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Microstructural Characterization of Concrete Prepared with Recycled Aggregates

Published online by Cambridge University Press:  15 May 2013

Mafalda Guedes*
Affiliation:
Department of Mechanical Engineering, Escola Superior de Tecnologia de Setúbal, Instituto Politécnico de Setúbal, 2910-761 Setúbal, Portugal ICEMS, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
Luís Evangelista
Affiliation:
Department of Civil Engineering, Instituto Superior de Engenharia de Lisboa, R. Conselheiro Emídio Navarro, 1, 1959-001 Lisboa, Portugal ICIST, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
Jorge de Brito
Affiliation:
ICIST, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal Department of Civil Engineering, Architecture and Georesources, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
Alberto C. Ferro
Affiliation:
ICEMS, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal Department of Mechanical Engineering, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
*
*Corresponding author. E-mail: [email protected]
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Abstract

Several authors have reported the workability, mechanical properties, and durability of concrete produced with construction waste replacing the natural aggregate. However, a systematic microstructural characterization of recycled aggregate concrete has not been reported. This work studies the use of fine recycled aggregate to replace fine natural aggregate in the production of concrete and reports the resulting microstructures. The used raw materials were natural aggregate, recycled aggregate obtained from a standard concrete, and Portland cement. The substitution extent was 0, 10, 50, and 100 vol%; hydration was stopped at 9, 24, and 96 h and 28 days. Microscopy was focused on the cement/aggregate interfacial transition zone, enlightening the effect of incorporating recycled aggregate on the formation and morphology of the different concrete hydration products. The results show that concretes with recycled aggregates exhibit typical microstructural features of the transition zone in normal strength concrete. Although overall porosity increases with increasing replacement, the interfacial bond is apparently stronger when recycled aggregates are used. An addition of 10 vol% results in a decrease in porosity at the interface with a corresponding increase of the material hardness. This provides an opportunity for development of increased strength Portland cement concretes using controlled amounts of concrete waste.

Type
Portuguese Society for Microscopy
Copyright
Copyright © Microscopy Society of America 2013 

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