Technical and Computational Aspects of the Measurement of Aggregate Shape by Digital Image Analysis

Abstract

Aggregates need to pass numerous tests to ensure the performance of asphalt and concrete structures and pavements. Some of these tests are fairly onerous, requiring manual, labor intensive, cost ineffective measurements that do not provide significant statistical validity, and are prone to errors through ignorance, negligence, or even in some cases through deliberate misrepresentation. This paper presents a vision based alternative to measure the shape of aggregate particles. The system, although requiring increased capital investment, will result in objective, cost effective, and timely testing of aggregate shape. The system uses dual, synchronized, double speed progressive scan cameras to image the aggregate piece from two directions. A dual image acquisition card simultaneously digitizes both images and does real-time thresholding to create a binary image, which is ported to the host computer. A software trigger determines the presence of an aggregate piece in the image, and the boundaries of the piece are delineated by a perimeter-walking routine. Measurements of aspect ratio and minimum curve radius are made on the perimeter array, and are compared to flat and elongated tests, coarse aggregate angularity ͑uncompacted voids͒, compacted voids, and fractured face counts.

Investigation of Maghra Al Hadida Formation as Coarse Aggregate, Gabel Shabrawet, Northeastern Desert, Egypt

“…In the pavement structure, proportion of aggregates is nearly 95% of the total volume of hot-mix asphalt (HMA). For this reason, shape of the aggregates; appreciably affect the overall quality and durability of the pavement [29]. The high quality of HMA mixture largely depends upon the presence of rough and angular aggregates [30].…”

A Laboratory Investigation into the Effects of Coarse Aggregate Angularity on Performance of WMA

“…Chandan et al [23] researched the texture, angularity, and form of aggregate particles using DIP method and described CAA by means of a gradient-based method. Maerz and Lusher [24,25] tested various shape factors of coarse aggregate using the DIP method, including principal axis ratios, roundness, sphericity, and angularity. Mora and Kwan [26], and Carlos [27] analyzed the particle size and shape of coarse aggregate using DIP and measured the shape parameters, including sphericity, shape factor, convexity ratio, and so on.…”

Análise De Imagens Na Determinação Da Forma E Textura De Areias

“…Entretanto, esse ensaio não permite obter outros parâmetros como a forma e rugosidade, por exemplo. Kwan et al (1999) e Maerz (2004) alertaram que, na interpretação dos resultados de granulometria obtida mediante o peneiramento, é preciso considerar que partículas que passam pela peneira de malha quadrada podem ter dimensões maiores do que a abertura de malha.…”