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1

Stabilization of Lateritic Soil using Fly Ash Based Geopolymer

Ahmad Muhammad Munsif, Razak Rafiza Abdul, Abdullah Mohd Mustafa Al Bakri, Muhamad Khairunnisa, Mydin Md Azree Othuman, Sandu Andrei Victor

Archives of Metallurgy and Materials

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2024

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Vol. 69, iss. 3

1165--1173

EN

Current development consists of a high-rise building and heavy traffic load demands for soil with good engineering properties. Lateritic soil is commonly treated with Ordinary Portland Cement (OPC) to improve its engineering properties in order to enhance its load bearing capacity. The production of OPC however emits a large amount of carbon dioxide (CO2) into the atmosphere. Geopolymer technology has been explored as an alternative replacement for the OPC. In this research, the unconfined compressive strength (UCS) of a lateritic soil treated with fly ash (FA) based geopolymer up to 40% by weight of the dry soil and activated using combination of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) was investigated by means of unconfined compression test (UCT). The effect of different molarity of NaOH (5-20 M), FA to alkali activator (AA) ratio (1-3) and different curing temperatures to the UCS of treated soil sample are being determined. In general, as the content of FA in the soil increases, the UCS increases more than 100% and almost 400% compared to the untreated soil for room curing temperature and oven curing temperature respectively. Based on the scanning electron microscopy (SEM) result, the molarity of NaOH solution reduces the pores in the treated soil sample. The geopolymerization process combines the soil particle and makes it denser, resulting in higher UCS than the untreated soil sample.

2

Feasibility of Treated Sand Brick Waste with Silica Fume Based Geopolymer for Coarse Aggregate Application

Razak Rafiza Abd, Kiong Alvin Ngieng Dong, Abdullah Mohd Mustafa Al Bakri, Mydin Md Azree Othuman, Sandu Andrei Victor, Yahya Zarina, Abdullah Alida, Risdanareni Puput, Arifi Eva

Archives of Metallurgy and Materials

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2024

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Vol. 69, iss. 2

739--745

EN

Construction and demolition waste (CDW) management should focus on reducing CDW or properly recycling the materials since this waste is now a global problem. Sand brick waste, a component of a building’s structure, is one type of CDW. To be used as recycled aggregate, these wastes are invariably categorised as low grade. Due of the improved qualities provided, geopolymer research has recently become more popular. The objective of this study is to investigate the physical and mechanical properties of recycled sand brick aggregate (RSB) treated with silica fume based geopolymer coating. Additionally, the effectiveness of the treated RSB will be applied in concrete as coarse aggregate. The sample was made using a solid-to-liquid ratio of 1.0, 1.2, 1.4, 1.6, and 1.8. At 2.5 and 10 M, alkaline activator is a constant variable. Testing of specific gravity, water absorption, and aggregate impact value were analysed. The treated RSB concrete will then be evaluated against normal concrete. In terms of density, water absorption, and compressive strength, natural concrete performs better than treated RSB concrete. In comparison to natural concrete, treated RSB concrete absorbs 5.8% more water. Treated RSB concrete has a density of 1815 kg/m3, compared to natural concrete’s 2080 kg/m3. The compressive strength of concrete made using treated RSB aggregate is 18.1 MPa after 7 days, and 27.1 MPa at 28 days. The testing revealed that the treated RSB aggregate concrete met the specifications. As a result, treated RSB aggregate concrete offers an advantage over natural OPC concrete while saving the environment.

3

Comparison of the Properties of Cold Work Tool Steels with the Same Hardness but Different Manufacturing Processes

Tóth László, Fábián Enikő Réka, Pinke Peter, Kovács Tunde Anna, Nabiałek Marcin, Sandu Andrei Victor, Vizureanu Petrica

Archives of Metallurgy and Materials

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2024

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Vol. 69, iss. 3

809--817

EN

The required important properties of cold work tool steels are hardness, wear resistance, suitable toughness and in many cases corrosion resistance. For cold work tool steels, hardness can be well controlled by heat treatment, but steels of the same hardness do not necessarily have similar wear, corrosion resistance or even toughness. These properties are influenced by the chemical composition of the steels and their manufacturing processes. The study is performed on Böhler K390 PM produced by powder metallurgy (PM) process, Böhler K360 ESR made by electro-slag remelting (ESR) methods and Böhler K110 produced conventionally (C). The specimens were heat treated to obtain the same hardness of 61 HRC. It was made a comparative test of the abrasive wear resistance, corrosion resistance and toughness of the heat-treated cold work tool steel test specimens. The comparative test results show that the Böhler K110 steel has the best corrosion resistance against the 20% acetic acid, and the Böhler K390 PM steel has the best wear resistance and toughness. The goal of the research was to find the optimal cold work tool steel quality for special applications (as a function of wear resistance, corrosion resistance and toughness). The K390 reached the best wear resistance which is two times better than the K360 and about ten times better than the K110. About the corrosion test results, it can be concluded that K110 showed the lowest weight loss after the corrosion test, and the K390 and K360 showed higher weight loss and lower corrosion resistance. Impact energy values from the Charpy impact test were the highest in the case of K390 followed by the K360 and the K110. The results were confirmed by the microscopic analysis.

4

XRD and STA Characterization of Phosphate Layers Deposited on the Carbon Steel Surface

Burduhos-Nergis Diana Petronela, Bejinariu Costica, Cazac Alin Marian, Sandu Andrei Victor, Vizureanu Petrica

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 3

955--960

EN

Carbon steel is one of the most widely used alloys in many industries, however, its use is limited by its low corrosion resistance. Depositing a layer of phosphate on its surface improves the corrosion resistance as well as other properties, such as wear resistance, adhesion etc. Accordingly, preliminary studies demonstrated that carbon steel coated with phosphate layers can be used in the manufacture of carabiners for various fields: civil engineering, oil industry etc. Whereas, to demonstrate their capacity to operate in severe conditions related to fire rescue and extinguishing operations, it is necessary to evaluate the thermal behaviour of these materials. Thus, the main goal of this paper is to study the behaviour at high temperatures of three different types of phosphate layers deposited on carbon steel surface, by STA analysis. Also, the paper aims to study the formation of different phosphate layers by determining the types of compounds formed after the completion of the phosphating process, by XRD analysis.

5

The Influence of Sintering Temperature on the Microstructure of Coal-Ash Based Geopolymers

Burduhos-Nergis Dumitru Doru, Vizureanu Petrica, Achitei Dragos C., Sandu Andrei Victor, Burduhos-Nergis Diana Petronela, Abdullah Mohd Mustafa Al Bakri

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 2

631--637

EN

Currently, one of the main challenges of civil engineering and science materials engineers is to develop a sustainable substitute for Ordinary Portland Cement. While the most promising solution is provided by the geopolymerisation technology, most of the studied geopolymers are based on natural raw materials (kaolin). The metakaolin is mainly preferred because of its rapid rate of dissolution in the activator solution, easy control of the Si/Al ratio, and white color. However, its high cost prevents it from being widely used in geopolymer composites or other materials that can become an industrial alternative for Ordinary Portland Cement. Several studies have shown that geopolymers with good performance can also be obtained from secondary raw materials (industrial wastes such as coal ash or slag). This explains why countries with rapidly developing economies are so interested in this technology. These countries have significant amounts of industrial waste and lack a well-developed recycling infrastructure. Therefore, the use of these by-products for geopolymers manufacturing could solve a waste problem while simultaneously lowering virgin raw material consumption. This study evaluates the effect of replacing different amounts of coal ash with sand on the microstructure of sintered geopolymers. Accordingly, scanning electron microscopy and energy dispersive X-ray analysis were involved to highlight the morphological particularities of room-cured and sintered geopolymers.

6

Study of the Effect of Intensity of Vibrations and Temperature on the Cooling Characteristics of Quenching Media

Perju Manuela-Cristina, Nejneru Carmen, Burduhos-Nergis Dumitru Doru, Vizureanu Petrica, Minciuna Mirabela G., Sandu Andrei Victor

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 3

997--1002

EN

Quenching technology requires the use of media with different cooling intensities and various shapes of cooling curves that show different particularities compared to that of conventional media such as water, oil, or emulsions. The use of synthetic quenching media is relatively new and also has multiple advantages such as non-flammability, safety in use and low cost. In this study, the cooling media tested was obtained by mixing 2 wt% carboxymethyl cellulose with 2 wt% NaOH in one litter of water. Moreover, three different temperatures (20°C, 40°C and 60°C) of the quenching media were evaluated. By dissolution in water, a synthetic solution with low viscosity, surfactant and lubricant was obtained. Because carboxymethyl cellulose is a biodegradable organic material, that is obtained as a by-product in the manufacture of paper, a basic substance with a preservative effect was added. According to this study, both the variation diagram of the heat transfer coefficient and the diagram of the cooling rates, during the cooling stages give important indications regarding the use of a liquid cooling medium for quenching.

7

Phosphate Conversion Coating - A Short Review

Burduhos-Nergis Diana Petronela, Sandu Andrei Victor, Burduhos-Nergis Dumitru Doru, Vizureanu Petrica, Bejinariu Costica

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 3

1029--1034

EN

Phosphating is the process of depositing, by conversion, a layer of insoluble phosphate compounds, on the metal’s surface. Although phosphate coatings have been studied since the early nineteenth century, they are not only still being studied, but are an area of interest due to their many applications. The advantages of these types of coatings are well known, such as the low cost of the deposition process, the improvement of corrosion resistance properties, and the improvement of wear resistance and adhesion of further deposited layers such as paint. All this, leads to studies on the constant improvement of the properties of the phosphate coating, by modifying the parameters of the phosphating process, as well as by modifying/replacing the substances used in the phosphating solutions with “environmentally friendly” solutions. Also due to these advantages, several researchers are studying the possibility of using phosphate coatings in fields such as civil engineering or medicine (biomaterials coatings). This paper aims to present some essential aspects of phosphating and to bring to the fore the latest research on “eco-friendly” phosphating solutions and the possibility of using the phosphating process in other fields, such as the medical field. Also, the paper aims to discuss the possibility of eliminating/reducing the harmful effect that the use of phosphating has on the environment.

8

Thermal Insulation and Mechanical Properties in the Presence of Glas Bubble in Fly Ash Geopolymer Paste

Shahedan Noor Fifinatasha, Al Bakri Abdullah Mohd Mustafa, Mahmed Norsuria, Ming Liew Yun, Abd Rahim Shayfull Zamree, Aziz Ikmal Hakem A., Kadir Aeslina Abdul, Sandu Andrei Victor, Ghazali Mohd Fathullah

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 1

221--226

EN

The density, compressive strength, and thermal insulation properties of fly ash geopolymer paste are reported. Novel insulation material of glass bubble was used as a replacement of fly ash binder to significantly enhance the mechanical and thermal properties compared to the geopolymer paste. The results showed that the density and compressive strength of 50% glass bubble was 1.45 g/cm3 and 42.5 MPa, respectively, meeting the standard requirement for structural concrete. Meanwhile, the compatibility of 50% glass bubbles tested showed that the thermal conductivity (0.898 W/mK), specific heat (2.141 MJ/m3 K), and thermal diffusivity (0.572 mm2 /s) in meeting the same requirement. The improvement of thermal insulation properties revealed the potential use of glass bubbles as an insulation material in construction material.

9

Studying the Behavior of the C45 Material when Changing the Tool Geometry Using the Finite Element Method

Pop Alina Bianca, Sandu Andrei Victor, Sachelarie Adrian, Țîțu Aurel Mihail

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 2

653--659

EN

Machining with tool that have cutting edge radius provides components with high fatigue strength, microhardness of a large surface layer and plastic deformation. Finite element simulations of the cutting process give a better knowledge of the chip generation phenomenon, heat generation in the machining area, stress and temperature field results. This study emphasizes the true importance of the mathematical model that underlies the shape of the tool in the pre-processing steps of finite element analysis. The argument is that its achievement and definition depend on the network difficulty. This research purpose is to perform simulations series of orthogonal machining with different radius and depth of cut. In this way, conclusions on the impact of these variations on the whole cutting process were drawn. The finite element application used is Deform 2D, the Lagrange incremental method and the Johnson-Cook material model. The temperature distribution, stress distribution, von Mises stress distribution, effects on specific tool pressure and wear, and fluctuations in the cutting resistance of the tool tip and C45 workpiece were analyzed.

10

Structural and Physical Characterization of New Ti-Based Alloys

Baltatu Iustinian, Sandu Andrei Victor, Baltatu Madalina Simona, Benchea Marcelin, Achitei Dragos, Ciolacu Florin, Perju Manuela-Cristina, Vizureanu Petrica, Benea Lidia

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 1

255--259

EN

Production of Ti-based alloys with non-toxic elements give the possibility to control the market of medical applications, using alloys with appropriate properties for human body, contributing to improving the health of the population. Determination of parameters of atomic and magnetic structure of functional biomaterials demonstrating interesting physical phenomena and being promising for medical applications in a wide range of thermodynamic parameters; exploration of the role of cluster aggregation in the formation of physical properties. Paper is about the obtaining of the new titanium system alloys, the determining their characteristics and structure, and obtaining information concerning phase transitions and some mechanical properties. Ti15Mo7ZrxTa (5 wt.%, 10 wt.% and 15 wt.%) alloys developed shows a predominant β phase highlighted by optical microstructure and XRD patterns. A very low young modulus of alloys was obtained (43-51 GPa) which recommends them as very good alloys for orthopedic applications.

11

Some Aspects Concerning Titanium Coverage with Hydroxyapatite

Perju Manuela-Cristina, Nejneru Carmen, Vizureanu Petrica, Aelenei Andra-Adorata, Sandu Andrei Victor, Sachelarie Liliana, Nabiałek Marcin

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 2

521--527

EN

Generally, the metallic implants do not exhibit any bio-integration properties in contact with bone tissues. To improve the interfacial properties of metallic implants in contact with bone, the coatings with thin biocompatible films are used. Two methods to coating titanium implants with hydroxyapatite are described. The first is a two phase method, where by cathodic polarization is deposed a monetite film followed by an alkaline treatment when the monetite is converted to hydroxyapatite. The second method is a biomimetic deposition on an alkaline activate titanium surface, using a five time more concentrated simulated body fluid (5xSBF). After deposition this samples was drying at 120℃ and was sintered at 700℃ for three hours. Optical microscopy, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray (EDX) were used to characterize structure, morphology and compositions of the deposed films. In this study, electrochemical deposition and biomimetic deposition of hydroxyapatite are compared.

12

Silica Bonding Reaction on Fly Ash Based Geopolymer Repair Material System with Incorporation of Various Concrete Substrates

Al Bakri Abdullah Mohd Mustafa, Aziz Ikmal Hakem A., Zailani Warid Wazien Ahmad, Rahim Shayfull Zamree Abd, Yong Heah Cheng, Sandu Andrei Victor, Peng Loke Siu

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 4

1277--1281

EN

This paper presents an experimental investigation on the mechanical properties and microstructure of geopolymer repair materials mixed using fly ash (FA) and concrete substrates. An optimal combination of FA and concrete substrate was determined using the compressive test of geopolymer mortar mixed with various concrete substrate classes. It was found that the contribution of (C35/45) concrete substrates with the FA geopolymer mortar increases the 28-day bonding strength by 25.74 MPa. The microstructure analysis of the samples using scanning electron microscopy showed the denser structure owing to the availability of high calcium and iron elements distribution. These metal cations (Ca2+ and Fe3+) are available at OPC concrete substrate as a result from the hydration process reacted with alumina-silica sources of FA and formed calcium aluminate silicate hydrate (C-A-S-H) gels and Fe-bonding linkages.

13

Review on Mechanical Properties of Metakaolin Geopolymer Concrete by Inclusion of Steel Fibers

Faris Meor Ahmad, Al Bakri Abdullah Mohd Mustafa, Muniandy Ratnasamy, Ramasamy Shamala, Abu Hashim Mohammad Firdaus, Junaedi Subaer, Sandu Andrei Victor, Tahir Muhammad Faheem Mohd

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 1

261--267

EN

This study summarised the recent achievement in developing fiber reinforced geopolymer concrete. The factor of replacing Ordinary Portland Cement (OPC) which is due to the emission of carbon dioxide that pollutes the environment globally is well discussed. The introduction towards metakaolin is presented. Besides, the current research trend involved in geopolymer also has been reviewed for the current 20 years to study the interest of researchers over the world by year. Factors that contribute to the frequency of geopolymer research are carried out which are cost, design, and the practicality of the application for geopolymer concrete. Besides, the importance of steel fibers addition to the geopolymer concrete is also well discussed. The fundamental towards metakaolin has been introduced including the source of raw material, which is calcined kaolin, calcined temperature, chemical composition, geopolymerisation process, and other properties. Alkali activators which are mixing solution between sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) have been reviewed. The mechanical properties of fibers reinforced metakaolin-based geopolymer concrete which is compressive and flexural are thoroughly reviewed. The compressive and flexural strength of fiber-reinforced metakaolin geopolymer concrete shows some improvement to the addition of steel fibers. The reviews in this field demonstrate that reinforcement of metakaolin geopolymer concrete by steel fibers shows improvement in mechanical performance.

14

New Ray on Remediation of High Rings Polycyclic Aromatic Hydrocarbons: Remediation of Raw Petroleum Sludge Using Solidification and Stabilization Method

Roslee Noor Faiza, Kamil Nor Amani Filzah Mohd, Kadir Aeslina Abdul, Jalil Abdul Rahim, Hamzah Nurhidayah, Noor Norazian Mohamed, Sandu Andrei Victor

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 4

1201--1208

EN

Solidification/Stabilization (S/S) method with cement as a binder to remediate metals in petroleum sludge has been successfully proven. However, this technique has not yet been explored to remediate organic contaminants since a high concentration of Total Petroleum Hydrocarbon (TPH) was also detected in the sludge. This study focuses on remediating 16 Polycyclic Aromatic Hydrocarbons (PAHs) compounds in raw petroleum sludge with Portland cement as a binder using the S/S method. The initial concentration of 16 PAHs in the raw sludge was first measured before the performance of the S/S method to remediate the PAHs were evaluated. The S/S matrices were tested for leaching behavior and strength after 7 and 28 days by air curing. The leaching test was measured using the Toxicity Characteristics Leaching Procedure (TCLP), and the remaining PAHs concentration in the matrices was analyzed using a Gas Chromatography-Mass Spectrometer (GC-MS). In the raw sludge, all 16 PAHs compounds were below the standard limit except for Benzo(a)anthracene, Benzo(a)pyrene, Dibenzo(ah)anthracene, and Indeno(1,2,3- cd_ pyrene), which are considered as high rings PAHs. The high rings PAHs show lower concentration in leachate than low rings PAHs, which indicates the potential of the S/S method in remediating high rings PAHs. The high sludge ratio in S/S matrices has shown that the percentage strength is increasing, similar to Portland cement. Therefore, this study contributed to the possibility of the S/S method in the remediation of PAHs in petroleum sludge by using only Portland cement as a binder.

15

Microstructural Analysis of Ambient Cured Phosphate Based-Geopolymers with Coal-Ash as Precursor

Burduhos Nergis Dumitru Doru, Vizureanu Petrica, Lupescu Stefan, Burduhos Nergis Diana Petronela, Perju Manuela-Cristina, Sandu Andrei Victor

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 2

595--600

EN

An alternative for Ordinary Portland cement (OPC) consumption is the production and integration of green cement. In other words, the clinker consumption has to be replaced with new low-carbon binders. A possible solution was introduced by the geopolymerisation technology. However, the alkaline activation of geopolymers offers the possibility of obtaining greener materials with high properties, superior to OPC, but due to the high price of sodium silicate, their industrial use is limited. In the past few years, a new activator has been discovered, namely phosphoric acid. This study approaches the obtaining of coal ash-based geopolymers activated with acid solution cured at room temperature. Accordingly, phosphoric acid, 85% by mass, was diluted in distilled water to obtain a corresponding activation solution for H3PO4/Al2O3 ratio of 1.0 and two types of geopolymers were ambient cured (22°C ±2°C). Moreover, to evaluate the geopolymerisation potential of this system (coal ash - phosphoric acid), SEM and EDS analysis was performed to investigate their morphologic characteristics.

16

Effect of Sodium Aluminate on the Fresh and Hardened Properties of Fly Ash-Based One-Part Geopolymer

Ooi Wan-En, Liew Yun Ming, Yong Heah Cheng, Ho Li-Nge, Al Bakri Abdullah Mohd Mustafa, Ong Shee-Ween, Sandu Andrei Victor

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 2

441--445

EN

The one-part geopolymer binder was synthesis from the mixing of aluminosilicate material with solid alkali activators. The properties of one-part geopolymers vary according to the type and amount of solid alkali activators used. This paper presents the effect of various sodium metasilicate-to-sodium aluminate (NaAlO2/Na2SiO3) ratios on fly ash-based one-part geopolymer. The NaAlO2/Na2SiO3 ratios were set at 1.0 to 3.0. Setting time of fresh one-part geopolymer was examined through Vicat needle apparatus. Mechanical and microstructural properties of developed specimens were analysed after 28 days of curing in ambient condition. The study concluded that an increase in NaAlO2 content delayed the setting time of one-part geopolymer paste. The highest compressive strength was achieved at the NaAlO2/Na2SiO3 ratio of 2.5, which was 33.65 MPa. The microstructural analysis revealed a homogeneous structure at the optimum ratio. While the sodium aluminium silicate hydrate (N-A-S-H) and anorthite phases were detected from the XRD analysis.

17

Correlation between Microstructure and Electrochemical Properties of Al-Si Alloys

Minciuna Mirabela G., Vizureanu Petrica, Jeż Bartłomiej, Sandu Andrei Victor, Nabiałek Marcin, Achitei Dragos C.

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 3

1067--1070

EN

The composition and structural modification of aluminium alloys influence their strength, tribological properties and structural stability. The phase composition of the structure as well as the characteristics of the elementary cell of each identified phase was established by X-ray diffraction, and the main objective was to determine the compositional phases, microstructure and microcomposition of the alloy. Based on the cyclic voltammograms it can be said that on the OCP interval (+1.5 V… -1.1 V), after the breakthrough potential is an intensification of the anodic process by the pronounced increase of the current density, in these conditions the Al-Si alloy has low values which means that it has a better corrosion resistance.

18

Effect of Rice Straw Ash (RSA) as partially replacement of cement toward fire resistance of self-compacting concrete

Razak Rafiza Abd, Chin Yi Qin, Abdullah Mohd Mustafa Al Bakri, Yahya Zarina, Ishak Mokhzani Khair, Garus Sebastian, Nabiałek Marcin, Zailani Warid Wazien Ahmad, Masri Khairil Azman, Sandu Andrei Victor, Śliwa Agata

Archives of Civil Engineering

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2022

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Vol. 68, nr 1

353--363

EN

Malaysia’s construction industry is experiencing rapid growth, translating into increased demand for cement. However, cement production pollutes the air to the detriment of the climate via CO2 emission, making research into a cementitious replacement in concrete a necessity. This paper details an experimental study of self-compacting concrete (SCC) with partial replacement of cement by rice straw ash (RSA), which is expected to result in environmental preservation due to the green materials being used in cement production. The physicomechanical properties of the SCC with RSA replacement were determined via its compressive strength, water absorption, self-workability, and fire resistance (residual strength after exposure to high temperatures). The proportion of RSA replacement used were 0%, 5%, 10%, 15%, 20%, and 25%, and all passed the slump flow test, except the 20% and 25% samples. The SCC samples with 15% of RSA replacement reported the highest compressive strength at 7 and 28 curing days and the highest residual strength post-exposure to high temperatures. The lowest percentage of water absorption was reported by the 15% of RSA replacement, with a density of 2370 kg/m3

19

Crumb rubber geopolymer mortar at elevated temperature exposure

Azmi Ahmad Azrem, Abdullah Mohd Mustafa Al Bakri, Ghazali Che Mohd Ruzaidi, Ahmad Romisuhani, Jaya Ramadhansyah Putra, Rahim Shayfull Zamree Abd, Almadani Mohammad A., Wysłocki Jerzy J., Śliwa Agata, Sandu Andrei Victor

Archives of Civil Engineering

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2022

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Vol. 68, nr 3

87--105

EN

Low calcium fly ash is used as the main material in the mixture and the crumb rubber was used in replacing fine aggregates in geopolymer mortar. Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) which were high alkaline solution were incorporated as the alkaline solution. The fly ash reacted with the alkaline solution forming alumino-silicate gel that binds the aggregate to produce a geopolymer mortar. The loading of crumb rubber in the fly ash based geopolymer mortar was set at 0% (CRGM-0), 5% (CRGM-5), 10% (CRGM-10), 15% (CRGM-15), and 20% (CRGM-20), respectively. NaOH solution (12M) and Na2SiO3 solution ratio is set constant at 2.5 for all geopolymer mixture and the fly ash to alkali activator ratio was kept at 2.0. The CRGM at 28 days of curing time was exposed to elevated temperature at 200ºC, 400ºC, 600ºC and 800ºC. The weight loss of the CRGM increases with increasing temperature at all elevated temperatures. However, the density and compressive strength of CRGM decrease with an increase of crumb rubber loading for all elevated temperature exposure. The compressive strength of CRGM reduced due to the fact that rubber decomposes between 200ºC and 600ºC thereby creating voids. CRGM-15 and CRGM-20 showed cracks developed with rough surface at 800ºC. Image obtained from scanning electron microscope (SEM) showed that, the CRGM changed significantly due to the decomposition of crumb rubber and evaporation of the free water at 400ºC, 600ºC and 800ºC.

20

Experimental modeling of the milling process of aluminum alloys used in the aerospace industry

Țîțu Aurel Mihail, Pop Alina Bianca, Nabiałek Marcin, Dragomir Camelia Cristina, Sandu Andrei Victor

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2021

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Vol. 69, nr 5

art. no. e138565

EN

This research presents an experimental study carried out for the modeling and optimization of some technological parameters for the machining of metallic materials. Certain controllable factors were analyzed such as cutting speed, depth of cut, and feed per tooth. A dedicated research methodology was used to obtain a model which subsequently led to a process optimization by performing a required number of experiments utilizing the Minitab software application. The methodology was followed, and the optimal value of the surface roughness was obtained by the milling process for an aluminum alloy type 7136-T76511. A SECO cutting tool was used, which is standard in aluminum machining by milling. Experiments led to defining a cutting regime that was optimal and which shows that the cutting speed has a significant influence on the quality of the machined surface and the depth of cut and feed per tooth has a relatively small impact on the chosen ranges of process parameters.