An experimental investigation into the bond-slip behaviour between CFRP composite and lightweight concrete

Abstract

Epoxy bonded fibre reinforced polymer (FRP) composites are widely used for the retrofit of ailing reinforced concrete structures, for both shear and flexure. The behaviour of retrofitted concrete structures is governed by the bond strength and the material characteristics of the epoxy bonded FRP and the concrete. Previous studies show that lightweight concrete (LWC), which uses Pulverised Fuel Ash (Lytag) instead of coarse granite aggregates, has significantly lower tensile strength and aggregate interlock compared to normal weight concrete. Performance of shear retrofitted concrete elements is primarily governed by the aggregate interlock and tensile strength. Thus the study of FRP enhancement techniques in LWC is paramount for limit state design. Many studies have been conducted to understand the bond-slip behaviour between normal weight concrete (NWC) and FRP composites, where the increasing interfacial (shear) and normal stresses with increasing plastic deformation lead to FRP debonding and/or FRP rupture failures. This paper presents the experimental pull-off test results obtained from lightweight concrete prisms with various configurations of epoxy bonded Carbon FRP (CFRP) sheets. The experimental results show that the LWC can successfully be applied in the strengthening of lightweight concrete structures. However, the lightweight concrete prisms failed due to a diagonal crack within the concrete materials. This was due to a lower tensile strength compared 2 to normal weight concrete specimens where peeling or rupture of FRP is the dominant failure mechanism.

Predictive Model to the Bond Strength of FRP-to-Concrete Under Direct Pullout Using Gene Expression Programming

“…The experimental database is collected from the tests that were conducted to measure the bond strength between CFRP sheets and the concrete surface under direct tension. Table A.1 in the Appendix summarizes a sample of the experimental training database from the collected specimens (Woo & Lee, 2010;Ming & Ansari, 2004;Mazzotti, Ferracuti, & Bilotta, 2012;Al-Allaf, Weekes, Augusthus-Nelson, & Leach, 2016;Ali-Ahmad, Subramaniam, & Ghosn, 2006;Al-Rousan et al, 2015;Biolzi, Ghittoni, Fedele, & Rosati, 2013;Czaderski et al, 2010;Wan, Jiang, & Wu, 2018;Ghorbani, Mostofinejad, & Hosseini, 2017;Haddad et al, 2013;Haddad, Al-Rousan, Ghanma, & Nimri, 2015;Haddad & Al Dalou, 2018;Hadigheh, Gravina, & Setunge, 2015;Hosseini & Mostofinejad, 2013Irshidat & Al-Saleh, 2016;Ko, Matthys, Palmieri, & Sato, 2014;Mostofinejad, M. H. Mofrad, Hosseini, & H. H. Mofrad, 2018;Nigro, Di Ludovico, & Bilotta, 2011;Pan & Leung, 2007;Serbescu, Guadagnini, & Pilakoutas, 2013;Sharma, Mohamed Ali, Goldar, & Sikdar, 2006;Toutanji & Ortiz, 2001;Toutanji, Saxena, Zhao, & Ooi, 2007;Wu & Jiang, 2013;Yao, Teng, & Chen, 2005). The training and testing or validation data are randomly selected from these data where 63% of the data set is used for training while 37% is used for testing and validation.…”

Hybrid artificial intelligence-based bond strength model of CFRP-lightweight concrete composite

“…These MATEC Web of Conferences 192, 02018 (2018) https://doi.org/10.1051/matecconf/201819202018 ICEAST 2018 datasets were summarized and utilized as the primary input in the development of the hybrid model. The following factors considered by Al-Allaf et al [9] in the DLS test such as the width of CFRP (b frp ), total CFRP bond length (L frp ), CFRP thickness (t f ), and CFRP angle of orientation (q frp ) were also used in this study as the influential parameters for the prediction of bond strength between LWC and CFRP.…”

“…In this study, a total of fifty-five datasets from the double lap shear (DLS) test were retrieved from the paper published by Al-Allaf et al [9] (Refer to table 1). These MATEC Web of Conferences 192, 02018 (2018) https://doi.org/10.1051/matecconf/201819202018 ICEAST 2018 datasets were summarized and utilized as the primary input in the development of the hybrid model.…”

“…Still, less attention is given in the investigation of bond performance between LWC and CFRP [9]. Thus, this present study aimed to model the underlying behavior of the bond strength performance between LWC and CFRP using a hybrid artificial intelligence (AI) model wherein recent studies [25][26][27][28] show its promising application in the field of civil engineering and construction materials.…”

“…Several studies account the success of CFRP as reinforcement in a wide variety of applications for different materials such as aluminum [2,3], steel [4,5], and concrete [6][7][8]. The utilization of CFRP as retrofitting material provides technically sound and cost-efficient due to its lightweight, resistance to corrosion, and ease of handling and installation [9][10][11]. CFRP can be in the form of laminates, sheets, or strips as shown in Fig.…”