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 336-11 is the standard test method for 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 of final CTE values in accordance with AASHTO T-336-11. The portable bench-top stainless steel water bath has 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, insuring 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 is constructed of Type 304 stainless steel, assuring 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 HM-271 CTE System includes a laptop computer pre-loaded with CTE software, and required computer interfaces, a bench-top stainless steel water bath with 20L (5gal) capacity, one stainless steel measuring frame with LVDT, a stand-alone water circulating unit with thermistor temperature probe, and a water level control device. Calibration and Verification Specimens are purchased separately. Both have dimensions of 4x7in (101.6x177.8mm), and each is provided with a certification of CTE values to ASTM E228 by an ISO 9001 facility, as required by AASHTO T 336-11. HMA-104 Calibration Specimen is 304 Stainless Steel, and HMA-115 Verification Specimen is 410 Stainless Steel. Grade 5 Titanium Steel Calibration Specimens are available and can be certified to ASTM E228 by an ISO 9001 facility for additional confidence, inquire. Also inquire for non-certified stainless steel Calibration and Verification specimens for use when testing to other specifications.
An additional HMA-114 CTE Measuring Frame with LVDT, purchased separately, allows 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. MA-113 LVDT Calibrator with Digital Micrometer can be purchased separately to verify performance of the LVDT.