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CHANGE IN RESILIENT MODULUS OF BASE LAYERS IN ASPHALT PAVEMENT STRUCTURES OVER TEXAS
Abstract
The properties of materials changeover time and the same case happens for the HMA pavement. The various components of HMA pavement such as surface, base, sub-base, and sub-grade have time related functions. In particular, the base layer which is the immediate layer below the surface, comprising of various materials such as crush aggregates and HMA also have a time related function. Among the numerous properties of the base layers which are dependent with time is its resilient modulus. Therefore, this paper correlates the effect of the change in resilient modulus with time including the various varying conditions such as rutting, thickness of base layer, precipitation, traffic, temperature, IRI index, wheel path length cracked, cracking percentage, crack length, liquid limit, plastic limit,optimum moisture content,and % fine passing below 200 sieve. Each individual factor has different effects over the resilient modulus of the base layer, but their effects are more severe when they act at once in a pavement structure.
... Sihombing et al, [13] reported that Resilient modulus value of asphalt mixture is largely influenced by bitumen stiffness modulus used in the mixture which is known that it has more influences the on the stiffness value at temperatures less than 35 °C. Bastola and Souliman, [14] correlates the effect of changing the resilient modulus with time. It includes varying conditions such as traffic, rutting, cracking percentage, crack length, thickness of base layer, temperature, IRI index, precipitation, cracked wheel path length, optimum moisture content, liquid and plastic limits, and % fine passing below 200 sieves. ...
Determination of resilient modulus of asphalt concrete is recommended by the Superpave system to be obtained from the repeated indirect tensile stress test and be implemented in the pavement design. Loading mode of asphalt concrete specimen is an important issue, although it is under-estimated issue for the detection of asphalt concrete resilient modulus. In The present work, a laboratory investigation conducted to verify the possibility of obtaining the resilient response of asphalt concrete in terms of resilient modulus, permanent deformation, and strength under repeated tensile, shear, flexure, and compressive stresses. Beams and cylindrical specimens of Asphalt concrete have been prepared at optimum asphalt content. Extra specimens having 0.5 % of asphalt binder content above and below the optimum value have also been prepared. Testing of specimens was conducted using the Pneumatic Repeated Load System PRLS at 25° C under repeated compressive, tensile, flexure, and shear stresses. The permanent deformation was monitored through LVDT (Linearly Variable Differential Transformer). The applied stress level was 138 kPa in the form of rectangular wave. A constant loading frequency of 60 cycles per minute was implemented. It includes 0.1 second of load duration and 0.9 second of rest period. The resilient modulus, permanent deformation, and strength properties were determined and compared among the various testing techniques. It was concluded that the resilient modulus (Mr) varies depending on the size of specimen, and mode of testing. The resilient modulus was (3650, 11030, 11600, and 11500) MPa under compression, tension, flexural and shear stresses respectively at optimum binder content. The permanent deformation under shear stresses is lower than that under tensile stresses by 16.8 %. On the other hand, the permanent deformation under compressive stresses is lower than that under flexure stresses by 89.4 %.
Currently, only empirical design methods are used in the application of well-known standards for pavement structure design. Given this fact, it is assumed that material characteristics correspond to average quality materials. Thus, the aim of this study included examining the influence of material characteristics on pavement design analyzing changes in the cement bound base layer (CBL) characteristics with respect to the occurrence of cracks and changes in the asphalt layer given typical seasonal changes. The study involved varying CBL modulus as 15 GPa, 10 GPa, and 5 GPa. Additionally, the moduli of asphalt layers were varied from 6 MPa to 2 MPa to simulate real conditions in pavement structure life. The analyses indicated that there was a significant difference in pavement behavior with respect to changes in material characteristics. Given these significant differences, it is extremely important to properly define material characteristics while using empirical design methods. Proper material characterization combined with the utilization of empirical and analytical methods increases the possibility of reducing layers thickness to design cost-effective structures.
This paper aims to evaluate flexible pavement responses and performance
affected by variations in the aggregate base layer properties. An
advanced three-dimensional finite element (FE) model was developed to
capture the nonlinear cross-anisotropic behavior of granular material.
The FE model characterized the hot-mix asphalt layer as a viscoelastic
material and used moving load to predict time- and temperature-dependent
pavement responses under different temperatures (258C and 458C).
Two asphalt pavement sections with different asphalt layer thicknesses
(3 and 5 in.) were analyzed, considering variations in aggregate properties.
The response changes in the asphalt layer, aggregate base layer,
and subgrade depended on the interaction between viscoelastic asphalt
layer and stress-dependent aggregate base layer. Fatigue cracking
and subgrade rutting were more affected by changes of aggregate
base layer properties among different failure mechanisms in each pavement
layer. The coefficient of curvature and complex maximum dry
density served as the contributing parameters most affecting fatigue
cracking potential, especially for the relatively thinner asphalt pavement
at the higher temperature. However, the moisture content ratio
affected the subgrade rutting potential more than other parameters did.
These conclusions serve as the basis for selecting optimum aggregate
properties for pavement design and developing a performance-related
specification for quality control and quality assurance in pavement
construction.
In order to implement MEPDG hierarchical inputs for unbound and subgrade soil, a database containing subgrade M R , index properties, standard proctor, and laboratory M R for 140 undisturbed roadbed soil samples from six different districts in Indiana was created. The M R data were categorized in accordance with the AASHTO soil classifications and divided into several groups. Based on each group, this study develops statistical analysis and evaluation datasets to validate these models. Stress-based regression models were evaluated using a statistical tool (analysis of variance (ANOVA)) and Z-test, and pertinent material constants (k 1, k 2 and k 3) were determined for different soil types. The reasonably good correlations of material constants along with M R with routine soil properties were established. Furthermore, FWD tests were conducted on several Indiana highways in different seasons, and laboratory resilient modulus tests were performed on the subgrade soils that were collected from the falling weight deflectometer (FWD) test sites. A comparison was made of the resilient moduli obtained from the laboratory resilient modulus tests with those from the FWD tests. Correlations between the laboratory resilient modulus and the FWD modulus were developed and are discussed in this paper.
Asphalt-treated bases (ATBs) are the most commonly used type of stabilized layer in Alaska because of locally available asphalt resources and its relatively lower cost. As an essential material input parameter for pavement design, resilient modulus (M(R)) of ATBs has been studied in laboratory evaluations, field investigations, and empirical and mechanistic modeling. However, most ATBs' M(R) values available in the database of the Alaska flexible pavement design software were obtained from in-service roadways through nondestructive testing and back calculation. Therefore, there was a need to characterize these stabilized materials by taking into account the main factors that influence their engineering behavior. In this study, the M(R) characterization of two types of ATBs was achieved through laboratory testing: hot asphalt-treated base (HATB) and foamed asphalt-treated base (FATB). The effects of loading amplitude, confining pressure, temperature, binder content, and aggregate source and properties on the resilient behaviors of HATB and FATB were investigated. Testing results were discussed and used to develop stress-dependent M(R) equations for both HATB and FATB that can be incorporated in current pavement design procedures. The effects of temperature and material variables were correlated to regression constants of the equations.
Mechanistic Pavement Design
- M Srsen
- D Tibljas
- M Cuculic
- M Vrkljan
M. Srsen, D. Tibljas, M. Cuculic and M. Vrkljan, "Mechanistic Pavement Design," Via Vita, Croatia, 2011.
Resilient modulus for unbound granular materials and subgrade soils in Egypt
- R Mousa
- A Gabr
- M G Arab
- A Azam
- S El-Badaway
R. Mousa, A. Gabr, M. G. Arab, A. Azam and S. El-Badaway, "Resilient modulus for unbound granular
materials and subgrade soils in Egypt," in MATEC Web of Conferences (120), 2017.
Resilient Behaviour of Ashpalt Treated Base Course Materials
- R Terrel
- I Awad
R. Terrel and I. Awad, "Resilient Behaviour of Ashpalt Treated Base Course Materials," Washington
State Highway Commission, Washington, 1972.