Investigating the effect of using three pozzolans (including the nanoadditive) in combination on the formation and development of cracks in concretes using non-contact measurement method

Grzegorz Ludwik Golewski Techno-Press 2024 Advances in nano research Vol.16 No.3

This paper presents results of visual analysis of cracks formation and propagation of concretes made of quaternary binders (QBC). A composition of the two most commonly used mineral additives, i.e. fly ash (FA) and silica fume (SF) in combination with nanosilica (nS), has been proposed as a partial replacement of the cement. The principal objective of the present study is to achieve information about the effect of simultaneous incorporation of three pozzolans as partial replacement to the OPC on the fracture processes in concretes made from quaternary binders (QBC). The modern and precise non-contact measurement method (NCMM) via digital image correlation (DIC) technique was used, during the studies. In the course of experiments it was established that the substitution of OPC with three pozzolans including the nanoadditive in FA+SF+nS FA+SF+nS combination causes a clear change of brittleness and behavior during fractures in QBCs. It was found that the shape of cracks in unmodified concrete was quasi-linear. Substitution of the binder by SCMs resulted in a slight heterogeneity of the structure of the QBC, including only SF and nS, and clear heterogeneity for concretes with the FA additive. In addition, as content of FA rises throughout each of QBC series, material becomes more ductile and shows less brittle failure. It means that an increase in the FA content in the concrete mix causes a significant change in fracture process in this composite in comparison to concrete with the addition of silica modifiers only.

Determination of fracture toughness in concretes containing siliceous fly ash during mode III loading

Grzegorz Ludwik Golewski 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.1

This paper describes laboratory tests carried out to evaluate the influence of class F fly ash (FA) on fracture toughness of plain concretes, specified at the third model fracture. Composites with the additives of: 0%, 20% and 30% siliceous FA were analysed. Fracture toughness tests were performed on axial torsional machine MTS 809 Axial/Torsional Test System, using the cylindrical specimens with dimensions of 150/300 mm, having an initial circumferential notch made in the half-height of cylinders. The studies examined effect of FA additive on the critical stress intensity factor KIIIc. In order to determine the fracture toughness KIIIc a special device was manufactured.The analysis of the results revealed that a 20% FA additive causes increase in KIIIc, while a 30% FA additive causes decrease in fracture toughness. Furthermore, it was observed that the results obtained during fracture toughness tests are convergent with the values of the compression strength tests.

The Use of Surface Interpolation Methods for Landslides Monitoring

Grzegorz Lenda,Marcin Ligas,Paulina Lewi ska,Anna Szafarczyk 대한토목학회 2016 KSCE Journal of Civil Engineering Vol.20 No.1

The subject of this study is selection of mathematical description (interpolation method) of landslides surface for the purpose of periodic control of terrain movements. Monitoring of landslides, considered in this work, concerns points of periodic GPS or tacheometric measurements carried out in a relatively regular grid. For economic reasons, the grid usually consists of limited group of about several dozen of points that do not allow for an exact description of the terrain surface, nevertheless a general movement of a landslide can be detected (observed). Replacement of discrete set of points to a continuous surface model allows for a better assessment of the phenomenon especially within the scope of its main directions of activity. The choice of best performing interpolation method in order to construct a reliable numerical terrain model was performed through tests carried out on complex model surfaces. These model surfaces encompassed various configurations of terrain relief. In this study four interpolation methods i.e. splines, kriging triangulation with linear interpolation and IDW are compared. Tests on model surfaces distinguished the method of splines as the best performing one as well as the method of kriging which is suitable in some instances. The selected method of splines was then applied to periodically monitored landslide in Milówka in the south of Poland. Interpolation by means of splines allowed for observing progressive movements of the landslide surface with accuracy up to several millimeters. This confirms the usefulness and reliability of this method in landslides monitoring. Specialized field: Surveying & Geo-Spatial Engineering : Deformation Surveying

Supercritical CO2 extraction in chia oils production: impact of process duration and co-solvent addition

Grzegorz Da˛browski,Iwona Konopka,Sylwester Czaplicki 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.3

This study was conducted to show impact of supercritical fluid extraction using pure SC-CO2 or SCCO2 enriched by 2, 6, and 10% of acetone, simultaneously varied by the extraction time (1 vs. 5 h), on the quality of chia seed oils. Obtained oils were relatively similar in the fatty acid composition, but they differed in total content of phytochemicals (from 4956 to 6391 mg/kg of oil). Among them, three oils were the most different: oil extracted 1 h with pure SC-CO2 (the most abundant in squalene, sterols, and tocopherols), oil extracted 5 h with pure SC-CO2 (the poorest in squalene, polyphenols, and carotenoids, with medium level of sterols and tocopherols) and oil extracted 1 h with SC-CO2 enriched by 10% acetone (the most abundant in polyphenols and carotenoids). Such unique chia oils can be valuable for special market needs, such as cosmetics, pharmaceuticals, functional food or diet supplement production.

The effect of partial transparency of spherical targets on TLS point clouds registration accuracy

Grzegorz Lenda,Urszula Marmol,Michał Buczek 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.7

Registering of point clouds from terrestrial laser scanning, is often carried out using spherical targets. Instead of expensive originaltargets, it is also possible to use other spherical elements. Such targets, encountered in practice, may be, for example, Styrofoamspheres, spheres built using 3D printers, spherical, milky lampshades. Most spheres which are used as substitutes, have a certaincommon feature: as a result of partial transparency of the material, the laser beam can penetrate inside, changing distancemeasurements. This applies both to glass spheres and a wide range of synthetic products. These materials may therefore have anegative effect on the accuracy of determining the centers of the reference spheres and, consequently, the accuracy of registrationpoint clouds in neighbouring scanners’ positions. This paper presents the results of the research studies allowing to assess this effect. Both the accuracy of determining the centers of the spherical targets, as well as the displacements occurring in the point cloudsmerged with their use were determined. Specialized field: Surveying & Geo-Spatial Engineering : Deformation Surveying

A new principles for implementation and operation of foundations for machines: A review of recent advances

Grzegorz Ludwik Golewski 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.71 No.3

The aim of this paper is to present the most important issues on the implementation, operation and maintenance of foundation for machines. The article presents the newest solutions both in terms of technology implementation as well as materials used in construction of such structures. Foundations for machines are special building structures used to transfer loads from an operating machine to the subsoil. The purpose of these foundations is not just to transfer loads, but also to reduce vibrations occurring during operation of the machine, i.e. their damping and preventing redistribution to other elements of the building. It should be noted that foundations for machines (particularly foundations for hammers) are the most dynamically loaded building structures. For these reasons, they require precise static and dynamic calculations, accuracy in their implementation and care for them after they have been made. Therefore, the paper in detail present the guidelines regarding: design, construction and maintenance of structures of this type. Furthermore, the most important parameters and characteristics of materials used for the construction of these foundations are described. As a result of the conducted analyzes, it was found that the concrete mix, in foundations for machines, should have a low water/binder ratio. For its execution, it is necessary to use broken aggregates from igneous rocks and binders modified with mineral additives and chemical admixtures. On the other hand, the reinforcement of composites should contain a large amount of structural reinforcement to prevent shrinkage cracks.

The North Korean Nuclear Crisis and U.S.-led Missile Defense Responses in Probabilistic Analysis

Grzegorz Nycz 한국학술연구원 2018 Korea Observer Vol.49 No.3

The paper examines the set of responses to North Korean ballistic and nuclear programs from the perspective of U.S.-supported diplomatic and military non-proliferation efforts with a special focus on missile defense. The XXI-century Pyongyang’s investments in securing the regime by weapons of mass destruction (nuclear-based deterrence) were seen as a potential source of serious international military conflict. Until the 2018 détente decades of sanctions aimed at dictatorial Pyongyang’s regime nuclear military programs showed the weaknesses of peaceful international attempts to limit dangerous WMD proliferation. Before 2018 Pyongyang under the Kim Jong Un regime reached strategic nuclear capacities through a provocative upgrade of its existing arsenal, proving the implemented sanctions-based measures to limit the North Korean ballistic and WMD armaments to be largely ineffective. The presented analysis employed the probabilistic model to analyze ballistic missile defense effectiveness as one of the discussed response options to the North Korean crisis by comparing the leakproof performance likelihood at various levels of single shot kill probability (SSKP) in scenarios of engaging additional interceptors against warheads attacking in a salvo.

On fixed points on compact Riemann surfaces

Grzegorz Gromadzki 대한수학회 2011 대한수학회보 Vol.48 No.5

A point of a Riemann surface X is said to be its fixed point if it is a fixed point of one of its nontrivial holomorphic automorphisms. We start this note by proving that the set Fix(X) of fixed points of a Riemann surface X of genus g≥ 2 has at most 82(g-1) elements and this bound is attained just for X having a Hurwitz group of automorphisms, i.e., a group of order 84(g-1). The set of such points is invariant under the group of holomorphic automorphisms of X and we study the corresponding symmetric representation. We show that its algebraic type is an essential invariant of the topological type of the holomorphic action and we study its kernel, to find in particular some sufficient conditions for its faithfulness.

Strength and microstructure of composites with cement matrixes modified by fly ash and active seeds of C-S-H phase

Grzegorz Ludwik Golewski,Bartosz Szostak 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.82 No.4

Fly ash (FA) is the main additive to concretes currently produced. This substitute of ordinary Portland cement (OPC) have a positive effect on the structure and mechanical parameters of mature concrete. Unfortunately, the problem of using FA as the OPC replacement is that it significantly reduces the performance of concretes in the early stages of their curing. This limits the possibility of using this type of concrete, e.g., in the prefabrication, where it is required to obtain high strength composites after short periods of their curing. In order to minimize these negative effects, research has been undertaken to increase the early strength of the concretes with FA through the application of a specially dedicated chemical nanoadmixture (NA) in the form of seeds of the C-S-H phase. Therefore, this paper presents results of tests of modified concretes both with the addition of FA and with NA. The analyses were carried out based on the results of the macroscopic and microstructural tests in 5 time periods, i.e. after: 4, 8, 12, 24 and 72 hours. The greatest increase in mechanical strength parameters and rapid development of the basic matrix phases in composites in the first 12 hours of composites curing was observed.

Study of strength and microstructure of a new sustainable concrete incorporating pozzolanic materials

Grzegorz Ludwik Golewski 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.86 No.4

The aim of this paper is to present a new sustainable ternary and quaternary binder by partially replacing ordinary Portland cement (OPC) with different percentages of supplementary cementitious materials. The motivation is to reduce our dependency on OPC to reduce CO2 emission and carbon foot print. As the main substitute for the OPC, siliceous fly ash was used. Moreover, silica fume and nanosilica were also used. During examinations the main mechanical parameters of concrete composites, i.e., compressive strength (fcm) and splitting tensile strength (fctm) were assed. The microstructure of these materials was also analysed. It was found that the concrete incorporating pozzolanic materials is characterized by a well-developed structure and has high values of mechanical parameters. The quaternary concrete containing: 80% OPC, 5% FA, 10% SF, and 5% nS have shown the best results in terms of good strength parameters as well as the most favourable microstructure, whereas the worst mechanical parameters with microstructure containing microcracks at phase interfaces were characterized by concrete with more content of FA additive in the concrete mix, i.e., 15%. Nevertheless, all concretes made on quaternary binders had better parameters than the reference one. It can be stated that sustainable concrete incorporating pozzolanic materials could be good substitute of ordinary concretes.