Effects of Particle and Mix Characteristics on Performance of Some Granular Materials

Abstract

Three types of aggregate—a dolomitic limestone, a granodiorite, and a gravel—were studied to investigate the relationship between the particle properties and their performance in terms of strength, elastic behavior, and resistance to permanent deformation. Particles of each material were assessed for their geometry at both coarse and fine scales. This was quantified using several different measures including particle shape, roughness factor, roundness, sphericity, surface friction characteristics, and angularity. Laboratory tests, using a large shear box (300 × 300 mm) and a large (280-mm-diameter) repeated-load triaxial apparatus, were carried out to understand the significance of the geometry of the particles as well as of their surface friction characteristics and the effect of grading and of compaction. Roundness and angularity are considered to be the major factors affecting ultimate shear strength and permanent deformation. The degree of compaction and consequent density also has a great effect on the shear strength and resistance to permanent deformation. However, an increase in surface friction and surface roughness tends to improve the resilient shear stiffness. A pavement trial on the three aggregates, 300 mm thick over a subgrade, was constructed. Subsequent trafficking indicated that the limestone and the granodiorite performed significantly better than the gravel. It confirms that high roundness and low angularity have a much greater impact on performance than does surface friction when rutting is the chief distress mechanism.

Algorithm for Virtual Aggregates’ Reconstitution Based on Image Processing and Discrete-Element Modeling

“…Similar results were shown by Kandhal and Parker [5], that the HMA mixtures consisting of excessive flat and elongated aggregate particles tended to break down, affecting the mix durability. The fatigue performance of the asphalt mixture was also affected by the particles' roundness and angularity, concluded based on Cheung and Dawson's research [6]. In their studies, with the angularity increasing, the ultimate shear strength increased, and permanent deformation decreased, respectively.…”

Development of Permanent Deformation Prediction Model for Trackbed Foundation Materials based on Shear Strength Parameters

“…From these test results, resilient and permanent deformation characteristic are analyzed so that a permanent deformation model is developed which can consider number of load repetition N, confining stress (σ 3 ), shear stress ratio(τ/τ f ) and stiffness of the material. 상관성이 있음이 지적되어 왔다 [9,10]. 또한 응력비 개념에 의 해 파괴시 축차응력에 대한 축차응력비(q/q f ) 또는 파괴시의 최대주응력에 대한 최소주응력비(σ 3 /σ 1 ) 및 재료의 전단강도 에 대한 전단응력의 비 즉, 전단응력비(τ/τ f ) 등이 영구변형의 발생에 중요한 영향을 미치는 변수로 지적된 바 있다 [8,11] (2) …”

Evaluation of the durability of asphalt mixtures depending on the physical properties of aggregates

“…Moreno and Rubio (2013) also concluded that the nature of coarse aggregate has an important effect in the fatigue-cracking life in asphalt mixes and should be considered in mix design. Cheung & Dawson (2002) agree that both angularity and the lack of it in the aggregates will have a strong impact on the performance of stiffness and permanent deformation, enhancing the performance of the mixture with the angularity of the particles. Regarding the shape, Kandhal & Parker (1998) indicated that the presence of elongated and flat particles affect the durability of the asphalt mixture because such particles tend to break during the mixing, laying and pavement service.…”