Asphalt modulus with

Figure 5. Variation of resilient modulus with temperature, soaking, and freeze-thaw cycling for a sulfur-modified asphaltic concrete and a concrete in which the asphalt is unmodified (46)...

Figure I. Variation of resilient modulus with sulfur and asphalt content...

The asphalts produced with thermosetting polymer-modified bitumen have excellent adhesive ability, excellent resistance to deformation, excellent fatigue performance and high stiffness modulus. 

A more simplified predictive model has been developed by Al-Khateeb et al. (2006), which, for the determination of dynamic modulus, uses only two parameters the voids in the mineral aggregate and the dynamic shear modulus of the binder. As concluded, the model is capable of predicting the dynamic modulus of an asphalt concrete at a broader range of temperatures and loading frequencies than the Hirsch model. It also has the advantage of estimating the dynamic modulus of an asphalt concrete with modified bitumen (Al-Khateeb et al. 2006). The mathematical formulation of the model developed is as follows ... 

Note AC, asphalt concrete and high stiffness asphalt concrete for surface or binder course, AC 10 and AC 14, with thickness between S and 9 cm AC-HS, asphalt concrete with high stiffness for surface or binder course, AC 10 and AC 14, with thickness between S and 9 cm AC-thin, asphalt concrete for surface or binder course, AC 10 and AC 14, with thickness between 3 and S cm AC-Airf, asphalt concrete for airfields for surface and binder course, AC 10 or AC 14 AC-VTL10, asphalt concrete for very thin layers with D = 10 mm AC-VTL6, asphalt concrete for very thin layers with D = 6 mm AC-GB, asphalt for road base, AC20, with thickness between 8 and 16 cm EME, high stiffness modulus mixtures, AC 10, with thickness between 7 and 13 cm,or ACI4, with thickness between 9 and IS cm. 

MPa), since asphalt concretes with higher elastic modulus values are more susceptible to thermal and fatigue cracking. 

The modulus of elasticity can also influence the adhesion lifetime. Some sealants may harden with age as a result of plasticizer loss or continued cross-linking. As a sealant hardens, the modulus increases and more stress is placed on the substrate—sealant adhesive bond. If modulus forces become too high, the bond may faH adhesively or the substrate may faH cohesively, such as in concrete or asphalt. In either case the result is a faHed joint that wHl leak. 

Sulfui>-Aggregate Interaction. Substantial increases in stiffness of SA binder-based mixes, as measured by the Marshall test, tensile strength, and resilient modulus of elasticity, have been observed with increasing sulfur-asphalt ratio of the binder used (11, 15, 16). Such increases can, of course, be attributed in part to the increase in viscosity of the SA... 

In both reinforced and normal asphaltic samples. It can be seen that with increasing the bitumen percent, the stiffness modulus is increased but this increasing in reinforced samples is more than normal samples. This topic due to twin effects of bitumen and tire thread mesh. 

When the wet process is employed, the homogeneity of mixture is ensured and the positive effect of the crumb rubber to the permanent deformation performance of the asphalts is more distinct. It has been reported that the permanent deformation characteristics, rut depth and the rut rate, of an asphalt concrete (AC 8 mm) with rubberised bitumen decreased in comparison to the AC 8 mm with Venezuela 50/70 grade bitumen, when the wet process was used (Neutag and Beckedahl 2011). The stiffness modulus determined by the indirect tensile test was found to increase. 

High-modulus asphalts (HiMAs) are bituminous materials with high stiffness modulus, high resistance to rutting, good spreading ability and good durability. They are used only for base or binder courses in roads, airfields or other paved areas. 

The most commonly used stiffness modulus is the elastic or dynamic stiffness modulus. It is used for ranking bituminous mixtures (asphalts), for estimating their structural behaviour in the road, as data for compliance with specifications requirements and as a property of asphalt for pavement design analytical calculations or procedures. 

Figure 7.10 Schematic representation of the dynamic modulus test, (a) Sample In testing device, (b) Details on the position of the LVDT (GL, gauge length d, specimen diameter). (From AASHTO T 342, Determining Dynamic Modulus of Hot Mix Asphalt [HMA], Washington, DC American Association of State Highway and Transportation Officials, 2011. With permission.)...

Source AASHTO T 342, Determining Dynamic Modulus of Hot Mix Asphalt (HMA), Washington, DC American Association of State Highway and Transportation Officials, 2011. With permission. 

In the resilient modulus test, the cylindrical specimens have a diameter of 101.6 3.8 mm or 152.4 9 mm and thickness ranging from 38.1 to 63.5 mm. The specimens are compacted in the laboratory with a gyratory compactor, or a Marshall compactor, or derived from field coring compacted asphalt layer(s). 

The assessment of the asphalt performance in resistance to permanent deformation is determined with reference to either creep rate and creep modulus or creep rate and cumulative strain after n load applications, or permanent shear strain, depending on the test employed. 

Bari J. and M.W. Witczak. 2007. New predictive models for the viscosity and complex shear modulus of asphalt hinders for use with the Mechanistic-Empirical Pavement Design Guide. Transportation Research Record Journal of the Transportation Research Board, No. 2001, pp. 9-19. 

Finally, the shear modulus, G, and the phase angle, s, measured by the DSR, in fact the ratio G /sin s, should be used for blending new bitumen with recycled asphalt, when the Superpave PG bitumen classification system is used (ARRA 2001). Relevant information can be found in the same manual (ARRA 2001). A procedure to develop blending charts for RA and virgin binders using the Superpave PG classification is described by McDaniel etal. (2001). 

Compacted soils and aggregates generally have good compressive modulus but poor tensile modulus and hence can be readily separated when subjected to high tensile loads. Geotextiles with fibres of suitable tensile moduli can effectively be used as reinforcing tension elements when embedded in compacted soils and aggregates. Some major uses are over soft soil unpaved roads, mnways, railroads and landfills, to stabilize a temporary bunds slope, as closure systems over unstable landfills, ash ponds and to reinforce asphalt pavement layers. 

Fig. 12-3 Complex modulus C of unmodified and 3 % SBR latex modified asphalt measured at 64 °C. The polymer modification results in 11 x increase in the elastic component, C with moderate increase in viscous component, G".

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