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Concern over water-induced damage in asphalt concrete pavements has resulted in the development of several new moisture susceptibility detection tests. This report compares two modifications of the water conditioning procedure for asphalt concrete specimens as described in the National Cooperative Highway Research Program (NCHRP) Reports 192 and 246. These modifications incorporate longer water exposure conditions for investigating the long-term durability of antistripping additives and paving mixtures. Significant and progressive changes in tensile strength were found to occur when asphalt concrete specimens were repeatedly exposed to freeze-thaw cycles. Factors, such as aggregate source, additive type, and additive quantity, influence the rate of strength loss during cyclical conditioning, and these rates are valuable in material selection. In particular, the sensitivity of cyclical conditioning to additive effectiveness was utilized to develop and select improved additives.

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