Characterization of aggregate shape properties using a computer automated system

Abstract

Shape, texture, and angularity are among the properties of aggregates that have a
\nsignificant effect on the performance of hot-mix asphalt, hydraulic cement concrete, and
\nunbound base and subbase layers. Consequently, there is a need to develop methods that
\ncan quantify aggregate shape properties rapidly and accurately. In this study, an
\nimproved version of the Aggregate Imaging System (AIMS) was developed to measure
\nthe shape characteristics of both fine and coarse aggregates. Improvements were made
\nin the design of the hardware and software components of AIMS to enhance its
\noperational characteristics, reduce human errors, and enhance the automation of test
\nprocedure.
\nAIMS was compared against other test methods that have been used for
\nmeasuring aggregate shape characteristics. The comparison was conducted based on
\nstatistical analysis of the accuracy, repeatability, reproducibility, cost, and operational
\ncharacteristics (e.g. ease of use and interpretation of the results) of these tests.
\nAggregates that represent a wide range of geographic locations, rock type, and shape
\ncharacteristics were used in this evaluation.
\nThe comparative analysis among the different test methods was conducted using
\nthe Analytical Hierarchy Process (AHP). AHP is a process of developing a numerical
\nscore to rank test methods based on how each method meets certain criteria of desirable
\ncharacteristics. The outcomes of the AHP analysis clearly demonstrated the advantages
\nof AIMS over other test methods as a unified system for measuring the shape
\ncharacteristics of both fine and coarse aggregates.
\nA new aggregate classification methodology based on the distribution of their
\nshape characteristics was developed in this study. This methodology offers several
\nadvantages over current methods used in practice. It is based on the distribution of shape
\ncharacteristics rather than average indices of these characteristics. The coarse aggregate
\nform is determined based on three-dimensional analysis of particles. The fundamental
\ngradient and wavelet methods are used to quantify angularity and surface texture,
\nrespectively. The classification methodology can be used for the development of
\naggregate shape specifications.