Fabric Reinforced Cementitious Matrix (FRCM) materials are composed of a dry fiber grid embedded in an inorganic matrix, which may contain short fibers.
These materials are particularly well-suited ...for the reinforcement of masonry structures due to their high compatibility with the substrate, vapor permeability and durability against environmental agents.
The most important information needed for the characterization of these composite systems, for use as strengthening materials of masonry structures, are the tensile behaviour and the shear bond properties. A Round-Robin Test was organized by the RILEM Technical Committee 250-CSM and the Italian association Assocompositi in order to experimentally characterize different FRCM systems composed of PBO, carbon, glass, basalt, aramid and steel textiles embedded in cementitious or lime-based mortars. The systems were tested at different universities and research centers in Europe in order to investigate the influence of samples preparation, test set-up and instrumentation.
In this paper, the experimental tests performed on Carbon-FRCM systems are described and discussed. Important aspects are analyzed herein: differences in the testing procedure and instrumentation, influence of textile geometry and mechanical properties of the constituent materials, importance of specimen preparation and curing conditions. Moreover, a comparison between tensile and shear tests is reported in order to determine a reliable procedure towards the complete characterization of an FRCM material.
AbstractConcrete structures deteriorate for various reasons and upgrading is needed to ensure their continued safe working conditions. Retrofitting reinforced concrete (RC) beams have been ...accomplished using various techniques, namely, steel plates, external posttensioning, externally bonded fiber-reinforced polymer (FRP), and near-surface-mounted FRP systems to increase flexural and shear capacity. The objective of this paper is to investigate the feasibility of fabric-reinforced cementitious-matrix (FRCM) materials as an alternative external strengthening technique for RC members. The FRCM is a composite material consisting of one or more layers of cement-based matrix reinforced with dry-fiber fabric. The experimental program consists of testing 18 RC beams strengthened in flexure with two different FRCM schemes (one and four reinforcement fabrics). An analysis and design are conducted following the well-established formulation to calculate the flexural capacity of the beams and compare their results with the experimental database.
Confined masonry (CM) buildings experienced some major damages in past earthquakes. Numerous studies have investigated various strengthening techniques to improve the seismic performance of CM walls. ...A state of the art for strengthening CM structures using externally bonded reinforced cementitious composites, subjected to inplane loads is presented. A database of previous test results was used to evaluate the effectiveness of the strengthening applications. The capacity prediction of strengthened CM walls was performed using available analytical models. A modification of the existing model is proposed by studying the correlation between the experimental parameters and the effective stress.
A new discretized homogenization approach is proposed in this study in order to predict the behavior of unreinforced and FRCM reinforced masonry structures. The proposed approach allows overcoming ...the common disadvantages of the existing homogenization approaches: (a) being difficult to implement and (b) not allowing to couple the in-plane and out-of-plane actions. Reference experimental results and detailed numerical modeling are used for validation of the proposed modeling strategy. In the proposed model, the elastic cells are linked by homogenized interfaces. The mechanical properties coming from the homogenization procedures are lumped at the interfaces by means of the generic Concrete Damage Plasticity model, allowing easy implementation and avoiding computational issues peculiar to other approaches available in the literature. The new approach shows accurate results in predicting the global behavior and the damage pattern for both unreinforced and FRCM strengthened masonry walls. The results are promising also with a view to be applied for more complex reinforced applications as double curvature masonry structures.
This paper provides a comprehensive review on the research of coir fibre and coir fibre reinforced cementitious composite (CFRC) in the past 20 years. In the first part, the extraction process, ...morphology, density, chemical composition, and tensile performance of coir fibres are discussed. Then, the pull-out performance, physical properties (i.e., density, thermal and acoustic insulation), short- and long-term properties (i.e., compressive, flexural, impact, and dynamic performance) of CFRC are reviewed. Existing modification methods (i.e., cementitious matrix and fibre surface modifications) to improve the bond and mechanical behaviour of CFRC and the practical application of CFRC in construction are presented. Future perspectives of CFRC studies are highlighted, including the validation of existing models (i.e., for the prediction of coir tensile strength as well as bond strength and total energy of CFRC), further investigations on long-term, seismic, fire performance of CFRC, and the use of coir fibre in geopolymer and coconut shell aggregate concrete towards practical application.
•Previous studies on strengthening of RC structures with FRCM are critically reviewed.•Factors affecting the performance of FRCM-strengthened RC elements are highlighted.•Research gaps are ...identified.•Directions for future research are outlined.
Fabric-reinforced cementitious matrix (FRCM) systems have recently been introduced in the construction industry as a viable alternative strengthening material, to circumvent problems associated with fiber-reinforced polymers (FRP). They are made of fabric grids and a cementitious agent which serves as matrix and binder. The cementitious matrix used in FRCM systems has higher thermal capacity and better compatibility with the concrete substrate compared to those of the epoxy resin used in FRP. The use of FRCM composites for strengthening and repair of reinforced concrete structures, though relatively recent, is gradually gaining popularity as an alternative to FRP. This paper presents a critical review of existing research on structural strengthening with FRCM composites, identifies gaps in knowledge, and outlines directions for future research.
•An analytical study on FRCM external confinement of masonry is presented.•Predictive strength models are proposed and experimentally validated.•Most commonly used FRCM systems are taken into account ...in the strength models.•Comparison with analytical formulas reported in guidelines is examined.
Fabric reinforced cementitious matrix (FRCM) composites have emerged as an appealing alternative to fiber reinforced polymer (FRP) for the external confinement of masonry members; nevertheless, their use in practice is limited due to the lack of reliable formulas to estimate the compressive strength and ultimate strain of confined members.
By following a recently published study, new formulas for the prediction of the compressive strength of the FRCM confined masonry are proposed here, which were obtained by considering an updated experimental database compiled from the literature.
These formulas were developed by applying error minimization techniques to the collected experimental results; test data were treated in different ways, such as: (a) separating the members made of natural stones from those built with artificial blocks, and (b) treating separately the fiber types (basalt, carbon, glass, PBO and steel) of the FRCM system, or (c) considering the experimental data all together.
Finally, to evaluate the reliability of the developed relationships, the strength predictions provided by the new proposals were compared with those obtained using the expressions reported in some international guidelines.
Fibre Reinforced Cementitious Matrix (FRCM) composites are now widely used for repair and retrofitting existing structures. Guidelines for product qualification are needed to characterize the ...strengthening systems before they are made available in the market and installed. The paper proposes a procedure that combines the results of direct tensile and shear bond tests to provide engineering design parameters for externally bonded FRCM reinforcements. Due to the possible occurrence of different failure modes, the procedure provides results on the base of the weakest mechanism that takes place. Thanks to its simplicity, the proposed method is suitable for standard product qualification and material assurance purposes. In order to investigate its feasibility, the qualification procedure is applied to different reinforcements comprising basalt, carbon, glass, and steel textiles, bonded with either cement or lime mortars to clay bricks and tuff units.
The cohesive material law (CML), i.e., relationship between the interfacial shear stress and slip between a fiber reinforced composite and the substrate, is a fundamental tool to model the structural ...behavior of composite-strengthened elements. A crucial problem that researchers working in the field of strengthening applications with fiber reinforced cementitious matrix (FRCM) composites face is how to obtain the CML. A direct method to determine the CML could be applied if the longitudinal strain is measured along the bonded length. However, since the critical interface for some FRCM composites appears to be the interface between the fibers and matrix, measuring the fiber strain in FRCM composites is a difficult task due to the presence of the matrix that embeds the fiber textile. To overcome this difficulty, an indirect method is proposed in this paper. The parameters of the CML are determined by fitting experimental data in terms of peak load measured for different composite bonded lengths. The procedure is applied to single-lap shear test results previously published by the authors. The CML obtained shows good correlation with the CML obtained from direct calibration of strain profiles measured along the bonded length and is able to predict the experimental load responses.
Display omitted
•The proposed indirect method to calibrate the cohesive material law of FRCM-concrete joints does not require strain measurements.•Indirect calibration of the CML is performed simply by employing peak load versus bonded length plot.•Peak strain and corresponding slip versus bonded length and analytical load responses compare well with experimental data.
The use of composite materials for repair and retrofit of structures has become a common use among the engineering community. Fabric Reinforced Cementitious Matrix (FRCM) is a composite material ...specifically designed for masonry and concrete rehabilitation and is becoming a viable alternative to FRP, whenever the project conditions do not allow the use of organic polymer based composites. FRCM is usually constituted by one or multiple plies of dry fabrics (carbon, glass, aramid, basalt or PBO fibers) embedded into an inorganic matrix. If a polymer is used to either cover or bond the fabric strands, such polymer does not fully penetrate and impregnate the fibers as it would for FRP. The purpose of this research work is to study how different types and amounts of organic coatings applied to a carbon fabric could affect the bond behavior between fabric and mortar. The effectiveness of coating treatments was studied by means of direct tensile, pull-off and shear-bond double-lap tests. Experimentation was carried out on different combinations of fabrics and mortars, by varying the levels of pre-impregnation of the fabric during its manufacturing. In addition, the use of a quartz sand layer applied to the fabric after impregnation was investigated. Experimental evidence shows a promising enhancement of the bond between fabric and matrix and, therefore, of the entire system even with the use of low percentages of resin, depending on the type of mortar used.
PDF
