Investigation of Relationships between AIMS Shape Properties and VST Friction Values

A thorough analysis was conducted for AIMS shape properties measured for virgin aggregates, aggregates polished in the Micro-Deval (MD) for 105 and 210 minutes, and VST friction samples. Excellent repeatability of AIMS angularity and texture measurements was observed. Investigating the relationships between AIMS-MD angularity and texture, a strong relationship was found between VST friction values and AIMS AMD-105 angularity and a combined angularity and texture of AIMS measurements also for AMD-105. This indicates that VST friction values are a function of both texture and angularity. Furthermore, the strong correlation between AIMS AMD-105 texture and the surface texture of VST friction samples indicated that MD is a viable option for replacing VST as a polishing mechanism and that current VST procedure might not be long enough to achieve terminal texture. Further analysis indicated that AIMS AMD-105 shape properties could potentially replace AMD- 210 for selecting and ranking aggregates for friction properties. However, the recommendation is to keep testing at both polishing intervals. Finally, clustering analysis was conducted to obtain threshold for classifying aggregate angularity and texture into acceptable and non-acceptable zones (i.e., defining the criteria for qualifying aggregates for friction purposes). In this study, two types of clustering were used: two-step cluster analysis and the K-means cluster analysis. The final outcome of this analysis was that an aggregate source with texture AMD- 105 > 140 and angularity AMD-105 > 1240 is recommended for friction purposes.Illinois Department of Transportation, R27-SP27Ope