scholarly journals Mechanical fracture parameters of concrete drill-core specimens supported by a slenderness ratio study

2021 ◽  
Vol 1209 (1) ◽  
pp. 012042
Author(s):  
D Lisztwan ◽  
I Kumpova ◽  
P Danek ◽  
P Frantík ◽  
Z Kersner
Keyword(s):  
Compressive Strength ◽  
Building Materials ◽  
Slenderness Ratio ◽  
Cement Matrix ◽  
Mechanical Fracture ◽  
Three Point Bending ◽  
Existing Structures ◽  
Fracture Parameters ◽  
Static Fracture ◽  
X Ray Computed

Abstract The detailed analytical and experimental investigation of the fracture behaviour of quasi-brittle materials is an endeavour which has been ongoing worldwide for many years. Such materials are usually characterized in terms of their mechanical fracture parameters, which are determined based on the evaluation of quasi-static fracture experiments. One of the most commonly used building materials with a quasi-brittle response is concrete, which is most often based on a cement matrix. It is sometimes also necessary to characterize concrete included in existing structures. In this case, test specimens are obtained by core drilling, and the investigation is conducted with the requirement to maximize the number of parameters obtained while minimizing the number of test specimens drilled from the structure. This paper focuses on the mechanical fracture parameters of core-drilled specimens taken from a selected concrete structure. Tests were performed on cylindrical specimens with a chevron-notched stress concentrator in the three-point bending configuration in order to determine modulus of elasticity, fracture toughness and fracture energy. Subsequently, theoretical compressive strength was estimated and tests for the determination of compressive strength values were performed focusing on dependence on the slenderness ratio, i.e. the relationship between the compressive strength and the length to diameter ratio of the cylindrical specimens. In relation to the obtained mechanical fracture parameters, selected specimens were analysed and three-dimensionally characterized via high-resolution X-ray computed tomography.

scholarly journals Effects of Meso-scale Modeling on Concrete Fracture Parameters Calculation

2019 ◽  
Author(s):  
Ali Permanoon ◽  
Amir Houshang Akhaveissy
Keyword(s):  
Cement Matrix ◽  
Homogeneous Material ◽  
Concrete Fracture ◽  
Ratio Distribution ◽  
Mechanical Fracture ◽  
Three Point Bending ◽  
Scale Modeling ◽  
Fracture Parameters ◽  
Beam Thickness ◽  
Release Ratio

Mechanical fracture brings about considerable financial and living costs to various communities. Since the early twentieth century, the issue has been scientifically under scrutiny. Hence, it is of necessity to explore the failure of various materials including concrete as one of the most widely used materials in the construction industry. In examining the concrete structures, while it is assumed that concrete is a homogeneous material, it consists of several components such as cement paste, an aggregate of sand, gravel, and air, and the components play an essential role in determining correct concrete behavior. Hence, in the present research, to calculate the concrete fracture parameters under the three-point bending experiment, 100 distributions of aggregates and cement matrix were considered, and fracture factor and integral J were investigated, and contrary to expectations, the second and third fracture modes were also created. Besides, energy release ratio distribution along the beam thickness becomes unsymmetrical, contributing to early failure and crack propagation.

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.

Fracture Response of Fine-Grained Cement-Based Composite Specimens with Special Inclusions

2019 ◽  
Vol 292 ◽  
pp. 63-68 ◽  
Author(s):  
Michal Vyhlídal ◽  
Iva Rozsypalová ◽  
Tomáš Majda ◽  
Petr Daněk ◽  
Hana Šimonová ◽  
...  
Keyword(s):  
Transition Zone ◽  
Interfacial Transition Zone ◽  
Mechanical Fracture ◽  
Three Point Bending ◽  
Fine Grained ◽  
Fracture Parameters ◽  
Edge Notch ◽  
Fracture Tests ◽  
Materials Used ◽  
Bending Fracture

This paper concerns research into the importance of the interfacial transition zone around inclusions of selected materials in fine-grained cement-based composite. Tests were performed on eight sets of prismatic test specimens. The sets differed in the inclusion materials used, which were placed at midspan above the initial central edge notch. The first was a reference set without any inclusion, the second contained a steel inclusion, four more contained different types of rock inclusion, the seventh contained an inclusion of extruded polystyrene, and the last contained a space of the same dimensions as that occupied by the inclusions in sets 2 to 7. The test specimens were subjected to three-point bending fracture tests at the age of (usually) 28 days. The fracture response was analysed by means of fracture mechanics theory, and apparent mechanical fracture parameters (modulus of elasticity, fracture toughness and fracture energy) were evaluated. The conclusion shows that a possible relationship exists between the differences in the mechanical fracture parameters of specimens with/without an inclusion and the existence of the interfacial transition zone.

Effect of Cement Dosage on Selected Mechanical Fracture Parameters of Concretes

2014 ◽  
Vol 617 ◽  
pp. 239-242 ◽  
Author(s):  
Hana Šimonová ◽  
Ivana Havlíková ◽  
Petr Daněk ◽  
David Lehký ◽  
Barbara Kucharczyková ◽  
...  
Keyword(s):  
Fresh Concrete ◽  
Mechanical Fracture ◽  
Bending Tests ◽  
Fracture Properties ◽  
Three Point Bending ◽  
Fracture Parameters ◽  
Edge Notch

Mechanical fracture parameters obtained from three-point bending tests on concrete specimens with a central edge notch are introduced in this paper. A total of four sets of specimens were tested. The concrete used in each set differed in cement dosage, which ranged from 250 to 455 kg per m3of fresh concrete. Three specimens in each set were tested at the age of 28 days. Increasing the dosage of cement influences the mechanical fracture properties of concretes in both positive and negative ways.

Evaluation of Three-Point Bending Fracture Tests of Selected Concrete: Mechanical Fracture Parameters

2017 ◽  
Vol 259 ◽  
pp. 64-69
Author(s):  
Hana Šimonová ◽  
Petr Daněk ◽  
David Lehký ◽  
Zbyněk Keršner ◽  
Lubos Pazdera
Keyword(s):  
Fracture Energy ◽  
Modulus Of Elasticity ◽  
Crack Model ◽  
Mechanical Fracture ◽  
Three Point Bending ◽  
Fracture Parameters ◽  
Fracture Tests ◽  
Specific Fracture ◽  
Bending Fracture ◽  
Work Of Fracture

In this paper, authors focus attention on mechanical fracture parameters obtained from records of three-point bending fracture tests on concrete specimens with initial notch. Total eight sets of specimens were tested. Three specimens at the age of 28 days were tested in each set. Concrete was different in dosage of Portland cement CEM I 42.5 R and amount of used superplasticizer. The Effective Crack Model (ECM) was used to evaluate the load vs deflection diagrams to obtain modulus of elasticity and effective fracture toughness; specific fracture energy was determined using work-of-fracture method. Modulus of elasticity, tensile strength and fracture energy were also subject of identification via inverse analysis based on artificial neural network, which aim is to transfer the input data obtained from the fracture test to the desired material parameters.

Mechanical Fracture Parameters of Extruded Polystyrene

2018 ◽  
Vol 776 ◽  
pp. 160-163 ◽  
Author(s):  
Hana Šimonová ◽  
Barbara Kucharczyková ◽  
Zbyněk Keršner
Keyword(s):  
Mechanical Fracture ◽  
Mean Values ◽  
Three Point Bending ◽  
Fracture Parameters ◽  
Coefficients Of Variation ◽  
Specimen Height ◽  
Edge Notch ◽  
Bottom Side ◽  
Fracture Tests ◽  
Specific Fracture

Extruded polystyrene (XPS) is a material with applications in the building industry, where it is typically used as thermal insulation. Fracture experiments in the three-point bending configuration were conducted on XPS beam specimens with an initial stress concentrator made before testing. The nominal dimensions of the beams were 40 × 40 × 160 mm. The depth of the initial edge notch on the bottom side of the specimen was approximately 1/3 of specimen height. The span length was 120 mm. Load vs. displacement diagrams were recorded during fracture tests, and subsequently the modulus of elasticity (E), effective fracture toughness (KIce) and specific fracture energy (GF) of the XPS were determined. The mean values obtained for the mechanical fracture parameters and coefficients of variation (number of specimens) were the following: E = 10.7 MPa, 9.2 % (7); KIce = 0.0547 MPa∙m1/2, 16.7 % (3); GF = 183.2 J∙m–2, 34.3 % (3).

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°[–].

Influence of Interfacial Transition Zone on Local and Overall Fracture Response of Cementitious Composites

2018 ◽  
Vol 784 ◽  
pp. 97-102 ◽  
Author(s):  
Vojtěch Zacharda ◽  
Jiří Němeček ◽  
Hana Šimonová ◽  
Barbara Kucharczyková ◽  
Michal Vyhlídal ◽  
...  
Keyword(s):  
Transition Zone ◽  
Interfacial Transition Zone ◽  
Cement Matrix ◽  
Mechanical Fracture ◽  
Three Point Bending ◽  
Fine Grained ◽  
Bulk Matrix ◽  
Electron Microscopes ◽  
Microstructure Measurements ◽  
Good Agreement

Mechanical fracture properties of interfacial transition zone (ITZ) of fine-grained composite based on cement matrix with different types – basalt, granite, marble and amphibolite – of rock inclusion were studied. Specimens with the initial stress concentrator were tested in standard three-point bending configuration. Fracture surfaces were examined with light and electron microscopes. Local ITZ response was characterized by nanoindentation in the vicinity of rock inclusions. Local elasticity, hardness and viscous properties were assessed. It has been shown that the ITZ is mechanically weaker compared to the bulk matrix in the region of ca. 0–20 μm from the inclusion for all specimen’s types. It exhibits gradual increase of elastic modulus and hardness, which can be approximately expressed by a power law. On the other hand, the creep in ITZ was found to be higher compared to the bulk matrix. The results of nanoindentation measurements are in a good agreement with overall mechanical properties, fracture response and microstructure measurements done by scanning electron microscopy.

Mechanical Fracture Parameters of Mortars Modified by Burnt Clays

2014 ◽  
Vol 969 ◽  
pp. 241-244
Author(s):  
Eva Navrátilová ◽  
Hana Šimonová ◽  
Barbara Kucharczyková ◽  
Ivana Havlíková ◽  
Jan Bedáň ◽  
...  
Keyword(s):  
Hydrated Lime ◽  
The Other ◽  
Mechanical Fracture ◽  
Lime Mortar ◽  
Three Point Bending ◽  
Fracture Parameters ◽  
Brick Powder ◽  
Fracture Tests ◽  
Bending Fracture ◽  
Reference Mixture

This paper presents the results of three-point bending fracture tests. Specimens were made from lime mortar modified by brick powder or metakaolin. The first, reference mixture only used hydrated lime, while the other mixtures were enhanced by brick powder or metakaolin in amounts of 25, 50 and 100 % of the weight of hydrated lime.

scholarly journals The influence of selected polymers on concrete tightness - current state of knowledge

2019 ◽  
pp. 78-83
Author(s):  
Krzysztof Powała
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Construction Projects ◽  
Building Materials ◽  
Water Resistance ◽  
Cement Matrix ◽  
Construction Market ◽  
Current State ◽  
Almost All

Today’s construction market of materials, contractors and building users, places new demands on individual building materials. Undoubtedly one such material is concrete, which is used in almost all construction projects as a binder for building materials. Therefore, it is necessary that this material is constantly subjected to new tests to find ways to improve its properties. Therefore, many scientists attempt to improve properties such as compressive strength, flexural strength and water resistance. One method is to modify the cement matrix with polymers.

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