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27 CHAPTER 9 Performance 9.1 Less Than One Year 9.2 Greater Than One Year Performance during the very early life of the chip seal is Performance after one year can be measured using texture judged based on chip loss or flushing. Chip loss can happen depth. Some specifications (Austroads 2006) limit design life as soon as a few hours after removing traffic control. If the based on texture of less than 0.9 mm on pavements with speeds loss is greater than 10% of the applied chip quantity (assuming greater than 43 mph. The following relationship has been pro- a one-layer chip application), the cause should be investigated. posed as a means of predicting approximate texture after one Often, early failures of this type are due to high chip applica- year (Gransberg et al. 2005): tion rates, low emulsion application rates, or both. Early chip loss can also be due to excess material passing the no. 200 Td1 = 0.07 ALD log Yd + 0.9 screen, or aggregate not meeting gradation requirements. Unexpected low temperatures, wet weather, or opening to traf- Where fic before adequate residue adhesion has developed can cause Td1 = texture depth in 1 year, mm; early chip loss. Yd = design life in years; and Inundation of chips occurs because of high emulsion appli- ALD = average least dimension of the aggregate, mm. cation rate, embedment of chips in the substrate, or both. Streaking or roping is caused by the spray bar on the as- Texture depth is determined using sand patch or CT meter phalt distributor being either too high or too low. Correction tests. If texture is less than the predicted value, the texture after construction is not possible without the application of should be monitored to determine if a loss of texture beyond another seal. 0.9 mm is expected.