scholarly journals RILEM Standard: testing methods for determination of the double-K criterion for crack propagation in concrete using wedge-splitting tests and three-point bending beam tests, recommendation of RILEM TC265-TDK

2021 ◽  
Vol 54 (6) ◽  
Author(s):  
Shilang Xu ◽  
Qinghua Li ◽  
Yao Wu ◽  
Lixin Dong ◽  
Yao Lyu ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Unstable Fracture ◽  
Calculation Methods ◽  
Testing Methods ◽  
Three Point Bending ◽  
Standard Testing ◽  
Fracture Parameters ◽  
Splitting Test ◽  
Wedge Splitting

AbstractIn this recommendation, standard testing methods for determination of the double-K criterion for Mode I crack propagation in concrete using wedge-splitting tests and three-point bending beam tests are specified for the fracture parameters of the initial cracking toughness $$K_{Ic}^{ini}$$ K Ic ini and the unstable fracture toughness $$K_{Ic}^{un}$$ K Ic un . Along with the recommendation of the standard testing methods, the theoretical background of the double-K criterion, the calculation methods and the results of round-robin testing for determining the double-K fracture parameters are presented in technical reports [1, 2]. The recommendation of the standard testing methods includes geometry for specimens, fabrication of specimens, testing machine, load transmission system and supports, measuring instruments, determination of initial cracking load Pini, determination of measured maximum load Pmax and initial compliance ci, calculation methods for wedge-splitting test and three-point bending beam test, as well as the testing results and testing report forms. According to these methods, the measured fracture parameters of double-K criterion can be used to describe the onset of cracking, and the onset of unstable cracking or failure for predicting crack initiation, structure failure and crack stability in concrete structures.

Fracture Resistance of AAAS Composites with Ceramic Precursor

2021 ◽  
Vol 322 ◽  
pp. 54-59
Author(s):  
Iva Rozsypalová ◽  
Petr Daněk ◽  
Pavla Rovnaníková ◽  
Zbyněk Keršner
Keyword(s):  
Mouth Opening ◽  
Crack Model ◽  
Arithmetic Means ◽  
Mechanical Fracture ◽  
Three Point Bending ◽  
Static Modulus ◽  
Fracture Parameters ◽  
Ceramic Precursors ◽  
Static Modulus Of Elasticity

The paper deals with selected alkali-activated aluminosilicate (AAAS) composites based on ceramic precursors in terms of their characterization by mechanical fracture parameters. Composites made of brick dust as a precursor and an alkaline activator with a silicate modulus of Ms = 0.8, 1.0, 1.2, 1.4 and 1.6 were investigated. The filler employed with one set of composites was quartz sand, while for the other set it was crushed brick. The test specimens had nominal dimensions of 40 × 40 × 160 mm and were provided with notches at midspan of up to 1/3 of the height of the specimens after 28 days. 6 samples from each composite were tested. The specimens were subjected to three-point bending tests in which force vs. displacement (deflection at midspan) diagrams (F–d diagrams) and force vs. crack mouth opening (F–CMOD) diagrams were recorded. After the correction of these diagrams, static modulus of elasticity, effective fracture toughness, effective toughness and specific fracture energy values were determined using the Effective Crack Model and the Work-of-Fracture method. After the fracture experiments, informative compressive strength values were determined from one of the parts. All of the evaluations included the determination of arithmetic means and standard deviations. The silicate modulus values and type of filler of the AAAS composites significantly influenced their mechanical fracture parameters.

scholarly journals Vibrated Concrete vs. Self-Compacting Concrete: Comparison of Fracture Mechanics Properties

2014 ◽  
Vol 601 ◽  
pp. 199-202
Author(s):  
Sara Korte ◽  
Veerle Boel ◽  
Wouter de Corte ◽  
Geert de Schutter
Keyword(s):  
Fracture Mechanics ◽  
Mouth Opening ◽  
Bending Test ◽  
Crack Mouth Opening Displacement ◽  
Self Compacting Concrete ◽  
Opening Displacement ◽  
Three Point Bending ◽  
Fracture Parameters ◽  
Wedge Splitting Test ◽  
Splitting Test

This study focuses on the fracture mechanics aspect of self-compacting concrete, compared to vibrated concrete. The most commonly used experiments to investigate the toughness and cracking behaviour of concrete are the three-point bending test (3PBT) on small, notched beams, and the wedge-splitting test (WST) on cubic samples with guiding groove and starter notch. From the resulting P-CMOD curves (applied load versus crack mouth opening displacement), different fracture parameters, such as fracture energy and fracture toughness, can be extracted. Moreover, using inverse analysis, the σ-w relationship (tensile stress versus crack width) can be derived. This paper lists the results of a series of tests on samples, made of VC, SCC of equal strength, and SCC with identical w/c factor. Subsequently, a comparison of the mechanical characteristics is made, revealing important differences regarding several fracture parameters.

Detailed Determination of Mechanical Fracture Parameters of Concrete after Fire Experiments

2018 ◽  
Vol 272 ◽  
pp. 220-225 ◽  
Author(s):  
Hana Šimonová ◽  
Tomáš Trčka ◽  
Michal Bejček ◽  
Iva Rozsypalová ◽  
Petr Daněk ◽  
...  
Keyword(s):  
Statistical Dependence ◽  
Crack Model ◽  
Mechanical Fracture ◽  
Three Point Bending ◽  
Fracture Parameters ◽  
Fracture Tests ◽  
Detailed Determination ◽  
Bending Fracture ◽  
Fire Experiments

The aim of this paper is to describe the procedure of determining the mechanical fracture parameters of selected concrete specimens taken from panels after the fire experiments. The records (in form load vs displacement diagrams) of three-point bending fracture tests of these specimens with initial stress concentrators was first advanced corrected and subsequently evaluated using the Effective Crack Model and the work-of-fracture method. The increasing temperatures during the fire experiments ranging between 550 to 1000 °C led to a decrease of modulus of elasticity and fracture toughness values and to the increase of fracture energy value. The 2D laser profile scanner was used to estimate the degree of complexity of fracture surfaces; its statistical dependence on the mechanical fracture parameters proved to be moderate – the absolute value of the correlation coefficient was about 0.5°[–].

Selecting a Suitable Specimen Shape with Low Constraint Value for Determination of Fracture Parameters of Cementitious Composites

2013 ◽  
Vol 577-578 ◽  
pp. 481-484 ◽  
Author(s):  
Stanislav Seitl ◽  
Sara Korte ◽  
Wouter de Corte ◽  
Veerle Boel ◽  
Jakub Sobek ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Building Materials ◽  
Crack Tip ◽  
Test Configuration ◽  
Three Point Bending ◽  
Finite Element Software ◽  
Splitting Test ◽  
T Stress ◽  
Low Constraint ◽  
Wedge Splitting

The stress intensity factor and the T-stress describing the near-crack-tip fields for selected specimen shapes of a test geometry based on wedge splitting and three point bending tests with several variants of boundary conditions are computed using finite element software ANSYS. The test configuration in question is expected to be a convenient alternative to classical fracture tests (especially the tensile ones) for investigation of the quasi-brittle fracture of building materials, when low constraint is requested. These specimens are investigated within the framework of two-parameter fracture mechanics; near-crack-tip stress field parameters are determined and compared with those of the wedge splitting test due to their shape similarity. The sensitivity of the values of these parameters to the boundary conditions is also shown. Suitable choice of the shape of the specimens is discussed.

Influence of Reinforcement Ratios on Concrete Fracture Parameters

2013 ◽  
Vol 438-439 ◽  
pp. 224-228
Author(s):  
Xiang Qian Fan ◽  
Shao Wei Hu ◽  
Jun Lu
Keyword(s):  
Reinforced Concrete ◽  
Crack Propagation ◽  
Relevant Literature ◽  
Reinforced Concrete Beams ◽  
Concrete Fracture ◽  
Propagation Length ◽  
Three Point Bending ◽  
Whole Process ◽  
Fracture Parameters ◽  
Initial Fracture

Based on double-K fracture model, adopt three-point bending beam which has been recommended by RILEM, the fracture properties of three groups reinforced concrete beams were studied. Refer to the relevant literature, fracture parameters of reinforced concrete three-point bending beams are examined. Through the analysis of whole process of crack propagation of reinforced concrete three-point bending beams, the results show that the reinforcement ratios can't preventing the cracking effectively, but can increase the maximum loads, thus improving the relative toughness; the precritical crack propagation length relative values show a linearly increasing trend with the increase of reinforcement ratios; the initial fracture toughness is not affected by the reinforcement ratios, but the unstable toughness has little effects by the reinforcement ratios.

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