Aggregate Morphology Affecting Resilient Behavior of Unbound Granular Materials

Abstract

The resilient modulus (M_R) defines the nonlinear elastic response of pavement geomaterials, such as the unbound aggregate base–subbase materials, under repeated traffic loading. The resilient behavior of unbound aggregate layers is affected by the stress states experienced because of wheel loading and physical properties of aggregate materials. Among the physical properties, the influence of aggregate morphology on the resilient behavior of base–subbase materials is not yet well understood because of a lack of quantitative measurements of shape, angularity, and surface texture characteristics of aggregate particles. This paper focuses on investigating the influence of aggregate angularity and surface texture properties on the resilient behavior of unbound granular materials expressed by a nonlinear, stress-dependent resilient response model. With an image analysis approach, two important aggregate morphological indices [the angularity index (AI) and the surface texture index (ST)] were defined to quantify accurately the angularity and surface texture properties of six types of commonly used aggregate materials with varying surface irregularities. Twenty-one unbound specimens were prepared with the blending of six aggregate materials and tested for resilient moduli in a laboratory triaxial setup as per the AASHTO T 307-99 protocol. Both AI and ST were found to be closely linked to M_R values of the aggregate specimens blended in different percentages. As the aggregate angularity and surface roughness increased, the resilient moduli were considerably improved, which was primarily because of the increased shear strength with better aggregate interlock and frictional properties and the increased confinement levels expressed by higher bulk stresses.

Get full access to this article

View all access options for this article.

References

Seed

H. C.

Chan

C. K.

and Lee

C. E.

Resilient Characteristics of Subgrade Soils and Their Relation to Fatigue Failures in Asphalt Pavements. Proc., International Conference on the Structural Design of Asphalt Pavements, University of Michigan, Ann Arbor, 1962.

AASHTO Guide for Design of Pavement Structures. AASHTO, Washington, D.C., 1986.

Barksdale

R. D.

and Itani

S. Y.

Influence of Aggregate Shape on Base Behavior. In Transportation Research Record 1227, TRB, National Research Council, Washington, D.C., 1989, pp. 173–182.

Gray

J. E.

Characteristics of Graded Base Course Aggregate Determined by Triaxial Tests. Engineering Research Bulletin No. 12, National Crushed Stone Association, 1962.

Tutumluer

and Seyhan

Effects of Fines Content on the Anisotropic Response and Characterization of Unbound Aggregate Bases. In Unbound Aggregates in Roads ( Dawson

A. R.

, ed.), A. A. Balkema Publishers, Oxford, United Kingdom, 2000.

Thompson

M. R.

and Robnett

Q. L.

Resilient Properties of Subgrade Soils. Transportation Engineering Journal, ASCE, Vol. 105, No. TE1, 1979.

Knutson

R. M.

and Thompson

M. R.

Resilient Response of Railway Ballast. In Transportation Research Record 651, TRB, National Research Council, Washington, D.C., 1977, pp. 31–39.

Elliott

R. P.

and Thornton

S. I.

Resilient Modulus and AASHTO Pavement Design. In Transportation Research Record 1196, TRB, National Research Council, Washington, D.C., 1988, pp. 116–124.

Rada

and Witczak

M. W.

Comprehensive Evaluation of Laboratory Resilient Moduli Results for Granular Materials. In Transportation Research Record 810, TRB, National Research Council, Washington, D.C., 1981, pp. 23–33.

10.

Tutumluer

and Seyhan

Neural Network Modeling of Anisotropic Aggregate Behavior from Repeated Load Triaxial Tests. In Transportation Research Record 1615, TRB, National Research Council, Washington, D.C., 1998, pp. 86–93.

11.

Thom

N. H.

Design of Road Foundation. PhD thesis. Department of Civil Engineering, University of Nottingham, United Kingdom, 1988.

12.

Hicks

R. G.

and Monismith

C. L.

Factors Influencing the Resilient Response of Granular Materials. In Highway Research Record 345, HRB, National Research Council, Washington, D.C., 1971, pp. 15–31.

13.

Masad

and Button

J. W.

Unified Imaging Approach for Measuring Aggregate Angularity and Texture. The International Journal of Computer-Aided Civil and Infrastructure Engineering—Advanced Computer Technologies in Transportation Engineering, Vol. 15, No. 4 2000, pp. 273–280.

14.

Tutumluer

Rao

and Stefanski

J. A.

Video Image Analysis of Aggregates. Final Project Report, FHWA-IL-UI-278. Civil Engineering Studies UILU-ENG-2000-2015, University of Illinois at Urbana–Champaign, Urbana, 2000.

15.

Rao

Tutumluer

and Kim

I. T.

Quantification of Coarse Aggregate Angularity Based on Image Analysis. In Transportation Research Record: Journal of the Transportation Research Board, No. 1787, Transportation Research Board of the National Academies, Washington, D.C., 2002, pp. 117–124.

16.

Pan

Tutumluer

and Carpenter

S. H.

Imaging Based Evaluation of Coarse Aggregate Used in the NCAT Pavement Test Track Asphalt Mixes. Proc., First International Conference on Design and Construction of Long Lasting Asphalt Pavements, Auburn, Ala., June 7–10, 2004.

17.

Pan

Tutumluer

and Carpenter

S. H.

Effect of Coarse Aggregate Morphology on Resilient Modulus of Hot-Mix Asphalt. In Transportation Research Record: Journal of the Transportation Research Board, No. 1929, Transportation Research Board of the National Academies, Washington, D.C., 2005, pp. 1–9.

18.

Uzan

Characterization of Granular Material. In Transportation Research Record 1022, TRB, National Research Council, Washington, D.C., 1985, pp. 52–59.

19.

Witczak

M. W.

and Uzan

The Universal Airport Pavement Design System, Report I of V: Granular Materials Characterization. University of Maryland, College Park, 1988.

20.

Rao

Pan

and Tutumluer

Determination of Coarse Aggregate Surface Texture Using Image Analysis. Proc., 16th ASCE Engineering Mechanics Division Conference (EM2003), Seattle, Wash., July 16–18, 2003.