Experimental Analysis of the Bond Behavior of Glass, Carbon, and Steel FRCM Composites

Abstract

In recent decades, the construction industry has witnessed a rapid growth of interest in strengthening and retrofitting of existing reinforced concrete (RC) and masonry structures. Fiber reinforced polymer (FRP) composites have gained great popularity, and several studies are now available in the literature on their use in strengthening and retrofit applications. Promising newly-developed composite materials are represented by the so-called fiber reinforced cementitious matrix (FRCM) composites. FRCM composites are comprised of high strength fibers embedded within a cementitious matrix that is responsible for the stress transfer between the existing structure and the strengthening material. FRCM composites are still in their infancy, and very limited results are available in the literature on RC and masonry strengthening applications. This study presents an experimental campaign conducted on different FRCM composites comprised of glass, carbon, or steel fibers embedded within two different cementitious matrices and applied to concrete prisms. The single-lap direct-shear test was used to study the stress-transfer mechanism between the FRCM composite and the concrete substrate. Two different composite bonded lengths were investigated. Debonding occurred at the matrix-fiber interface for some of the composites tested and at the concrete-matrix interface for others. This work contributes to the study of the bond behavior of FRCM composites, which represents a key issue for the effectiveness of FRCM composite strengthening.

State of research on shear strengthening of RC beams with FRCM composites

“…According to their findings, the type of failure depends on the strengthening configuration with slippage being more pronounced in side bonded configurations and almost eliminated for fully wrapped configurations in which fiber rupture is the dominating failure mechanism. Fiber slippage is another form of debonding that has been observed in some types of FRCM composite-concrete joints [29,30,31]. Table 2 summarizes the type of failure mode reported for the different strengthening configurations for beams without anchors.…”

“…Although beams with and without anchors exhibited a diagonal tension shear failure, the presence of the anchors slightly changed the inclination of the shear crack around the anchors. Considering that failure of the strengthened beams by fiber slippage has been reported for certain FRCM composites [29,30,31], the lack of effectiveness of this type of anchor may be linked to the fact that they are intended to restrain out-of-plane peeling of the composite and do not restrain the in-plane fiber slippage [36].…”

Use of image correlation system to study the bond behavior of FRCM-concrete joints

“…It should be noted that details about such specimen preparation or adjustments are not commonly reported in the available literature. Also, several types LVDT-plate assemblies have been used in single lap direct shear tests of FRCM-concrete joints [2,17,46], however it is not discussed if such effects were observed. On the other hand, measurements with ICS did not appear to be influenced by the rotation of the L-plate at the beginning of the test.…”

“…1a). A similar test setup was used by others [2,46,47] to test other FRCM-concrete joints. Two aluminum plates were glued to the end of the fiber net using a thermosetting epoxy resin (Fig.…”

An Investigation of PBO FRCM-Concrete Joint Behavior using a Three-Dimensional Numerical Approach

“…Failure of FRCM-strengthened concrete elements is generally reported to be debonding of the FRCM composite [16,17]. Debonding may occur at the matrixfiber interface, at the composite-concrete interface, or within the concrete substrate depending on the materials employed [18] and on the strengthening configuration [19]. The study of the bond characteristics of FRCM-concrete joints is crucial to understand the behavior of FRCM-strengthened elements and to develop reliable design models.…”