scholarly journals Experimental and numerical analysis of the fracture response of alkali-activated slag-based materials

2020 ◽  
Vol 323 ◽  
pp. 01006
Author(s):  
Martin Lipowczan ◽  
David Lehký ◽  
Hana Šimonová ◽  
Barbara Kucharczyková
Keyword(s):  
Crack Model ◽  
Fracture Test ◽  
Mechanical Fracture ◽  
Alkali Activated Slag ◽  
Fine Grained ◽  
Shrinkage Reducing Admixture ◽  
Edge Notch ◽  
Fracture Tests ◽  
Activated Slag ◽  
Alkali Activated

The paper deals with the experimental and numerical determination of mechanical fracture parameters of fine-grained composites based on the alkali-activated slag (AAS) at different ages of hardening. Two AAS composites, which differed only in the presence of shrinkage reducing admixture, were studied. The prismatic specimens with the nominal dimensions of 40 × 40 × 160 mm and initial central edge notch were subjected to fracture tests in a three-point bending configuration. The results of the fracture tests in the form load F versus deflection d diagrams were used as input data for the identification of parameters via the inverse analysis based on the artificial neural network whose aim is to transfer the fracture test response data to the desired material parameters. The modulus of elasticity, tensile strength, and fracture energy values were identified and subsequently compared with values obtained based on the direct fracture test evaluation using the effective crack model and work-of-fracture method.

scholarly journals Components of the Fracture Response of Alkali-Activated Slag Composites with Steel Microfibers

2019 ◽  
Vol 9 (9) ◽  
pp. 1754 ◽  
Author(s):  
Hana Šimonová ◽  
Petr Frantík ◽  
Zbyněk Keršner ◽  
Pavel Schmid ◽  
Pavel Rovnaník
Keyword(s):  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Model Parameters ◽  
Crack Model ◽  
Mechanical Fracture ◽  
Alkali Activated Slag ◽  
Fracture Parameters ◽  
Fracture Tests ◽  
Activated Slag ◽  
Alkali Activated

Knowledge of the mechanical and primarily fracture parameters of composites with a brittle matrix is essential for the quantification of their resistance to crack initiation and growth, and also for the specification of material model parameters employed for the simulation of the quasi-brittle behavior of structures made from this type of composite. Therefore, the main target of this paper is to quantify the mechanical fracture parameters of alkali-activated slag composites with steel microfibers and the contribution of the matrix to their fracture response. The first alkali-activated slag composite was a reference version without fibers; the others incorporated steel microfibers amounting to 5, 10, 15 and 20% by weight of the slag. Prism specimens with an initial central edge notch were used to perform the three-point bending fracture tests. Load vs. displacement (deflection at midspan) and load vs. crack mouth opening displacement diagrams were recorded during the fracture tests. The obtained diagrams were employed as inputs for parameter identification, the aim of which was to transfer the fracture test response data to the desired material parameters. Values were also determined for fracture parameters using the effective crack model, work-of-fracture method and double-K fracture model. All investigated mechanical fracture parameters were improved by the addition of steel microfibers to the alkali-activated matrix. Based on the obtained results, the addition of 10 to 15% of microfibers by weight is optimal from the point of view of the enhancement of the fracture parameters of alkali-activated slag composite.

Shrinkage of Fine-Grained Composites Based on Alkali-Activated Slag

2018 ◽  
Vol 761 ◽  
pp. 7-10 ◽  
Author(s):  
Barbara Kucharczyková ◽  
Vlastimil Bílek Jr. ◽  
Dalibor Kocáb ◽  
Ondřej Karel
Keyword(s):  
Experimental Investigation ◽  
Experimental Determination ◽  
Alkali Activated Slag ◽  
Fine Grained ◽  
Shrinkage Reducing Admixture ◽  
Activated Slag ◽  
Alkali Activated

The paper deals with the experimental determination of shrinkage development of the composites based on the alkali-activated slag (AAS). The main aim of the experimental investigation was to verify the effect of the addition of shrinkage-reducing admixture (SRA) on the overall process of shrinkage properties during AAS composites ageing.

scholarly journals Mechanical Fracture and Fatigue Characteristics of Fine-Grained Composite Based on Sodium Hydroxide-Activated Slag Cured under High Relative Humidity

2020 ◽  
Vol 11 (1) ◽  
pp. 259
Author(s):  
Hana Šimonová ◽  
Barbara Kucharczyková ◽  
Vlastimil Bílek ◽  
Lucie Malíková ◽  
Petr Miarka ◽  
...  
Keyword(s):  
Material Behavior ◽  
Sustainable Construction ◽  
Crack Model ◽  
Direct Evaluation ◽  
Practical Utilization ◽  
Mechanical Fracture ◽  
Fine Grained ◽  
Activated Slag ◽  
Alkali Activated

A typical example of an alternative binder to commonly used Portland cement is alkali-activated binders that have high potential as a part of a toolkit for sustainable construction materials. One group of these materials is alkali-activated slag. There is a lack of information about its long-term properties. In addition, its mechanical properties are characterized most often in terms of compressive strength; however, it is not sensitive enough to sufficiently cover the changes in microstructure such as microcracking, and thus, it poses a potential risk for practical utilization. Consequently, the present study deals with the determination of long-term mechanical fracture and fatigue parameters of the fine-grained composites based on this interesting binder. The mechanical fracture parameters are primarily obtained through the direct evaluation of fracture test data via the effective crack model, the work-of-fracture method, the double-K fracture model, and complemented by parameter identification using the inverse analysis. The outcome of cyclic/fatigue fracture tests is represented by a Wöhler curve. The results presented in this article represent the complex information about material behavior and valuable input parameters for material models used for numerical simulations of crack propagation in this quasi-brittle material.

Influence of Polymer Additives on Mechanical Fracture Properties and on Shrinkage of Alkali Activated Slag Mortars

2018 ◽  
Vol 761 ◽  
pp. 39-44
Author(s):  
Olesia Mikhailova ◽  
Hana Šimonová ◽  
Libor Topolář ◽  
Pavel Rovnaník
Keyword(s):  
Drying Shrinkage ◽  
Polypropylene Glycol ◽  
Mechanical Fracture ◽  
Fracture Properties ◽  
Alkali Activated Slag ◽  
Shrinkage Reducing Admixture ◽  
Emission Activity ◽  
Polyethylene Glycol 1000 ◽  
Activated Slag ◽  
Alkali Activated

Alkali-activated slags represent an alternative to ordinary Portland cement due to reducing the environmental impact of the building industry. In spite of the numerous advantages of alkali activated slag mortars, alkali-activated aluminosilicates have big disadvantage – high value of shrinkage followed by formation of microcracks. This effect is caused by both autogenous and drying shrinkage and it finally results in volume contraction, microcracking and deterioration of the mechanical fracture properties. Therefore, using various types of polymer admixtures can overcome these problems. The aim of this paper is to present the effect of shrinkage-reducing admixture Peramin® SRA 40, polymer polyethylene glycol 1000 and polypropylene glycol on shrinkage and mechanical fracture characteristics of alkali-activated slag mortars. These admixtures were used in amount 0–2.0% weight of slag. The results showed that with increasing content of admixtures compressive and flexural strength decreased. Fracture tests with acoustic emission activity during this testing were carried out. Addition of 2% Peramin® SRA decreased shrinkage by 55%, but with 1% of Peramin® SRA the shrinkage was reduced only by 10%. Specimen with 1% of Peramin® is the most durable material, but more brittle compared to specimens with 1 and 2% of polypropylene glycol.

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.

Alkali Activated Binders Based Concrete Specimens: Length Change and Fracture Tests

2016 ◽  
Vol 258 ◽  
pp. 623-626 ◽  
Author(s):  
Vlastimil Bílek Jr. ◽  
Hana Šimonová ◽  
Ivana Havlíková ◽  
Libor Topolář ◽  
Barbara Kucharczyková ◽  
...  
Keyword(s):  
Stress Concentrator ◽  
Length Change ◽  
Bending Test ◽  
Crack Model ◽  
Mechanical Fracture ◽  
Three Point Bending ◽  
Fracture Tests ◽  
Alkali Activated Binders ◽  
Work Of Fracture ◽  
Alkali Activated

The aim of this paper is to quantify mechanical fracture and length change parameters of the two types of concrete with alkali activated binder. The six beam specimens (75 × 75 × 295 mm) were made from each mixture. After demolding specimens were placed in air storage for 28 days. During this period length change (shrinkage) were recorded in accordance with ASTM C490 (2011). After that the three-point bending test was performed on these specimens with initial stress concentrator at the age of 28 days to obtain the mechanical fracture parameters. Records of fracture tests in form load versus deflection (F–d) diagrams were evaluated using effective crack model and work of fracture method.

scholarly journals Mechanical fracture characterization of alkali-activated slag mortars with standardized and natural sand

2020 ◽  
Vol 310 ◽  
pp. 00021
Author(s):  
Hana Šimonová ◽  
Barbara Kucharczyková ◽  
Vlastimil Bílek ◽  
Dalibor Kocáb
Keyword(s):  
Grain Size ◽  
Time Interval ◽  
Sample Standard Deviation ◽  
Natural Sand ◽  
Fracture Characterization ◽  
Mechanical Fracture ◽  
Alkali Activated Slag ◽  
Average Value ◽  
Activated Slag ◽  
Alkali Activated

This paper is focused on the development of the physical, mechanical and fracture characteristics of alkali-activated slag (AAS) mortars during ageing. The two AAS mortars were selected for the purpose of the experiment. The difference was in a type of used sand: first mortar was made using the standardized siliceous sand with the maximum nominal grain size of 2 mm and the second mortar using the natural sand with a maximum grain size of 4 mm. The results of the elastic, fracture and strength parameters determined within the time interval of 3 to 330 days of ageing are summarized in the paper. All experimental results were evaluated for the prismatic specimens with dimensions of 40 × 40 × 160 mm and were expressed by the average value and sample standard deviation calculated from three independent measurements.

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