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Title: Recycled concrete
Authors: United States. Assistant Secretary of the Army (R & D).
Buck, Alan D.
Keywords: Concrete
Concrete aggregates
Compressive strength
Resistance to freezing and thawing
Temperature/moisture effects
Waste concrete
Publisher: Concrete Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Miscellaneous paper (U.S. Army Engineer Waterways Experiment Station) ; C-72-14.
Description: Miscellaneous paper
Abstract: Supplies of natural mineral aggregates are diminishing even as their usage increases. Disposal problems exist because of steadily increasing accumulation of solid wastes. In light of these two situations an investigation was made to evaluate the use of crushed waste concrete similar to pavement concrete as concrete aggregates. A discarded concrete driveway that contained siliceous aggregates and a laboratory concrete beam that contained limestone as coarse and natural siliceous sand as fine aggregate were selected to represent pavement concretes. Portions of each kind of concrete were processed into aggregate sizes. Three concrete mixtures were made to evaluate the driveway concrete as aggregate, and two other mixtures were made to evaluate the crushed concrete beam as aggregate. Specimens from each round of each mixture were tested for compressive strength at different ages up to six months, for resistance to accelerated and thawing, and for volume changes due to temperature changes or to moisture effects at a constant temperature. The aggregate particles produced by crushing concrete had good particle shape, high absorptions, and low specific gravities by comparison with conventional natural mineral aggregates. Other results included: (a) use of crushed concrete as coarse aggregate had no significant effect on the mixture proportions or workability of the mixtures by comparison with the control mixtures; (b) when the crushed driveway concrete was also used as fine aggregate, the mixture was slightly less workable and required more cement than the control mixture; (c) use of waste concrete as coarse aggregate results in concrete strength 300 to 1100 psi lower than comparable strengths of control mixtures; (ct) use of the driveway waste concrete substantially improved frost resistance; (e) use of the crushed concrete beam as coarse aggregate apparently lowered frost resistance slightly; and (f) use of waste concrete as aggregate had no significant effect on the volume response of specimens to temperature or moisture effects. It is concluded that the present results are promising for the use of recycled pavements or similar concretes as concrete coarse aggregate and perhaps as fine aggregate. It is emphasized, however, that the results in this work do not pertain to concrete from demolished buildings since the 1.-laste concrete used in this work was free of contamination by other materials such as sulfates. Recycled building concrete is likely to be contaminated by sulfates from plaster and gypsum wallboard, which creates a possibility of sulfate attack. The possible use of that kind of waste concrete as concrete aggregate should be evaluated in future work.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Miscellaneous Paper

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