Digital image correlation to characterize the flexural behavior of lightweight ferrocement slab panels Amirhossein Madadi a,⇑ , Hamid Eskandari-Naddaf a,⇑ , Rasoul Shadnia a , Lianyang Zhang b a Department of Civil Engineering, Hakim Sabzevari University, Sabzevar, Iran b Department of Civil and Architectural Engineering and Mechanics, University of Arizona,Tucson, AZ, USA highlights  DIC technique is used for the first time on perlite-contained FSPs.  Effect of volume fraction of reinforcement and expanded perlite on mechanical properties of FSPs is investigated.  DIC technique can appropriately monitor flexural behavior, crack properties and ductility of FSPs.  Effect of expanded perlite on porosity of ferrocement mortar is evaluated. article info Article history: Received 14 August 2017 Received in revised form 18 August 2018 Accepted 14 September 2018 Keywords: Digital image correlation (DIC) Ferrocement slab panel Expanded perlite Flexural behavior abstract Digital image correlation (DIC) is a relatively new technique for measuring whole-field displacements and strains. In this study, the DIC technique was used to characterize the flexural behavior of ferrocement slab panels containing expanded perlite lightweight aggregate (LWA). Specifically, 12 slab panels con- taining different number of expanded rib lath layers (1, 2, and 3) and different amount of expanded per- lite LWA (55, 35, 15, and 0 vol%) were produced and subjected to three-point loading flexural test. Then the load-deflection curves obtained from displacement sensors were used to verify the DIC results. Afterward, the DIC results were used to evaluate the cracking behavior of all specimens. Scanning elec- tron microscopy (SEM) imaging along with energy dispersive spectroscopy (EDS) analysis was also per- formed to characterize the microstructure of the mortar of various mixture designs. As expected, the DIC results are in close agreement with those obtained from displacement sensors. The DIC results indicate that the flexural behavior of lightweight ferrocement slab panels is influenced by the number of expanded rib lath layers. The DIC results also show that, although the load bearing capacity of the slab panels were enhanced by increasing the number of expanded rib lath layers, the specimens containing two layers of expanded rib lath has the smallest crack width. The results of the SEM imaging indicate that the increased amount of expanded perlite LWA has resulted in increased porosity (95–380%) and thus decreased density (18–37%) of the lightweight ferrocement mortar. Ó 2018 Elsevier Ltd. All rights reserved. 1. Introduction Ferrocement panel is a thin slab reinforced by layers of mesh and used to produce thin structures with high strength and flexi- bility [1,2]. The characteristics of the ferrocement slab panel heav- ily depend on numerous parameters such as cement type, dosage of cement and aggregate, wire mesh strength, geometry and num- ber of layers [3–7]. For example, closer placement and distribution of mesh layers reduces the crack spacing and width in the ferroce- ment panels [8]. In addition, ferrocement slab panels show better performance regarding the modulus of rupture, flexural strength, and cracking behavior compared to reinforced concrete slabs [9,10]. Although ferrocement productions are typically suggested as lightweight structures [11,12], there is still a need to utilize the alternative building materials like lightweight aggregates (LWAs) as partial replacement of sand. LWAs are available in abundance worldwide and can be utilized in producing cementitious materi- als in a wide range of suitable strength values and with reduced weight [13–15]. One of these LWAs is expanded perlite, which https://doi.org/10.1016/j.conbuildmat.2018.09.079 0950-0618/Ó 2018 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors. E-mail addresses: Madadihsu@yahoo.com (A. Madadi), Hamidiisc@yahoo.com (H. Eskandari-Naddaf). Construction and Building Materials 189 (2018) 967–977 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat