Evaluation of the contact characteristics of graded aggregate using coarse aggregate composite geometric indexes

摘要

The influence of the aggregate's geometric properties on its contact characteristics was investigated by testing the geometric parameters of three aggregates types using the aggregate imaging system (AIMS). The graded aggregate's composite geometric indexes were formulated to analyze and evaluate its contact characteristics; additionally, an aggregate contact-slip tester was developed to determine the contact characteristics of various graded aggregates. Results show that particle shape and angularity are affected by mechanical processing; angularity and textural characteristics are influenced by the rock material's nature, and particle size has little effect on the aggregate's geometric characteristics. The values of the composite geometric parameters of graded aggregates with different nominal maximum aggregate sizes increase with the increasing specific gravity of the coarse aggregate. As the ratio of coarse to fine aggregate increases, the graded geometric index of the coarse aggregate in the aggregate increases. Higher the coarse aggregate in the gradation system, lesser is the fine aggregate, and hence, greater is the contact effect on the aggregate. CITX has a good correlation with the graded aggregate's contact characteristics. Thus, the particle contact effect of graded aggregate and the degree of skeletal interlocking can be effectively evaluated using CITX. (C) 2020 Published by Elsevier Ltd.