DETERMINE IMPACT OF FIELD SANDS ON WORKABILITY AND ENGINEERING PROPERTIES OF SUPERPAVE MIXTURES IN TEXAS

Field sands have been used in hot mix asphalt (HMA) pavements to improve workability since they are readily available and less expensive than crushed materials. However, due to their potential adverse effects on performance, field sands are typically limited to 10% of the aggregates. A key issue is the presence of harmful clay particles that can significantly impact asphalt concrete (AC) performance.

Understanding the impact of these clay particles on AC performance is the subject of this research. The upper limit of specific field sand, given the amount of active clay present in it, the process to determine the clay content, and how they affect the performance of AC mixes shall be evaluated. Since field sands are more round compared to the crushed aggregates, mixes containing more field sands can be compacted to a given density at lower binder contents. Given the less particle to particle interlocking of such mixes, however, they are more suspect to excessive rutting. Thus, this research shall investigate the effect of clay minerals as well as the sand properties on the performance of AC mixes (with a focus on Superpave mixtures) and evaluate their combined/interactive effects, as the natural sands are a combination of both. To that end, the main goal of the project is to provide guidelines that can be used to select the maximum allowable percentage of a given field sand.