Abstract
This work focuses on the mechanical characterization of the inorganic matrix used for Fiber-Reinforced Cementitious Matrix (FRCM) composites, nowadays widely used to retrofit existing reinforced concrete and masonry structures. While several works in technical literature investigate the experimental behavior of the whole FRCM composite, few information are available on the mechanical characterization of the mortar, which contains polymers and synthetic fibers in its admixture. However, the knowledge of its behavior in tension, especially after crack formation, is an important feature for the calibration of constitutive models to be adopted in the study of structural elements strengthened with FRCM. To this aim, an experimental program was performed on mortar specimens characterized by different shapes and dimensions, tested under direct tension or three-point-bending. From the performed tests, it was possible to characterize inorganic matrix behavior both in the uncracked stage, through the determination of the elastic parameters (elastic modulus and Poisson’s coefficient), and in the cracked stage. The use of digital image correlation (DIC) technique also allowed the study of the evolution of crack propagation in the specimens. Lastly, a correlation factor between axial and flexural tensile strength is proposed, for both design and numerical modelling purposes.
Highlights
I n recent years, Fibre Reinforced Cementitious Matrix (FRCM) composites gained an increasing attention as a sustainable methodology to retrofit existing masonry and reinforced concrete structures
For numerical modelling, this conversion factor is in many cases necessary to calibrate constitutive laws to implement into numerical models [9, 10], if only flexural tensile strength is available
I n this work the behavior of fiber-reinforced mortar for FRCM composites is experimentally investigated, by comparing direct tensile and three-point-bending tests
Summary
I n recent years, Fibre Reinforced Cementitious Matrix (FRCM) composites gained an increasing attention as a sustainable methodology to retrofit existing masonry and reinforced concrete structures. Among the several gripping mechanisms that have been developed for uniaxial testing, a Clevis grip was adopted, so applying the axial load by means of shear stresses to the specimen. First cracking occurs immediately at the reaching of mortar tensile strength; subsequently the specimen can still bear load, even if reduced, thanks to the random presence of dispersed fibres, which allow cracking development until high crack opening values (Fig. 5a). By considering the cracking loads from all the two series of performed tests, a mean value of tensile strength of 1.95 MPa with a standard deviation of 0.45 MPa could be obtained. From direct tensile tests the mortar elastic modulus as well as Poisson’s coefficient were evaluated before cracking This was possible through the strain measurements recorded by the longitudinal and transversal strain gauges placed in three specimens of the second series. (b) Figure 8: Specimen B-1-3 (a) crack development and (b) corresponding horizontal strain field around the notch from DIC
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