NUMERICAL SIMULATION OF THERMO-HYGRAL ALKALI-SILICA REACTION MODEL IN CONCRETE AT THE MESOSCALE

This research aims to model Alkali-Silica Reaction gel expansion in concrete under the influence of hygral and thermal loading, based on experimental results. ASR provokes a heterogeneous expansion in concrete leading to dimensional changes and eventually the premature failure of the concrete structure. This can result in map cracking on the concrete surface which will decrease the concrete stiffness. Factors that influence ASR are parameters such as the cement alkalinity, the number of deleterious silica from the aggregate used, concrete porosity, and external factors like temperature, humidity and external source of alkali from ingression of deicing salts. Uncertainties of the influential factors make ASR a difficult phenomenon to solve; hence my approach to this matter is to solve the problem using stochastic modelling, where a numerical simulation of concrete cross-section with integration of experimental results from Finger-Institute for Building Materials Science at the Bauhaus-Universität Weimar. The problem is formulated as a multi-field problem, combining heat transfer, fluid transfer and the reaction rate model with the mechanical stress field. Simulation is performed as a mesoscale model considering aggregates and mortar matrix. The reaction rate model will be conducted using experimental results from concrete expansions due to ASR gained from concrete prism tests. Expansive strains values for transient environmental conditions due to the reaction rate will be determined from calculation based on the reaction rate model. Results from these models will be able to predict the rate of ASR expansion and the cracking propagation that may arise

Numerical Simulation of Thermo-Chemo-Hygro-Mechanical Alkali-Silica Reaction Model in Concrete at the Mesoscale and Macroscale

Alkali-silica reaction causes major problems in concrete structures due to the rapidity of its deformation which leads to the serviceability limit of the structure being reached well before its time. Factors that affect ASR vary greatly, including alkali and silica content, relative humidity, temperature and porosity of the cementitious matrix,all these making it a very complex phenomenon to consider explicitly. With this in mind, the finite element technique was used to build models and generate expansive pressures and damage propagation due to ASR under the influence of thermo-hygrochemoelastic loading. Since ASR initializes in the mesoscopic regions of the concrete, the accumulative effects of its expansion escalates onto the macroscale level with the development of web cracking on the concrete surface, hence solution of the damage model as well as simulation of the ASR phenomenon at both the macroscale and mesoscale levels have been performed. The macroscale model realizes the effects of ASR expansion as a whole and shows how it develops under the influence of moisture, thermal and mechanical loading. Results of the macroscale modeling are smeared throughout the structure and are sufficient to show how damage due to ASR expansion orientates. As opposed to the mesoscale model, the heterogeneity of the model shows us how difference in material properties between aggregates and the cementitious matrix facilitates ASR expansion. With both these models, the ASR phenomenon under influence of thermo-chemo-hygro-mechanical loading can be better understood

Carbon Dioxide Sequestered Concrete

Carbon dioxide, CO2accounts for most of the emission from all the types of greenhouse gasses in the whole world. The ability of CO2to remain longer than other greenhouse gases and the convenience of producing CO2has resulted in its high projection in a yearly manner. The prime factor for the emission of CO2are from the actions of human beings. One such human act is the concrete industry. Total emissions from the concrete industry could therefore contribute as much as 8% of global CO2emissions. Sequestered CO2in concrete can provide an impact on reducing the carbon footprint and also is able to improve the compressive strength of concrete. During this process, the sequestered carbon dioxide chemically reacts with cement to produce a mineral, trapping the carbon dioxide gas in the concrete. Hence, sequestering the carbon dioxide gas in concrete does not only on a bigger scale, reduce carbon footprint but also reduces the impact the construction industry has on the environment. This paper presents a detailed review on the chemical reaction that takes place during the sequestration of carbon dioxide and the research published on the effects of carbon dioxide sequestered concrete on its properties. The impact this process has on the concrete industry and the environment is discussed in this paper

Characterization of cenospheres from Malaysian coal generated power plants: Jimah, Kapar and Manjung

Cenosphere is a component of fly ash (FA) and has been used as part of sustainable material in wastewater treatment, automotive, ceramic, and construction industries due to its properties. This research presents the first study on characterization of cenospheres from Malaysian power plants namely Jimah, Kapar and Manjung. The characterization was conducted via X-ray fluorescence (XRF), particle size analyzer (PSA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The XRF analysis consisted of oxides elements ranged from 14.70 to 22.63% (aluminum oxide, Al2 O3 ), 3.78 to 13.44% (calcium oxide, CaO), 34.73 to 57.67% (silicon dioxide, SiO2 ), 0.42 to 1.07% (sulphur trioxide, SO3 ), 9.09 to 24.92% (iron oxide, Fe2 O3 ), 3.62 to 3.67% (potassium oxide, K2 O), 1.76 to 4.24% (titanium oxide, TiO2 ) and 0.16 to 0.93% (magnesium oxide, MgO). The classifications of cementitious materials by American Standard of Testing Materials were Class F (Jimah, Kapar) and Class C (Manjung). The classification represents the quality and capability of cementitious materials as cement replacement material, additive, and filler in concrete mix. The sizes of cenospheres were Kapar > Jimah > Manjung. The sizes of cenosphere were found to be larger than FA (Jimah: 2.720-49.21 µm, Kapar: 5.069-98.29 µm, Manjung: 1.084-3.986 µm). Cenospheres contained quarts (Jimah, Kapar, Manjung: 26°) and silicates (Kapar, Manjung: 45°). Ferrospheres, cenospheres, aluminosilicate-spheres, plerospheres and carbon fragments were observed. The cenosphere from Manjung showed high quality as cement replacement material, additive, and filler with 13.44% of CaO

State of the Art Compendium of Macro and Micro Energies

In the span of past few decades, population, urbanization and industrialization have transformed the mankind living standard and dynamics of the nature. Certainly, energy is the basic need for all living organisms. Energy is the route towards the economic growth. The evidence shows that the countries faced with energy crises are left behind in the economic activities; as a result, people are deprived. This study reviewed the available renewable energy resources and potential with positive and negative aspects. This study comprehensively discusses the renewable macro and micro energy resources studied in the past two decades reported in various studies. The paper is divided into two sections; the first section discusses the energy produced in the macro level and the second section discusses the energy produced using different strategies and techniques in the micro level. The potential and positive outcomes of the energy resources were identified. New paradigm of micro energies and importance of reusing the available resource of micro energy using different resources like energy harvesting on the road surface, vibration, airflow, radio frequency and thermal energy etc. were discussed. Lastly, the study focus does not only review but also finds the potential and opportunities for the researchers in the future to utilize the renewable energy resources

Performance analysis of full assembly glass fiber-reinforced polymer composite cross-arm in transmission tower

The usage of glass fiber reinforced polymer (GFRP) composite cross-arms in transmission towers is relatively new compared to wood timber cross-arms. In this case, many research works conducted experiments on composite cross-arms, either in coupon or full-scale size. However, none performed finite element (FE) analyses on full-scale composite cross-arms under actual working load and broken wire conditions. Thus, this work evaluates the performance of glass fiber reinforced polymer (GFRP) composite cross-arm tubes in 275 kV transmission towers using FE analysis. In this study, the performance analysis was run mimicking actual normal and broken wire conditions with five and three times more than working loads (WL). The full-scale assembly load test experiment outcomes were used to validate the FE analysis. Furthermore, the mechanical properties values of the GFRP composite were incorporated in simulation analysis based on the previous experimental work on coupons samples of GFRP tubes. Additionally, parametric studies were performed to determine the ultimate applied load and factor of safety for both normal and broken wire loading conditions. This research discovered that the GFRP composite cross-arm could withstand the applied load of five times and three times working load (WL) for normal and broken wire conditions, respectively. In addition, the factor of safety of tubes was 1.08 and 1.1 for normal and broken wire conditions, respectively, which can be considered safe to use. Hence, the composite cross-arms can sustain load two times more than the design requirement, which is two times the working load for normal conditions. In future studies, it is recommended to analyze the fatigue properties of the composite due to wind loading, which may induce failure in long-term service

Effect of Stacking Sequence on Long-Term Creep Performance of Pultruded GFRP Composites

Pultruded glass-fibre reinforced polymer (pGFRP) composites are classified as lightweight material, which exhibit high strength-to-weight ratio for structural usage. This composite material has been applied as cross-arm members in transmission towers due to its ability in thermal and electrical insulation. However, the influence of the stacking sequence of pGFRP composite on its mechanical performance has not been fully covered in the literature to explain the long-term durability of the current cross-arm designs. The study expected to evaluate five fiber layers with various stacking sequences in terms of quasi-static and creep tests in a four-point bending mode. The creep test was performed for 1440 h (60 days). These composites were fabricated using the pultrusion process in the form of a square hollow structure. Later, it was cut into composite coupons with various sizes depending on the test conducted. The results showed that nine layers with 0°/45°/0°/−45°/0°/−45°/0°/45°/0° had the ultimate flexural strength. This stacking sequence configurations seemed to be optimally manufactured in continuous roving fibre by alternating between 0° and ±45° fiber orientations. Additionally, the S-9 pGFRP composite sample showed that it had a low-creep deflection with high elastic and apparent creep moduli in 1440 h. In terms of strength reduction factor, this configuration was recorded as the highest. The findings showed that the nine layers of pGFRP composites with alternation of 0° and ±45° fiber orientations were highly suitable for structural application at transmission towers for a long-term operation

Experimental and predictive evaluation of mechanical properties of kenaf-polypropylene fibre-reinforced concrete using response surface methodology

Fibre-reinforced concrete (FRC) is an emerging construction material. However, improving its mechanical properties using sustainable materials remains a concern. In this paper, a combination of experimental and numerical techniques is applied to investigate the combined influence of kenaf (K) and polypropylene fibre (PPF) on the mechanical properties of KPPFRC. The optimal design component of Response Surface Methodology was utilised with combined fibre content between 0.5% and 2%. The results show a general increase in the mechanical properties with KF being the main contributing factor, and corresponding decreases in all responses with the increase in PPF. Nonetheless, the predicted optimal volume fraction of 1.5% consisting of 1.0 kg kF and 0.51 kg PPF gives a 100%, 174% and 100% rise in compressive, split tensile, and flexural strength respectively compared to the control sample. Hence, these optimal proportions of KF and PPF can be utilised as an eco-friendly sustainable material in concrete

Sugar Palm Fibre-Reinforced Polymer Composites: Influence of Chemical Treatments on Its Mechanical Properties

In the era of globalisation, decreasing synthetic resources, especially petroleum, have encouraged global communities to apply biomass waste as a substitute material for green technology development. The development of plastic products from lignocellulosic fibre-reinforced composites has been a hot topic among material scientists and engineers due to their abundance, sustainable in nature, and less toxic towards health. For the Malaysian scenario, sugar palm is a plant found in the wild and locally planted in certain areas in Malaysia and Indonesia. Generally, sugar palm can be harvested for traditional foods, fruits, starch sugar (gula kabung), and alcohol, whereas sugar palm fibre (SPF) is used in conventional products (brushes and brooms). Various researchers are working on the characterisation of fibre and its composites for engineering and packaging products. The main drawback of SPF is its hydrophilic behaviour, which leads to high moisture uptake and inhibits a good bond between the fibre and the matrix. Thus, a solution for this problem is by implementing chemical treatments on the fibre. From the literature review, no comprehensive review paper has been published on the influence of chemical treatment on the mechanical behaviour of SPF-reinforced polymer composites. Thus, the present review examines recent studies on the mechanical properties of sugar palm lignocellulosic fibres with various chemical treatments to evaluate their potential in structural applications

The Versatility of Polymeric Materials as Self-Healing Agents for Various Types of Applications: A Review

The versatility of polymeric materials as healing agents to prevent any structure failure and their ability to restore their initial mechanical properties has attracted interest from many researchers. Various applications of the self-healing polymeric materials are explored in this paper. The mechanism of self-healing, which includes the extrinsic and intrinsic approaches for each of the applications, is examined. The extrinsic mechanism involves the introduction of external healing agents such as microcapsules and vascular networks into the system. Meanwhile, the intrinsic mechanism refers to the inherent reversibility of the molecular interaction of the polymer matrix, which is triggered by the external stimuli. Both self-healing mechanisms have shown a significant impact on the cracked properties of the damaged sites. This paper also presents the different types of self-healing polymeric materials applied in various applications, which include electronics, coating, aerospace, medicals, and construction fields. It is expected that this review gives a significantly broader idea of self-healing polymeric materials and their healing mechanisms in various types of applications