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RISS 인기검색어
- 검색키워드
- 저자 : Janusz Konkol (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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Janusz Konkol,Grzegorz Prokopski 한국계산역학회 2004 Computers and Concrete, An International Journal Vol.1 No.4
The examinations carried out have confirmed a relationship existing between the character of fracture surfaces and the composition and structure of (basalt and gravel) concretes. For both concretes investigated, a very good correlation was obtained between the profile line development factor, RL, and the fracture surface development factor, RS. With the increase in the RL parameter, the fracture surface development factor RS also increased. Agreement between the proposed relationship of RS = f(RL) and the proposal given by Coster and Chermant (1983) was obtained. Stereological examinations carried out along with fractographic examinations made it possible to obtain a statistical model for the determination of RL (or RS) based on the volume of air voids in concrete, Vair , the specific surface of air pores, the specific surface of coarse aggregate, SVagg., and the volume of mortar, Vm. An effect of coarse aggregate type on the obtained values of the profile line development factor, RL , as well as on the relationship RS = f(RL) was observed. The increment in the fracture surface development factor RS with increasing RL parameter was larger in basalt concretes than in gravel concretes, which was a consequence of the level of complexity of fractures formed, resulting chiefly from the shape of coarse aggregate grains.
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The necessary number of profile lines for the analysis of concrete fracture surfaces
Konkol, Janusz,Prokopski, Grzegorz Techno-Press 2007 Structural Engineering and Mechanics, An Int'l Jou Vol.25 No.5
The article describes a technique for the measurement of the level of complexity of fracture surfaces by the method of vertical sections, and a performed statistical analysis of the effect of profile lines on the fractographic and fractal parameters of fractures, i.e. the profile line development factor, $R_L$, and the fracture surface development factor, $R_S$, (as defined by the cycloid method), as well as the fractal dimension, $D_C$, (as determined by the chord method), and the fractal dimension, $D_{BC}$, (as determined by the box method). The above-mentioned parameters were determined for fracture surfaces of basalt and gravel concretes, respectively, which had previously been subjected to fracture toughness tests. The concretes were made from mixtures of a water/cement ratio ranging from 0.41 to 0.61 and with a variable fraction of coarse aggregate to fine aggregate, $C_{agg.}/F_{agg.}$, in the range from 1.5 to 3.5. Basalt and gravel aggregate of a fraction to maximum 16 mm were used to the tests. Based on the performed analysis it has been established that the necessary number of concrete fracture profile lines, which assures the reliability of obtained testing results, should amount to 12.
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The fractal analysis of the fracture surface of concretes made from different coarse aggregates
Grzegorz Prokopski,Janusz Konkol 한국계산역학회 2005 Computers and Concrete, An International Journal Vol.2 No.3
The article presents the results of examination of the fractal dimension D of concrete specimenfracture surfaces obtained in fracture toughness tests. The concretes were made from three different types of coarse aggregate: gravel, dolomite and basalt aggregate. Ordinary concretes (C40) and highperformance concretes (HPC) were subjected to testing after 7, 14, 28 and 90 days of curing, respectively. In fracture toughness and compressive tests, different behaviours of concretes were found, depending on the type of aggregate and class of concrete (C40, HPC). A significant increase in the strength parameters tested occurred also after a period of 28 days (up to the 90th day of curing) and was particularly large for concretes C40. Fractal examinations performed on fracture replicas showed that the fractal dimension D was diverse, depending on the coarse aggregate type and concrete class being, however, statistically constant after 7 and 14 days for respective concretes during curing. The fractal dimension D was the greater, the worse strength properties were possessed by the concrete. A cross-grain crack propagation occurred in that case, due to weak cohesion forces at the coarse aggregate/mortar interface. A similar effect was observed for C40 and HPC made from the same aggregate. A greater dimension D was exhibited by concretes C40, in which case the fracture was easier to form compared with highperformance concretes, where, as a result of high aggregate/mortar cohesion forces, the crack propagation was of inter-granular type, and the resulted fracture was flatter.
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