Resilient modulus

Asphalt concrete is properly proportioned to resist the potentially damaging effects in the road. Asphalt concrete paving mixtures should be evaluated for the following properties stability, flow, air voids, stripping resistance, resilient modulus, compacted density, and unit weight. Table 4.18 provides a list of standard laboratory tests that are presently used to evaluate the mix design or expected performance of fresh and hardened asphalt concrete. 

An instrument for measuring the mechanical properties of rubbers in relation to their use as materials for the absorption and isolation of vibration. These properties are resilience, modulus (static and dynamic), kinetic energy, creep and set. The introduction of an improved version has recently been announced. 

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)...

Specimen disintegrated in final resilient modulus test. 

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... 

Figure 9. Relationships between resilient modulus and sulfur content...

Resilient Modulus of Elasticity. The addition of sulfur produced an increase in stiffness in terms of resilient modulus of elasticity, Figure 9. Generally this increase required the addition of 50% sulfur, although in some cases 20% sulfur produced a substantial increase. 

Schmidt, R. J., A Practical Method for Determining the Resilient Modulus... 

Mix design is the choice of the best combination of aggregate, binder, and compaction effort to produce desirable pavement material properties. The choice has been made normally based on the results of simple indicator and control tests such as the Marshall stability, Marshall flow, Hveem stability, resilient modulus, and indirect tension tests. 

For the screening test phase, three replicate specimens of each combination of independent variables were made, and each of the indicator or control tests was run on the specimens of sulfur-asphalt concrete. These indicator tests (dependent variables) included bulk specific gravity, air voids, voids in the mineral aggregate (VMA), resilient modulus, Hveem stability, Marshall stability, and Marshall flow. Table II presents the range of dependent variables determined during the screening test for the AAS system mixtures. 

Mechanical Characterization of Sulfur-Asphalt. The serviceable life of a pavement comes to an end when the distress it suffers from traffic and climatic stresses reduces significantly either the structural capacity or riding quality of the pavement below an acceptable minimum. Consequently, the material properties of most interest to pavement designers are those which permit the prediction of the various forms of distress—resilient modulus, fatigue, creep, time-temperature shift, rutting parameters, and thermal coefficient of expansion. These material properties are determined from resilient modulus tests, flexure fatigue tests, creep tests, permanent deformation tests, and thermal expansion tests. 

Table III. Resilient Modulus Results of Sulfur -Asphalt Concrete Mixes...

Type Aggregate in Mix Asphalt Content (w/o) Sulfur Content (w/o) Resilient Modulus X (psi)... 

Resilient Modulus. The Schmidt test device (22) was used to measure the resilient modulus of all samples at 68°F. A load pulse time of 0.1 sec and a rest time between pulses of 2.9 sec was used in this procedure. The results of these tests are presented in Table III. 

Resilient modulus results of the limestone and volcanic aggregate mixes are shown grapically in Figure 1. As the sulfur content increases,... 

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

Sulfur New Asphalt Soften- ing Agent Resilient Modulus Bulk Air Specific Voids Marshall Stability ... 

Samples tested imder this experimental work are nominally with 100 mm diameter and 70 mm height for ITSM test. Before determination of stiffness modulus, the resilient modulus of samples were ealeulated (According to the ASTM D 4123)[7],... 

Annual Book of ASTM Standard, Road and Paving Materials Vehicle- Pavement system, Standard Test Method for Indirect Tension Test for Resilient Modulus of Bituminous Mixtures , D 4123-82, 2002. 

It should be re-emphasized that this analysis was only preliminary and based on assumed elastic properties of the sulfur-asphalt material. A more representative analysis using dynamic properties obtained from fatigue and resilient modulus tests is now in progress. 

Modulus of Resilience Modulus of resilience is a mechanical property of a material that shows how eflfective the material is in absorbing mechanical energy without sustaining any permanent damage. 

The application of static loading instead of dynamic loading, which really exists on site, in conjunction with the difficulty of executing the test under different moisture content or density, and given the fact that soils and aggregates are nonelastic materials (load duration dependent), led to laboratory determination of the stiffness modulus ( ) or resilient modulus (Mr). 

The apparatus used for the determination of the resilient modulus is as shown in Figure 1.10. 

The deviator stress Oa (=Oi - 02) is repeated, at a fixed magnitude and frequency. The loading of the soil specimen, under the influence of deviator stress, results in a deformation, part of which is recoverable during the stage of unloading. This recoverable strain along with the deviator stress determines the resilient modulus (Mr), or the modulus of elasticity ( ), of the material tested, using the equation... 

For a pavement design study, the above procedure may be repeated for different percentages of moisture contents hence, the curve of resilient modulus versus moisture content is obtained. Upon knowing the representative moisture content of the layer during a pavement s service life, a more representative resilient modulus (Mr) or stiffness modulus (E) can be determined for further calculations. 

The analytical and some semianalytical pavement design methodologies use a fundamental mechanical property for expressing the bearing capacity or strength of the subgrade soil and not the empirical CBR value. This property is the resilient modulus (Mr) or the stiffness... 

Equations 1.2 and 1.3 are proposed to be used by the Asphalt Institute of the United States (Asphalt Institute MS-1). They are applicable to materials classified as A-7, A-6, A-5, A-4 and finer A-2 soils (AASHTO designation) or CL, CH, ML, SC and SP (USCS), or in general for materials that are estimated to have a resilient modulus of 207 MPa or less. 

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