Elsevier

Construction and Building Materials

Volume 193, 30 December 2018, Pages 323-331
Construction and Building Materials

Concrete with fine and coarse recycled aggregates: E-modulus evolution, compressive strength and non-destructive testing at early ages

https://doi.org/10.1016/j.conbuildmat.2018.10.209Get rights and content

Highlights

  • More studies are needed to move forward the standards to a more eco-friendly path.

  • Effect of fine and coarse recycled aggregate on the E-Modulus evolution was studied.

  • Its relationship with compressive strength and non-destructive testing was studied.

  • Effect of high curing temperature on E-Modulus evolution was tested at early ages.

  • Concretes with recycled aggregate are more susceptible to crossover effect.

Abstract

The combined use of fine and coarse recycled aggregates in the manufacture of concrete has multiple advantages from the economic and environmental points of view. There is a lack of knowledge about the behavior of concretes containing recycled aggregates, manifested by strong limitations (even prohibitions) in international standards for structural purposes. This paper aims to study the influence of fine and coarse recycled aggregate of concrete (jointly), with particular emphasis on the evolution of the kinetics of E-Modulus and its relationship with compressive strength and non-destructive testing.

Concretes with different degrees of replacement of natural aggregates by recycled aggregates were studied: 0% (reference concrete), 8%, 20% and 31% of the total amount of aggregates. E-Modulus Measurement through Ambient Response Method (EMM-ARM) was used to monitoring the E-Modulus evolution. We also studied the influence of these recycled aggregates on the correlation between E-Modulus and compressive strength, as well as with two non-destructive testing techniques: Ultrasonic Pulse Velocity, and electrical conductivity. The activation energy of the studied concretes, based on data computed from compressive strength measurements at different curing temperatures was calculated.

We observed a negative influence of recycled aggregate on the evolution of E-Modulus from the first 12 h, compared to the reference mixture. The crossover effect on E-Modulus evolution produced by high curing temperatures affects more to the concretes with recycled aggregate. Our data evidenced that the maturity correction for E-Modulus evolution, based on the activation energy of compressive strength, produced accurate superposition of E-modulus in the equivalent age domain.

Introduction

The European Union has established a new strategy on circular economy, in which a more clever use and management of wastes is intended. Indeed, EU-issued documentation [1], [2] claims that improvements in eco-design, prevention and reuse of wastes could produce a net saving of up to 600.000 million euros per year for the European Companies. Similar pathways are being paved throughout the world in view of the recent Paris climate agreement [3]. In fact, developing ways to transform wastes in by-products, has a significant importance from the environmental and economical points of view. A relevant branch of this type of approach is the valorization of construction and wastes, using them as materials for manufacturing concrete and other construction materials [4], [5], [6], [7], [8], [9], [10], [11], [12], [13]. In such context, the use of concrete wastes as recycled aggregates is an interesting option [3], [6], [14]. There is a significant number of studies on the influence of coarse recycled aggregate on the mechanical and physical properties of concrete [9], [15], [16], [17], [18] and it is known that its use produces a decrease of density, compressive strength and E-modulus in concrete, as compared to identical mixtures based on natural aggregates. Nevertheless, some standards like EHE-08 [19], consider that the use of coarse aggregate substitution percentages under 20% does not induce any significant effect on concrete properties. Therefore, it allows the use of recycled aggregates to produce structural concrete within such limits, without requiring any additional studies (as compared to those required for conventional concrete with natural aggregates).

There are studies on the influence of coarse recycled concrete aggregate on the relationship between compressive strength and E-modulus, which is a very important matter in view of the prescriptive aspects of nowadays regulations, being centered on defining concrete classification of mechanical performance with basis on compressive strength only. For example, in the work of Kakizaki et al. [20] and Katz [21] a correction was proposed. The correction uses one variable: density. Other authors proposed to take into account two factors: density and percentage of substitution of coarse recycled concrete aggregate [22]. Genetic programing, model tree and/or artificial neural networks have been used in order to predict certain properties of concrete in the last few years [15], [17], [23], [24]. Some researchers have proposed formulas to estimate the compressive strength and/or E-Modulus in concretes with coarse recycled aggregates [15], [23], [24], [25], [26]. A recent study [17] proposed new formulations (analytical and based on genetic programing) for estimating the compressive strength using a combination of non-destructive tests and other factors related to the curing conditions and composition of the eco-concrete. In that study several types of eco-concrete were investigated, including concretes with different replacement percentages of fine and coarse recycled aggregate. The proposed formulas are very accurate but they estimate compressive strength only; the E-Modulus has not yet been studied with such framework.

The studies about the influence of the fine recycled aggregate on the physical and mechanical properties of concrete are scarce, but there is some literature on the subject [14], [27], [28], [29]. These studies conclude that for low percentages of substitution of fine recycled aggregate (equal or less than 25%) the decrease in compressive strength is not significant and, in some cases, even a slight increase is observed. However, another particular study by Khatib [27] observed an important decrease of the compressive strength (24%) with 25% of replacement. Also, in that particular study [27], for percentages higher than 25%, there is agreement that an important decrease of compressive strength is to be expected. For E-Modulus, with a replacement of 30%, the variation is small. With a 100% of replacement of fine aggregate, the decrease is important, close to 20% [27]. Note that, nowadays, the use of fine recycled aggregate of concrete is not allowed for structural concrete in several standards [19], [30], [31], [32].

In comparison with the use of coarse or fine recycled aggregate alone, the combined use of fine and coarse aggregate produces a higher economic and energetic saving in the concrete production process because the sieving for separating fractions is not necessary and all of the produced recycled material is used, which means that there is no generation of a new by-waste.

There are some studies on concretes with the combined use of fine and coarse recycled aggregates [6], [14], [17], [33], [34], [35], [36], [37], [38], [39]. Some of these studies [14], [17], [34], [35] suggest that the use of coarse recycled aggregate has a higher impact on the compressive strength and on E-modulus than the use of fine recycled aggregate. A recent paper studied the influence of replacement of fine and coarse recycled aggregate on the evolution of compressive strength and its relation with ultrasonic pulse velocity depending on the curing temperature [14]. None of the contributions found in the literature has yet focused on the influence of the replacement on the evolution of the E-Modulus at early ages of concrete beams, neither on its relationship with several UPV tests and compressive strength. In addition, there are several studies relating the electrical conductivity with the mechanical properties of concrete [40], [41], [42]. It was found only one recent paper [41] about the influence of the coarse recycled aggregate on the electrical conductivity (at 56 days). No studies about the influence of the recycled aggregate on the electrical conductivity at early ages were found. No studies about the influence of the partial replacement of the recycled aggregates on the relationship between E-Modulus and electrical conductivity at early ages were found.

The aim of the research reported herein is precisely to close such research gaps and contribute to a better understanding of the influence of fine and coarse recycled aggregate on the mechanical properties of concrete at early ages and in order to advance towards more permissive and more sustainable standards, without incurring structural risk.

Section snippets

Materials

The recycled aggregate used in this research originates from decommissioned precast concrete sleepers with compressive strength higher than 30 MPa. After an adequate treatment (crushed and removed impurities with magnetic separation) a recycled aggregate with 0/12 mm fraction (RA-0/12) was obtained. This is the same recycled aggregate used in a recent study [14] dedicated to the study of the influence of the partial replacement of this recycled aggregates on the relationship between compressive

Influence of the recycled aggregates in the evolution of E-Modulus at early ages

Fig. 2 shows the evolution of E-Modulus at early ages for concretes with different replacement percentages of natural aggregate by recycled aggregate. Two beams were tested for each concrete. The differences between the results of the two beams of each concrete are negligible (less than 1%), for that reason, the averaged curve of each is presented. The evolution of E-Modulus of the four concretes is similar during the first hours and no influence of recycled aggregate is observed. However, from

Conclusions

From the first 12 h, the influence of the fine and coarse recycled aggregate starts to be noted; the higher the amount of recycled aggregate is, the lower the E-Modulus. From the first 24 h, the loss of E-Modulus due to the use of recycled aggregate has certain proportionality with the amount of recycled aggregate replacement.

The replacement of natural aggregate by recycled aggregate has a clear influence on the relationship between E-Modulus and the NDT used: UPV and internal electrical

Conflict of interest

None.

Acknowledgments

This study was developed with the support of the project of Program FEDER-INNTERCONECTA ITC-20113055 “Development of value adding technologies for RCDs for innovative applications”, convened by the Center for Industrial Technological Development (CDTI, for its initials in Spanish), dependent on the Ministry of Economy and Competitiveness and co-funded by the Technological Fund – FEDER Funds. Funding provided by the Portuguese Foundation for Science and Technology (FCT) to the Research Project

References (72)

  • I. Martínez-Lage et al.

    Properties of plain concrete made with mixed recycled coarse aggregate

    Constr. Build. Mater.

    (2012)
  • A. Katz

    Properties of concrete made with recycled aggregate from partially hydrated old concrete

    Cem. Concr. Res.

    (2003)
  • X. Li

    Recycling and reuse of waste concrete in China. Part I. Material behaviour of recycled aggregate concrete

    Resour. Conserv. Recycl.

    (2008)
  • E.M. Golafshani et al.

    Automatic regression methods for formulation of elastic modulus of recycled aggregate concrete

    Appl. Soft Comput.

    (2018)
  • E.M. Golafshani et al.

    Application of soft computing methods for predicting the elastic modulus of recycled aggregate concrete

    J. Clean. Prod.

    (2018)
  • I. González-Taboada et al.

    Prediction of the mechanical properties of structural recycled concrete using multivariable regression and genetic programming

    Constr. Build. Mater.

    (2016)
  • J.M. Khatib

    Properties of concrete incorporating fine recycled aggregate

    Cem. Concr. Res.

    (2005)
  • L. Evangelista et al.

    Mechanical behaviour of concrete made with fine recycled concrete aggregates

    Cem. Concr. Compos.

    (2007)
  • V. Corinaldesi et al.

    Influence of mineral additions on the performance of 100% recycled aggregate concrete

    Constr. Build. Mater.

    (2009)
  • S.C. Kou et al.

    Properties of self-compacting concrete prepared with coarse and fine recycled concrete aggregates

    Cem. Concr. Compos.

    (2009)
  • A.E.B. Cabral et al.

    Mechanical properties modeling of recycled aggregate concrete

    Constr. Build. Mater.

    (2010)
  • A.G. Khoshkenari et al.

    The role of 0–2mm fine recycled concrete aggregate on the compressive and splitting tensile strengths of recycled concrete aggregate concrete

    Mater. Des.

    (2014)
  • M. Gesoglu et al.

    Failure characteristics of self-compacting concretes made with recycled aggregates

    Constr. Build. Mater.

    (2015)
  • D. Xuan et al.

    Durability of recycled aggregate concrete prepared with carbonated recycled concrete aggregates

    Cem. Concr. Compos.

    (2017)
  • B. González-Fonteboa et al.

    Concretes with aggregates from demolition waste and silica fume

    Mater. Mech. Propert. Build. Environ.

    (2008)
  • M. Azenha et al.

    Measurement of concrete E-modulus evolution since casting: a novel method based on ambient vibration

    Cem. Concr. Res.

    (2010)
  • M. Azenha et al.

    Continuous monitoring of concrete E-modulus since casting based on modal identification: a case study for in situ application

    Cem. Concr. Compos.

    (2012)
  • L. Maia et al.

    Influence of the cementitious paste composition on the E-modulus and heat of hydration evolutions

    Cem. Concr. Res.

    (2011)
  • L. Maia et al.

    Identification of the percolation threshold in cementitious pastes by monitoring the E-modulus evolution

    Cem. Concr. Compos.

    (2012)
  • L. Maia et al.

    E-modulus evolution and its relation to solids formation of pastes from commercial cements

    Cem. Concr. Res.

    (2012)
  • C. Zhou et al.

    Mechanical properties of recycled concrete made with different types of coarse aggregate

    Constr. Build. Mater.

    (2017)
  • Ilker B. Topçu et al.

    Using waste concrete as aggregate

    Cem. Concr. Res.

    (1995)
  • J. Zhang et al.

    New perspectives on maturity method and approach for high performance concrete applications

    Cem. Concr. Res.

    (2008)
  • European Parliament, Directive 2008/98/EC of the European Parliament and of the Council of 19 November 2008 on waste...
  • European Commission, EC COMMUNICATION: Roadmap to a Resource Efficient Europe, Eur. Comm. (2011) 32. doi: COM(2011) 571...
  • United Nations FCCC, Paris Agreement, 21st Conf. Parties. (2015) 3. doi:...
  • Cited by (0)

    View full text