Interface role in composite RC beams with a light-weight concrete core and an ultra high-durability concrete skin. (1st February 2021)

• Record Type: Journal Article
• Authors: Martins, R.; Carmo, R.N.F.; Costa, H.; Júlio, E.; Cordeiro, T.; Almeida, V.
• Is Part Of: Engineering structures. Volume 228(2021)
• Publication Date: 2021-02-01
• Subjects: Composite beams -- Flexural behavior -- Shear capacity -- LWAC -- UHDC -- Interface; Structural engineering -- Periodicals; Structural analysis (Engineering) -- Periodicals; Construction, Technique de la -- Périodiques; Génie parasismique -- Périodiques; Pression du vent -- Périodiques; Earthquake engineering; Structural engineering; Wind-pressure; Periodicals; 624.105
• DOI: 10.1016/j.engstruct.2020.111524
• Languages: English
• ISSNs: 0141-0296

Abstract

Highlights: Interface between LWAC and UHDC. Composite beams with more durability and simultaneously more eco-friendly. Thirteen different beams were tested varying the interface between the core and the outer layer. Experimental evaluation of the flexural and shear capacity of beams with 'super skin' Abstract: This present paper describes an experimental study focused on the influence of the interface strength, between the lightweight aggregate concrete (LWAC) and the ultra-high durability concrete (UHDC), on the structural behavior of composite beams. The beams were produced with a new concept which consists of using an UHDC layer only in the cover, being the core produced with LWAC. The great benefit of using this 'superskin' is to apply UHDC only where it is greatly needed for durability purpose and not in the total cross section of the structural members, avoiding high cement consumption, which is important to reduce the environmental impact associated to cement production. Thirteen different beams were tested until bending – or shear – controlled failure, varying the type of interface between the LWAC core and the UHDC cover: i) smooth; b) rough; c) with steel connectors; and d) indented. Several slant shear tests (SST) were performed to evaluate the longitudinal shear strength of the LWAC-UHDC interfaces. The main goals of this study were: 1) to analyze if composite beams' behavior is monolithic under load increasing, in both flexural an shear tests, i.e., to check for possible slip of the outer layer; 2) to evaluate the influence of the interface roughness and of UHDC cover on structural performance, and finally 3) to evaluate which is the most proper interface to produce this type of composite beams. The results show that the superskin greatly enhances the structural behavior of the beams and that an appropriate roughness is necessary at the interface between the two concretes, to make the proposed solution viable and reliable.