquette University per ASTM D570-98(2010)e1 standards. Three SR3 pavers (S/N's 003A, 003B, 003C) underwent multiple submersion cycles: 24 hours, 7 days, 14 days, and an additional 14 days.
Test Results
| Paver S/N | Total Submersion Time | Weight Gain | Physical Condition |
|---|---|---|---|
| 003A | 35.97 days | 0.04 lbs (0.06%) | No degradation |
| 003B | 35.95 days | 0.04 lbs (0.06%) | No degradation |
| 003C | 35.95 days | 0.04 lbs (0.06%) | No degradation |
Weight measurements using 100 lb load cell with 0.02 lb resolution. All panels maintained structural integrity throughout testing.
Freeze-Thaw Cycling Testing
Test Methodology
Testing conducted between February 23, 2018 and April 20, 2018 at Marquette University per ASTM C1645/C1645M standards. Six SR3 pavers (S/N's 1A-1F) underwent 10 complete freeze-thaw cycles in fresh water and salt water (3% NaCl solution) environments.
Freeze-Thaw Cycle Parameters
- Freeze Phase: -20°C for 48 hours
- Thaw Phase: +50°C for 48 hours
- Total Cycles: 10 (approximately 50 days)
- Test Environments: Fresh water and 3% salt water solution
Test Results
| Measurement | Result |
|---|---|
| Weight Gain (all pavers) | 0.00 lbs (below measurement resolution) |
| Physical Degradation | None observed |
| Surface Cracks/Delamination | None observed |
| Structural Integrity | Fully maintained |
Conclusion: No adverse effects from rigorous freeze-thaw cycling. Panels showed no moisture infiltration or structural degradation in either fresh water or corrosive salt water environments.
Shear Strength Testing
Test Methodology
Testing conducted between January 31, 2018 and April 5, 2018 at Marquette University EMSTL. Four SR3 pavers underwent rotational shear testing using a custom-designed fixture with an MTS 36 Kip hydraulic actuator.
Test Results
| Paver ID | Maximum Shear Stress | Maximum Applied Torque | Failure Mode |
|---|---|---|---|
| Paver #1 | 254.7 psi | 89,413 ft-lbs | Test stopped before mechanical failure |
| 002B | 266.1 psi | 96,838 ft-lbs | Bottom glass panel fracture |
| 007C | 238.3 psi | 86,735 ft-lbs | Top glass panel fracture |
| 004B | 293.4 psi | 106,783 ft-lbs | Elastomeric layer delamination |
Under maximum braking conditions with a 9,000 lb wheel load and coefficient of friction = 1.0, the expected shear stress on the paver would be approximately 21 psi. All tested panels exceeded 238 psi, providing a safety margin of more than 11× the expected maximum field loading.
Accelerated Loading (Heavy Vehicle Simulation) Testing
Test Methodology
Testing conducted between July 9, 2018 and September 18, 2018 at Marquette University on an outdoor installation. Six SR3 pavers (S/N's 015A-015F) were subjected to continuous heavy vehicle simulation (HVS) testing at slow speeds.
Test Parameters
- Wheel Load: 9,500 lbs (super single tire)
- Speed: 1.4 MPH (worst-case slow speed loading)
- Path: Bi-directional passes along centerline without wheel wander
- Base: 8-10" Portland cement concrete on 6" crushed aggregate
Test Results (as of September 18, 2018)
| Metric | Result |
|---|---|
| Actual Load Cycles | 543,246 cycles |
| Equivalent 18K Single Axle Load (ESAL) | 1,079,244 ESALs |
| Test Duration | 71 days (ongoing) |
| Mechanical Degradation | No visible wear or damage observed |
| Surface Integrity | No cracks, chips, or delamination |
Testing continued toward goal of 1,000,000 actual cycles (approximately 1,986,000 ESALs), representing decades of real-world traffic loading.
Testing Facility Information
| Testing Laboratory | Tests Conducted |
|---|---|
| University of Toledo Department of Engineering Technology | Traction/Skid Resistance (ASTM E303) |
| Norwich University Structures Testing Laboratory | Load Testing, Impact Resistance |
| Marquette University Opus College of Engineering Engineering Materials and Structural Testing Lab | Moisture Conditioning, Freeze-Thaw, Shear Testing, Accelerated Loading |
Summary and Conclusions
Solar Road Panel Performance
- Traction: All surface configurations exceeded DOT minimum skid number requirements (35.0), with values ranging from 34.96 to 54.62
- Load Capacity: Panels withstood loads ranging from 20,100 to 47,400 lbs depending on configuration, far exceeding typical 9,000 lb vehicular wheel loads
- Impact Resistance: Withstood impacts up to 10 feet drop height (9.2 ft-lbs) at panel center without failure
- Moisture Resistance: Essentially zero weight gain (less than 0.1%) after 36 days continuous water submersion
- Freeze-Thaw Durability: No degradation after 10 complete freeze-thaw cycles (-20°C to +50°C) in both fresh and salt water
- Shear Strength: Average shear strength of 263 psi, more than 11× greater than expected maximum field loading
- Long-term Durability: No mechanical degradation observed after 543,246 heavy vehicle load cycles (1,079,244 ESALs)
Compliance with Standards
Testing conducted in accordance with ASTM standards including E303 (traction), C1161 (flexural strength), D570 (water absorption), C1645 (freeze-thaw), and D143 (shear), as well as DOT Federal Highway Administration specifications for rigid pavement surfaces.
Download Complete Test Reports
Detailed technical reports are available for download:
Traction Test Report (PDF, 362 KB) Load Test Report (PDF, 974 KB) Moisture Conditioning Report (PDF, 1.3 MB) Freeze-Thaw Test Report (PDF, 200 KB) Shear Test Report (PDF, 1.4 MB) Accelerated Loading Report (PDF, 379 KB)About Solar Roadways
Solar Roadways has developed modular paving panels containing solar cells that can be installed on roads, parking lots, driveways, sidewalks, bike paths, playgrounds, and other surfaces. The Solar Road Panels combine structural integrity with solar energy generation, LED lighting, and heating elements for snow/ice management.
Contact Information:
Solar Roadways, Incorporated
721 Pine Street
Sandpoint, Idaho 83864
Email: info@solarroadways.com
Testing conducted between 2012 and 2018. All test results represent actual performance data from independent third-party testing laboratories.