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ASTM C1550 has been used for post-crack performance assessment of fiber reinforced concrete (FRC) and shotcrete (FRS) for several years and has proven to be an excellent tool for quality control testing due to the very low level of within-batch performance variability typically obtained using this test method. Experience in the field indicates that...
Citations
... The square panel test (SPT) specified in EN 14488-5 (EN, 2006b) and the round panel test (RPT) defined in ASTM C1550 (ASTM C1550, 2020) are widely used to assess the post-cracking mechanical response of FRSC. The RPT has great acceptance due to the lower scatter of results and greater within-batch repeatability if compared with other test methods (Tran et al., 2005;Bernard and Xu, 2008;Bernard et al., 2010;di Prisco et al., 2009). During the test, the round panel experiences bi-axial flexure in response to a central point load that simulates one of the most common modes of failure found in FRSC tunnel linings (Morgan et al., 1989;Barrett and McCreath, 1995;Bernard, 2000). ...
... In a yield line analysis of an ASTM C1550like test configuration, the governing mode of failure is taken to comprise three symmetrically arranged yield lines (cracks) emanating from the centre of the face, opposite the point load and running radially to the edge while bisecting each sector between adjacent pivot supports ( Figure 2). This mode of failure has been extensively studied and demonstrated to occur in the majority of ASTM C1550 panel tests (Bernard and Xu 2008). The load resistance P at the centre is related to the moment of resistance per unit length m at each yield line by the expression ...
Concrete slabs-on-grade and other plate elements have for a long time been designed on the basis of elastic analyses of stress distribution. This typically results in a very conservative estimate of the minimum thickness required to resist design point loads because an elastic analysis does not account for the capacity of even quasi-brittle materials to redistribute stress following initial cracking. Fibre-reinforced concrete (FRC) is a material that can exhibit significant post-crack performance. The existence of a residual moment capacity in a FRC slab allows the slab to redistribute stress such that the peak in load resistance may occur beyond the point of first cracking in the concrete matrix. The present experimental investigation has demonstrated that residual moment capacity in the immediate post-crack range can influence the magnitude of the first peak in load resistance associated with cracking. The results suggest that the method of structural analysis used to design concrete slabs should consider the residual moment resistance in the immediate post-crack range when estimating the first peak load resistance associated with cracking.
... The hooked-end steel FRS specimens typically exhibited a relatively broad load-deflection curve at early-age with substantial post-crack capacity up to 40 mm central deflection (equivalent to 13 mm average maximum crack width (Bernard and Xu, 2008). However, as the concrete aged, load resistance increased slightly at small crack widths but fell substantially at wider crack widths leading to a dramatic fall in total energy absorption at 40 mm for the higher shotcrete strength grades (40 and 50 MPa). ...
It is commonly assumed that when a mix achieves satisfactory performance in Quality Control tests at 28 days this result will translate into satisfactory performance throughout the design life of the corresponding concrete structure. While this is generally true of the compressive strength of concrete it is not necessarily true for other parameters. The post-crack performance of fibre reinforced concrete (FRC) differs from that of conventionally reinforced concrete in that the post-crack performance of fibres is related in a complex manner to the characteristics of the concrete matrix. Age-dependent changes in the characteristics of the concrete matrix can effect changes in the post-crack behaviour of fibres. The present investigation has examined how the post-crack energy absorption of fibre reinforced shotcrete (FRS) changes with aging and has found that some types of fibre exhibit dramatically different performance characteristics at late age compared to that displayed at 28 days. This change can have significant consequences for the design of ground support based on fibre reinforced shotcrete. Tunnel linings required to resist sustained ground stresses, or which may be subject to deformation associated with seismicity or ground movement at later ages, should be designed with consideration of a possible long-term loss of ductility exhibited by some types of fibre reinforced shotcrete.
This paper reports the results of 27 tests on determinant round panels undertaken to determine the postcracking resistance to repeated cycling (fatigue) loading of steel fiber reinforced concrete (SFRC) of low fiber dosages. The experiments were conducted for both precracked and uncracked panels to examine the contribution of postcracking tensile strength, and the effectiveness of steel fibers in providing resistance to fatigue damage. The results quantify the improvements of fibers to fatigue life of SFRC and, particularly, to the important second stage of crack growth during cyclic loading. From the outcomes of the testing program, a damage prediction model is proposed for forecasting postcracking fatigue damage during repeated cyclic loading. The model is shown to accurately predict the overall load‐stiffness response, capture the development crack openings with increasing cycles, as well as quantify the stiffness development and number of load cycles to failure.
Recycled Steel Fibers (RSF) derived from the tire recycling industry have been successfully used in concrete to improve its post-cracking load bearing capacity and energy absorption performance. For structural elements exposed to chloride environments, an important aspect of Recycled Steel Fiber Reinforced Concrete (RSFRC) durability is the corrosion resistance. However, research on the durability of RSFRC is almost inexistent, namely concerning the effects of chloride attack, which may limit the mobilization of the full potential of RSFRC.
The present thesis aims to assess the mechanical behavior and durability performance of RSFRC under chloride attack involving both experimental and analytical/numerical research, which knowledge may contribute for future design guidelines and design tools for RSFRC structures. The research activities carried out covered two main fields, the technology of RSFRC manufacturing and the investigation on the corrosion susceptibility of RSFRC.
In the first field, an experimental program was carried out to characterize the RSF in terms of geometry, chemical composition, mechanical properties and microstructure. The influence of rubber particles attached to RSF surface was assessed in the performance of RSF as concrete reinforcement and in its corrosion resistance. A sustainable mix composition of RSFRC was attained and their mechanical properties were evaluated by three-point notched beam bending tests and compressive tests.
The second research field involved an experimental program to characterize the RSF corrosion and to investigate the corrosion effects of RSF on the fiber reinforcement mechanisms developed during the fiber pull-out from cracked concrete previously exposed to corrosive environment. Additionally, the post-cracking behavior of RSFRC under chloride attack was characterized from double edge wedge splitting tests and round panel tests. In these tests, the influence of the crack width, chloride exposure period and fiber distribution/orientation profile was considered. The experimental results were used to perform numerical simulations by inverse analysis, aiming to derive the post-cracking constitutive laws of RSFRC. A simplified prediction of the critical chloride content corresponding to the beginning of fiber corrosion and of the long-term performance of a RSFRC structural element exposed to a specific dry-wet aggressive maritime environment was performed.
In addition, the technical, environmental and economic benefits of using the developed RSFRC for application to structural elements were assessed at material level and compared to Industrial Steel Fiber Reinforced Concrete.
In this paper, the post cracking behaviour of macro synthetic polypropylene fibre reinforced concrete is investigated through a series of matched tests that measure tension directly through uniaxial tension tests and indirectly through prism bending and determinate round panel tests. An analytical model previously developed by the authors for the determination of the residual tensile strength provided by steel fibres in prism bending tests is adapted for the round panel tests and is shown to correlate well with the collected experimental data.
