Fatigue Equation of Cement-Treated Aggregate Base Materials under a True Stress Ratio

Gradation segregation strongly affects the service performance of asphalt pavement. However, rare studies focus on the influences of segregation on asphalt mixture as it is difficult to simulate segregation in a laboratory. This paper presents a research aiming to evaluate the effects of gradation segregation using the two dimensional (2D) discrete element method (DEM). To achieve this objective, the gradation segregation levels are defined according to the differences between control and segregated gradations. Based on this, asphalt mixtures with three gradations at three segregation levels were selected. The corresponding 2D DEM models were then built using Particle Flow Code 2D (PFC 2D). The aggregate skeletons in the asphalt mixture were determined separately by means of the contact point and contact force. Based on this, the variations on the aggregate skeleton, aggregate distribution, and mechanical properties of the asphalt mixture under vertical load were studied at three different segregation levels. This study indicates that the aggregate skeleton in asphalt mixture can be affected by the gradation segregation. The correlation between gradation segregation and mechanical property is also determined in this study.

Section: Introductionmentioning

confidence: 99%

Effect of Gradation Segregation on Mechanical Properties of an Asphalt Mixture

Zhu

et al. 2019

“…With regard to the characteristics of soil-cement, these depend mainly on the quantity and type of fine aggregate of the soil, the amount of added cement and water, the mixing and compacting procedure, the curing process and the age of the compacted materials. The added cement reduces the plasticity and modifies the maximum dry density and the optimum moisture content of the mixture [1,[16][17][18]. Additionally, the compressive strength of the soil-cement is directly proportional , 28003 Madrid, Spain; jdiaz@ieca.es r of cement-treated base materials is a key factor ntally friendly pavement base materials.…”

Section: Introductionmentioning

confidence: 99%

New Procedure for Compacting Prismatic Specimens of Cement-Treated Base Materials

Linares-Unamunzaga

Gonzalo-Orden

Minguela³

et al. 2018

Understanding the long-term behaviour of cement-treated base materials is a key factor to improve its design and obtain environmentally friendly pavement base materials. Their characterization requires manufacturing prismatic specimens. However, various authors highlight the absence of standardized test methods for fabricating beams in the field and laboratory, which is not an easy task because it depends on the qualification and experience of the testing team. The aim of this paper is to present a new device and procedure for compacting prismatic specimens of cement-treated base materials. In this research, it was used for compacting soil-cement to simulate its performance as a road base material. This device employs elements that are generally available in a concrete laboratory test, such as a vibrating table or prismatic moulds. Once the procedure was established, and in order to verify its suitability, flexural and compressive strength tests were carried out. Results showed that the values obtained were consistent with this material and, despite the heterogeneity of the material, specimens from the same batch provided similar results and, hence, validated the compaction process. This new compacting procedure can improve understanding of the long-term performance of cement-treated materials from flexural and fatigue tests.

“…To model the fatigue life of cement-treated aggregate base materials, considerable research and practice have been conducted domestically and internationally. Lv et al [8] improved the fatigue equation based on the true stress ratio and the four-point bending fatigue test. Jameson [9] studied different cement-treated aggregate base materials to evaluate the fatigue properties with tensile strain, and established individual fatigue equation for each material.…”

Section: Introductionmentioning

confidence: 99%

Standardization of Fatigue Characteristics of Cement-Treated Aggregate Base Materials under Different Stress States

Xie

Tang

et al. 2018

Self Cite

In this study, to decrease the evaluation uncertainty of the fatigue characteristics of cement-treated aggregate base materials under different test conditions, unconfined compressive, indirect tensile, flexural tensile strength tests and fatigue tests of these base materials with different cement content and at different curing times were carried out. The Weibull distribution was employed to analyze fatigue test results. The standardization model of fatigue characteristics for cement-treated aggregate base materials under different stress states was established. Based on the interval analysis theory, the fatigue characteristic model under different stress states was established using interval parameters. Results revealed that the curing time and cement content considerably affect the strength and fatigue characteristics of cement-treated aggregate base materials, and with increasing cement content and curing time, the fatigue resistance of cement-treated aggregate base materials can be improved. Clear differences between the fitting parameters a and b of the S-N fatigue equation of cement-treated aggregate base materials under different stress states were observed, which can be eliminated by using the analysis method based on the Weibull distribution and the standardization model, and a unified expression for the cement-treated aggregate base materials under different test conditions was realized. A Standardization model of fatigue characteristics based on the interval analysis new method could solve several problems such as inadequate sampling representation, low precision, and insufficient stability of test equipment; thus, the errors caused by materials, structures, the environment, and loads can be reduced, making the fatigue life interval more reasonable and scientific compared to the point numerical fatigue life. Regression parameters a and be were in intervals [9.0, 10.6] and [9.9, 11.3], respectively, and parameters a and b were similar, which improve the test accuracy and reduce the data error.