Test method to determine the degree of asphalt stripping from aggregates

Graduation date:1990Moisture damage has long been recognized as one of the most\ud critical factors influencing the performance of asphalt concrete (AC)\ud pavements. This moistureinduced damage occurs from either the\ud physical separation of the asphalt film from the aggregate or the\ud softening of the asphalt binder within the AC mixture in the presence\ud of water. This phenomenon is often termed stripping.\ud Although many test procedures have been developed over the years\ud to identify stripping potential of AC mixtures, none have received\ud wide acceptance by the engineering profession. The purpose of this\ud research was to develop a standard test procedure that will allow for\ud a quantitative means of predicting moisture susceptibility of AC\ud mixtures and provide for an assessment on the effectiveness of\ud antistripping additives.\ud The measure of response made in this study was the resilient\ud modulus obtained from a pneumatic repeatedload test system. Dense\ud graded, laboratorycompacted test specimens fabricated from two\ud aggregate sources in the state of Oregon were evaluated in this\ud research.\ud The test procedure and specimen preparation developed was\ud implemented with a saturation and freezethaw moisture condition\ud cycling. Results indicate that the procedure can significantly\ud differentiate between a proven stripping aggregate and a proven non\ud stripping aggregate. The comparison can be made following full\ud saturation plus one freezethaw cycle. Results also indicate that\ud caution must be used when comparing mixes of different air void\ud contents. The results of the procedure developed appear to over\ud predict moisture susceptibility of low air void groups (<6.5%) and\ud under predict moisture susceptibilty of high air void groups (>8.5%).\ud The procedure also has a strong potential to assess the effectiveness\ud of antistripping additives, although some of the additives evaluated\ud in this study generally did not improve the mixtures sensitivity to\ud moisture damage