Potential of using virgin cork as aggregates in development of new lightweight concrete

• Published in: Construction & building materials Vol. 265; p. 120734
• Main Authors: Tedjditi, Ahmed Kamel, Ghomari, Fouad, Taleb, Omar, Belarbi, Rafik, Tarik Bouhraoua, Rachid
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 30-12-2020; Elsevier
• Subjects: Engineering Sciences; ITZ; Lightweight concrete; Mechanics; Porosity; Strengths; Thermal conductivity; Thermics; Virgin cork; Thermal conductivity; Virgin cork; Porosity; Lightweight concrete; Strengths; ITZ
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2020.120734

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•Virgin cork lightweight concretes with density lower than 720 kg/m3 were produced.•The use virgin cork reduced both workability and plastic viscosity of concrete.•As non-structural materials, concretes showed competitive mechanical strengths.•Interesting thermal conductivities were obtained for high amount of virgin cork.•Poor ITZ between virgin cork aggregate and cementitious matrix was observed.
This paper examines the potential to develop a lightweight concrete for building applications using cork aggregates. The main contribution of the proposed work is the use of virgin cork, which presents, compared to reproduction cork, different structure, density and surface type so that it has insufficient quality for cork stoppers. The experimental work was carried out by producing four concrete mixtures containing, in volume of aggregates: 25, 50, 75 and 100% of virgin cork aggregates. Cork concretes were assessed and compared with an ordinary concrete in terms of: workability, plastic viscosity, density, ultrasonic pulse velocity (UPV), porosity, capillary absorption, mechanical properties, microstructure and thermal conductivity. The experimental work shows that the incorporation of virgin cork into concrete reduces its workability and plastic viscosity and produces lightweight concretes with density lower than 720 kg/m3. Remarkably, depending on virgin cork amount, the increase of concrete porosity varied between 26 and 470%, compared to ordinary concrete. When replacing the totality of mineral aggregates, concretes showed values of only 0.48 and 0.72 MPa for compressive and flexural strength, respectively. Nonetheless, for non-structural materials, these mechanical strengths can be considered as competitive. Investigation of the Interfacial Transition Zone (ITZ) between cork aggregates and cementitious matrix revealed porous layer with thickness ranging between 90 and 150 µm. In terms of insulation capacity, the use of virgin cork leads to enhance thermal conductivity of concrete by 28–98 %, depending on cork percentage. Findings suggest that the developed virgin cork concretes can be used in several building application, namely, as filling blocks and insulation screeds.