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Materials, Volume 8, Issue 12 (December 2015)

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Open AccessFeature PaperArticle Development of Porous Piezoceramics for Medical and Sensor Applications
Materials 2015, 8(12), 8877-8889; https://doi.org/10.3390/ma8125498
Received: 4 November 2015 / Revised: 4 December 2015 / Accepted: 10 December 2015 / Published: 21 December 2015
Cited by 5 | PDF Full-text (2899 KB) | HTML Full-text | XML Full-text
Abstract
The use of porosity to modify the functional properties of piezoelectric ceramics is well known in the scientific literature as well as by the industry, and porous ceramic can be seen as a 2-phase composite. In the present work, examples are given of
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The use of porosity to modify the functional properties of piezoelectric ceramics is well known in the scientific literature as well as by the industry, and porous ceramic can be seen as a 2-phase composite. In the present work, examples are given of applications where controlled porosity is exploited in order to optimise the dielectric, piezoelectric and acoustic properties of the piezoceramics. For the optimisation efforts it is important to note that the thickness coupling coefficient kt will be maximised for some non-zero value of the porosity that could be above 20%. On the other hand, with a good approximation, the acoustic velocity decreases linearly with increasing porosity, which is obviously also the case for the density. Consequently, the acoustic impedance shows a rather strong decrease with porosity, and in practice a reduction of more than 50% may be obtained for an engineered porous ceramic. The significance of the acoustic impedance is associated with the transmission of acoustic signals through the interface between the piezoceramic and some medium of propagation, but when the porous ceramic is used as a substrate for a piezoceramic thick film, the attenuation may be equally important. In the case of open porosity it is possible to introduce a liquid into the pores, and examples of modifying the properties in this way are given. Full article
(This article belongs to the Special Issue Piezoelectric Materials)
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Open AccessArticle Surface Effects and Challenges for Application of Piezoelectric Langasite Substrates in Surface Acoustic Wave Devices Caused by High Temperature Annealing under High Vacuum
Materials 2015, 8(12), 8868-8876; https://doi.org/10.3390/ma8125497
Received: 14 October 2015 / Revised: 8 December 2015 / Accepted: 14 December 2015 / Published: 19 December 2015
Cited by 3 | PDF Full-text (16491 KB) | HTML Full-text | XML Full-text
Abstract
Substrate materials that are high-temperature stable are essential for sensor devices which are applied at high temperatures. Although langasite is suggested as such a material, severe O and Ga diffusion into an O-affine deposited film was observed during annealing at high temperatures under
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Substrate materials that are high-temperature stable are essential for sensor devices which are applied at high temperatures. Although langasite is suggested as such a material, severe O and Ga diffusion into an O-affine deposited film was observed during annealing at high temperatures under vacuum conditions, leading to a damage of the metallization as well as a change of the properties of the substrate and finally to a failure of the device. Therefore, annealing of bare LGS (La 3 Ga 5 SiO 14 ) substrates at 800 ∘ C under high vacuum conditions is performed to analyze whether this pretreatment improves the suitability and stability of this material for high temperature applications in vacuum. To reveal the influence of the pretreatment on the subsequently deposited metallization, RuAl thin films are used as they are known to oxidize on LGS at high temperatures. A local study of the pretreated and metallized substrates using transmission electron microscopy reveals strong modification of the substrate surface. Micro cracks are visible. The composition of the substrate is strongly altered at those regions. Severe challenges for the application of LGS substrates under high-temperature vacuum conditions arise from these substrate damages, revealing that the pretreatment does not improve the applicability. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Efficiency Enhancement of Dye-Sensitized Solar Cells’ Performance with ZnO Nanorods Grown by Low-Temperature Hydrothermal Reaction
Materials 2015, 8(12), 8860-8867; https://doi.org/10.3390/ma8125499
Received: 5 September 2015 / Revised: 9 December 2015 / Accepted: 10 December 2015 / Published: 19 December 2015
Cited by 9 | PDF Full-text (2377 KB) | HTML Full-text | XML Full-text
Abstract
In this study, aligned zinc oxide (ZnO) nanorods (NRs) with various lengths (1.5–5 µm) were deposited on ZnO:Al (AZO)-coated glass substrates by using a solution phase deposition method; these NRs were prepared for application as working electrodes to increase the photovoltaic conversion efficiency
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In this study, aligned zinc oxide (ZnO) nanorods (NRs) with various lengths (1.5–5 µm) were deposited on ZnO:Al (AZO)-coated glass substrates by using a solution phase deposition method; these NRs were prepared for application as working electrodes to increase the photovoltaic conversion efficiency of solar cells. The results were observed in detail by using X-ray diffraction, field-emission scanning electron microscopy, UV-visible spectrophotometry, electrochemical impedance spectroscopy, incident photo-to-current conversion efficiency, and solar simulation. The results indicated that when the lengths of the ZnO NRs increased, the adsorption of D-719 dyes through the ZnO NRs increased along with enhancing the short-circuit photocurrent and open-circuit voltage of the cell. An optimal power conversion efficiency of 0.64% was obtained in a dye-sensitized solar cell (DSSC) containing the ZnO NR with a length of 5 µm. The objective of this study was to facilitate the development of a ZnO-based DSSC. Full article
(This article belongs to the Special Issue Photovoltaic Materials and Electronic Devices) Printed Edition available
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Open AccessArticle Preparation and Compatibility Evaluation of Polypropylene/High Density Polyethylene Polyblends
Materials 2015, 8(12), 8850-8859; https://doi.org/10.3390/ma8125496
Received: 23 September 2015 / Revised: 8 December 2015 / Accepted: 11 December 2015 / Published: 17 December 2015
Cited by 14 | PDF Full-text (4123 KB) | HTML Full-text | XML Full-text
Abstract
This study proposes melt-blending polypropylene (PP) and high density polyethylene (HDPE) that have a similar melt flow index (MFI) to form PP/HDPE polyblends. The influence of the content of HDPE on the properties and compatibility of polyblends is examined by using a tensile
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This study proposes melt-blending polypropylene (PP) and high density polyethylene (HDPE) that have a similar melt flow index (MFI) to form PP/HDPE polyblends. The influence of the content of HDPE on the properties and compatibility of polyblends is examined by using a tensile test, flexural test, Izod impact test, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), polarized light microscopy (PLM), and X-ray diffraction (XRD). The SEM results show that PP and HDPE are incompatible polymers with PP being a continuous phase and HDPE being a dispersed phase. The FTIR results show that the combination of HDPE does not influence the chemical structure of PP, indicating that the polyblends are made of a physical blending. The DSC and XRD results show that PP and HDPE are not compatible, and the combination of HDPE is not correlated with the crystalline structure and stability of PP. The PLM results show that the combination of HDPE causes stacking and incompatibility between HDPE and PP spherulites, and PP thus has incomplete spherulite morphology and a smaller spherulite size. However, according to mechanical property test results, the combination of HDPE improves the impact strength of PP. Full article
(This article belongs to the Special Issue Selected Papers from ICBEI2015)
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Open AccessArticle A Novel Approach of Using Ground CNTs as the Carbon Source to Fabricate Uniformly Distributed Nano-Sized TiCx/2009Al Composites
Materials 2015, 8(12), 8839-8849; https://doi.org/10.3390/ma8125495
Received: 2 November 2015 / Revised: 7 December 2015 / Accepted: 9 December 2015 / Published: 17 December 2015
Cited by 14 | PDF Full-text (4057 KB) | HTML Full-text | XML Full-text
Abstract
Nano-sized TiCx/2009Al composites (with 5, 7, and 9 vol% TiCx) were fabricated via the combustion synthesis of the 2009Al-Ti-CNTs system combined with vacuum hot pressing followed by hot extrusion. In the present study, CNTs were used as the carbon
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Nano-sized TiCx/2009Al composites (with 5, 7, and 9 vol% TiCx) were fabricated via the combustion synthesis of the 2009Al-Ti-CNTs system combined with vacuum hot pressing followed by hot extrusion. In the present study, CNTs were used as the carbon source to synthesize nano-sized TiCx particles. An attempt was made to correlate the effect of ground CNTs by milling and the distribution of synthesized nano-sized TiCx particles in 2009Al as well as the tensile properties of nano-sized TiCx/2009Al composites. Microstructure analysis showed that when ground CNTs were used, the synthesized nano-sized TiCx particles dispersed more uniformly in the 2009Al matrix. Moreover, when 2 h-milled CNTs were used, the 5, 7, and 9 vol% nano-sized TiCx/2009Al composites had the highest tensile properties, especially, the 9 vol% nano-sized TiCx/2009Al composites. The results offered a new approach to improve the distribution of in situ nano-sized TiCx particles and tensile properties of composites. Full article
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Open AccessArticle Utilization of Palm Oil Clinker as Cement Replacement Material
Materials 2015, 8(12), 8817-8838; https://doi.org/10.3390/ma8125494
Received: 28 July 2015 / Revised: 2 December 2015 / Accepted: 7 December 2015 / Published: 16 December 2015
Cited by 13 | PDF Full-text (6935 KB) | HTML Full-text | XML Full-text
Abstract
The utilization of waste materials from the palm oil industry provides immense benefit to various sectors of the construction industry. Palm oil clinker is a by-product from the processing stages of palm oil goods. Channelling this waste material into the building industry helps
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The utilization of waste materials from the palm oil industry provides immense benefit to various sectors of the construction industry. Palm oil clinker is a by-product from the processing stages of palm oil goods. Channelling this waste material into the building industry helps to promote sustainability besides overcoming waste disposal problems. Environmental pollution due to inappropriate waste management system can also be drastically reduced. In this study, cement was substituted with palm oil clinker powder as a binder material in self-compacting mortar. The fresh, hardened and microstructure properties were evaluated throughout this study. In addition, sustainability component analysis was also carried out to assess the environmental impact of introducing palm oil clinker powder as a replacement material for cement. It can be inferred that approximately 3.3% of cement production can be saved by substituting palm oil clinker powder with cement. Reducing the utilization of cement through a high substitution level of this waste material will also help to reduce carbon emissions by 52%. A cleaner environment free from pollutants can be created to ensure healthier living. Certain industries may benefit through the inclusion of this waste material as the cost and energy consumption of the product can be minimized. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
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Open AccessArticle Improvement of Bearing Capacity in Recycled Aggregates Suitable for Use as Unbound Road Sub-Base
Materials 2015, 8(12), 8804-8816; https://doi.org/10.3390/ma8125493
Received: 25 September 2015 / Revised: 2 December 2015 / Accepted: 4 December 2015 / Published: 16 December 2015
Cited by 2 | PDF Full-text (2436 KB) | HTML Full-text | XML Full-text
Abstract
Recycled concrete aggregates and mixed recycled aggregates are specified as types of aggregates with lower densities, higher water absorption capacities, and lower mechanical strength than natural aggregates. In this paper, the mechanical behaviour and microstructural properties of natural aggregates, recycled concrete aggregates and
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Recycled concrete aggregates and mixed recycled aggregates are specified as types of aggregates with lower densities, higher water absorption capacities, and lower mechanical strength than natural aggregates. In this paper, the mechanical behaviour and microstructural properties of natural aggregates, recycled concrete aggregates and mixed recycled aggregates were compared. Different specimens of unbound recycled mixtures demonstrated increased resistance properties. The formation of new cement hydrated particles was observed, and pozzolanic reactions were discovered by electronon microscopy in these novel materials. The properties of recycled concrete aggregates and mixed recycled aggregates suggest that these recycled materials can be used in unbound road layers to improve their mechanical behaviour in the long term. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessReview Melt-Flow Behaviours of Thermoplastic Materials under Fire Conditions: Recent Experimental Studies and Some Theoretical Approaches
Materials 2015, 8(12), 8793-8803; https://doi.org/10.3390/ma8125492
Received: 16 September 2015 / Revised: 26 October 2015 / Accepted: 8 December 2015 / Published: 15 December 2015
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Abstract
Polymeric materials often exhibit complex combustion behaviours encompassing several stages and involving solid phase, gas phase and interphase. A wide range of qualitative, semi-quantitative and quantitative testing techniques are currently available, both at the laboratory scale and for commercial purposes, for evaluating the
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Polymeric materials often exhibit complex combustion behaviours encompassing several stages and involving solid phase, gas phase and interphase. A wide range of qualitative, semi-quantitative and quantitative testing techniques are currently available, both at the laboratory scale and for commercial purposes, for evaluating the decomposition and combustion behaviours of polymeric materials. They include, but are not limited to, techniques such as: thermo-gravimetric analysis (TGA), oxygen bomb calorimetry, limiting oxygen index measurements (LOI), Underwriters Laboratory 94 (UL-94) tests, cone calorimetry, etc. However, none of the above mentioned techniques are capable of quantitatively deciphering the underpinning physiochemical processes leading to the melt flow behaviour of thermoplastics. Melt-flow of polymeric materials can constitute a serious secondary hazard in fire scenarios, for example, if they are present as component parts of a ceiling in an enclosure. In recent years, more quantitative attempts to measure the mass loss and melt-drip behaviour of some commercially important chain- and step-growth polymers have been accomplished. The present article focuses, primarily, on the experimental and some theoretical aspects of melt-flow behaviours of thermoplastics under heat/fire conditions. Full article
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Open AccessArticle Investigation on the Mechanical Properties of a Cement-Based Material Containing Carbon Nanotube under Drying and Freeze-Thaw Conditions
Materials 2015, 8(12), 8780-8792; https://doi.org/10.3390/ma8125491
Received: 8 October 2015 / Revised: 23 November 2015 / Accepted: 30 November 2015 / Published: 14 December 2015
Cited by 12 | PDF Full-text (2741 KB) | HTML Full-text | XML Full-text
Abstract
This paper aimed to explore the mechanical properties of a cement-based material with carbon nanotube (CNT) under drying and freeze-thaw environments. Mercury Intrusion Porosimetry and Scanning Electron Microscopy were used to analyze the pore structure and microstructure of CNT/cement composite, respectively. The experimental
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This paper aimed to explore the mechanical properties of a cement-based material with carbon nanotube (CNT) under drying and freeze-thaw environments. Mercury Intrusion Porosimetry and Scanning Electron Microscopy were used to analyze the pore structure and microstructure of CNT/cement composite, respectively. The experimental results showed that multi-walled CNT (MWCNT) could improve to different degrees the mechanical properties (compressive and flexural strengths) and physical performances (shrinkage and water loss) of cement-based materials under drying and freeze-thaw conditions. This paper also demonstrated that MWCNT could interconnect hydration products to enhance the performance of anti-microcracks for cement-based materials, as well as the density of materials due to CNT’s filling action. Full article
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Open AccessArticle Effect of Different Manufacturing Methods on the Conflict between Porosity and Mechanical Properties of Spiral and Porous Polyethylene Terephthalate/Sodium Alginate Bone Scaffolds
Materials 2015, 8(12), 8768-8779; https://doi.org/10.3390/ma8125488
Received: 16 September 2015 / Revised: 3 December 2015 / Accepted: 7 December 2015 / Published: 14 December 2015
Cited by 6 | PDF Full-text (7194 KB) | HTML Full-text | XML Full-text
Abstract
In order to solve the incompatibility between high porosity and mechanical properties, this study fabricates bone scaffolds by combining braids and sodium alginate (SA) membranes. Polyethylene terephthalate (PET) plied yarns are braided into hollow, porous three dimensional (3D) PET braids, which are then
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In order to solve the incompatibility between high porosity and mechanical properties, this study fabricates bone scaffolds by combining braids and sodium alginate (SA) membranes. Polyethylene terephthalate (PET) plied yarns are braided into hollow, porous three dimensional (3D) PET braids, which are then immersed in SA solution, followed by cross-linking with calcium chloride (CaCl2) and drying, to form PET bone scaffolds. Next, SA membranes are rolled and then inserted into the braids to form the spiral and porous PET/SA bone scaffolds. Samples are finally evaluated for surface observation, porosity, water contact angle, compressive strength, and MTT assay. The test results show that the PET bone scaffolds and PET/SA bone scaffolds both have good hydrophilicity. An increasing number of layers and an increasing CaCl2 concentration cause the messy, loose surface structure to become neat and compact, which, in turn, decreases the porosity and increases the compressive strength. The MTT assay results show that the cell viability of differing SA membranes is beyond 100%, indicating that the PET/SA bone scaffolds containing SA membranes are biocompatible for cell attachment and proliferation. Full article
(This article belongs to the Special Issue Selected Papers from ICBEI2015)
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Open AccessArticle Failure Progress of 3D Reinforced GFRP Laminate during Static Bending, Evaluated by Means of Acoustic Emission and Vibrations Analysis
Materials 2015, 8(12), 8751-8767; https://doi.org/10.3390/ma8125490
Received: 9 October 2015 / Revised: 29 November 2015 / Accepted: 3 December 2015 / Published: 14 December 2015
Cited by 1 | PDF Full-text (5849 KB) | HTML Full-text | XML Full-text
Abstract
The work aimed to assess the failure progress in a glass fiber-reinforced polymer laminate with a 3D-woven and (as a comparison) plain-woven reinforcement, during static bending, using acoustic emission signals. The innovative method of the separation of the signal coming from the fiber
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The work aimed to assess the failure progress in a glass fiber-reinforced polymer laminate with a 3D-woven and (as a comparison) plain-woven reinforcement, during static bending, using acoustic emission signals. The innovative method of the separation of the signal coming from the fiber fracture and the one coming from the matrix fracture with the use of the acoustic event’s energy as a criterion was applied. The failure progress during static bending was alternatively analyzed by evaluation of the vibration signal. It gave a possibility to validate the results of the acoustic emission. Acoustic emission, as well as vibration signal analysis proved to be good and effective tools for the registration of failure effects in composite laminates. Vibration analysis is more complicated methodologically, yet it is more precise. The failure progress of the 3D laminate is “safer” and more beneficial than that of the plain-woven laminate. It exhibits less rapid load capacity drops and a higher fiber effort contribution at the moment of the main laminate failure. Full article
(This article belongs to the Special Issue Failure Analysis in Materials)
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Open AccessCommunication The ZrO2 Formation in ZrB2/SiC Composite Irradiated by Laser
Materials 2015, 8(12), 8745-8750; https://doi.org/10.3390/ma8125475
Received: 3 November 2015 / Revised: 30 November 2015 / Accepted: 3 December 2015 / Published: 14 December 2015
Cited by 1 | PDF Full-text (3685 KB) | HTML Full-text | XML Full-text
Abstract
In order to clearly understand the details of ZrO2 formation during ablation, high intensity continuous laser was chosen to irradiate ZrB2/SiC. The results reveal that there are two different modes of ZrO2 formation depending on whether liquid SiO2
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In order to clearly understand the details of ZrO2 formation during ablation, high intensity continuous laser was chosen to irradiate ZrB2/SiC. The results reveal that there are two different modes of ZrO2 formation depending on whether liquid SiO2 is present. When liquid SiO2 is present, ZrO2 generated by the oxidation of ZrB2 is firstly dissolved into SiO2. Then, ZrO2 will precipitate again, the temperature will decrease and the SiO2 will evaporate. Otherwise, the ZrB2 will be oxidized to ZrO2 directly. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Experimental Characteristics of Dry Stack Masonry under Compression and Shear Loading
Materials 2015, 8(12), 8731-8744; https://doi.org/10.3390/ma8125489
Received: 11 October 2015 / Revised: 6 December 2015 / Accepted: 8 December 2015 / Published: 12 December 2015
Cited by 4 | PDF Full-text (5718 KB) | HTML Full-text | XML Full-text
Abstract
The behavior of dry stack masonry (DSM) is influenced by the interaction of the infill with the frame (especially the joints between bricks), which requires further research. This study investigates the compression and shear behaviors of DSM. First, a series of compression tests
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The behavior of dry stack masonry (DSM) is influenced by the interaction of the infill with the frame (especially the joints between bricks), which requires further research. This study investigates the compression and shear behaviors of DSM. First, a series of compression tests were carried out on both masonry prism with mortar (MP_m) and DSM prism (MP_ds). The failure mode of each prism was determined. Different from the MP_m, the stress-strain relationship of the MP_ds was characterized by an upward concavity at the initial stage. The compression strength of the MP_ds was slightly reduced by 15%, while the elastic modulus was reduced by over 62%. In addition, 36 shear-compression tests were carried out under cyclic loads to emphasize the influence of various loads on the shear-compression behavior of DSM. The results showed that the Mohr-Coulomb friction law adequately represents the failure of dry joints at moderate stress levels, and the varying friction coefficients under different load amplitudes cannot be neglected. The experimental setup and results are valuable for further research. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessCorrection Correction: Electrochemical Investigation of the Corrosion of Different Microstructural Phases of X65 Pipeline Steel under Saturated Carbon Dioxide Conditions. Materials 2015, 8, 2635–2649
Materials 2015, 8(12), 8728-8730; https://doi.org/10.3390/ma8125485
Received: 26 November 2015 / Accepted: 10 December 2015 / Published: 11 December 2015
Cited by 1 | PDF Full-text (147 KB) | HTML Full-text | XML Full-text
Abstract
In the published manuscript “Electrochemical Investigation of the Corrosion of Different Microstructural Phases of X65 Pipeline Steel under Saturated Carbon Dioxide Conditions. [...] Full article
Open AccessArticle Prediction of the Chloride Resistance of Concrete Modified with High Calcium Fly Ash Using Machine Learning
Materials 2015, 8(12), 8714-8727; https://doi.org/10.3390/ma8125483
Received: 9 October 2015 / Revised: 16 November 2015 / Accepted: 30 November 2015 / Published: 11 December 2015
Cited by 2 | PDF Full-text (519 KB) | HTML Full-text | XML Full-text
Abstract
The aim of the study was to generate rules for the prediction of the chloride resistance of concrete modified with high calcium fly ash using machine learning methods. The rapid chloride permeability test, according to the Nordtest Method Build 492, was used for
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The aim of the study was to generate rules for the prediction of the chloride resistance of concrete modified with high calcium fly ash using machine learning methods. The rapid chloride permeability test, according to the Nordtest Method Build 492, was used for determining the chloride ions’ penetration in concrete containing high calcium fly ash (HCFA) for partial replacement of Portland cement. The results of the performed tests were used as the training set to generate rules describing the relation between material composition and the chloride resistance. Multiple methods for rule generation were applied and compared. The rules generated by algorithm J48 from the Weka workbench provided the means for adequate classification of plain concretes and concretes modified with high calcium fly ash as materials of good, acceptable or unacceptable resistance to chloride penetration. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
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