Influence of aggregate chemical and mineralogical composition on stripping in bituminous mixtures

Abstract

The influence of aggregate chemical and mineralogical composition on moisture sensitivity was investigated using 11 aggregates from typical tropical and temperate climates and one bitumen. Mix design and compaction were based on Swedish Road 94 hot mix base specifications and moisture damage was determined using resilient modulus and tensile strength ratios. As much as practically possible, air voids, gradation, compaction level, bitumen content and curing were controlled. Mixtures from aggregates containing sodium and potassium exhibited relatively high moisture sensitivity. The converse was apparent for aggregates with calcium, magnesium and iron. No significant correlation was observed between the strength ratios and contents of Al₂O₃ and SiO₂. Stripping was generally high for aggregates with quartz and alkali feldspars, although one aggregate with practically 100% quartz showed low moisture sensitivity. Statistical analysis showed good correlation between resilient modulus and tensile strength ratios.

Keywords:

• Stripping
• Aggregate
• Resilient modulus
• Tensile strength
• Moisture sensitivity

Keywords:

• 65K05
• 90C30

Acknowledgements

The authors acknowledge the financial support by Sida/SAREC. The resources at the Division of Highways, Royal Institute of Technology, Stockholm, Sweden have been of great value, as was the technical support by Mr Jonas Ekblad.