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Number of results: 116
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Abstract

Recycling construction and demolition waste not only reduces project costs; and saves natural resources, but also solves the environmental threat caused by construction waste disposal. In this paper, C25 waste road concrete is used as an experimental material, the uniaxial compression strength and tensile splitting strength of C25 RAC whose coarse aggregate replacement rate is 0%, 25%, 50%, 75%, and 100% are tested under the condition that the water-to-cement ratio is 0.47, 0.55 and 0.61. The results show: (1) the uniaxial compression strength and tensile splitting strength decrease with the increase of RAC; (2) for concrete with the same water-to-cement ratio, when the coarse aggregate replacement rate changes from 0% to 50%, the uniaxial compression strength and tensile splitting strength of RAC changes slightly. When the coarse aggregate replacement rate changes from 50% to 100%, the uniaxial compression strength and tensile splitting strength of RAC decreases rapidly

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Authors and Affiliations

X.H. Deng
Z.L. Lu
P. Li
T. Xu
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Abstract

Searching for new refrigerants is one of the most significant scientific problems in refrigeration. There are ecological refrigerants commonly known: H2O and CO2. H2O and CO2 known as natural refrigerants, but they have problems:a high freezing point of H2O and a low triple point of CO2. These problems can be solved by the application of a hybrid sorption-compression refrigeration cycle. The cycle combines the application possibility of H2O in the high temperature sorption stage and the low temperature application of CO2 in the compression stage. This solution gives significant energy savings in comparison with the two-stage compressor cycle and with the one-stage transcritical CO2 cycle. Besides, the sorption cycle may be powered by low temperature waste heat or renewable heat. This is an original idea of the authors. In the paper an analysis of the possible extension of this solution for high capacity industrial refrigeration is presented. The estimated energy savings as well as TEWI (Total Equivalent Warming Impact) index for ecological gains are calculated.

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Authors and Affiliations

Piotr Cyklis
Karina Janisz
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Abstract

In this paper, the semi-empirical model, formulated in the earlier paper [1], was used to control engine exhaust emission under steady-state conditions. The presented optimization method enables us to find the values of engine control parameters that lead to minimization of nitrogen oxide emission. Moreover, the presented method ensures proper engine operating parameters such as mean indicated pressure, thermal efficiency and maximum pressure in the cylinder. Results of numerical calculations are compared with experiment data. An acceptable accuracy was achieved.

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Authors and Affiliations

Krzysztof Brzozowski
Jan Nowakowski
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Abstract

Recent investigations of micro engines have documented the problem of low efficiency of steady compression devices [2]. As a solution, the application of unsteady processes has been proposed [1, 6, 17-20]. Closer investigations have shown the applicability of pure unsteady devices for gas compression, but it is also shown that they are practically not applicable for torque generation [21]. A new concept of the wave engine has to be developed.

This paper presents such a new concept and numerical investigation of the hybrid wave engine. A hybrid wave engine combines in a single machine components realizing unsteady compression, steady expansion, and mixed unsteady and steady scavenging due to the centrifugal force action. MEMS technology requires or prefers a flat geometry. Therefore, the use of a radial type of wave compression device for air compression is proposed. A numerical, two-dimensional complete model of this device was built, and several numerical simulations of engine operations were performed. The numerical model includes the simplified model of the combustion chamber closing the flow loop between the high-pressure compressed air port and the high-pressure hot exhaust gas port. The model represents the complete flow scheme of the hybrid wave engine. A special type of turbine in radial configuration with serial flow layout is used for torque generation.

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Authors and Affiliations

Janusz Piechna
Dawid Dyntar
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Abstract

The aim of this paper is to analyze various CO2 compression processes for post-combustion CO2 capture applications for 900 MW pulverized coal-fired power plant. Different thermodynamically feasible CO2 compression systems will be identified and their energy consumption quantified. A detailed thermodynamic analysis examines methods used to minimize the power penalty to the producer through integrated, low-power compression concepts. The goal of the present research is to reduce this penalty through an analysis of different compression concepts, and a possibility of capturing the heat of compression and converting it to useful energy for use elsewhere in the plant.

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Authors and Affiliations

Andrzej Witkowski
Mirosław Majkut
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Abstract

In order to grasp the strength characteristics and permeability of chlorite schist, the triaxial compression permeability test of chlorite schist was carried out by using a rock triaxial servo testing machine equipped with seepage device. Based on the test results, the failure strength, initial permeability and permeability development of rock samples under different confining pressure and different pore water pressure are compared, and the failure types of rock samples under triaxial compression permeability and their influence on permeability are analyzed. The results show that the increase of confining pressure is conducive to the improvement of failure strength of chlorite schist, and the increase of pore water pressure reduces the failure strength, which is related to the inhibition of crack development in rock samples by confining pressure and the promotion of crack expansion by pore water pressure. The mechanical deformation of chlorite schist in triaxial compression permeability process has experienced initial compaction stage, linear elastic stage and crack stable propagation to failure stage. As a consequence, permeability shows three trends of decline, stable development and rise, which is closely related to the development of the internal structure of rock samples at each stage. During the failure of triaxial compression permeability, there is a local compression zone in chlorite schist, and the rising rate slows down due to the influence of the compression zone.
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Authors and Affiliations

Fuqi Wang
1
ORCID: ORCID
Weipei Xue
2
ORCID: ORCID
Zhongdong Qiao
1
ORCID: ORCID
Jun Wu
1
ORCID: ORCID
Laiwang Jing
2
ORCID: ORCID

  1. Huating Coal Industry Daliu Coal Mine Co., Ltd, Shixinyao Town, Chongxin County, Pingliang, China
  2. Anhui University of Science and Technology, State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines, 168 Taifeng Street, Tianjia’an District, Huainan, China
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Abstract

The durability of building structures reinforced by steel is one of the main concerns in civil engineering. Currently, research in the field is focused on the possibility of replacing steel with relatively corrosion-resistant reinforcement, such as BFRP (Basalt Fiber Reinforced Polymers) bars. The behaviour of BFRP bars during compression has not yet been determined. The experimental results pertaining to BFRP bars subjected to compression were presented and discussed in the paper. The research program involved the preparation of 45 BFRP samples with varying unbraced length and nominal diameter of 8 mm that were subjected to compression. For samples with the unbraced length of up to 85 mm, the destruction was caused by crushing. The bars with the unbraced length greater than 120 mm were destroyed as a result of global buckling of the bar and subsequent fiber kinking. Based on the relationship between the buckling load strength – unbraced length, the optimal unbraced length of BFRP bar was determined, for which buckling load strength reaches its maximum value. The buckling load strength decreased, as the unbraced length increased. The values of modulus of elasticity under compression for variable unbraced lengths were slightly different for the samples, and were similar to the modulus of elasticity obtained at the tensile testing. The relationship between the buckling load strength and the unbraced length of BFRP bars was determined. This may contribute to the optimization of the transverse reinforcement spacing in compressed elements and to the development of standard provisions in the area of elements reinforced with FRP bars being subjected to compression.
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Authors and Affiliations

Marek Urbański
1
ORCID: ORCID
Kostiantyn Protchenko
1
ORCID: ORCID

  1. Warsaw University of Technology, Faculty of Civil Engineering, Al. Armii Ludowej 16, 00-637 Warsaw, Poland
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Abstract

The objective of this work is to present an energy analysis of different absorption refrigerating systems operating with diverse refrigerants. Also is applied the method of experimental design to optimize configurations proposed by the absorption pairs used and the operating conditions. Both acceptable coefficient of performance and low operating generator temperature are scrutinised. Therefore, a computer program is developed. An investigation of the thermodynamic properties is presented. Results show the coefficient of performance evolution versus respectively the evaporator temperature, temperature of condensation and generator temperature. A particular interest is devoted to the intermediate pressure effect on the performance of different systems. In order to better converge in the selection of the configuration and the refrigerant, which can ensure a high coefficient of performance associated to relatively low operating generator temperature the plan of experiments has been developed, taking in account all parameters influencing the system performance and the function of operating temperature. Results show that the refrigerating machine containing a compressor between the evaporator and the absorber has a coefficient of performance quite acceptable and that it can work at low generator temperature for about 60 ◦C and using the NH3/LiNO3 as refrigerant.

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Authors and Affiliations

Ridha Ben Iffa
Lakdar Kairouani
Nahla Bouaziz
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Abstract

One of the worst accidents that can take place in industrial presses is related to the risk of generating cracks in the columns. In order to avoid press columns from being subjected to tensile stress in the loading phase, the columns are sometimes assembled precompressed, so that nominal stress maintains negative values throughout the work cycle. Previous researches have considered cracks propagating under cyclic compressive loads in notched specimens. In these cases, the fatigue cracks are initiated at the notch root due to residual tensile stresses and grew at a progressively decreasing speed before arresting. The subject of the present paper is to give a paradigmatic example of crack initiation and propagation also in a general compressive field.
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Authors and Affiliations

Giorgio Olrni
Alessandro Freddi
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Abstract

Paper deals with theoretical analysis of possible efficiency increase of compression refrigeration cycles by means of application of a twophase ejector. Application of the two phase ejector in subcritical refrigeration system as a booster compressor is discussed in the paper. Results of exergy analysis of the system operating with various working fluids for various operating conditions have been shown. Analysis showed possible exergy efficiency increase of refrigeration compression cycle.

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Authors and Affiliations

Jarosław Karwacki
Adam Dudar
Dariusz Butrymowicz
Kamil Śmierciew
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Abstract

Recently a new technology of piezoelectric transducers based on PZT thick film has been developed as a response to a call for devices working at higher frequencies suitable for production in large numbers at low cost. Eight PZT thick film based focused transducers with resonant frequency close to 40 MHz were fabricated and experimentally investigated. The PZT thick films were deposited on acoustically engineered ceramic substrates by pad printing. Considering high frequency and non-linear propagation it has been decided to evaluate the axial pressure field emitted (and reflected by thick metal plate) by each of concave transducer differing in radius of curvature - 11 mm, 12 mm, 15 mm, 16 mm.

All transducers were activated using AVTEC AVG-3A-PS transmitter and Ritec diplexer connected directly to Agilent 54641D oscilloscope. As anticipated, in all cases the focal distance was up to 10% closer to the transducer face than the one related to the curvature radius. Axial pressure distributions were also compared to the calculated ones (with the experimentally determined boundary conditions) using the angular spectrum method including nonlinear propagation in water. The computed results are in a very good agreement with the experimental ones. The transducers were excited with Golay coded sequences at 35-40 MHz. Introducing the coded excitation allowed replacing the short-burst transmission at 20 MHz with the same peak amplitude pressure, but with almost double center frequency, resulting in considerably better axial resolution. The thick films exhibited at least 30% bandwidth broadening comparing to the standard PZ 27 transducer, resulting in an increase in matching filtering output by a factor of 1.4-1.5 and finally resulting in a SNR gain of the same order.

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Authors and Affiliations

Marcin Lewandowski
Andrzej Nowicki
Janusz Wójcik
Ryszard Tymkiewicz
Rasmus Lou-Moller
Wanda Wolny
Tomasz Zawada
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Abstract

Despite the growing importance of packet switching systems, there is still a shortage of thorough analyses of VoIP transmission effect on speech and speaker recognition performance. Voice over IP transmission systems use packet switching. There is no guarantee of delivery. The main disadvantage of VoIP is a packet loss which has a major impact on the performance experienced by the users of the network. There are several techniques to mask the effects of a packet loss, referred to as packet loss concealment. In this study, the effect of voice transmission over IP on automatic speaker verification system performance was investigated. The analyzed system was based on MAP-EM-GMM modelling methods. Four various speech codecs of H.323 standard were investigated with special emphasis placed on the packet loss phenomenon and various packet loss concealment techniques.
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Authors and Affiliations

Waldemar Maciejko
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Abstract

The paper analyzes the estimation of the fundamental frequency from the real speech signal which is obtained by recording the speaker in the real acoustic environment modeled by the MP3 method. The estimation was performed by the Picking-Peaks algorithm with implemented parametric cubic convolution (PCC) interpolation. The efficiency of PCC was tested for Catmull-Rom, Greville, and Greville two- parametric kernel. Depending on MSE, a window that gives optimal results was chosen.
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Authors and Affiliations

Zoran N. Milivojević
Darko Brodić
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Abstract

In this paper the influence of high power airborne ultrasound on drying biological material (Lobo apple) properties is considered. Apple samples were dried convectively at 75 ◦C and air flow of 2 m/s with and without ultrasound assist at 200W. During experiments, sun-drenched and not sun-drenched part of fruits were considered separately to show, how the maturity of the product influences dry material properties. Dried apple crisps in a size of small bars were subjected to compression tests during which acoustic emission (AE) was used. Analysis of AE and strength test results shows that correlations between received acoustic signals and sensory attributes (crispness, brittleness) of dried apples can be found. It was noted that ultrasound improved fruit brittleness in comparison with pure convective processes, where fruit maturity determines a kind of destruction and behaviour of dried apple crisps.

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Authors and Affiliations

Jacek Banaszak
Andrzej Pawłowski
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Abstract

Three commercially available intercooled compression strategies for compressing CO2 were studied. All of the compression concepts required a final delivery pressure of 153 bar at the inlet to the pipeline. Then, simulations were used to determine the maximum safe pipeline distance to subsequent booster stations as a function of inlet pressure, environmental temperature, thickness of the thermal insulation and ground level heat flux conditions. The results show that subcooled liquid transport increases energy efficiency and minimises the cost of CO2 transport over long distances under heat transfer conditions. The study also found that the thermal insulation layer should not be laid on the external surface of the pipe in atmospheric conditions in Poland. The most important problems from the environmental protection point of view are rigorous and robust hazard identification which indirectly affects CO2 transportation. This paper analyses ways of reducing transport risk by means of safety valves.

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Authors and Affiliations

Mirosław Majkut
Andrzej Witkowski
Andrzej Rusin
Katarzyna Stolecka
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Abstract

The criteria, with which one should be guided at the assessment of the binding properties of bentonites used for moulding sands, are proposed in the paper. Apart from the standard parameter which is the active bentonite content, the unrestrained growth indicator should be taken into account since it seems to be more adequate in the estimation of the sand compression strength. The investigations performed for three kinds of bentonites, applied in the Polish foundry plants, subjected to a high temperature influences indicate, that the pathway of changes of the unrestrained growth indicator is very similar to the pathway of changes of the sand compression strength. Instead, the character of changes of the montmorillonite content in the sand in dependence of the temperature is quite different. The sand exhibits the significant active bentonite content, and the sand compression strength decreases rapidly. The montmorillonite content in bentonite samples was determined by the modern copper complex method of triethylenetetraamine (Cu(II)-TET). Tests were performed for bentonites and for sands with those bentonites subjected to high temperatures influences in a range: 100-700ºC.
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Authors and Affiliations

S. Żymankowska-Kumon
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Abstract

Recently, attempts have been made to use porous metal as catalysts in a reactor for the hydrogen manufacturing process using steam methane reforming (SMR). This study manufactured Ni-Cr-Al based powder porous metal, stacked cubic form porous blocks, and investigated high temperature random stack creep property. To establish an environment similar to the actual situation, a random stack jig with a 1-inch diameter and height of 75 mm was used. The porous metal used for this study had an average pore size of ~1161 μm by rolling direction. The relative density of the powder porous metal was measured as 6.72%. A compression test performed at 1073K identified that the powder porous metal had high temperature (800°C) compressive strength of 0.76 MPa. A 800°C random stack creep test at 0.38 MPa measured a steady-state creep rate of 8.58×10–10 s–1, confirming outstanding high temperature creep properties. Compared to a single cubic powder porous metal with an identical stress ratio, this is a 1,000-times lower (better) steady-state creep rate. Based on the findings above, the reason of difference in creep properties between a single creep test and random stack creep test was discussed.

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Authors and Affiliations

Tae-Hoon Kang
Kyu-Sik Kim
Man-Ho Park
Kee-Ahn Lee
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Abstract

The paper presents Improved Adaptive Arithmetic Coding algorithm for application in future video compression technology. The proposed solution is based on the Context-based Adaptive Binary Arithmetic Coding (CABAC) technique and uses the authors mechanism of symbols probability estimation that exploits Context-Tree Weighting (CTW) technique. This paper proposes the version of the algorithm, that allows an arbitrary selection of depth D of context trees, when activating the algorithm in the framework of the AVC or HEVC video encoders. The algorithm has been tested in terms of coding efficiency of data and its computational complexity. Results showed, that depending on depth of context trees from 0.1% to 0.86% reduction of bitrate is achieved, when using the algorithm in the HEVC video encoder and 0.4% to 2.3% compression gain in the case of the AVC. The new solution increases complexity of entropy encoder itself, however, this does not cause an increase of the complexity of the whole video encoder.
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Authors and Affiliations

Damian Karwowski
Marek Domański
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Abstract

The main objective of this investigation is to assess the feasibility of strengthening of corroded (damaged) square hollow steel tubular sections subjected to compression and to develop or predict the suitable wrapping scheme of fibre reinforced polymer (FRP) to enhance the structural behaviour of it.For this study, compact mild steel tubes were used with the main variable being FRP characteristics. Carbon fibre reinforced polymer (CFRP) fabrics was used as horizontal strips (lateral ties) with other parameters such as the number of layers and spacing of strips. Among fourteen specimens, six were externally bonded by CFRP strips having a constant width of 50 mm with a spacing of 20 mm and the remaining six were externally bonded by CFRP strips having a constant width of 70 mm with a spacing of 20 mm, two columns were unbonded. Experiments were undertaken until the failure of columns to fully understand the influence of FRP characteristics on the compressive behaviour of the square sections including their failure modes, axial stress-strain behaviour, enhancement in the load carrying capapcity, and effect of distribution of CFRP layers. Finally, the behaviour of externally bonded hollow tubular sections was compared with one another and also with the control specimens. Evaluation of the results will lead to optimum CFRP jacketing/wrapping arrangements for the steel tubes considered here.

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Authors and Affiliations

M.C. Sundarraja
P. Sriram
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Abstract

The policy of sustainable development seeks to improve energy efficiency of industrial equipment. Efforts to improve energy efficiency also apply to the paint shops, where the recovery of waste heat is sought. The main source of a large amount of low-temperature waste heat in the paint shop is the spray booth. The second place where a large amount of low temperature waste heat is released is the room where the compressed air is prepared. Low energy efficiency of air compressors requires a large electric power supply. As a result, the emitted large heat fluxes become waste energy of the technological process. Heat is equivalent to up to 93% of the electric power supplied in the air compression process. There are solutions for recovering heat from compressors coming from the oil cooling water, but then the waste heat from the cooling of the compressed air and from the electric motor is released into air in the room. A method for recovering low-temperature waste heat from the air preparation room by means of an air-source heat pump has been proposed. An energy balance of the air compression and dehumidification process for the paint shop was made. A Matlab’s built-in numerical model includes air compressor and dehumidifier, heat recovery and accumulation for the purposes of use in the spray booth. A simulation experiment was carried out on the effectiveness of heat recovery from the air preparation room. The use of combined energy management in paint shops was proposed.

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Authors and Affiliations

Andrzej Adamkiewicz
Piotr Nikończuk
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Abstract

The article presents the results of CRL research on glacial till contaminated with JET A1 aviation fuel and mineral oil 15W40. The conducted research has shown that the compressibility of fine grained soils contaminated with hydrocarbons during a constant rate of loading tests depends on the physical properties of the soil, properties of oil contaminants, their content in the soil pores as well as the adopted loading velocity. The implemented laboratory test program shows that the contamination of glacial till with hydrocarbons increases their compressibility. Moreover, this research shows that the CRL test method may be recommended in the compressibility research of fine grained soils contaminated with hydrocarbons.
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Authors and Affiliations

Piotr Stajszczak
1

  1. Geoteko Geotechnical Consultants Ltd., ul. Wałbrzyska 14/16, 02-739 Warszawa, Poland
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Abstract

The aim of the paper was to analyse the possibility to use waste material which is created during the production of mineral-asphalt mixes as a side effect of the process of drying and dedusting diabase aggregate in high temperature. Experimental studies included the analysis of the influence of the addition of diabase dust on the improvement of the properties of cement concrete destined for the construction of local roads. The mineral additive in the form of diabase dust, which constitutes natural waste, was inserted into the concrete mix as a mineral additive substituting a part of the aggregate with the constant amount of cement and water, and additionally as the substitute for cement. The performed studies resulted in the conclusion that adding diabase dust significantly increased the tightness and density of concrete, which impacts the increase of compressive strength by 7, 21 and 28% in reference to model concrete. The insertion of the waste diabase dust into the concrete mix significantly improved the freeze-thaw resistance of concrete after 150 cycles of testing and reduced the water absorption by 6, 15 and 21%. Using diabase dust as a substitute in the following amount: 50, 100 and 150 kg/m3 did not cause significant changes in the scope of density and water absorption, whereas the reduction of the compressive strength was from 8, 23 and 33% in reference to the model concrete. The application of dust as the substitute for cement resulted in the reduction of the costs of concrete by 6, 12 and 18% and resulted in the possibility to fully apply waste material, which confirms the justness of undertaking implementation research. Concrete with the use of waste rock dusts may be qualified as concrete that is environmentally friendly and compliant with the sustainable development of modern construction materials.
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Authors and Affiliations

Tomasz Rudnicki
1
ORCID: ORCID
Robert Jurczak
2
ORCID: ORCID

  1. Faculty of Civil Engineering and Geodesy, Military University of Technology in Warsaw, ul. Gen. S. Kaliskiego 2, 01-476 Warsaw, Poland
  2. Faculty of Civil and Environmental Engineering, West Pomeranian University of Technology in Szczecin, al. Piastów 50a, 70-311 Szczecin, Poland
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Abstract

The mechanical characteristics of transversely isotropic rocks are significantly different under various levels of inclination, and it is difficult to describe exactly the mechanical behaviour of transversely isotropic rocks. Assuming that rock consists of a great deal of microelements, and the microelement strength controlled by Mohr–Coulomb criterion follows the log normal distribution. The elastic modulus is used to reflect the anisotropy of rock, and the weak patches stiffness model is verified and employed to depict the variation of elastic modulus with different inclination angle. Based on basic damage mechanics theory and statistical method, a nonlinear statistical empirical model for transversely isotropic rocks is proposed under uniaxial compressive condition. In order to verify the correctness of the proposed model, comparison analyses between predicted results and experimental data taken from published literature are carried out, which have good consistency. Finally, the discussions on the influences of the distribution parameters ��, �� and elastic modulus with different inclination angle, ����, on proposed model is offered.
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Authors and Affiliations

Yansheng Deng
1
ORCID: ORCID
Chenjie Shen
1
ORCID: ORCID
Baoping Zou
1
ORCID: ORCID

  1. School of Civil Engineering and Architecture, Zhejiang University of Science and Technology, Hangzhou 310023, China

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