Pavement test sections

Figure 17. Pavement test sections used in fatigue life analysis...

The blending of GRT with asphalt was begun in the 1960s by McDonald, who developed and patented a patching material consisted of 25 wt% scrap and asphalt blended at 375°F for 20 minutes [193]. MacDonald continued his work by expanding it to actual road pavement test sections as a seal coat, and in 1968, Sahmaro Petroleum and Asphalt conducted application of a blend of GRT and asphalt as a binder for hot premix. The hot premix is a mixture of stone aggregate, sand, and the tire-asphalt binder all premixed in a batch- or drum-type mixer. This material is then applied as a carpet on top of the road... 

Various types of sulfur-asphalt pavement field test sections have been placed in the U.S., Canada, and Europe. Shell Canada Ltd. has conducted field trials in Canada (1,18,19,20). Gulf Oil Canada has also placed test sections of sulfur-asphalt pavement in which the sulfur and asphalt cement were incorporated into the mixture as an emulsion (4). Societe Nationale des Petroles D Aquitaine (SNPA) placed field test sections in France using the emulsion process (5). 

The U.S. Bureau of Mines participated in a field trial of sulfur-asphalt concrete pavement on U.S. Highway 93 near Boulder City, Nev. in January 1977. This test section is 2100 ft long. The aggregate-asphalt-sulfur (AAS) system was used to mix the ingredients. The sulfur and AC 40 asphalt cement were introduced into the pugmill as individual components. The sulfur comprised 27 w/o of the total binder. The aggregate used in the mixture was a crushed volcanic rock which conformed to the Asphalt Institute type IVb gradation. This test section is now in post-construction evaluation. 

To assess and characterize the appropriate TBR or BCR values, the user is advised to refer to product-specific studies and test sections that demonstrate the value added by the geotextile reinforcement in pavement stmctures, because all geotextiles do not behave the same in this application. 

Figure 1.12 Cross section of springbox. (From Edwards J.P. et ai., Deveiopment of a simpiifled test for unbound aggregates and weak hydrauiicaiiy bound materiais utiiizing the NAT. Proceedings of the 6th International Symposium on Pavements Unbound, A.R. Dawson [ed.], pp. 3-i i. Rotterdam, The Netheriands A. A. Baikema, 2004.)...

Apart from the dynamic modulus, the term resilient modulus, Mr, is also used in the evaluation of the bituminous mixture s quality and as an input for pavement design, evaluation or analysis. Resilient modulus is quite similar to the stiffness value determined by the indirect tension test in CEN EN 12697-26 (2012), Annex C the differences are outlined in Section 7.4. 

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). 

Additionally, the performance of a bituminous mixture to rut can be evaluated by the indirect tensile strength test at high temperatures. The test, known as high-temperature indirect tensile test (HT-IDT), is performed as described in AASHTO T 283 (2011) for unconditioned (dry) specimens, but at test temperature 10°C below the average 7-day maximum pavement temperature 20 mm below the surface (see Section 7.6.2.4). 

The deflection procedures for asphalt overlay design are based on pavement deflection data collected by dynamic, static or vibratory non-destructive testing (NDT) devices. Examples of such devices are as follows Benkelman beam, deflectograph, falling weight deflectometer (FWD), Dynaflect or Road Rater for details of the testing devices, see Section 16.4. 

In an assessment study of a continuous pavement measuring device (Flintsch et al. 2013), it was also found that, at least for the section investigated, the strains at the bottom of the asphalt layer estimated with measurements using the FWD and TSD resulted in an approximately one-to-one relationship. Similarly, it was concluded that the effective SN estimated with measurements obtained from TSD testing at two sites broadly matched the expected SN calculated from the layer composition and surface condition. 

The most impressive section of the book to my mind, which is not covered in nearly as much depth in other texts, is the treatment of bituminous materials... in particular their characteristics, appropriate methods to characterize their performance in the laboratory, and means of building and maintaining a road using these materials. In addition, the book provides a comprehensive coverage of the constituent layers of a road pavement, the material properties of these layers, and associated laboratory tests required to characterize these. The different types of methods appropriate to structural design are covered nicely, as are methods of recycling and maintenance. ... 

American Society of Testing and Materials. 2010. Annual Book of ASTM Standards. Section 4, Construction Volume 4.02, Concrete and Aggregates Volume 4.03, Road and Paving Materials and Vehicle-Pavement Systems. Philadelphia ASTM. Covers road and paving materials. Provides specifications, tests, and practices for field measurements, traffic monitoring, and vehicle-to-roadside communication. 

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