Effects of Recycled Aggregate Characteristics on Performance Parameters of Recycled Aggregate Concrete


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Title: Effects of Recycled Aggregate Characteristics on Performance Parameters of Recycled Aggregate Concrete

Author(s): S. Nagataki, A. Gokce, and T. Saeki

Publication: Special Publication

Volume: 192


Appears on pages(s): 53-72

Keywords: compressive strength; mortar; porosity; recycling; water

Date: 4/1/2000

This study points out the close relationship between several quality indicators of recycled aggregate and the performance of recycled aggregate concrete. Regarding the diversity in quality and composition of the recycled concrete products, three laboratory produced air-entrained-concretes with low, medium and high water-cement ratios and a non-air-entrained concrete with medium W/C were processed for recycling. Recycled aggregate concretes were produced with a water/cement of .55, and tested after 28 days of moist curing. Results of the capillary water immersion and permeable porosity tests indicate that structure and amount of adhered mortar as well as the recovery percent of original coarse aggregate and other physical properties of recycled coarse aggregate, especially the inclusion of recycled fine aggregate into the system are the mean reasons creating important differences in the permeable pore system and captivity of recycled aggregate concretes. Relatively low pore content of the non-air-entrained type adhered mortar compared with the air-entrained ones influences the concrete porosity in the same way. The volume of permeable pores in concrete produced with non-air entrained type of recycled aggregate seems to be reduced. Although entrained air pores of the adhered mortar increase the total volume of the permeable voids, they play a role of interrupting the capillaries. The findings of this research indicate that all possible variations in recycled aggregate properties must be taken into account to be able to design durable recycled aggregate concretes.