scholarly journals Changes in the Fracture Toughness under Mode II Loading of Low Calcium Fly Ash (LCFA) Concrete Depending on Ages

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5241 ◽  
Author(s):  
Grzegorz Ludwik Golewski
Keyword(s):  
Fracture Toughness ◽  
Fly Ash ◽  
Mode Ii ◽  
Test Results ◽  
Shear Loads ◽  
Concrete Mixtures ◽  
Low Calcium ◽  
Plastic Process ◽  
Mode Ii Loading ◽  
Different Content

This study investigated the influence of the curing time on the fracture toughness of concrete produced with different content of low calcium fly ash (LCFA). During the study, the amounts of 20% and 30% of pozzolanic additive were used. In order to observe the effect of the applied pozzolanic additive on the analyzed concrete properties, the obtained results were compared with the values obtained for the reference concrete. Compressive strength—fcm and fracture toughness, by using mode II loading—KIIc (shearing), were determined between the 3rd and 365th days of curing. In the course of experiments, changes in the development of cracks in individual series of concrete were also analyzed. In addition, the microstructures of all composites and the nature of macroscopic crack propagation in mature concretes were assessed. It was observed that the greatest increase in fracture toughness at shear was in the case of reference concrete during the first 28 days, whereas, in the case of concretes containing LCFA, in the period of time above 4 weeks. Furthermore, concrete without the LCFA additives were characterized by a brittle fracture. In contrast to it, concretes with LCFA additives are mainly characterized by a quasi-plastic process of failure. Moreover, most of the samples showed a typical pattern of the destruction that occurs as a result of shearing. The presented test results may be helpful in selecting the composition of concrete mixtures containing LCFA to be used in concrete and reinforced concrete structures subjected to shear loads.

scholarly journals Practical Prediction Models of Tensile Strength and Reinforcement-Concrete Bond Strength of Low-Calcium Fly Ash Geopolymer Concrete

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 875
Author(s):  
Chenchen Luan ◽  
Qingyuan Wang ◽  
Fuhua Yang ◽  
Kuanyu Zhang ◽  
Nodir Utashev ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Fly Ash ◽  
Bond Strength ◽  
Prediction Models ◽  
Splitting Tensile Strength ◽  
Geopolymer Concrete ◽  
Structural Factors ◽  
Test Results ◽  
Portland Cement Concrete ◽  
Low Calcium

There have been a few attempts to develop prediction models of splitting tensile strength and reinforcement-concrete bond strength of FAGC (low-calcium fly ash geopolymer concrete), however, no model can be used as a design equation. Therefore, this paper aimed to provide practical prediction models. Using 115 test results for splitting tensile strength and 147 test results for bond strength from experiments and previous literature, considering the effect of size and shape on strength and structural factors on bond strength, this paper developed and verified updated prediction models and the 90% prediction intervals by regression analysis. The models can be used as design equations and applied for estimating the cracking behaviors and calculating the design anchorage length of reinforced FAGC beams. The strength models of PCC (Portland cement concrete) overestimate the splitting tensile strength and reinforcement-concrete bond strength of FAGC, so PCC’s models are not recommended as the design equations.

scholarly journals Fracture Toughness Testing for Sheet Specimens under Mode II Loading

1985 ◽  
Vol 28 (246) ◽  
pp. 2867-2872
Author(s):  
Masahiro ICHIKAWA ◽  
Tohru TAKAMATSU
Keyword(s):  
Fracture Toughness ◽  
Mode Ii ◽  
Fracture Toughness Testing ◽  
Toughness Testing ◽  
Mode Ii Loading

Microstructural Effects on Fracture Toughness of Polycrystalline Ceramics in Combined Mode I and Mode II Loading

1989 ◽  
Vol 111 (1) ◽  
pp. 174-180 ◽  
Author(s):  
D. Singh ◽  
D. K. Shetty
Keyword(s):  
Fracture Toughness ◽  
Mode I ◽  
Mode Ii ◽  
Mixed Mode Fracture ◽  
Transgranular Fracture ◽  
Pure Mode ◽  
Polycrystalline Alumina ◽  
Polycrystalline Ceramics ◽  
Mode Ii Loading ◽  
Combined Mode

Fracture toughness of polycrystalline alumina and ceria partially stabilized tetragonal zirconia (CeO2-TZP) ceramics were assessed in combined mode I and mode II loading using precracked disk specimens in diametral compression. Stress states ranging from pure mode I, combined mode I and mode II, and pure mode II were obtained by aligning the center crack at specific angles relative to the loading diameter. The resulting mixed-mode fracture toughness envelope showed significant deviation to higher fracture toughness in mode II relative to the predictions of the linear elastic fracture mechanics theory. Critical comparison with corresponding results on soda-lime glass and fracture surface observations showed that crack surface resistance arising from grain interlocking and abrasion were the main sources of the increased fracture toughness in mode II loading of the polycrystalline ceramics. The normalized fracture toughness for pure mode II loading, (KII/KIc), increased with increasing grain size for the CeO2-TZP ceramics. Quantitative fractography confirmed an increased percentage of transgranular fracture of the grains in mode II loading.

A Study of Mode III Fracture Toughness in Young and Mature Concrete with Fly Ash Additive

2016 ◽  
Vol 254 ◽  
pp. 120-125 ◽  
Author(s):  
Grzegorz Ludwik Golewski ◽  
Tomasz Sadowski
Keyword(s):  
Fracture Toughness ◽  
Fly Ash ◽  
Fracture Mechanics ◽  
Test System ◽  
Special Device ◽  
Mode Iii ◽  
Concrete Mixtures ◽  
Young Concrete ◽  
Torsional Test ◽  
Class F Fly Ash

A description of processes of formation and propagation of cracks in material requires the knowledge of all fracture mechanics parameters, i.e.: KIc, KIIcand KIIIc. In this study a new testing method and estimation of the fracture toughness in Mode III (antiplane shear) of concretes containing: 0, 20 and 30% volume content of the class F fly ash (FA) was proposed. Fracture toughness tests were performed on axial torsion machine MTS 809 Axial/Torsional Test System. The studies examined effect of FA additive on the parameter KIIIc. In order to determine the fracture toughness KIIIca special device was made. Experimental investigation under third mode fracture was carried out both in young and mature concrete composites (after: 3, 7, 28, 90, 180 and 365 days). 20% addition of FA as well as a 30% addition of FA causes a reduction in fracture toughness of young concrete. After 28 days of couring a significant increase of the KIIIc was noticed in composites with a 20% additive of FA while concrete mixtures with a higher additive of FA still had lower analyzed fracture mechanics parameter.

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