ABSTRACT
Abstract The objective of this investigation was to develop acceptance criteria for concrete aggregates which have been obtained by crushing old concrete pavements so that these recycling aggregates are suitable for the production of new concrete pavements. Concretes with water-cement-ratios of 0.38, 0.45 and 0.52 were made from recycling aggregates as well as from natural aggregates. The recycling aggregates were prepared either from the debris of demolished concrete pavements or from laboratory concretes with compressive strengths ranging from 47 MPa to 68 MPa. Air entrainment as well as superplasticizers were employed for the recycling concretes. The recycling concretes were either moist cured or treated with a curing compound. For freeze-thaw testing the CDF-method has been employed. All concretes tested satisfied the criteria for concretes with a high resistance to freezing, thawing and deicing salts. The experiments showed that air entrainment of the old concretes is not a necessary requirement for their use as recycling aggregates. Nevertheless, the air void characteristics of the recycling concrete are dominant parameters for the scaling resistance of such concretes. There is a trend that the extent of scaling decreases with increasing compressive strength of the old concretes from which the recycling aggregates have been obtained. Keywords: Aggregate freeze-thaw resistance, air entrainment, concrete aggregates, concrete compressive strength, concrete deicing salt resistance, concrete freeze-thaw resistance, recycling concrete.
