Incremental Model for Prediction of Permanent Deformation of Asphalt Concrete in Compression

Abstract

Permanent deformation (rutting) is one of the major distresses in asphalt pavement. To predict permanent deformation of asphalt concrete, repeated creep and recovery (or flow number) tests are typically used in the laboratory. However, models for the prediction of permanent deformation that incorporate flow number testing cannot represent the primary region because they concentrate on the secondary region. A new simple permanent deformation model called the incremental model is proposed. The proposed model is derived from the rate model, which is a rigorous mechanical model based on viscoplasticity. Four parameters of the new model provide an understanding of the permanent deformation. Parameter A is related to the initial permanent strain level, and Parameter C provides information about where the secondary region starts. That is, Parameters A and C govern the primary region, where α (alpha) is the slope of the secondary region, and B represents the permanent deformation level of the secondary region. Two mixtures are selected to investigate the deformation characteristics, and repeated creep and recovery tests are performed in compression. The incremental model is verified by applying it to various loading conditions for two mixtures. Furthermore, it is found that α is the material constant and the time-temperature superposition principle is applicable to each parameter. All parameters, except a, depend on both deviatoric stress and reduced load time, which is the product of load time and temperature. The incremental model describes ways to apply the time-temperature supposition principle to permanent deformation.

Critérios para os resultados do ensaio uniaxial de carga repetida de misturas asfálticas em laboratório a partir do desempenho em campo

“…Essa metodologia ja foi validada nacionalmente , mas requer ainda a continuidade da pesquisa com vistas a realizar o maior nu mero possí vel de ensaios em misturas locais. Ale m de considerar o confinamento, o ensaio TSS possibilita o uso do Shift Model, derivado do modelo incremental viscopla stico (Choi et al, 2012;Subramanian et al, 2013), que analisa o comportamento de misturas asfa lticas quanto a resiste ncia a deformaça o permanente. A associaça o do Shift Model ao programa LVECD (Layered Viscoelastic Continuum Damage) (Eslaminia et al, 2012;Choi e Kim, 2014) permite a previsa o de desempenho de pavimentos asfa lticos quanto a essa falha.…”

Avaliação em laboratório e em campo da deformação permanente de pavimentos asfálticos do Ceará e de São Paulo

“…O Triaxial Stress Sweep (TSS, triaxial de varredura de tensões) é um ensaio de compressão cíclica sob pressão confinante constante que emprega um pulso de carga haversine seguido por um período de repouso. Esse ensaio vem sendo adotado em modelos mecânicos avançados para investigação da deformação permanente (Gibson e Schwartz, 2006;Yun, 2008;Subramanian, 2011;Choi et al, 2012;Lacroix, 2013;Choi, 2013;Borges, 2014 (Choi, 2013).…”

Development of Calibration Testing Protocol for Permanent Deformation Model of Asphalt Concrete

“…The shift model is composed of one reference permanent strain evolution curve, which is called the permanent strain master curve, and two shift functions, as expressed in Equation 1. As illustrated in Equation 1, the permanent strain master curve is represented by the incremental model (5), which is derived from a rigorous model, the rate model, so that each coefficient has a physical meaning. A and C govern the primary region, and B and α determine secondary region behavior; therefore, the model can fit both the primary and secondary region behavior of asphalt concrete in a single function.…”

“…The construction of the dynamic modulus master curve leads to the time-temperature shift factor (a T ). In the shift model, the timetemperature shift factor obtained from the dynamic modulus test is applied to all the data first because the time-temperature superposition principle is found to be valid even with growing damage and significant viscoplastic strain (5)(6)(7)(8). Therefore, the time-temperature superposition principle converts the load time to the reduced load time by applying the time-temperature shift factor.…”

“…NY9.5B is a densegraded mixture with polymer-modified PG 64-22 binder whose nominal maximum aggregate size is 9.5 mm. Detailed information about both mixtures can be found elsewhere (5). Three temperatures (i.e., T H , T I , and T L ) are selected as 47°, 37°, and 17°C, respectively, as shown in Figure 1.…”