Few-Layers Graphene-Based Cement Mortars: Production Process and Mechanical Properties

Cement is the most-used construction material worldwide. Research for sustainable cement production has focused on including nanomaterials as additives to enhance cement performance (strength and durability) in recent decades. In this concern, graphene is considered one of the most promising additives for cement composites. Here, we propose a novel technique for producing few-layer graphene (FLG) that can fulfil the material demand for the construction industry. We produced specimens with different FLG loadings (from 0.05% to 1% by weight of cement) and curing processes (water and saturated air). The addition of FLG at 0.10% by weight of cement improved the flexural strength by 24% compared to the reference (bare) sample. Similarly, a 0.15% FLG loading by weight of cement led to an improvement in compressive strength of 29% compared to the reference specimen. The FLG flakes produced by our proposed methodology can open the door to their full exploitation in several cement mortar applications, such as cementitious composites with high durability, mechanical performance and high electrical conductivity for electrothermal applications.

Mathematical Modeling of the Process of Reduction of the Material Consumption of Gas Transmission System Elements

The new method for a comprehensive assessment of the strength, durability and material capacity of the critical elements of the main gas pipelines, taking into account the combined impact of factors causing damage (environment, corrosion, random loading, geometry variation, material defects, etc.), which are changing the bearing capacity and material capacity of these structures, is proposed. As the main damaging factor, the process of corrosion fatigue is accepted, the qualitative and quantitative assessment of which are realized by applying a set of equations of comparable fatigue lines obtained by fatigue tests carried out in air and in corrosive environment. By the joint solution of these equations, the functions of the corrosion action coefficients are obtained in a wide range of cyclic strength and durability, which in standard calculation procedures are performed only for cyclic strength and only at the inflection point of the fatigue lines (NG 5  106 cycles).The issues of reducing the material consumption and ensuring the cost-effectiveness of structures, by using relatively cheap materials for pipelines - low-carbon and low-alloy structural steels subjected to surface hardening in stressed sections of pipes (edge welds) in order to significantly increase the physical and mechanical characteristics of the used steel grades are considered. In order to increase the corrosion resistance of these sections, contemporary polymer anticorrosive coatings are used.

The Structural Formation of Cement Stone Modified by a Solution of Superabsorbent Polymer

With the development of 3D technologies in construction, the development of formulations that are indifferent to the influence of the environment is in demand. Conditions of intense water loss from cement systems arise during the layer-by-layer printing process. This leads to a decrease in density, high shrinkage, and a decrease in the strength and durability of the composite. The use of superabsorbent polymer (SAP) solutions, in contrast to granules, will provide hardening Portland cement with a water supply for internal care of hydration processes. The aim of the work is to study the effect of SAP solution on the processes of structure formation of cement stone, hardening in unfavorable conditions. In this paper, the features of the structure formation of cement systems in the presence of SAP are established. It is shown that the use of polymer in an amount of no more than 1.5% by the weight of Portland cement provides the formation of a more perfect crystalline structure of the cement stone, which allows for an increase in the degree of cement hydration. When the amount of SAP is ≥ 1.5% by the weight of Portland cement, a decrease in the intensity of the maxima corresponding to hydration products is observed.

Rheological Behavior of High-Performance Shotcrete Mixtures Containing Colloidal Silica and Silica Fume Using the Bingham Model

There have been numerous studies on shotcrete based on strength and durability. However, few studies have been conducted on rheological characteristics, which are very important parameters for evaluating the pumpability and shootability of shotcrete. In those studies, silica fume has been generally used as a mineral admixture to simultaneously enhance the strength, durability, pumpability, and shootability of shotcrete. Silica fume is well-known to significantly increase the viscosity of a mixture and to prevent material sliding at the receiving surface when used in shotcrete mixtures. However, the use of silica fume in shotcrete increases the possibility of plastic shrinkage cracking owing to its very high fineness, and further, silica fume increases the cost of manufacturing the shotcrete mixture because of its cost and handling. Colloidal silica is a new material in which nano-silica is dispersed in water, and it could solve the above-mentioned problems. The purpose of this research is to develop high-performance shotcrete with appropriate levels of strength and workability as well as use colloidal silica for normal structures without a tunnel structure. Thereafter, the workability of shotcrete with colloidal silica (2, 3, and 4%) was evaluated with a particle size of 10 nm and silica fume replacement (4 and 7%) of cement. In this study, an air-entraining agent for producing high-performance shotcrete was also used. The rheological properties of fresh shotcrete mixtures were estimated using an ICAR rheometer and the measured rheological parameters such as flow resistance and torque viscosity were correlated with the workability and shootability. More appropriate results will be focusing on the Bingham model properties such that the main focus here is to compare all data using the Bingham model and its performance. The pumpability, shootability, and build-up thickness characteristics were also evaluated for the performance of the shotcrete. This research mainly focuses on the Bingham model for absolute value because it creates an exact linear line in a graphical analysis, which provides more appropriate results for measuring the shotcrete performance rather than ICAR rheometer relative data.

Corrosion Resistance, Evaluation Methods, and Surface Treatments of Stainless Steels

Stainless steels are widely recognized and find applications in many engineering industries and companies due to their excellent properties including high resistance to corrosion as a result of their minimum 10.5% chromium content, exceptional strength and durability, temperature resistance, high recyclability, and easy formability. In the present book chapter, the basic concepts of stainless steel including its applications, classifications, and corrosion properties will first be discussed. Thereafter, their corrosion behaviour will then be explained. The various methods by which the corrosion resistance behaviour can be significantly improved including surface treatments such as coatings/electrodepositions, alloying, mechanical treatment, and others will be discussed in detail.

Design and Structural Testing of Blades for a 2MW Floating Tidal Energy Conversion Device

The floating tidal energy is increasingly recognised to have the potential of delivering a step-change cost reduction to the tidal energy sector, by extracting energy from deeper water sites through energy conversion devices. To ensure the normal operation of a tidal energy convertor within its service life, the device should be designed properly and evaluated through a series of strength and durability testing. The Large Structures Research Group at NUI Galway is working closely with, renewable energy company, Orbital Marine Power and, blade manufacture, ÉireComposites Teo, to design and test the next generation of SR2000 tidal turbine blade, with aims to increase the turbine power production rate and to refine the design for low cost. This paper presents a brief description of the structural design and testing of a blade for the O2-2000 tidal turbine, one of the largest tidal turbines in the world. NUI Galway will utilise their in-house software, BladeComp, to find a blade laminates design that balances both blade strength and material cost. The structural performance of the designed blade will be assessed by conducting static and fatigue testing. To achieve this objective, a support frame to fix the blade is designed, a load application device is introduced and the methodology for design tidal loading conversion is proposed in order to complete the testing at NUI Galway.

Study on Strength and Durability Properties of Bacterial Concrete

The primary thought of this review is to assess the strength and durability properties of high strength concrete specimens by replacing cement with bacteria for healing cracks. Concrete is the most commonly used construction material all around the world. Cracks are formed due to various reasons. The cracks act as a pathway through which water and toxic salts enter. This causes corrosion and also leads to failure of structure. Repair and Rehabilitation works are costly to be done. In order to overcome this, bacteria is induced into the concrete which leads to the process of Microbial Induced Calcium Precipitate (MICP). The cracks heal by self-healing mechanism and results in crack free concrete structure. It also improves the compressive and tensile strength. In this article a new bacterium has been cultured and identified and is used as a self-healing material in M30 Grade concrete.

Impact Analysis and Structural Optimization of Crash Barriers

The primary thought of this review is to assess the impact absorbance, strength and durability properties using non-linear finite element simulations of analytical model of crash barriers. Before manufacturing and erection of crash barriers on site are generally simulated for impact performance using finite element analysis various parameters are checked such as 1) Crash performance 2) Vehicle trajectory after collision 3) Safety of the vehicular occupant.