Optimise Low Temperature Performance of Asphaltic Concrete Mixtures. Complies with AASHTO TP10 and EN 12697-46
In the uniaxial tension stress test (UTST), a specimen is pulled with a constant strain rate at constant temperature until failure. Results of the UTST are the maximum stress (tensile strength) b t(T) and the corresponding tensile failure strain e failure(T) at the test temperature T (figure 1).
In the thermal stress restrained specimen test (TSRST), a specimen, which length is held constant, is subjected to a temperature decrease with constant temperature rate. Due to the prohibited thermal shrinkage, cryogenic stress is built up in the specimen. The results are the progression of the cryogenic stress over the temperature scry(T) and the failure stress scry, failure at the failure temperature Tfailure
In the relaxation test (RT), the specimen is subjected to a spontaneous strain e, which is held on constant level. The decrease of tension stress by relaxation over the testing time is monitored. The results are the time of relaxation trel and the remaining tension stress srem after the test ended (figure 3).
In the tensile creep test (TCT), the specimen is subjected to a constant tension stress s at a constant temperature T. The progression of the strain e is measured. After a given time, the stress is withdrawn. Rheological parameters describing the elastic and viscous properties of the asphalt can be determined by interpreting the strain measurements (figure 4).
A stepper-motor driven screw-jack applies tensile strain or maintains the specimen in a static position.
Two or four Linear Variable Differential Transformers (LVDTs) monitor changes in the length of the specimen, while the load cell monitors the tensile load. Spring-loaded guide rods mounted between the upper and lower platens minimize unwanted tensile stress due to gravity. Two or four Resistance Temperature Devices (RTDs), are used to monitor air or specimen temperature. An environmental cabinet RTD senses the enclosure temperature.
Position the prepared asphaltic concrete specimen perpendicular and central to the platens using the Specimen Alignment Stand. Epoxy the specimen ends to both platens. Place the specimen in the environmental cabinet, attach the transducers and adjust the LVDTs, run the required test procedure. On completion of the required test period, or at test failure the APTTS software will stop the test and adjust the cabinet temperature as required.
The APTTS software controls your test, logs data, plots the data points and produces graphs.