Coefficient of Thermal Expansion (CTE) determinations predict thermally induced expansion and contraction movements in concrete pavement. CTE values help in developing concrete pavement mix designs that maximize service life. The NCHRP 1-37A research program found that these thermal movements have a significant impact on concrete pavement performance, and integrated the use of CTE values into the Mechanistic-Empirical Pavement Design Guide (MEPDG). AASHTO T 336 is the standard test method for the determination of CTE values, and other agencies are evaluating its development.
Once the saturated 4x7in (101.6x177.8mm) Dia.xL concrete specimen is mounted in the measuring frame and immersed in the water bath, the test is initiated simply by pressing the start button. Precise length change measurements of the specimen are recorded at specified controlled temperatures over a range of 10°—50°C (50°—122°F). At completion, the CTE value is computed and reported.
Gilson CTE System components all work together to achieve significant improvements in accuracy, repeatability, and versatility over currently available systems. Pre-loaded software on the included laptop computer completely automates measuring, recording, and calculating final CTE values in accordance with AASHTO T 336. The portable bench-top stainless steel water bath has the capacity for testing two samples simultaneously. A water circulation unit uses a thermistor with 0.01°C resolution and ±0.05°C accuracy to control and record bath temperatures. Water is recirculated every twenty seconds, ensuring uniform temperature levels. The effects of evaporative loss are eliminated by a water level control device that precisely maintains a constant water level throughout the test. The heavy-duty adjustable specimen measuring frame adjusts for sample heights from 4 to 8.5in (102 to 216mm) and is constructed of Type 304 stainless steel to assure uniform expansion characteristics. An LVDT securely mounted to the measuring frame has 1.27mm of travel with a resolution of 3.1x10- 8mm, assuring extremely precise length change measurements.
The CTE System operates at 115V/60Hz or 240V/50Hz and includes a laptop computer pre-loaded with CTE software, and required computer interfaces, a bench-top stainless steel water bath with 10gal (38L) capacity and dimensions 25x15x13in (635x381x330mm) WxDxH, one stainless steel measuring frame with LVDT, stand-alone water circulating unit with thermistor temperature probe, and a water level control device.
Calibration and Verification Specimens are purchased separately. HMA-104 Calibration Specimen is 304 Stainless Steel, and HMA-115 Verification Specimen is 410 Stainless Steel. Grade 5 Titanium Steel and Nickel Calibration Specimens are available and can be certified to ASTM E228 by an ISO 9001 facility for additional confidence. Inquire for additional information.
An additional HMA-114 CTE Measuring Frame with LVDT purchased separately allows the testing of two specimens simultaneously for greater sample efficiency. The frames are supplied ready to connect the LVDT directly to the USB port of the computer. The HMA-113 LVDT Calibrator with Digital Micrometer can be purchased separately to verify the performance of the LVDT.
- Predicts thermal expansion and contraction in concrete pavement
- Precisely measures length changes of laboratory specimens
- CTE-software driven process meets AASHTO T 336
- Type 304 stainless steel adjustable measuring frame with LVDT
- Verification Specimen can optionally be certified to ASTM E228 by ISO 9001 facility
- Coefficient of Thermal Expansion (CTE) Concrete System
- Specimen Measuring Frame with LVDT
- Insulated Water Bath (stainless steel), approximately 10gal (38L) capacity
- Water Circulating Unit w/ temperature probe
- Water Control Device
- Laptop Computer w/ CTE software and interfaces