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Geopolymer is an emerging material alternative to Portland cement and has potential as a refractory material. Adding filler in geopolymer material is a strategy to increase the advantages of its physical and mechanical properties. It has been previously reported that adding nanoparticles can increase the compressive strength value, but there is no reported interaction between nanoparticles and geopolymer during the geopolymerization process. This study aims to study the effect of adding nano-zirconia fillers on the physical and mechanical changes of metakaolin-based geopolymers with nano-zirconia fillers. The geopolymer paste was prepared with 100 g of metakaolin as the base material and added with variations of nano-zirconia 2gr, 5gr, 10 gr, and 15 gr. Further characterization was carried out by XRD, FTIR, SEM-EDX, and DTA-TG. This study showed that the compressive strength of the MZr05 sample increased significantly by 58.7% compared to the control sample. The test results of the structure and functional groups did not lead to any new compounds formed in the geopolymerization reaction. Therefore, the interaction of metakaolin geopolymer with nano-zirconia only creates an interfacial bonding.

The increasing of infrastructure development has an impact on increasing demand for construction materials. Generally, construction materials come from nature and still being exploited, which could lead to environmental degradation. Visually, nickel slag resembles gravel and sand which can be used as an alternative material. Therefore, this literature study aims to determine the characteristics and potential utilization of nickel slag gathered from Indonesian lateritic nickel ore and its application as an aggregate in mortar and concrete. The method used in this study is a review of several literatures from a reputable digital publication database with the keywords "terak nikel" and "nickel slag". In addition, several criteria are also used as filters in order to get the more focused literatures. Although the fluctuations in its mechanical properties was reported, it can still be overcome by using slag nickel slag as coarse and fine aggregate simultaneously. The results also show that nickel slag can be used as fine or coarse aggregate in concrete up to 100% content as well and as fine aggregate in asphalt application mortars up to 50% content.

Nowadays, either keeping or throwing out the final product of dental cast is the most common thing to do. The waste from dentistry can be considered toxic if not handled specifically and separately to other waste. Hence, the recycling process can reduce its effect and the waste of dental casts. It can also reduce the cost of producing new high-grade dental gypsum. This paper studies the behavior of before-after recycle and heat treatment to several grades of dental gypsum that will be used as impression material or dies. As it is designed to be an impression material that will undergo heat treatment, Simultaneous Thermogravimetry and Differential Scanning Calorimetry (TGA-DSC) will be applied to understand the Phase Transformation to its mass change and the behavior to a temperature difference. The result will be validated using an experimental approach. X-ray Diffraction (XRD) and Scanning Electron Microscope will also be done to identify the crystalline phases and the surface microstructure, and it will be validated using an experimental approach as well. A range of gaps between parameter values is expected between the fresh/new dental gypsum and the recycled one. However, it is expected some similar values between the heat-treated and the fresh/new dental gypsum.

Nickel slag is a solid waste produced from the nickel smelting process. At present, In Indonesia, the total capacity of domestic nickel smelting reaches 5 million tons/year with the assumption of NPI or FeNi production with a Ni level of 10%, requiring the input of Ni ore raw materials around 40 million tons/year in which around 30 million tons will become waste/slag. Currently, the area of Southeast Sulawesi has a potential of huge nickel resources of 97.4 billion tons, which spread over 480 thousand hectares of land. This has led to a continuous increase in the demand of concrete towards infrastructural development in Indonesia. Therefore, the aim of this research is to reuse nickel slag powder in the context of environmentaly friendly by analyzing the tensile strength using nickel slag powder (NSP) as a cement substitution material for the manufacture of high-performance concrete. Specimens were made with water-cement ratio of 0.31 and compared with 100% OPC Type 1 cement (as reference). Furthermore, the NSP substitution of cement were 5%, 10%, 15%, 20%, 25% and 30% with a concrete age of 3, 7, 14 and 28 days. Analysis of physical characteristics of nickel slag powder and cement were carried out by using the Le Chatelier method, while the mechanical characteristics comprised ease of work in the field (workability) and split tensile strength. The manufactured concrete was made by using Sika Viscocrete 8015 superplasticizer admixture with split tensile strength test results for NSP substitution at 28 days ≥ 5% of the value of compressive strength. Keywords: High-performance concrete, Nickel slag powder, Split tensile strength

Indonesia's infrastructure growth is increasing rapidly in recent years. One of the main components in infrastructure development is concrete which uses cement as the binder. Higher infrastructure development will also increase the demand for cement. However, cement industry is known as a significant source of CO2 emissions with total of 8% contribution to the global CO2 emissions. If cement remains the main component in the manufacture of concrete, this number of emissions will continue to increase year after year. Preventive action needs to be done by conducting research to find alternative other than cement. This research is aimed to observe the feasibility of geopolymer concrete to be proposed as that alternative, since it does not need cement for the application. The geopolymer concrete was made from Geofast nickel slag as the main component following standard for Concrete Mix Design for Normal Concrete. The result shows that geopolymer concretes which tested after 28 days have higher compressive strength and flexural strength compared to those which tested after 14 days. The strength of all testing obtained from geopolymer concrete in this study is also higher than the Portland cement. Thus, this geopolymer concrete holds promising potential to be used as alternative for Portland cement. Nevertheless, the use of normal concrete mix proportion for geopolymer should be studied further.

This paper investigates the characteristics of concrete made from blast furnace nickel slag powder (BFNSP) and fly ash (FA) to use an alternative binder to conventional Portland cement (PC) by making a geopolymer concrete using an alkali activator. Samples for testing were made using 100% of BFNSP, and 50% BFNSP + 50% FA combination binder, as a direct replacement for the PC in concrete. These test samples were evaluated by compression and slump tests, also using the Le Chatelier’ method, XRF, and SEM analysis of microstructure properties. The samples with BFNSP were activated with alkaline activators with molarities of 12M and 6M with a ratio of Na2SiO3 to NaOH of 2.5. The test samples with 100% BFNSP and 12M activator showed the most slump and workability. However, the 50% BFNSP + 50% FA mix and 12M activator had the highest compressive strength at 55.97Mpa at 28 days. These results compare very favorably with the control Portland cement sample.

Recently, zinc (Zn) is extensively observed as biomaterial or biodegradable implant for medical application. A biomaterial is any substance that has been engineered to interact with biological systems for a medical purpose. Zn is chosen because it has moderate degradation compared to Mg and Fe. Unfortunately, Zn has limitation on its mechanical properties that still low. The Alloying element is needed to improve the mechanical properties of Zn. Alloying element, such as zirconium (Zr) can improve the mechanical properties of Zn. In this study the addition of Zr with the composition variations of 0%, 0.5%, 1%, and 2% were used. Two kinds of alloying method used are centrifugal casting and box furnace with a temperature of 550°C. The aims of this study are to know the effect of each fabrication method to the mechanical properties and the result of Zn-Zr alloy microstructures. The results show that the microstructure of the alloy from centrifugal casting is more homogenous than the box furnace method. The mechanical properties of centrifugal casting are also higher than the box furnace method. The hardness value obtained from centrifugal casting of 0, 0.5, 1, 1.5 and 2% of Zr are 35.162 HV, 41.988 HV, 42.324 HV, 57.112 HV, respectively.

In this work, corrosion behaviour of zinc-based alloys with addition of 0.5%, 1%, and 2% of zirconium for biodegradable material as orthopaedic implant were investigated. The potentiodynamic polarization method is carried out to determine the corrosion resistance and corrosion rate of each composition in order to observe the effect of zirconium addition in a Kokubo simulated body fluid solution. The result showed that the addition of 0.5% and 1% of zirconium would decrease the corrosion rate of Zn-xZr alloys corresponding to 0.079 mm/year and 0.116 mm/year whereas the 2% addition would increase the rate to 0.188 mm/year due to the formation of Zr-rich precipitates inside the alloys. The passivation zone on the polarization curve showed the formation of the protected thin layer on the surface of the alloys which caused the corrosion rate to decrease, therefore confirmed the degradable ability of the Zn-xZr alloys. In general, the corrosion rates of Zn-xZr alloys were higher than Fe-based alloys and lower than Mg-based alloys. Moreover, the corrosion rates were much lower than the maximum rate of 0.4 mm/year for biodegradable implants so Zn-xZr alloys were suitable as biodegradable material implant for orthopaedic application.

Magnesium (Mg) alloys have unique biodegradable property with low density, non-toxicity, and mechanical properties that are similar to human bones attracting many biomedical applications from bone to cardiovascular implants. The combination of mechanical strength and degradability of Mg makes it suitable for bone fixation. Rapid degradation rate of Mg, however, is very challenging and prevents the widespread use of the implants. Trace amounts of Zn contribute to Mg strength by a process of solid solution strengthening, and then refined effectively by Zr. The addition of Sn to Mg alloys could enhance mechanical and corrosion properties by forming Mg2Sn phase. The difference in melting points of the elements and easy oxidation make low-alloyed Mg alloys hard to control alloying compositions during casting process. The objectives of the current research were to study the effect of Sn addition on mechanical and corrosion properties along with its effect on hydrogen evolution rate of Mg-1Zn-1Zr-xSn (x = 1, 2, 3, 4, 5) alloys prepared by Powder in Tube Rolling (PTR) method. In this research, quaternary Mg-1Zn-1Zr-xSn (x = 1, 2, 3, 4, 5) alloys were manufactured by PTR method. Steel tube was used in order to hold the powder during the rolling process and to further prevent the oxidation of Mg during sintering process. The PTR treated Mg alloys reached 98.3% of theoretical density. There were several porosities observed on the surface of the PTR specimen even with high density. The hardness value increased as the amount of Sn addition increased. SEM and XRD observation revealed that there are two main intermetallic phases emerging on the surface of the alloys, which are Mg2Sn and Zn2Zr3. The intensity of Mg2Sn increased as the amount of Sn increased as well as Zn2Zr3 reached its maximum intensity when the addition of Sn was 5 wt.%. The observed Mg2Sn intermetallic phase was distributed along the grain boundaries, while Zn2Zr3 particles diffused inside Mg matrix. The degradation behavior of the alloys was evaluated by potentiodynamic polarization test (PDP) in SBF solution at temperature of 37±1°C. The addition of Sn simply shifts the corrosion potential towards positive zone and lowered the corrosion current density. More Sn was added to alloys, the corrosion potential was in negative zone and corrosion current were increased.

This research aims to use high-magnesium nickel slag crushed into a powder as a replacement for cement and to study their properties and microstructure in concrete. The particle diameter of the nickel slag powder was obtained lower than 75 μm after a process of crushing and sieving. The specific areas, absolute dry densities and particle size distribution (PSD) were analysed to obtain the physical properties of the material. The techniques applied to study their chemical and mineralogical composition were the X-Ray Florescence (XRF), the Scanning Electron Micrograph (SEM). The OPC type 1 was used as a reference in comparison to the experimental material of this research. Without a chemical admixture, the compressive strength of concrete after 28 days is fc’ 30 MPa and the specific surface area is 4360 cm2/gr. The compressive strength of high-magnesium nickel slag powder is capable of replacing cement by 20% without altering properties of concrete. According to the XRF technique results, the nickel slag contains silica, calcium, magnesia, and alumina. Furthermore, the image of the SEM-EDS illustrated the slag particle to be sharp, irregular, and containing calcium, silicon, alumina, oxygen, and magnesium. This result confirmed that the XRF technique and SEM-EDS were accurate.

Summary Polyvinyl alcohol (PVA) needs to be reinforced with other material to increase its mechanical strength and electrical conductivity to get wider applications. In this research effect of addition of carbon fiber on the mechanical properties and electrical conductivity of PVA based composites was observed. Concentrations of carbon fiber applied were 0, 2, 4 and 6% w/w based on PVA dry weight. PVA film was synthesized by dilute solid PVA in water at temperature of 80 °C for 6 hours with 8% w/w of water, and continued with chilling for 12 h. Carbon fiber was added and stirred by ultra-turrax for 40 seconds, and the solution was film-casted. Characterization the composites include morphology analysis (optical microscope and SEM), crystallite size (X-ray diffraction), mechanical test and electrical conductivity measurement. The result showed that tensile strength increase with increased of carbon fiber added. The optimal value of tensile strength (34.08 MPa) was obtained from 2% w/w of carbon fibers. Addition of 6% w/w of carbon fiber increased electrical conductivity up to 1.33 × 10−3 S/cm, this was significantly enhanced from that net PVA of 2.3 × 10−8 S/cm. Generally, addition of carbon fiber increase tensile strength and electrical conductivity of PVA based composites.

The effect of steel slag substitution as coarse aggregate on compressive strength in fly ash based-geopolymer concrete was studied. The compressive strength was evaluated by measuring the maximum acceptable load using compression testing equipment. Compressive strength depends on several factors, such as time and temperature of curing and the mixing proportion. The compressive strength of geopolymer concrete with steel slag substitution was higher compared to geopolymer concrete with gravel aggregate. The optimum compressive strength was found on the third day of curing at a temperature of 60 o C for both the geopolymer concrete with steel slag substitution and normal geopolymer concrete. Reinforcement corrosion was evaluated by measuring the corrosion current density using a linear polarization potentiostatic scan. The corrosion rate of reinforcing steel in geopolymer concrete with steel slag substitution was found to be higher compared to normal geopolymer concrete without steel slag in seawater medium, whereas in an acid rain environment, steel slag substitution increased corrosion resistance. The corrosion rate of geopolymer concrete with steel slag substitution was found to be lower compared to normal geopolymer concrete. The corrosion rate was found to be very high at an early stage and decreased with time.

Geopolymer material is an advanced material that is now being looked for its use as a refractory material, additive for building material, as well as other applications. Geopolymer is produced by polymerizing the precursor used in the process. One of the common precursors being used as geopolymer is metakaolin. The metakaolin was produced by thermal treatment (calcination) of kaolin minerals, which will convert its mineral structure from crystaline into amorphous and make it more reactive. This paper presents the fabrication and characterization of metakaolin using kaolin from Bangka island. The main structure of kaolin used in this study are kaolinite and muscovite according to XRD results obtained. Metakaolin was produced by thermal treatment using three different calcination temperatures ranged from 600 to 700°C and calcined for 4 hours. Prior to calcination, some specimens will be mechanically milled using planetary ball mill for 15 minutes with the milling speed of 20.00 rad/s and will also be calcined with the same parameter. As a comparison, commercial metakaolin MetaStar also be used to compare it to all metakaolin produced. All metakaolin produced are characterized by XRD and SEM, and STA test will be performed to kaolin to examine its thermal behavior. The STA test performed to both milled and non-milled sample shows that dehydroxylation and reconstruction process occurs at temperature range of 460-520°C and 520-640°C for kaolin sample, and at temperature of 426-537°C and 537-618°C for milled kaolin sample. XRD pattern obtained shows that almost all metakaolin produced have the relatively similar pattern to each other as well as to MetaStar, with the main peak of quartz (SiO2) at 2= 26.60° to 26.65°. The SEM results shows the characteristic layered-laminate plate-like structure of kaolin. Compared to another SEM results obtained, it can be concluded that there are no changes to the visible structure of metakaolin produced with the same kaolin used after calcination.

Various aluminosilicate material have been used as precursor for geopolymer. Geopolymer gets its strength from the polycondensation of silicate and alumina. Metakaolin, calcinated kaolin, is pozzolan with the highest alumina and silicate purity. Indonesia, especially Bangka Island, has a large amount of kaolin deposit that being sold at low price. This price could be increased ten times when being sold as metakaolin. This study aimed to compare mechanical and metallurgical properties of commercial metakaolin and Bangka kaolin which calcinated at 700°C. Both metakaolins reacted with NaOH and waterglass as the activator followed by curing at room temperature for 7, 14 and 28 days and elevated temperature of 60°C for 4, 12 and 24 hours. Mechanical properties will be examined by compressive strength and flexural strength test, while the metallurgical properties will be evaluated with SEM, and TAM. The results of the mechanical test will be used to determine which geopolymer will perform well with the microstructure and thermal activity to support the finding. These attempts will be done in order to improve the properties of Bangka metakaolin geopolymer superior to commercial metakaolin.

Various This paper presents the results of the investigation on the use of Metakaolin (Al2Si2O2) as a supplementary cementing materials to improve the strength of cement. The most effective way to increase the strength of cement is the substitution of a proportion of cement with supplementary cementing materials. One of them was Metakaolin. Metakaolin was produced by thermal treatment calcination from Kaolin at 600-800 Celcius and has highest alumina and silicate purity. By added Metakaolin to Portland Cement type I (OPC), the amount of Calcium Silicate Hydrate (CSH) will increase through binding with Calcium Hydroxide (CaOH). There were two kinds of Metakaolin used in this investigation, commercial metakaolin named Metakaolin Metastar compared with Metakaolin Bangka which derived from Indonesia local resources, Bangka Island. Four Metakaolin replacement levels were employed in this investigation: 5%, 0%, 15%, and 20% with water per cement ratio 0.35, 0.40, and 0.50 both of Metakaolin Metastar and Metakaolin Bangka. The cement pastes cured at room temperature for 7, 14, and 28 days. The mechanical strength examined by compressive strength test, the microstructure were examined by SEM-EDS. The results of the study revealed both Metakaolin Metastar and Metakaolin Bangka enhanced the compressive strength of OPC. The most appropriate strength was obtained for a substitution of 20% metakaolin metastar which had 46,15% higher than OPC and 5% metakaolin Bangka which had 39,06% higher than OPC. The hydration rate was examined by Thermal Analysis Monitor. The results indicated that metakaolin metastar released higher heat than metakaolin Bangka. It can be concluded that Metakaolin metastar was more effective than metakaolin Bangka as additive in OPC.