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Cement and Concrete Research 37 (2007) 735 – 742

Influence of amount of recycled coarse aggregates and production process
on properties of recycled aggregate concrete
M. Etxeberria ⁎, E. Vázquez, A. Marí, M. Barra
Universitat Politécnica de Catalunya (UPC), Department of Construction Engineering, Faculty of Civil Engineering, 08034 Barcelona, Spain
Received 22 December 2005; accepted 7February 2007

Abstract
In this study recycled coarse aggregates obtained by crushed concrete were used for concrete production. Four different recycled aggregate
concretes were produced; made with 0%, 25%, 50% and 100% of recycled coarse aggregates, respectively. The mix proportions of the four
concretes were designed in order to achieve the same compressive strengths. Recycled aggregates wereused in wet condition, but not saturated, to
control their fresh concrete properties, effective w/c ratio and lower strength variability. The necessity to produce recycled aggregate concrete with
low–medium compressive strength was verified due to the requirement of the volume of cement. The influence of the order of materials used in
concrete production (made with recycled aggregates) withrespect to improving its splitting tensile strength was analysed. The lower modulus of
elasticity of recycled coarse aggregate concretes with respect to conventional concretes was measured verifying the numeral models proposed by
several researchers.
© 2007 Elsevier Ltd. All rights reserved.
Keywords: Mixture proportioning; Workability; Mechanical properties; Aggregates; Recycled aggregates;Recycled aggregate concrete

1. Introduction
To obtain good quality concrete using recycled aggregate it is
necessary to follow the minimum requirements defined by the
BCSJ [1], RILEM [2], DIN 4226.100 [3], and prEN
13242:2002 [4]. Acceptable properties of aggregates are an
elemental base for concrete quality, however adequate mix
proportions and concrete production methods are highlyimportant in concrete quality too. Recycled aggregates are
composed of original aggregates and adhered mortar. The
physical properties of recycled aggregates depend on both
adhered mortar quality and the amount of adhered mortar. The
adhered mortar is a porous material, its porosity depends upon
the w/c ratio of the recycled concrete employed [5]. The
crushing procedure and the dimension of therecycled aggregate
have an influence on the amount of adhered mortar [6–9]. The
density and absorption capacity of recycled aggregates are

⁎ Corresponding author. Tel.: +34 93 401 17 88; fax: +34 93 401 72 62.
E-mail address: miren.etxeberria@upc.edu (M. Etxeberria).
0008-8846/$ - see front matter © 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.cemconres.2007.02.002

affected byadhered mortar and they must be known prior to the
utilization of recycled aggregates in concrete production in
order to control properties of fresh and hardened concrete. The
absorption capacity is one of the most significant properties
which distinguishes recycled aggregate from raw aggregates,
and it can have an influence both on fresh and hardened
concrete properties. Some researcherssuggest a limit of 30% of
recycled aggregate in order to maintain the standard requirements of 5% of absorption capacity of aggregates for structural
concrete [10,11].
The increased absorption of recycled aggregate, means that
concrete made with recycled coarse aggregates and natural sand
typically needs 5% more water than conventional concrete in
order to obtain the same workability [12–17]. Ifrecycled
aggregates are employed in dry conditions the concrete's
workability is greatly reduced due to their absorption capacity.
Some researchers argue that the recycled aggregates should be
saturated before use [18].
In general the workability of recycled aggregate concretes is
affected by the absorption capacity of the recycled aggregates.
The shape and texture of the aggregates can...