United States Department of Transportation
i
Concrete Pumping Effects on Air-Entrained Voids in Concrete Mixtures
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2019-05-01
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[PDF-1.18 MB]
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Edition:Final report, 2014-2019
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Abstract:Placing concrete using a concrete pump has placement advantages due to the increased speed, accessibility, and convenience of operation. Unfortunately, the pumping of air-entrained concrete is known to affect the fresh air content in the fresh concrete. This has caused concern about the durability of concrete in environments where the concrete will experience repeated freezing and thawing cycles. The research described in this report investigated the impact concrete pumping has on air-entrained voids in concrete. The study examines the effects of different air contents, pumping time, and pressure has on the air volume and the stability of the air void system. The laboratory tests conducted show a significant amount of air volume was lost in the fresh concrete as a result of pumping. In many cases, the quality of the air void system in the fresh concrete would predict the concrete would have poor performance in freeze-thaw testing; however, all mixtures showed satisfactory performance in ASTM C666 freeze-thaw testing. This indicates the quality of the air void system in the fresh concrete after pumping is not representative of the hardened concrete for the materials and procedures used in this testing. The results suggest that if a high-quality air void system is present prior to pumping, that the air void system after pumping should be sufficient f or freeze-thaw durability.
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