Materials and Construction

Characterization of Particle Shape Distribution of Construction Aggregates

There are huge research needs in the construction aggregate community to better understand the aggregate shape effect on the construction materials such as paving concrete, and to develop a systematic metrics for shape characteristics to optimize the mechanical performances of the aggregate-based materials. The current guidelines and standard specifications for use of construction aggregates (such as ACI 211, ASTM C33, C136 and D75) define the required nominal particle sizes and their distribution typically plotted in terms of the retained and/or passing percentage by weight on a linear or semi-log graph. The significance of the aggregate shape effect also has been well recognized in the construction materials community; however, there is no well-defined metrics/standards to describe the particle shape distribution (unlike the size distribution). This lack of a systematic protocol to quantitatively characterize the range and proportions (i.e., distribution) of particle shapes has significantly hindered to achieve enhanced predictive capabilities in the mechanical properties of cement-based and paving materials. For example, a research team of Western New England University tested two different groups of concrete cylinders, where aggregates used in both specimens strictly met the standard specifications, and all the properties were closely comparable to each other (e.g. the size distribution of the aggregates was same) except the shape: Aggregate A had a shape spectrum with relatively high angularities, while Aggregate B were more circular and rounded. A set of lab experiments showed strengths of the specimens are significantly different. However, the current specifications classify those aggregates equally acceptable. Therefore, a systematic way that can quantify the particle shape distribution needs to be developed to better design / estimate the performances of aggregate-based construction materials. The research will be able to use newly developed techniques to quickly characterize the shapes of different aggregates and investigate the effects on the mechanical properties of the construction materials.

Last Edited by Seung Jae Lee

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Idea Submitted by : Seung Jae Lee; Chang Hoon Lee; Moochul Shin

List your MnDOT Office,District,City, County, Univ. or Other : Florida International University; Western New England University

Idea Champion - Who at MnDOT/LRRB? : John Siekmeier

Why is this a priority and what are the benefits for the State/County/City? :

The potential benefits of this research will include advanced understanding of the effect of particle shape distribution on the engineering properties of aggregate-based materials, which will significantly enhance the predictive capabilities in the material performance estimation. The outcome will improve the mix design and material sustainability by identifying the optimal aggregate blends. Considering Minnesota is one of the leading states producing construction aggregates the most, the research will have a huge impact on the aggregate production industry. Furthermore, the current practice in the aggregate production is unsure of what particle shapes to generate. Therefore, crushers and grinders in aggregate plants have a wide range of different performances in generated aggregate shapes. The new knowledge from this research will significantly influence the industry by better controlling the production process, and in return, a better quality control is expected.

Project Type - MnDOT or LRRB / Research, Implementation or TRS : MnDOT Research

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