Bond behavior of self-compacting mortar containing construction and demolition waste under elevated temperatures
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ORIGINAL PAPER
Bond behavior of self‑compacting mortar containing construction and demolition waste under elevated temperatures Amar Benyahia1 Received: 20 June 2020 / Accepted: 2 November 2020 © Springer Nature Switzerland AG 2020
Abstract The aim of the current study is to provide useful data and information on the compatibility between self-compacting mortar (SCM) mixes containing recycled powder (RP) from construction and demolition waste (C&DW) and parent concrete under temperatures in excess of the current. For this purpose, four SCM mixes were prepared with replacement ratios of 0%, 10%, 20% and 30% RP, according to the EFNARC specifications. The compatibility was measured at 28-day curing age via slant shear test on composite cylindrical samples (half SCM/half concrete) cured in water curing tank and then held at different levels of elevated temperature: 200 °C, 400 °C and 600 °C for a duration of 2 h. The results of fresh mortar and also hardened unit weight, compressive strength and water absorption were assessed. The study concluded that the partial replacement of the cement with RP decreased both dry unit weight and compressive strength and increased water absorption of SCMs. In addition, the obtained data of slant shear test showed that mortars containing up to 20% RP exhibited sufficient adhesion with the concrete substrate (compatible mortar) at elevated temperatures (200–400 °C) during 2 h. Beyond 400 °C, only composites containing up to 10% RP could withstand this temperature. Keywords Recycled powder · Self-compacting mortar · Elevated temperatures · Adhesion · Compatibility
Introduction Concrete is a composite material frequently used in all civil engineering structures. When concrete surfaces are exposed to fire, their mechanical properties (compressive strength, tensile strength, ductility, volume stability, modulus of elasticity, etc.) can dramatically change under the effect of heat. This leads to undesirable structural failures (spalling and cracking of the concrete) (Short et al. 2001). Nevertheless, after a sever fire, reinforced concrete structures can maintain a certain structural integrity (Annerel and Taerwe 2013). In this case, it is better to repair or even strengthen rather than demolish and rebuild these structures. In the last several decades, wide range of products for repair (unmodified Portland cement mortar, latex modified Portland cement mortar or concrete and polymer concrete) was used to overcome damage in deteriorated structures (Emberson and Mays 1990). The choice of them depends * Amar Benyahia a.benyahia@univ‑chlef.dz 1
Geomaterials Laboratory, Civil Engineering Department, University of Chlef, BP 151, 02000 Chlef, Algeria
on performances (adhesion with old concrete, strength development of material with old concrete, durability and appearance of finished surface), cost and exposure conditions of concrete structure. However, Portland cement mortar remains the most common type of material used to repair damaged concrete structures because it usually offers the
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