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Calibration of indirect methods for maesurement of properties of alkali activated concretes
Vrba, Pavel ; Kocáb, Dalibor (referee) ; Bílek, Vlastimil (advisor)
This work solves creation of calibration relations to determine cube compressive strength, dynamic and static elastic modulus of alkali-activated concrete by non-destructive methods. Alkali-activated concrete is spoken of as a new material used in civil engineering. It shows different properties than normal concrete based on Portland cement. That's why the modification of common calibration relation seems necessary. Fresh concrete was made in the concrete plan ŽPSV a.s., Uherský Ostroh in three mixtures and always in the number of 18 cubes and 3 prisms. The samples were tested by impact hammer Schmidt type L, type N, SilverSchmidt PC-N and by ultrasound in 6 time periods of three specimens. After that, the cube compressive strength was determined. Status of static elastic modulus was determined in a time period of 28 days. The results are calibration relations to determine the progress of compressive strength and modulus of elasticity for each method and their combination.
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Polymeric metamaterials with advanced mechanical properties
Štaffová, Martina ; Lehocký,, Marian (referee) ; Kotoul, Michal (referee) ; Jančář, Josef (advisor)
Práce se zabývá 3D tištěnými polymerními auxetickými strukturami s důrazem na jejich mechanické vlastnosti. Pro zlepšení mechanických vlastností, zejména poměru schopnosti absorpce energie k hmotnosti při tlakovém zatížení, byly použity různé návrhy auxetických re-entrantních struktur. Struktury byly vytištěny pomocí stereolitografické 3D tiskárny. Byl vyvinut a systematicky demonstrován nový nástroj pro komplexní charakterizaci 3D tištěných těles s využitím komerční fotopolymerizační pryskyřice s volnými radikály. Metoda se opírá o statický a oscilační mechanický test kombinující měření teploty průhybu při zatížení (HDT) s dynamickou mechanickou analýzou (DMA) v jediném testu pro rychlou a spolehlivou charakterizaci parametrů určujících chování fotopolymeru při vytvrzování. Byly zkoumány podmínky tisku a doba vytvrzení, aby byl objasněn jejich vliv na vnitřní napětí v 3D tištěných tělesech. Auxetické struktury byly vytištěny pomocí flexibilní a tuhé pryskyřice a byl zkoumán vliv poréznosti, velikosti buněk a strukturálních gradientů na mechanické vlastnosti. Výsledky byly vyhodnoceny z konstrukčního a materiálového hlediska pro fotopryskyřice nad a pod Tg. Nejlepší účinnost absorbování energie byla zjištěna u biaxiálně orientované struktury s nejvyšší lokální porozitou umístěnou ve středu. Prezentovaná data přispívají k základnímu pochopení účinků designu buněk na deformační odezvu auxetických struktur a mohou pomoct při návrhu nových struktur s lepšími mechanickými vlastnostmi. Výsledky zároveň demonstrují všestrannost 3D tisku při realizaci komplexních, přírodou inspirovaných struktur.
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Creating conditions for evaluation of high-strength concrete characteristics using non-destructive testing methods
Procházka, David ; Horký,, Ondřej (referee) ; Kolář,, Karel (referee) ; Adámek, Jiří (referee) ; Brožovský, Jiří (advisor)
High-strength concrete (HSC) belongs in the recent years to frequently used types of concrete. It allows realization of static challenging structures and also shows due to its dense structure greater durability especially against aggressive media. Currently HSC construction realization abroad is not exceptional. It’s using in the Czech Republic is still limited. When realized, then in a small scale in civil engineering works. The realization of high-strength concrete structures is closely related with the concrete construction quality verification. Good efficiency of the quality control methods can provide non-destructive testing methods (NDT), especially when investigating strength of concrete built in structure. A lack on relevant data for non-destructive testing of HSC in technical and normative rules is to be considered as a significant deficiency. Evident for HSC generally is the lack in literature on deeper analysis of the factors affecting their non-destructive testing, as well a meaningful methodology or practically usable calibration relationships. HSC differs from ordinary concrete not only by used components, but also by more compact structure with different strength – elastic characteristics. Considering these differences, HSC strength prediction can not be performed by using calibration relationships developed for ordinary concrete. Moreover, the question is to what extent the current knowledge of the NDT results influencing factors can be considered as valid. The paper presents findings on the effects of the key factors affecting the measurement results of Schmidt hardness method and ultrasonic pulse method, including recommendations for the practical application of these methods. The problematic of static vs. dynamic modulus of elasticity was also solved. Calibration equations for predicting the compressive strength of HSC from the non-destructive testing parameter were elaborated, showing high cohesion among variables and practically usability.
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Creating conditions for evaluation of high-strength concrete characteristics using non-destructive testing methods
Procházka, David ; Horký,, Ondřej (referee) ; Kolář,, Karel (referee) ; Adámek, Jiří (referee) ; Brožovský, Jiří (advisor)
High-strength concrete (HSC) belongs in the recent years to frequently used types of concrete. It allows realization of static challenging structures and also shows due to its dense structure greater durability especially against aggressive media. Currently HSC construction realization abroad is not exceptional. It’s using in the Czech Republic is still limited. When realized, then in a small scale in civil engineering works. The realization of high-strength concrete structures is closely related with the concrete construction quality verification. Good efficiency of the quality control methods can provide non-destructive testing methods (NDT), especially when investigating strength of concrete built in structure. A lack on relevant data for non-destructive testing of HSC in technical and normative rules is to be considered as a significant deficiency. Evident for HSC generally is the lack in literature on deeper analysis of the factors affecting their non-destructive testing, as well a meaningful methodology or practically usable calibration relationships. HSC differs from ordinary concrete not only by used components, but also by more compact structure with different strength – elastic characteristics. Considering these differences, HSC strength prediction can not be performed by using calibration relationships developed for ordinary concrete. Moreover, the question is to what extent the current knowledge of the NDT results influencing factors can be considered as valid. The paper presents findings on the effects of the key factors affecting the measurement results of Schmidt hardness method and ultrasonic pulse method, including recommendations for the practical application of these methods. The problematic of static vs. dynamic modulus of elasticity was also solved. Calibration equations for predicting the compressive strength of HSC from the non-destructive testing parameter were elaborated, showing high cohesion among variables and practically usability.
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Calibration of indirect methods for maesurement of properties of alkali activated concretes
Vrba, Pavel ; Kocáb, Dalibor (referee) ; Bílek, Vlastimil (advisor)
This work solves creation of calibration relations to determine cube compressive strength, dynamic and static elastic modulus of alkali-activated concrete by non-destructive methods. Alkali-activated concrete is spoken of as a new material used in civil engineering. It shows different properties than normal concrete based on Portland cement. That's why the modification of common calibration relation seems necessary. Fresh concrete was made in the concrete plan ŽPSV a.s., Uherský Ostroh in three mixtures and always in the number of 18 cubes and 3 prisms. The samples were tested by impact hammer Schmidt type L, type N, SilverSchmidt PC-N and by ultrasound in 6 time periods of three specimens. After that, the cube compressive strength was determined. Status of static elastic modulus was determined in a time period of 28 days. The results are calibration relations to determine the progress of compressive strength and modulus of elasticity for each method and their combination.
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