Potential of structural pozzolanic matrix–hemp fiber grid composites Domenico Asprone a,⇑ , Massimo Durante b , Andrea Prota a , Gaetano Manfredi a a Department of Structural Engineering, University of Naples ‘‘Federico II’’, Naples, Italy b Department of Materials and Production Engineering, University of Naples ‘‘Federico II’’, Naples, Italy article info Article history: Received 1 September 2010 Received in revised form 13 December 2010 Accepted 24 December 2010 Available online xxxx Keywords: Hemp fiber Pozzolanic mortar Sustainability Inorganic composite Structural retrofit abstract Currently, sustainability represents a primary issue for construction industry. New material and techno- logical solutions are widely proposed and investigated to meet sustainability requirements and natural fibers represent one of the most studied materials. The work presented here investigated the mechanical behavior of a sustainable composite system made by pozzolanic mortar reinforced with hemp fiber grids. To improve the durability of the system and in particular of the fibers in the pozzolanic mortar environ- ment a latex coating was used. The objective of the study was to investigate the mechanical behavior of the proposed composite system and assess the feasibility of using the system for structural retrofit appli- cations on existing structures. A mechanical characterization of the fibers was conducted and the effec- tiveness of the latex coating in improving the durability of the fibers was investigated. The mechanical behavior of the composite system was studied, through a three-point bending test program. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Low environmental impact of operations on built environment is often a primary condition to be respected by construction designers and operators. Thus, recently, new technological solu- tions are proposed and new materials are investigated and used [1,2]. For this reason, in recent years, natural fibers have been widely investigated, to be used as an alternative to carbon, glass or plastic fibers, in several composite applications for construction industry. In fact, given their low environmental impact both in pro- duction and in disposal phase, natural fibers represent a highly ‘‘sustainable’’ material. Furthermore, natural fibers can be locally supplied, ensuring a sustainable production chain. The recent increasing scientific interest in natural fibers as a component of construction applications is also due to the good mechanical properties exhibited by natural fibers. Available litera- ture provides the mechanical characterization of natural fibers, in terms of elastic properties and tensile strength [3–5]; in particular, attention has been focused on different fibers, e.g. flax [6], jute [7,8], hemp [9,10], sisal [11]. The available reviews [3,5] reports the main mechanical properties of various natural fibers. It can be observed that the tensile strength can reach more than 1000 MPa, in case of flax fiber and vary from about 400 MPa to 800 MPa in case of jute fiber, whereas hemp fiber exhibits a tensile strength of 690 MPa. Furthermore, the ultimate tensile strain var- ies from 1.5% for the jute fiber to 3.2% for the flax fiber, whereas hemp fiber presents an ultimate tensile strain of 1.6%. Young’s modulus is equal to 26.5 GPa and 27.6 GPa for jute and flax fiber, respectively, whereas, according to Dhakal et al. [10], Young’s modulus for hemp fiber varies from 30 GPa to 60 GPa. Thus, the values of the main mechanical properties of natural fibers are not so far from those exhibited by the most used synthetic fiber, i.e. glass or carbon. Hence, given these properties, natural fibers can be feasibly used as a component of composite materials, in different applica- tions. In fact, whereas in industrial applications natural fibers are already used in fiber-reinforced plastic composites, structural applications in construction industry represent an interesting development for natural fiber use. In scientific literature, several works from structural and material engineering communities have investigated these applications. In particular, fiber reinforced mor- tars composed of short natural fibers reinforcing inorganic matri- ces have been studied [12–14]. Also textile reinforced laminates, composed of inorganic matrices reinforced by long natural fibers have been investigated [15–17]. A number of works have been also conducted on the development of natural fiber reinforced concrete [18–21]. The objective of these works is to study and develop new materials and technological solutions for structural applications. On the contrary, the objective of the current paper is to develop a composite material, made by a pozzolanic mortar reinforced by a hemp fiber grid, to be potentially used in retrofitting application of civil structures and in particular in seismic retrofitting opera- tions of existing masonry structures. In fact, Italian guidelines from National Research Council [22] permit to use, for seismic retrofitting of masonry structures, exter- nally bonded fiber reinforced composite systems, using inorganic 0950-0618/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.conbuildmat.2010.12.046 ⇑ Corresponding author. Address: via Claudio, 21 80125 Naples, Italy. Tel.: +39 081 7683672; fax: +39 081 7683491. E-mail address: [email protected] (D. Asprone). Construction and Building Materials xxx (2011) xxx–xxx Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat Please cite this article in press as: Asprone D et al. Potential of structural pozzolanic matrix–hemp fiber grid composites. Constr Build Mater (2011), doi:10.1016/j.conbuildmat.2010.12.046
Potential of structural pozzolanic matrix–hemp fiber grid composites
May 03, 2023
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