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原文传递 Air Content of Concrete Pavements Produced in Conventional versus 30-Second Mixers.

题名：	Air Content of Concrete Pavements Produced in Conventional versus 30-Second Mixers.
作者：	smith, b. j.
关键词：	aggregates, petrographic analysis, air voids
摘要：	Cores were obtained from eight undamaged locations with conventional and short mixing times in equal number. These cores were divided crosswise of the length into thirds, as top, middle, and lower portions. The pieces were further divided lengthwise removing the vertical, middle to 1- inch piece for polishing. The polished pieces were analyzed by image analysis giving air content based on areas. All nine pieces of each core were then observed for petrographic information on aggregates used, condition of the paste, relation of fine and coarse aggregates in the paste, air content distribution and its relation to the other components of the concrete. Petrographic observations indicate that aggregates and paste are well distributed. What is easily observable about the air content is the large number of large, irregularly shaped air voids. With closer observation, smaller air voids in the size ranges for entrained air needed to protect the concrete from freezing and thawing damage are minimally present. The air content analyses indicate these sizes are minimally present in the lower two sections and subminimally present in the top third of the pavement. Also, the three zones of the cores indicate different amounts of total air content as well as differing in amounts of entrained and entrapped air. One separate related core analyzed from a damaged zone showed indications of chemical attack and freeze/thaw damage after saturation with water. Mixer times with vibrator locations during placement relative to the cores has provided some information not available in simple comparisons of mixer times. Short mixer times provided more entrained air but with a larger standard deviation in measurement. Regular mixer times yielded slightly less entrained air but with a smaller standard deviation. / NOTE: Final rept. / Supplementary Notes: Sponsored by Federal Highway Administration, Kansas City, KS. Kansas Div. / Availability Note: Product reproduced from digital image. Order this product from NTIS by: phone at 1-800-553-NTIS (U.S. customers); (703)605-6000 (other countries); fax at (703)605-6900; and email at orders@ntis.gov. NTIS is located at 5285 Port Royal Road, Springfield, VA, 22161, USA.
总页数：	u0709；23p
报告类型：	科技报告