Cyclic compression tests

According to EN test methods, the total number of pulses applied is 3600 (approximately 2 h), for the uniaxial cyclic compression test with confinement, or 10,000 pulses (approximately 6 h), for the triaxial cyclic compression test (vacuum induced). 

According to the US test method, the total number of pulses is 5000 (approximately 90 min) or 10,000 (approximately 180 min) for the complex shear modulus and permanent shear strain test. 

The total duration of loading in case the uniaxial static (creep) test is employed is 1 h. 

According to CEN EN 12697-25 (2005), two test methods are described to determine the resistance to permanent deformation of a bituminous mixture by cyclic compression with confinement. The tests make it possible to rank various mixes or to check on the acceptability of a given mix. They do not allow raking a quantitative prediction of rutting in the field to be made. 

Test method A determines the creep characteristics of bituminous mixtures by means of a uniaxial cyclic compression test with some confinement present. To achieve a certain 

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Permanent deformation behaviour can also be determined by using the triaxial cyclic compression test (see Section 7.6.2). Figure 3.13 shows results obtained when asphalt concrete mixtures were used (AC 20 mm) with and without polymer-modified bitumen. 

CEN EN 12697-25. 2005. Bituminous mixtures - Test methods for hot mix asphalt - Part 25 Cyclic compression test. Brussels CEN. 

In addition to the above, the maximum permissible bitumen content is determined by executing the triaxial cyclic compression test according to CEN EN 12697 (2012), Method B, or the unconfined static creep test (see Section 7.6.3). This ensures sufficient resistance of the CAM to permanent deformation. 

The creep coefficient, 6, is the slope from the least square linear fit on the log e versus log M-values (n = load applications) determined from the triaxial cyclic compression test in... 

Two specimens per bitumen content (use five levels of bitumen content), after curing for Marshall testing, are subjected to either the triaxial cyclic compression test or the static creep test at 40°C 0.5 C. 

Test method B determines the creep characteristics of bituminous mixtures by means of the triaxial cyclic compression test. In this test, the confining stress is induced by vacuum and the cylindrical specimen is subjected to a cyclic axial stress. This test is most often used for the purpose of evaluation and development of new types of mixtures. 

According to the American practice, the resistance to permanent deformation, or resistance to rutting as it is called, of the bituminous mixtures is determined with the recently introduced flow number test. The test is a uniaxial repeated (dynamic or cyclic) compression test executed with a test device specially developed for Superpave mix design procedure. The test device is known as AMPT, which is also capable of determining the dynamic modulus of the mixture. The test is carried out at an elevated temperature determined from the average 7-day maximum pavement temperature 20 mm below the surface (see Section 7.6.23). The test is carried out in accordance to AASHTO TP 79 (2013). 

Uniaxial cyclic compression test with confinement - method A... 

In the uniaxial cyclic compression test, the cylindrical specimen is subjected to a cyclic axial block-pulse load (pressure) (see Figure 7.12a). There is no additional lateral confinement pressure applied. The confinement pressure is induced indirectly by using a smaller diameter loading plate (100 mm) than the diameter of the specimen (150 mm) (see Figure 7.17). 

In the triaxial cyclic compression test, the cylindrical specimen is subjected to a confining pressure, c, on which a cyclic axial pressure is superposed. 

Figure 7.19 Schematic representation of pressures exerted on a cylindrical specimen in the case of (a) haversinusoidal cyclic loading, or (b) block-pulse cyclic loading. (Adapted from CEN EN 12697-25, Bituminous Mixtures - Test Methods for Hot Mix Asphalt - Part 25 Cyclic Compression Test, Brussels CEN, 2005. With permission [ CEN].)...

Figure 7.21 presents creep results from the triaxial cyclic compression test, using asphalt concrete mixtures with nominal maximum size aggregate 20 mm (AC 20 mm) with varied... 

The apparatus used is much simpler than the apparatus used in the cyclic compression test (Cabrera and Nikolaides 1987 Jongeneel et al. 1985). It is mentioned that the CRT-UTM-NU (Cooper Research Technology Ltd. 2014) apparatus is also capable of performing the static creep test. 

In a study to compare the permanent deformation behaviour of asphalt concrete (AC 20 mm) when gradation and binder content were varied but within the tolerance limits using different testing procedures, it was found that the ranking of the mixtures was the same regardless of the procedure used, with the triaxial cyclic compression test included... 

Zeng et al. (2013) have demonstrated a fibre nanogenerator made from a PVDF-NaNbOs nanofibre non-woven web, which is capable of generating a peak open-circuit voltage of 3.4 V and a peak current of 4.4 pA in a cyclic compression test. The non-woven web was sandwiched between elastic-conducting knitted fabrics made from segmented polyurethane yams wrapped with silver-coated polyamide multifilament yams. The whole device was packaged between layers of poly dime thy Isi-loxane to enhance its mechanical robustness. 

In a fuel cell, a gas diffusion layer is compressed to minimize the contact resistance losses. Both carbon papers and carbon cloths are relatively soft and easily deformable materials. Cloth is more compressible than paper, as can be seen from Figure 4-17. When exposed to a cyclic compression test they both exhibit a weakening of the material—the first compression stress-strain curve is different than the one resulting from subsequent cycles [31]. 

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