Quantifying the role of coarse aggregate strength on resistance to load in HMA

Jaime Reyes, University of Texas at El Paso

Abstract

The performance of the new generation of HMA mixture relying more on a stone-on-stone contact is greatly influenced by the properties of the aggregate blends such as gradation and strength. As a result, aggregates have a significant and direct effect on the performance of bituminous pavements and it is important to maximize the quality of aggregate to ensure the proper performance of roadways. ^ The objective of this research is to evaluate the effect of stress concentrations at contact points on coarse aggregates that could cause aggregate fracture. To achieve the objectives, an extensive series of tests from geological evaluation of quarries and rocks retrieved from them, to rock strength tests, to traditional and new aggregate tests, to geotechnical strength tests were carried out on six aggregates to rank. To establish the performance of mixes, specimens of four different mix types were prepared and subjected to a number of performance related tests. Through correlation analysis and statistical analysis, the redundant aggregate related and performance related were simplified. Based on these activities, several tests for characterizing and ranking aggregates were proposed. ^ From the characterizing the aggregate point and bulk strength results, the Aggregate Crushing Value (ACV) test and its surrogate parameters were found to correlate well with performance. ^ The compressive strength obtained using the Schimdt Hammer seems to be the most appropriate test for estimating the quality of the bulk rock before crushing in the field or lab. The V-meter seems to be an appropriate tool for estimating the modulus as well as the quality of the rock in tension. ^ From the traditional tests, the Los Angeles Abrasion test, Mg Soundness test, the Micro-Deval test, and AIMS angularity after Micro-Deval are appropriate. ^ An approach for the modeling the response of HMA bituminous was developed in this study. The aggregate properties (stiffness, compressive strength, and tensile strength) were determined by matching the model results to experimental measurements conducted on aggregate samples. The PFC mixes are shown to have more localized high stresses within the aggregates than the Superpave and CMHB mixes. ^ A database of the information obtained and a ranking scheme was implemented that can be readily used to rank the aggregates. Based on the average value of each parameter and the coefficient of variation of the test associated with that parameter, the acceptance limits can be set rationally considering the aggregate sources available. ^

Subject Area

Engineering, Civil

Recommended Citation

Reyes, Jaime, "Quantifying the role of coarse aggregate strength on resistance to load in HMA" (2007). ETD Collection for University of Texas, El Paso. AAI1449756.
http://digitalcommons.utep.edu/dissertations/AAI1449756

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