bluuebunny/crossref_metadata_2025 huggingface dataset:
Aerodynamic study of a suspension bridge deck by CFD simulations, wind tunnel tests and full-scale observations
Authors: Kusano I. , Cheynet E. , Jakobsen J. B. , Snæbjörnsson J.
Published: November 2021

Assessing the aerodynamic characteristics of long-span bridges is fundamental for their design. Depending on the terrain complexity and local wind conditions, episodes of large angles of attack (AoA) of 15° may be observed. However, such large AoAs ( above 10°) are often overlooked in the design process. This paper studies the aerodynamics properties of a flow around a single-box girder for a wide range of AoAs, from –20° to 20°, using numerical simulations. The simulations are based on a 2D unsteady Reynolds-averaged Navier–Stokes (URANS) approach using the k − ω SST turbulence model with a Reynolds number of 1.6 × 105. Numerically obtained aerodynamic static coefficients were compared to wind tunnel test data. The CFD results were generally in good agreement with the wind tunnel tests, especially for small AoAs and positive AoAs. More discrepancies were observed for large negative AoA, likely due to the limitation of modelling 3D railings with 2D simulations. The simulated velocity deficit downstream of the deck was consistent with the one measured in full-scale using short-range Doppler wind lidar instruments. Finally, the Strouhal number from the CFD simulations were in agreement with the value obtained from the full-scale data.
Determining reservoir parameters with nonisothermal real gas flow
Authors: Aminev D A , Kravchenko M N
Published: November 2021

Creation and developing methods of determining gas reservoir properties are one of the most important gas hydrodynamics tasks as production project efficiency and reservoir exploitation depend upon layer properties knowledge. Nonstationary gas hydrodynamics investigations are one of the base well and layer researching methods. Results of these investigations are interpreted based on solving of linear isothermal gas flow equation. The current investigation describes the nonstationary gas hydrodynamic survey results interpretation algorithm, which is based on nonlinear equations system solving. The system consists of nonlinear nonisothermal real gas flow and energy equations accounting well influence, Joule-Thompson and adiabatic expansion effects. Integro-interpolation and iteration finite methods were used for creating their own numerical algorithm. Numerical programs allow solving as direct as inverse gas flow tasks in the cylindrical layer. For verification of inverse task solution, the survey interpretation results from the real gas field were paralleled with currently methods results and showed sufficient accuracy. The described method allows to interpret survey gas hydrodynamic results accounting real gas and porous matrix properties, and well influence to enhance integrity and precision reservoir properties estimation.
CFD investigation of internal elbow pipe flows in laminar regime
Authors: Taibi R , Yin G , Ong M C
Published: November 2021

Elbow pipes are crucial parts of many fluid transport systems in the oil and gas industry. The curved shape of such pipes induces centrifugal forces on the internal flow, ultimately affecting the flow velocity and creating pressure differences within the elbow. The present study aims to investigate the effects of the curvature ratio of an elbow pipe on the internal pipe flow using three-dimensional numerical simulations. For laminar flows, the simulations are based on four Reynolds numbers ranging from 200 to 2000 and three curvature ratios of Ro=5.6, 11.2 and 22.4. A mesh convergence study is carried out for 3 meshes with increasing resolution. The results based on the optimal mesh is then compared with the published experimental and numerical results for validation. Once the validation is confirmed, further simulation and analysis are performed for each combination of curvature ratio and Reynolds number. The results reveal that there is flow separation due to the centrifugal forces induced by the curved shape. It is also shown that secondary flows consisting of symmetrical helical vortices called Dean vortices are generated. The intensity of this secondary flow is shown to increase with the increasing Dean number.
Duplex steel welding in artic conditions – Correlation of welding parameters in relation to HISC
Authors: Czarnacki Z , Xing Y
Published: November 2021

Duplex steel is an austenitic-femtic steel alloy commonly used in the offshore and subsea oil and gas industry. Duplex steel provides a unique combination of good mechanical properties and corrosion resistance in sweet and sour hydrocarbon environment, as well as in seawater. However, the combination of tensile loading, post-weld residual stresses, cathodic protection and other factors related to subsea implementation significantly increase the probability of hydrogen induced stress cracking (HISC). This paper aims to find a relationship between the formation of residual stresses and the imperfection of the welding process carried out on Duplex steel in extremely cold conditions. Based on a finite element (FE) welding transient simulation from a thermal perspective, the correlation between the welding parameters and heat distribution is established and analysed when the welding takes place in the cold arctic conditions. Pearson parameter correlation analysis method will be used to investigate the impact of extreme ambient temperatures on the welding process. The results and conclusions provide a solid foundation for welding process optimization in connection with HISC.
Hydrodynamic model of an oil spill on the Earth’s surface and the use of expert technologies in its implementation to assess pollution methods
Authors: Lokhov A S , Gubaidullin M G , Korobov V B
Published: November 2021

A volumetric model of accidental oil spills on the land surface was developed, based on numerical methods for solving hydrodynamic equations, and taking into account the processes of oil spreading over the surface, its filtration into the soil and evaporation into the atmosphere. Based on the results of calculations using the hydrodynamic model for the most probable scenarios of oil spills, it is possible to obtain an estimate of the spatial-temporal scale of the spill, which, together with data on the terrain and the presence of water bodies, is the input data for the expert model. Based on the joint use of the hydrodynamic model of the oil spill and expert technologies, the territory of the Nenets Autonomous Okrug and the South Khylchuyu-Varandey oil pipeline were zoned in more detail. It makes it possible to predict the scale and areas most susceptible to negative impact in the event of an accidental oil spill, and to make the necessary decisions for the location of the spill response facilities, as well as the facilities themselves, already at the stage of selection and design of the pipeline route.
A practical design procedure for initial sizing of heaving point absorber wave energy converters
Authors: Jouybari M B , Xing Y
Published: November 2021

Designing a wave energy converter with the proper size has always been challenging since it is a trade-off between many factors including cost, practicality, and energy output. In this paper a practical design procedure for sizing of heaving point absorbers wave energy converters is presented. Size can be represented by the body volume. Budal power bounds are deployed to obtain the body volume and annual mean absorbed power of the wave energy converter. Budal power bounds are determined for each sea state. Aiming a specific power capture ratio, several sets of design sea states with related design volume and annual mean absorbed power are defined. With the design objective of maximizing the ratio of mean power to submerged volume, and considering suitable design constraints, the best size is obtained. The proposed procedure will be then deployed for a case study and the design will be compared with an existing similar point absorber. The results show that the mean absorbed power does not depend on the size but is a function of selected sea states. Furthermore, the comparison study reveals that the proposed design procedure yields reasonable power characteristics.
A 2D model for the study of equilibrium glide paths of UiS Subsea Freight-Glider
Authors: Ahmad U N , Xing Y
Published: November 2021

A planar mathematical model for the analysis of equilibrium glide paths of the UiS subsea freight-glider (USFG) is presented. The model is developed using Simscape Multibody in MATLAB/Simulink to study the ever-changing dynamics of the glider. Motion along the heave and pitch direction is regulated by two separate PID controllers. Controllers are tuned for the optimal bandwidth and phase margin to provide the system with ideal gains which satisfy the system requirements. A wide-ranging sensitivity investigation is carried out on the USFG by changing the two key variables, pump flow rate and ballast fraction. The results reflect the advantages of using higher flow capacity and ballast fraction, which should be preferred according to the application, provided if there are no space and weight restrictions. Finally, different glide paths were simulated to observe that, controller gains obtained from the linear model can be improved to acquire better performance in terms of robustness and stability of the system.
Global analysis of floating offshore wind turbines with shared mooring system
Authors: Munir H , Lee C F , Ong M C
Published: November 2021

Floating wind turbines (FWTs) with shared mooring systems can be one of the most cost- effective solutions in reducing mooring costs. First, the static configuration of a shared line is estimated using the elastic catenary equation. The present study investigates the global responses of two FWT with a shared mooring system. Two shared mooring configurations with different horizontal distances between the FWTs are considered. In the first configuration, the FWTs are placed 750m apart; and in the second configuration, they are placed 1000m apart. Two different environmental conditions (ECs) are used to simulate the global responses of the system in time domain. The shared mooring line results in higher extreme motions in surge and sway (degree of freedoms) DOFs due to the reduction of mooring restoring stiffness. The lower mooring restoring stiffness can be attributed to the reduction of one seabed anchoring point for each FWT as compared to a single FWT with three anchors installed. In the rotational DOFs, the shared mooring line configurations result in slight mean offset in each direction and significant increase in the motion standard deviations. This is caused by the reduced mooring stiffness associated with the change in platform orientation.
Safety related study of Expanding Pin systems application in lifting and drilling equipment within Construction, Offshore, and Marine sectors
Authors: Karlsen Ø , Lemu H G
Published: November 2021

A questionnaire-based survey has been performed among original equipment manufacturers (OEMs), sub-suppliers, engineering companies, end-users, service & maintenance, and “others”, as part of an investigation to clarify their relationship to expanding pin system, compared to standard, cylindrical pins. In addition, a short literature study on onshore cranes is conducted. The survey is based on 9 questions about safety for personnel and machine, breakage, and wear of pins and supports, and installation and retrieval easiness of pins. The analysis of the responses indicates that safety for personnel and machines/equipment is regarded mainly as either “Important” or “Crucial and decisive”, and that the expanding pin solution is regarded as “better” or “equal” compared to the standard, cylindrical pin, both for “safety level”, “risk for breakage of pin & support”, “tear & wear on pin & support” and “installation and retrieval time”.
Code for calculating wave technology of thermal-gas-chemical formation treatment for oil recovery enhancement
Authors: Kravchenko M N , Kroshilin V E , Dieva N N
Published: November 2021

Transition to the development of hard-to-recover hydrocarbons, including in regions the far north, is fraught with difficulties in using classical technologies development. This is due to the low porosity and permeability of the reservoirs, high viscosity of the formation fluid and the manifestation of abnormal (non-Newton) properties of hydrocarbon fluids. In this regard, for more than ten years, pilot field research (FPI) in terms of the selection and optimization of technologies for collectors of complex structures. Since 2011, at the departments of the underground hydromechanics of Gubkin Russian State University of Oil and Gas (NRU) and gas wave dynamics of the Lomonosov Moscow State University, research is underway on the use of thermogas-chemical method with an injection of a binary mixture to stimulate the inflow. Since 2011, several settlement codes of different levels were created, which allowed carrying out support (pilot) in various fields. Based software products managed to evaluate the characteristics in the chemical reaction zone decomposition of the working chemical composition, evaluate safe regimes, excluding damage to the wellbore and assess the prolongation of the effect. Published more than 20 works (including patents) with the participation of the authors. Since 2019 the mathematical model is significantly complicated: the multiphase and non-isothermality of the process, non-uniformity of the flow. Currently established generalizing code, in the mathematical model of which is additionally taken into account different compressibility of phases and rheological properties of fluids, which allows more fine-tune the computational code for the type of a specific field, taking into account its geological features and damage to the bottomhole zone in the previous stages of development.
Multi-objective optimization and analysis for laser beam cutting of stainless steel (SS304) using hybrid statistical tools GA-RSM
Authors: Tura A D , Mamo H B , Desisa D G
Published: November 2021

A laser beam machine is a non-traditional manufacturing technique that uses thermal energy to cut nearly all types of materials. The quality of laser cutting is significantly affected by process parameters. The purpose of this study is to use a genetic algorithm (GA) in conjunction with response surface approaches to improve surface roughness in laser beam cutting CO2 with a continuous wave of SS 304 stainless steel. The effects of the machining parameters, such as cutting speed, nitrogen gas pressure, and focal point location, were investigated quantitatively and optimized. The tests were carried out using the Taguchi L9 orthogonal mesh approach. Analysis of variance, main effect plots, and 3D surface plots were used to evaluate the impact of cutting settings on surface roughness. A multi-objective genetic algorithm in MATLAB was used to achieve a minimum surface roughness of 0.93746 μm, with the input parameters being 2028.712 mm/m cutting speed, 11.389 bar nitrogen pressure, and a focal point position of - 2.499 mm. The optimum results of each method were compared, as the results the response surface approach is less promising than the genetic algorithm method.
Characterization of acoustic emission signals under 3-point bending test
Authors: Nguyen N B G , Lemu H G , Gabrielsen O , El-Thalji I
Published: November 2021

This paper summarizes a master’s thesis project which explored whether the characteristics of Acoustic Emission Testing (AET) signals can be used to detect yielding in steel samples undergoing a three-point bending test. A subset of existing data from a three-point bending test was exported and used as input. Data was processed by utilizing and developing tools to visualize and analyse the signal characteristics, primarily through a parameter-based approach. Signals were visualized, and parameters were optimized to identify and classify signal types. According to the obtained results, some limitations on classification were experienced due to the length of the hit data recorded. Though the work reported in this article lead to a reliable method for detecting yielding, the developed algorithms were not successful in identifying characteristics that could be used to detect yielding.
Bending capacity of multi-layered FRP pipelines during offshore installation
Authors: Pavlou Dimitrios
Published: November 2021

The Fiber Reinforced Polymeric (FRP) pipelines have higher strength than steel, and excellent fatigue behavior and corrosion resistance. Because of their superior performance in mechanical loads and corrosive environment, they are a good choice for offshore applications. Since FRP materials are anisotropic and the pipelines are multilayered, the calculation of stresses is difficult. Stress analysis can be performed numerically with the aid of commercial software packages. However, the numerical solutions are approximate and the parametric study is problematic. In the present work, an analytical solution for bending stress calculation of multilayered FRP pipelines during offshore installation is presented. Typical examples are solved and bending capacity of multilayered FRP pipelines versus the fiber orientation angle and number of layers is provided and discussed.
Subsea FRP pipeline performance in external pressure: Failure and external pressure-induced buckling
Authors: Pavlou Dimitrios
Published: November 2021

The Subsea pipelines are subjected to high hoop stresses due to the hydrostatic pressure. When the internal pressure of the liquid has a higher value than the external hydrostatic one, there is a balance of the tensile and compressive stresses. However, during the offshore installation, the subsea pipelines are empty and the compression due to the hydrostatic pressure of the sea is predominant. High compressive stresses in FRP pipelines can cause failure or buckling. In the present work, an investigation of the external pressure-induced failure and buckling is carried out. Analytical formulae and results are provided and discussed.
Bending-induced local buckling during offshore installation of multi-layered FRP pipelines
Authors: Pavlou D , Adasooriya N D
Published: November 2021

In the last two decades FRP pipelines have attracted the attention of the oil industry because of their high strength, excellent fatigue performance and low specific weight. On the other hand, the final cost of installation of FRP pipelines is comparable to the cost of carbon steel ones. Therefore, their implementation in offshore applications seems to be advantageous. During offshore installation, the curvatures of the pipes during the S-lay or J-lay installation processes cause high bending stresses and risk for bending-induced local buckling. Since the pipe wall is multi-layered and the laminae are anisotropic, the calculation of critical bending moments is difficult. In the present work, an analytical solution of critical bending moments for bending-induced local buckling is provided. The proposed method uses the classical lamination theory of multi-layered anisotropic materials and Flügge’s assumption for local buckling analysis of pipelines. Results for E-Glass fiber reinforced polymeric pipelines are provided and discussed.
Fatigue life analysis of wheel-rail contacts at railway turnouts using finite element modelling approach.
Authors: Jelila Y D , Lemu H G , Pamuła W , Sirata G G.
Published: November 2021

The article deals with wheel-rail contact analysis at railway turnout using a finite element modelling approach. The focus is understanding the wheel-rail contact problems and finding the means of reducing these problems at railway turnouts. The main aim of the work reported in this article is to analyse fatigue life and simulate the wheel-rail contact problems for a repeated wheel loading cycle by considering the effect of normal and tangential contact force impact under different vehicle loading conditions. The study investigates the impact of tangential contact force generated due to different-angled shapes of the turnout and aims to reveal how it affects the life of contacting surfaces. The obtained results show that the maximum von-Mises equivalent alternating stress, maximal fatigue sensitivity, and maximum hysteresis loop stresses were observed under tangential contact force. These maximum stresses and hysteresis loops are responsible for rolling contact fatigue damage, and excessive deformation of the wheel-rail contact surface. At a constant rotational velocity, the tangential contact force has a significant impact on the fatigue life cycle and wheel-rail material subjected to fatigue damage at lower cycles compared to the normal contact force. The finite element modelling analysis result indicated that the contact damages and structural integrity of the wheel-rail contact surface are highly dependent on contact force type and can be affected by the track geometry parameters.
Solutions for monitoring the technical condition of metal structures and pipelines located at an altitude
Authors: Pshenin V V , Borisov A V , Menshikov S O
Published: November 2021

Periodic monitoring of the technical condition of metal constructions and pipelines at an altitude is an important part of their safe operation. For this purpose, as a rule, drones or methods of industrial climbing are used. In this research we propose a method of robotic inspection of such structures, which will substantially reduce the costs of maintenance work at an altitude and increase their level of safety. The main scientific interest is the creation of a universal kinematics adjusted to different obstacles not only on the pipelines but also on the metal constructions. In the course of the works there was conducted a fundamentally different experience in the mounting of supporting structures and metal constructions. The received knowledge was systematized in an album of the obstacles, on the basis of which the kinematics of the robotic device was modified.
A simple machine learning based framework for processing the inline inspection data of subsea pipelines
Authors: Liu Z , Dahl S S , Larsen E S , Yang Z
Published: November 2021

This paper presents a simple machine learning based framework for diagnosing the inline inspection data (ILI) of subsea pipelines. ILI data are obtained by intelligent pigging devices operating along subsea pipelines. The wall thickness (WT) and standoff distance (SO) are collected by the sensors installed on the pigging, which are normally in the format of 2D arrays. There are many uncertainties for the ILI data collected from the offshore survey. An attempt was made to apply the machine learning method to diagnose the uncertainties. A convolutional neural network (CNN) is used, the ILI data are discretized and processed in 64x64 grid size. Fabricated training datasets were made for training the machine learning model since the ground truth information (actual corroded wall thickness) is hardly known in this case. The trained model was successfully. It is demonstrated that certain corrosion patterns have been recognized by the trained model. Comparisons were performed between the new method and traditional methods with case studies on real ILI data. The validity of the methodology was discussed.
Experimental investigation on the mechanical and chemical properties of lightweight aggregate concrete with CO2 curing
Authors: Wang Z , Dehestani S , Kakay S , Sha Y
Published: November 2021

In the cement and concrete industry, enormous amounts of Carbon Dioxide (CO2) are emitted during their production processes. Carbon dioxide emission significantly contributes to the global climate change, which has been one of the biggest challenges of our times. Some novel solutions have been proposed for CO2 capture and storage, as well as reducing CO2 emission in concrete production. Carbonation curing is an effective alternative for conventional water curing for concrete. It can store CO2 in the hardened concrete and meanwhile improve early mechanical properties of concrete. Partial replacement of cement with fly ash shows environmental benefits, such as reducing greenhouse gas emissions and industrial waste destined for landfills. There has been some previous research studying on the effect of carbonation curing on normal Portland concrete in the past decade. Nevertheless, few studies have focused on the CO2 curing for lightweight aggregate concrete (LWAC). In this paper, the influence of early carbonation curing on LWAC is studied. LWAC specimens with two different water-to-cement ratios are cast and cured for a series of experimental investigations. The mechanical and chemical properties including the 1-day compressive strength, 28-day compressive strength, flexural strength, CO2 uptake, heat development, and pH level are investigated. Specimens with ordinary Portland cement are also tested as references in terms of compressive strength and CO2 uptake.
Use of digital technology to follow the consequences of a warming Arctic climate
Authors: Hætta Myrmel L B , Gudmestad O T
Published: November 2021

The rapid warming climate is causing the Arctic ice to retreat and the permafrost to melt. These visible manifestations of the ongoing climate change are few of many environmental and societal changes that take place in the Arctic. The acceleration of digitalization and implementation of digital technology bring new opportunities to follow the consequences of the warmer arctic climate, but also introduces new challenges in this region as the dependency on the digital technology increases. This paper focuses on the cyber ecosystem and discusses digital technology available for monitoring the consequences of a warming Arctic and its impact on Critical Infrastructure (CI) in Norway, such as communication networks, electric power transfer systems, water and wastewater, transportation infrastructure, oil and gas infrastructure. The need for reliable satellite communications is emphasized.
Problems of development and economic evaluation of production of natural hydrocarbons on the offshore of the Arctic Seas
Authors: Bogatkina Y , Eremin N , Sardanashvili O
Published: November 2021

The purpose of this article is to substantiate taxation models that have contributed to an increase in the efficiency of offshore oil and gas fields that are at the stage of mature development in the harsh Arctic conditions. The development of Arctic fields under the current tax regime is on the verge of profitability. As an experiment, an economic assessment of the main economic indicators of the option for the development of the Prirazlomnoye field was carried out, taking into account various tax mechanisms used to assess the effectiveness of the development of offshore oil and gas fields. The calculation results showed that the application of the tax regime in force in Russia makes the development of the Prirazlomnoye field efficient, but with a relatively low profitability for the license holder. As an alternative, the tax mechanisms laid down in the production sharing agreements in China and Russia were used, which showed a high economic effect with a low level of risk. It can be concluded that the use of taxation models, which are similar in nature to a production sharing agreement, significantly increases the efficiency of the Prirazlomnoye field development, and can bring greater financial benefits to the license holder in comparison with the current tax regime in the Russian Federation.
Computer technologies to determine offshore facilities suitable for the climatic conditions
Authors: Shatrovskii I , Zolotukhin A
Published: November 2021

This article provides an overview of computer technologies and an analysis of their application possibilities to determine the quantitative and qualitative composition of the facilities for the development of offshore oil and gas fields for given climatic conditions. The first question covered in the article is how to form a data set including the information about offshore fields development conditions. The author gives examples of using the Python programming language, NumPy, Tesseract and OpenCV libraries for that purpose. For each designated variable, a test program code was done to obtain the required value. Another question, which is given in the article, is how to analyze the obtained results and determine which offshore facilities are best suited for certain climatic conditions. For this purpose, a deep neural network of forwarding propagation was created with the help of Keras, TensorFlow and Scikit-learn Python libraries. The network performance was tested on a sample of a small size, the results were analyzed, and future research tasks were defined.
Transformation of the energy sector in the Arctic in the context of sustainable development of the region
Authors: Fedorova V A , Kadzhaeva E T , Vovkodav K V
Published: November 2021

The Arctic is the northernmost region of our planet, including the outskirts of the continents of Eurasia and North America, as well as the corresponding islands and archipelagos, the Arctic Ocean and parts of the Atlantic and Pacific oceans. Despite the still existing discrepancy in the concept of the boundaries of the Arctic region, all researchers agree in one opinion: this region is most sensitive to the climate change, and the consequences may be irreversible. As a part of the commitments on sustainable development undertaken by Russia and taking into account the importance and special status of the Arctic region, it seems necessary to consider the possibility of transforming the energy sector of the Arctic as one of the main sources of emissions of pollutants and CO2 in the region. The combination of energy sources proposed in the article - natural gas and renewable energy sources - is the cleanest and most environmentally friendly, and a hybrid energy system based on this alliance is the most sustainable and allows to use advantages of proposed energy sources, hedging each other's limitations. Proposed hybrid system could contribute to the development of the region and the well-being of its population and the environment.
Deep learning based restoration of lost sections in Micro-CT core plugs
Authors: Arsenyev-Obraztsov S S , Plusch G O
Published: November 2021

Lack of petrophysical information is critical for reservoirs development composed of poorly consolidated rocks or for zones bearing wells with core damaged by improper coring operations. The restoration complexity of the digital-core lost sections is associated with the need to consider an enormous amount of data from the existing core image and the necessity to include lithological expert knowledge. That makes deep learning methods a natural choice for solving such problems. We proposed, examined, and compared several deep learning methods convenient for analyzing micro-computed tomography digital core data. It was done under the most simplistic problem statement when the destroyed part (a set of slices) is completely lost. Here, we present the results of comparison interpolation/extrapolation procedures under proposed quality metrics. We discover that the variational autoencoder method can be trained to extract some petrophysical parameters from the digital core plug in an unsupervised manner.
Performance of sodium lignosulfonate as thickening additive in compositions for matrix acidizing of bottom hole zone
Authors: Sentemov A A
Published: November 2021

The work considers one of the promising directions for optimizing matrix acidizing using sodium lignosulfonate as a thickening agent. The mechanism of the interaction of acid solutions containing lignosulfonate with carbonate reservoirs is described. The use of sodium lignosulfonate in acid solutions solves several problems. Slowing the reaction rate allows the acid solution penetrate deeper into the formation, with maintaining the HCl concentration. The increased viscosity of the compositions increases the sweep efficiency of the bottomhole zone in the process of matrix acidizing. These two aspects increase the efficiency of matrix acidizing and the permeability of the bottomhole zone. In the course of this work, the chemical reaction rate of sodium lignosulfonate and hydrochloric acid solutions with carbonate core samples were evaluated. Sodium lignosulfonate in an acid solution reduces the dissolution rate of carbonate samples. It is assumed that slowing down the reaction rate allows the acid solution to form long high permeability channels which increases the efficiency of acidizing.
The effect of volatile organic acids and CO2 on the corrosion rate of carbon steel from a Top-of-Line-Corrosion (TLC) perspective
Authors: Gjertsen S B , Palencsar A , Seiersten M , Hemmingsen T H
Published: November 2021

Models for predicting top-of-line corrosion (TLC) rates on carbon steels are important tools for cost-effectively designing and operating natural gas transportation pipelines. The work presented in this paper is aimed to investigate how the corrosion rates on carbon steel is affected by acids typically present in the transported pipeline fluids. This investigation may contribute to the development of improved models. In a series of experiments, the corrosion rate differences for pure CO2 (carbonic acid) corrosion and pure organic acid corrosion (acetic acid and formic acid) on X65 carbon steel were investigated at starting pH values; 4.5, 5.3, or 6.3. The experiments were conducted in deaerated low-salinity aqueous solutions at atmospheric pressure and temperature of 65 °C. The corrosion rates were evaluated from linear polarization resistance data as well as mass loss and released iron concentration. A correlation between lower pH values and increased corrosion rates was found for the organic acid experiments. However, the pH was not the most critical factor for the rates of carbon steel corrosion in these experiments. The experimental results showed that the type of acid species involved and the concentration of the undissociated acid in the solution influenced the corrosion rates considerably.
Failure prediction of reservoir pressure maintenance system at the Prirazlomnoye Arctic Offshore field
Authors: Kurchatov I M
Published: November 2021

Failures of reservoir pressure maintenance system at offshore facilities cause production losses and a significant increase in OPEX. Predicting failures of a water injection pump or its parts can highly improve the overall performance by promptly adjusting operating parameters to prevent failure occurrence or by scheduling maintenance to reduce unplanned repairs and to minimize downtime. This is particularly relevant for Arctic offshore projects, characterized by considerable logistical challenges and substantial environmental safety risks. The paper presents a data-analytic approach for failure prediction for the water injection pump operated at the ice-resistant GBS Prirazlomnaya. The study used pump failure history and field sensor data to predict the technical condition and identify a failed component in advance. An ARIMA model implemented in the R software environment was developed for the analysis. The results demonstrate that the approach works appropriately based on the generalized risk assessment and feedback from subject matter experts.
Effect of mechanical activation on the properties of Portland cement
Authors: Ravaszová S , Dvořák K
Published: November 2021

The paper deals with the mechanical activation of cement by grinding in a high-speed mill, and compares the parameters found with the commonly used grinding method in cement production, which uses grinding of cement by means of a ball mill. The aim is to verify the influence of the aging time of the ground material on the preservation of the mechanical activation effect and on the properties of the final product at different stages of hydration. It evaluates the physical-mechanical properties, the compressive and tensile strength after 1, 2, 7, 14 and 28 days, as well as the course of the hydration process. The evaluated results suggest the existence of mechanical activation, but this effect is very difficult to achieve and depends on many other factors.
Shotcrete using ternary binder made from coal combustion products: from lab tests to an application
Authors: Šmilauer Vít , Sovják Radoslav , Pešková Šárka , Šulc Rostislav , Škvára František , Šídlová Martina , Snop Roman , Rüžička Pavel
Published: November 2021

The paper presents a ternary binder development and its utilization in shotcrete. The binder is made from fluidized bed combustion (FBC) fly ash, siliceous fly ash, and Ca(OH)2 addition, now available under the name Sorfix. XRD and TGA identified ettringite and C-S-H as two main hydration products. In addition, thermodynamic modeling verified robustness in terms of space-filling capabilities when varying input oxide composition.

Since alkali-free accelerators produce mostly ettringite in Portland-based systems, a fraction of Portland cement was advantageously replaced with the ternary binder, forming early ettringite as well. Extensive testing led to 45% replacement of Portland cement, following J2 curve for early strength gain used commonly in shotcrete tunnel linings. The shotcrete was successfully tested in a mock-up experiment in a 2 m3 Prague served for the full-scale application, utilizing over 1000 tons of Sorfix and saving over 700 tons of CO2
Light autoclaved foam concrete with foam glass-based aggregate
Authors: Bibora P , Prachar V , Svitak O , Zavrelova R.
Published: November 2021

The presented research aims to develop new optimized composition of novel lightweight concrete with a very low bulk density. Low bulk density of developed lightweight concrete is achieved by using a combination of non-traditional lightweight artificial fillers, dispersed fibre reinforcement and pre-generated technical foam. The methodology of lightweight concrete test specimen production, based on technologies commonly applied for the production of lightweight concrete, foam concrete or autoclaved aerated concrete was also designed and verified. Not only the physical and mechanical parameters, but also the thermal insulation properties were verified on the produced test specimens of the developed lightweight concrete.
Impact performance of rubber reinforced concrete with waste steel fibres
Authors: Drdlova M , Bibora P , Prachar V
Published: November 2021

This study introduces cementitious composite with rubber granulate and waste steel fibres as a new material for construction industry with an enhanced energy absorption capability and impact toughness. Detailed research on physico-mechanical properties of high-performance concrete with waste steel fibres and partial replacement of the aggregates by rubber granulate was performed, with emphasis on impact energy absorption potential. Different aggregate replacement ratios (0–30% wt.) and fibre amount (0–3% wt.) were investigated. The influence of rubber sizes, rubber content and steel fibre content on the mechanical parameters of the rubberized concrete at both quasistatic and dynamic loads was evaluated and discussed. With increasing amount of rubber granulate, the concrete suffered from reduction of its mechanical parameters – compressive and flexural strength, however the energy dissipation capability showed rising trend. This study demonstrated the potential of rubberized concrete with waste steel fibres for use in structures with higher impact resistance requirements.
Lime-based mortars with various binder composition: characterization and freeze-thaw resistance assessment
Authors: Janotova D , Slizkova Z
Published: November 2021

The study focused on lime mortars with different lime binder types regarding the frost attack effects on their microstructure and mechanical characteristics. The performances of studied mortars in hardened state was significantly influenced by the amount of mixing water and by curing conditions. Inhomogeneous microstructure was observed inside the 360 days old specimens with dimensions 40 × 40 × 160 mm in the case of all lime mortars types. The different state of the binder hardening with respect to various distances from the specimen surface and the different behaviour of matured outer part and immature inner part of lime mortar specimens influenced performed tests and reflected in all results. After 10 and 20 freeze cycles, respectively, the compressive strength of all lime mortar specimens with the hydraulic binder component increased, indicating a beneficial effect of the water on the hydration previously unreacted hydraulic binders. On the other hand, the flexural strength of the frost-aged specimens decreased significantly, indicating the drastic procedure of the test performed concerning lime mortars characteristics, especially when the pure air lime binder was used. Improvement of the testing procedure especially for lime mortars, which are characterized by slow hardening, was recommended.
The effect of consolidation treatment on selected mechanical properties of sandstone
Authors: Gajdos E , Sperl M , Slizkova Z , Drdlova M
Published: November 2021

An investigation was made into selected mechanical properties of sandstone of Božanov mining site in Czechia using both natural specimens of the sandstone and specimens impregnated with consolidants – liquid products aimed at improving strength and durability of degraded stones. Experiments in three-point bending of notched and cracked specimens made it possible to determine (i) the quasi-static notch toughness as well as the fracture toughness of specimens when they were subjected to static loading, and (ii) the impact fracture toughness and total energy of fracture when specimens were subjected to impact loading. The results of the tests are presented and are discussed with a view to the effects of consolidants.
Determination of ballistic resistance of cementitious composites
Authors: Vojtisek J , Bystrianska E , Koutny O , Kratochvil J , Drdlova M
Published: November 2021

The paper describes the possibility of using the DOP test, standardly used to evaluate the ballistic resistance of ceramics, to determine the ballistic resistance of cement composites. DOP - Depth of penetration test - is based on measurement of residual penetration of projectile in witness system after the sample perforation; this parameter is used to determine differential efficiency factor (DEF), characterizing the ballistic resistance of the particular material. To verify the method for non-ceramic materials, four variants of cementitious composites with compressive strengths in the range of 30–150 MPa have been tested. The obtained results confirm the method’s suitability for determining the ballistic resistance of cement composites in terms of ease of implementation, sensitivity, and accuracy of the obtained results for both composites of common strengths and high-performance variants. The paper also discusses some aspects of the relationship between the mechanical parameters of cement composites under static loading and their ballistic resistance.
Development of lightweight structural concrete with the use of aggregates based on foam glass
Authors: Zach J , Bubeník J , Sedlmajer M
Published: November 2021

Lightweight concretes are increasingly being used in the construction industry, either for the overall lightweighting of the structure itself, reducing material consumption for construction and thus CO2 emissions, or for specific reasons such as improving the thermal insulation properties of the structure or acoustic properties. Today, lightweight concretes with lightweight expanded aggregates (expanded clay, agloporite) are most commonly used. This paper deals with the production of lightweight concretes lightweighted with foamed glass-based aggregates. Foamed glass is a lightweight material characterised by a very good ratio of thermal insulation and mechanical properties. Foamed glass is made of approximately 90% recycled glass waste (mostly mixed), which cannot be used in any other way, as well as water glass and glycerine. When concrete is lightened with foamed glass, these concretes achieve unique properties while conserving primary aggregate resources, avoiding landfilling of glass waste and efficiently using the waste material to produce lightweight concrete with higher added value. The paper discusses the possibilities of developing lightweight structural concretes using glass foam-based aggregates to achieve higher strength classes while reducing the weight and thermal conductivity of the concrete. As part of the research work, new types of lightweight concrete with a bulk density in the range of 1750–1930 kg/m3 and a thermal conductivity from 0.699 to 0.950 W/(m·K) were developed.
Décalcification resistance of various alkali-activated materials
Authors: Hruby P , Bilek V , Topolar L , Kalina L , Marko M , Soukal F , Dvorak R , Hercik T
Published: November 2021

The resistance of alkali-activated materials (AAMs) to degradation processes, particularly the decalcification, was studied in this paper. The ground granulated blast furnace slag was alkali-activated using various activators with the same activator dosage 6% Na2O by slag weight (sodium hydroxide, sodium waterglass and sodium carbonate) and subjected to testing of decalcification resistance (immersion in 6M NH4 NO3) for 84 days. The reference samples were stored in water. The progress of degradation was studied using the phenolphthalein technique, mechanical properties testing (compressive and flexural strength), and dilatometry analysis or weight measurements. The results obtained were compared to the CEM III/A 32.5R. The significant loss of mass along with the deterioration of mechanical properties were observed for all binder types, still some of the AAMs showed better durability than the cementitious one.
Testing of biocidal properties of thermal insulation system during material life cycle
Authors: Kukletova I , Chromkova I
Published: November 2021

With the growing number of realized thermal insulation systems, fast growing number of buildings with facades attacked by microorganisms occurs. Such surface attack can occur even in the first years after thermal insulation completion, and it can be a serious problem in a very short time. Problem is both in realization and maintaining of thermal insulation, and directly in the used material. The paper presents results of laboratory experiments on resistance to biological attack, carried out for five commercial materials available on the Czech market. Before the experiments, materials were subjected to accelerated ageing for 4 and 10 years. Resistance testing comprises regulated application of algae and mould strains on samples and incubation in a defined environment. Materials resistant after ageing simulation of the longer time period were found as well as materials susceptible to attack already after completion of a facade set.
The use of aluminum slag waste in the preparation of roof tiles
Authors: Ahmed M M , Abadir M F , Yousef Ayman , El-Naggar K A M
Published: November 2021

Abtract

Aluminum slag waste generated from the smelting process of bauxite was used to prepare roof tiles samples. Clay was substituted by slag waste in percentages reaching 40% in the basic mix and the plasticity of the obtained mud was determined. This was followed by pressing the mud in steel molds and drying. The effect of waste addition on drying shrinkage was subsequently assessed. Firing of the green bodies was carried out at three temperatures (900, 1000 and 1100 °C) and hour soaking at each temperature. Fired roof tile properties improved on increasing the percentage of alumina sludge and firing temperature possibly because of the presence of high amounts of fluxing oxides in aluminum slag. This caused a drop in porosity that increased the mechanical strength of tiles. The results showed that the substitution of clay by 40% waste and firing at 1100 °C resulted in products conforming to ASTM C-1167 for clay type roof tiles. Cold water absorption dropped to 12%, below the maximum permissible limit of 15%, the value of Saturation Coefficient was 0.83, below the 0.86 limit and the obtained breaking strength of 3370N significantly exceeded the minimum requirement of 890N.