Solidification/Stabilization Technology for Radioactive Wastes Using Cement: An Appraisal.

Across the world, any activity associated with the nuclear fuel cycle such as nuclear facility operation and decommissioning that produces radioactive materials generates ultramodern civilian radioactive waste, which is quite hazardous to human health and the ecosystem. Therefore, the development of effectual and commanding management is the need of the hour to make certain the sustainability of the nuclear industries. During the management process of waste, its immobilization is one of the key activities conducted with a view to producing a durable waste form which can perform with sustainability for longer time frames. The cementation of radioactive waste is a widespread move towards its encapsulation, solidification, and finally disposal. Conventionally, Portland cement (PC) is expansively employed as an encapsulant material for storage, transportation and, more significantly, as a radiation safeguard to vigorous several radioactive waste streams. Cement solidification/stabilization (S/S) is the most widely employed treatment technique for radioactive wastes due to its superb structural strength and shielding effects. On the other hand, the eye-catching pros of cement such as the higher mechanical strength of the resulting solidified waste form, trouble-free operation and cost-effectiveness have attracted researchers to employ it most commonly for the immobilization of radionuclides. In the interest to boost the solidified waste performances, such as their mechanical properties, durability, and reduction in the leaching of radionuclides, vast attempts have been made in the past to enhance the cementation technology. Additionally, special types of cement were developed based on Portland cement to solidify these perilous radioactive wastes. The present paper reviews not only the solidification/stabilization technology of radioactive wastes using cement but also addresses the challenges that stand in the path of the design of durable cementitious waste forms for these problematical functioning wastes. In addition, the manuscript presents a review of modern cement technologies for the S/S of radioactive waste, taking into consideration the engineering attributes and chemistry of pure cement, cement incorporated with SCM, calcium sulpho-aluminate-based cement, magnesium-based cement, along with their applications in the S/S of hazardous radioactive wastes.

Mechanical Properties of Fly Ash-Based Geopolymer Concrete Incorporation Nylon66 Fiber.

This study was carried out to investigate the effect of the diamond-shaped Interlocking Chain Plastic Bead (ICPB) on fiber-reinforced fly ash-based geopolymer concrete. In this study, geopolymer concrete was produced using fly ash, NaOH, silicate, aggregate, and nylon66 fibers. Characterization of fly ash-based geopolymers (FGP) and fly ash-based geopolymer concrete (FRGPC) included chemical composition via XRF, functional group analysis via FTIR, compressive strength determination, flexural strength, density, slump test, and water absorption. The percentage of fiber volume added to FRGPC and FGP varied from 0% to 0.5%, and 1.5% to 2.0%. From the results obtained, it was found that ICBP fiber led to a negative result for FGP at 28 days but showed a better performance in FRGPC reinforced fiber at 28 and 90 days compared to plain geopolymer concrete. Meanwhile, NFRPGC showed that the optimum result was obtained with 0.5% of fiber addition due to the compressive strength performance at 28 days and 90 days, which were 67.7 MPa and 970.13 MPa, respectively. Similar results were observed for flexural strength, where 0.5% fiber addition resulted in the highest strength at 28 and 90 days (4.43 MPa and 4.99 MPa, respectively), and the strength performance began to decline after 0.5% fiber addition. According to the results of the slump test, an increase in fiber addition decreases the workability of geopolymer concrete. Density and water absorption, however, increase proportionally with the amount of fiber added. Therefore, diamond-shaped ICPB fiber in geopolymer concrete exhibits superior compressive and flexural strength.

The dataset for validation of factors affecting teachers' decision to integrate character values into curriculum.

The objective of this dataset is to examine the effect of factors of pedagogical content knowledge (PCK) and teachers' beliefs (TB) on teachers' decisions (TD) to select character values to integrate into the curriculum in primary school in Indonesia. The data propose that PCK factors and teachers' beliefs (TB) factors significantly influence TD. PCK factors consist of content knowledge (CK), pedagogical knowledge (PK), and pedagogical content knowledge (PCK). While, TB factors consist of Attitude (ATT), Subjective norm (SN), and perceived behavioural control (PBC). The survey approach obtained 50 responses from one public school and two private schools in Indonesia. After adapting the survey instrument, face and content validity were conducted. Further, to examine the validity and reliability of the measurement model, a Partial Least Squares Structural Equation Model (PLS-SEM) was applied. For this purpose, the statistical process presents the load of the reflection indicator, the reliability of internal consistency, and the validity of convergence and discrimination. The dataset consists of demographic information, PCK, beliefs on character values integration, and teachers' decision to select character values to integrate into the curriculum. The dataset is beneficial to curriculum developers, school principals, and teachers for measuring factors affecting teachers' decisions to integrate character values into the curriculum.

A State-of-the-Art Review on Innovative Geopolymer Composites Designed for Water and Wastewater Treatment.

There is nothing more fundamental than clean potable water for living beings next to air. On the other hand, wastewater management is cropping up as a challenging task day-by-day due to lots of new additions of novel pollutants as well as the development of infrastructures and regulations that could not maintain its pace with the burgeoning escalation of populace and urbanizations. Therefore, momentous approaches must be sought-after to reclaim fresh water from wastewaters in order to address this great societal challenge. One of the routes is to clean wastewater through treatment processes using diverse adsorbents. However, most of them are unsustainable and quite costly e.g. activated carbon adsorbents, etc. Quite recently, innovative, sustainable, durable, affordable, user and eco-benevolent Geopolymer composites have been brought into play to serve the purpose as a pretty novel subject matter since they can be manufactured by a simple process of Geopolymerization at low temperature, lower energy with mitigated carbon footprints and marvellously, exhibit outstanding properties of physical and chemical stability, ion-exchange, dielectric characteristics, etc., with a porous structure and of course lucrative too because of the incorporation of wastes with them, which is in harmony with the goal to transit from linear to circular economy, i.e., "one's waste is the treasure for another". For these reasons, nowadays, this ground-breaking inorganic class of amorphous alumina-silicate materials are drawing the attention of the world researchers for designing them as adsorbents for water and wastewater treatment where the chemical nature and structure of the materials have a great impact on their adsorption competence. The aim of the current most recent state-of-the-art and scientometric review is to comprehend and assess thoroughly the advancements in geo-synthesis, properties and applications of geopolymer composites designed for the elimination of hazardous contaminants viz., heavy metal ions, dyes, etc. The adsorption mechanisms and effects of various environmental conditions on adsorption efficiency are also taken into account for review of the importance of Geopolymers as most recent adsorbents to get rid of the death-defying and toxic pollutants from wastewater with a view to obtaining reclaimed potable and sparkling water for reuse offering to trim down the massive crisis of scarcity of water promoting sustainable water and wastewater treatment for greener environments. The appraisal is made on the performance estimation of Geopolymers for water and wastewater treatment along with the three-dimensional printed components are characterized for mechanical, physical and chemical attributes, permeability and Ammonium (NH4+) ion removal competence of Geopolymer composites as alternative adsorbents for sequestration of an assortment of contaminants during wastewater treatment.

Assessment of the Suitability of Ceramic Waste in Geopolymer Composites: An Appraisal.

Currently, novel inorganic alumino-silicate materials, known as geopolymer composites, have emerged swiftly as an ecobenevolent alternative to contemporary ordinary Portland cement (OPC) building materials since they display superior physical and chemical attributes with a diverse range of possible potential applications. The said innovative geopolymer technology necessitates less energy and low carbon footprints as compared to OPC-based materials because of the incorporation of wastes and/or industrial byproducts as binders replacing OPC. The key constituents of ceramic are silica and alumina and, hence, have the potential to be employed as an aggregate to manufacture ceramic geopolymer concrete. The present manuscript presents a review of the performance of geopolymer composites incorporated with ceramic waste, concerning workability, strength, durability, and elevated resistance evaluation.

The Effects of Various Concentrations of NaOH on the Inter-Particle Gelation of a Fly Ash Geopolymer Aggregate.

Aggregates can be categorized into natural and artificial aggregates. Preserving natural resources is crucial to ensuring the constant supply of natural aggregates. In order to preserve these natural resources, the production of artificial aggregates is beginning to gain the attention of researchers worldwide. One of the methods involves using geopolymer technology. On this basis, this current research focuses on the inter-particle effect on the properties of fly ash geopolymer aggregates with different molarities of sodium hydroxide (NaOH). The effects of synthesis parameters (6, 8, 10, 12, and 14 M) on the mechanical and microstructural properties of the fly ash geopolymer aggregate were studied. The fly ash geopolymer aggregate was palletized manually by using a hand to form a sphere-shaped aggregate where the ratio of NaOH/Na2SiO3 used was constant at 2.5. The results indicated that the NaOH molarity has a significant effect on the impact strength of a fly ash geopolymer aggregate. The highest aggregate impact value (AIV) was obtained for samples with 6 M NaOH molarity (26.95%), indicating the lowest strength among other molarities studied and the lowest density of 2150 kg/m3. The low concentration of sodium hydroxide in the alkali activator solution resulted in the dissolution of fly ash being limited; thus, the inter-particle volume cannot be fully filled by the precipitated gels.

The dataset for validation of factors affecting pre-service teachers' use of ICT during teaching practices: Indonesian context.

This dataset describes two main variables, technological pedagogical and content knowledge (TPACK) and Beliefs on ICT, which may affect pre-service teachers' (PSTs) use of ICT (UICT) during teaching practices. TPACK assumes that PSTs should actively combine some domains of knowledge to design good quality of ICT-integrated courses lessons. Beliefs on ICT in this study consist of a mix of behavioral, normative, and control beliefs on ICT integration in education. In addition, UICT is defined as ICT used by PSTs during teaching practices. Three approaches were applied for the purification of the dataset; development of instruments, survey, and exploratory factor analysis (EFA). The dataset consists of demographic information, TPACK, Beliefs on ICT, and UICT. The dataset is beneficial to teacher educators in designing effective programs that best nurture PSTs' UICT during teaching practices. Researchers sharing similar sample characteristics in developing countries may adapt this dataset for more rigorous statistical analyses.

Optimization of NaOH Molarity, LUSI Mud/Alkaline Activator, and Na2SiO3/NaOH Ratio to Produce Lightweight Aggregate-Based Geopolymer.

This paper presents the mechanical function and characterization of an artificial lightweight geopolymer aggregate (ALGA) using LUSI (Sidoarjo mud) and alkaline activator as source materials. LUSI stands for LU-Lumpur and SI-Sidoarjo, meaning mud from Sidoarjo which erupted near the Banjarpanji-1 exploration well in Sidoarjo, East Java, Indonesia on 27 May 2006. The effect of NaOH molarity, LUSI mud/Alkaline activator (LM/AA) ratio, and Na2SiO3/NaOH ratio to the ALGA are investigated at a sintering temperature of 950 °C. The results show that the optimum NaOH molarity found in this study is 12 M due to the highest strength (lowest AIV value) of 15.79% with lower water absorption and specific gravity. The optimum LUSI mud/Alkaline activator (LM/AA) ratio of 1.7 and the Na2SiO3/NaOH ratio of 0.4 gives the highest strength with AIV value of 15.42% with specific gravity of 1.10 g/cm3 and water absorption of 4.7%. The major synthesized crystalline phases were identified as sodalite, quartz and albite. Scanning Electron Microscope (SEM) image showed more complete geopolymer matrix which contributes to highest strength of ALGA produced.

The Effect of Various Waste Materials' Contents on the Attenuation Level of Anti-Radiation Shielding Concrete.

Samples of concrete contain various waste materials, such as iron particulates, steel balls of used ball bearings and slags from steel industry were assessed for their anti-radiation attenuation coefficient properties. The attenuation measurements were performed using gamma spectrometer of NaI (Tl) detector. The utilized radiation sources comprised 137Cs and 6°Co radioactive elements with photon energies of 0.662 MeV for 137Cs and two energy levels of 1.17 and 1.33 MeV for the 6°Co. Likewise the mean free paths for the tested samples were obtained. The aim of this work is to investigate the effect of the waste loading rates and the particulate dispersive manner within the concrete matrix on the attenuation coefficients. The maximum linear attenuation coefficient (µ) was attained for concrete incorporates iron filling wastes of 30 wt %. They were of 1.12 ± 1.31×10-3 for 137Cs and 0.92 ± 1.57 × 10-3 for 6°Co. Substantial improvement in attenuation performance by 20%-25% was achieved for concrete samples incorporate iron fillings as opposed to that of steel ball samples at different (5%-30%) loading rates. The steel balls and the steel slags gave much inferior values. The microstructure, concrete-metal composite density, the homogeneity and particulate dispersion were examined and evaluated using different metallographic, microscopic and measurement facilities.