EFFECT OF COAL-CONTAMINATED AGGREGATE ON ASPHALTIC CONCRETE PAVEMENT PERFORMANCE

Author(s)
DIYALJEE, VA
Abstract

Crushed aggregate containing approximately 8% by weight of soft coal was used in the construction of asphaltic concrete pavements on23 km of secondary and primary roadways. Within 5 months after construction, surface distress in the form of raveling, pitting, and localized potholing occurred along and outside the wheelpaths. The presence of coal in the aggregate had been identified during the quarrying and crushing stages. Normal and 24-hr soaked marshall stability tests were undertaken to evaluate the quality of the crushed aggregate. Retained stabilities of 20% to 69% were obtained using samples obtained from the crushing plant and dryer of the asphalt plant, respectively. On the basis of the higher stability obtained from the asphalt plant-processsed material, it was decided to use the aggregate. This decision was also influenced by a contract deficiency pertaining to the "acceptable" amount of deleterious material. For productionasphaltic concrete, a 70% retained stability was chosen as a minimum requirement for an acceptable mix. During the first 6 km of paving, retained stability lower than the target resulted in the contaminated aggregate being blended with 20% of clean aggregate. This blend resulted in 80 to 90% retained stability. Despite this, all roadwayssuffered pavement distress. To stop the progressive pavement deterioration, a fog seal was applied to the secondary roadways, with a subsequent single-surface seal applied to all roadways in 1985. Since then, no further pavement distresses have been reported and the roadways are performing well. This paper appears in transportation research record no. 1228, Asphalt mixtures and asphalt chemistry.

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Publication

Library number
I 834665 IRRD 9012
Source

TRANSPORTATION RESEARCH RECORD WASHINGTON D.C. USA 0361-1981 SqMIAL 1989-01-01 1228 PAG:22-31 T8

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