Concrete produced with recycled aggregates

Tatiana Frassy Falcão De Alencar ,Paulo César Correia Gomes ,J. J. L. Tenório,Christiano Cantarelli Rodrigues

doi:10.1590/s1983-41952012000500006

Tatiana Frassy Falcão De Alencar , Paulo César Correia Gomes + Show 2 more

Open Access

https://doi.org/10.1590/s1983-41952012000500006

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Abstract

This paper presents the analysis of the mechanical and durable properties of recycled aggregate concrete (RAC) for using in concrete. The porosity of recycled coarse aggregates is known to influence the fresh and hardened concrete properties and these properties are related to the specific mass of the recycled coarse aggregates, which directly influences the mechanical properties of the concrete. The recycled aggregates were obtained from construction and demolition wastes (CDW), which were divided into recycled sand (fine) and coarse aggregates. Besides this, a recycled coarse aggregate of a specific mass with a greater density was obtained by mixing the recycled aggregates of the CDW with the recycled aggregates of concrete wastes (CW). The concrete was produced in laboratory by combining three water-cement ratios, the ratios were used in agreement with NBR 6118 for structural concretes, with each recycled coarse aggregates and recycled sand or river sand, and the reference concrete was produced with natural aggregates. It was observed that recycled aggregates can be used in concrete with properties for structural concrete. In general, the use of recycled coarse aggregate in combination with recycled sand did not provide good results; but when the less porous was used, or the recycled coarse aggregate of a specific mass with a greater density, the properties of the concrete showed better results. Some RAC reached bigger strengths than the reference concrete.

Highlights

The heterogeneity of the composition; the specific mass with lower density; the adhered mortar quality and the amount of adhered mortar and the variability of the properties are all important characteristics of recycled aggregates, which represent obstacles for their use as well as for the reliability of the same in concretes used in structural applications (Lovato et al [1], Etxeberria et al [2], Tabsh et al [3], Kwan et al [4], Cabral et al [5])
The results obtained from the recycled aggregate properties: water absorption and particles percentage with D < 0.075 mm, which obeyed the minimum requirements defined by the NBR 15116
The absorbed water from the aggregates needs to be controlled; and the density of the recycled coarse aggregate may be a parameter for selection of recycled aggregates with structural purpose. n The values of the strength obtained were inside of the structural concrete norms and specified in the Brazilian norm for the calculation of structures of armed concrete. n The compressive strength of the recycled aggregate concrete (RAC) was approximately 20 MPa for the w/c = 0.67, the strength was approximately 30 MPa for the w/c = 0.50 and was approximately 40 MPa for the smallest w/c = 0.40

Summary

Introduction

The heterogeneity of the composition; the specific mass with lower density; the adhered mortar quality and the amount of adhered mortar and the variability of the properties are all important characteristics of recycled aggregates, which represent obstacles for their use as well as for the reliability of the same in concretes used in structural applications (Lovato et al [1], Etxeberria et al [2], Tabsh et al [3], Kwan et al [4], Cabral et al [5]) The consequences of these characteristics are observed in the recycled aggregates themselves. The studies of CARRIJO [10] and ANGLE [11] prove these facts

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