Effect of Aggregates on Isothermal (Steric) Hardening of Asphalts

Asphalt/aggregate mixes were studied to determine if extreme embrittlement, which usually leads to severe cracking, and which has been reported by state highway departments for many years, was a simple problem of improper materials. Eighteen different combinations of aggregate and asphalt were studied over eight months in an experiment designed to maximize the chance of identifying aggregate- induced embrittlement. Aggregates seem to have no influence on embrittlement, and none of the mixes in the test suffered from it during the test period. The results suggest other possible causes, which could include overheating the asphalt in the mix plant, improper compaction, loads in excess of the pavement's capacity or excessive moisture.