Alkali Hydroxide Research Articles

Spalling of concrete caused by ASR – a review

A very well-known fact is that cracks in concrete members can allow water to enter the member, thus jeopardizing the concrete member integrity by changing the chemical composition of concrete and causing the aggregates to expand. This initiates the consequent chemical reactions that may evoke spalling of concrete thus creating a cycle of undesirable occurrences in concrete. As a final result, the concrete member can be deteriorated affecting the serviceability, but sometimes even leading the reduction of its load bearing capacity. An overlooked cause of concrete spalling of a chemical nature is the spalling caused by the Alkali-aggregate reaction. This is colloquially known as “concrete cancer”. It is a specific type of a reaction between alkali hydroxides and specific types of aggregate that occurs in concrete. Two main types of alkali-aggregate reactions are the alkali-silica reaction (ASR) and the alkali-carbonate reaction (ACR). The main goal of this research was to review the alkali-silica reaction in concrete as well as the mechanism of aggregate expansion it causes, which ultimately results in concrete spalling. Finally, the ways of prevention the alkali-silica reaction were reviewed and discussed.

Novel phenolate salts of bioactive agents: Cannabidiol phenolate salts

Bioactive phenolic compounds are commonly found in medications, with examples including apomorphine, estrone, thymol, estradiol, propofol, o-phenylphenol, l-Dopa, doxorubicin, tetrahydrocannabinol (THC), and cannabidiol (CBD). This study is the first to explore the creation and assessment of metal and ammonium phenolate salts using CBD as an example. CBD is used in medicine to treat anxiety, insomnia, chronic pain, and inflammation, but its bioavailability is limited due to poor water solubility. In this study exploit a synthetic route to convert CBD into anionic CBD-salts to enhance water solubility. Various CBD-salts with metal and ammonium counterions such as lithium (Li+), sodium (Na+), potassium (K+), choline hydroxide ([(CH3)3NCH2CH2OH]+), and tetrabutylammonium ([N(C4H9)4]+) have been synthesized and characterized. These salts are obtained in high yields, ranging from 74 % to 88 %, through a straightforward dehydration reaction between CBD and alkali metal hydroxides (LiOH, NaOH, KOH) or ammonium hydroxides (choline hydroxide, tetrabutylammonium hydroxide). These reactions are conducted in either ethanol, methanol, or a methanol:water mixture, maintaining a 1:1 molar ratio between the reactants. Comprehensive characterization using Fourier-Transform Infrared Spectroscopy (FT-IR), Nuclear Magnetic Resonance (NMR) spectroscopy, and elemental (CHN) analysis confirms the formation of CBD-salts, as evidenced by the absence of aromatic hydroxyl resonances or stretching frequencies. The molecular formulas of CBD salts were determined based on CHN analysis, and CBD quantification from acid regeneration experiments. Characterization data confirms that each CBD phenolate in a specific CBD salt was electrostatically stabilized by one of the either alkali metal or ammonium ion. The CBD-salts are highly susceptible to acidic conditions, readily reverting back to the original CBD. The percentage and purity of CBD in the CBD-metal/ammonium salts have been studied using High-Performance Liquid Chromatography (HPLC) analysis. Solubility studies indicate that the conversion of CBD into CBD salts significantly enhances its solubility in water, ranging from 110 to 1606 folds greater than pure CBD. Furthermore, the pharmacokinetic evaluation of oral administration of CBD-salts compared to CBD were determined in rats.

Molten salts for efficient removal of radioactive contaminants from stainless steel surface: Mechanisms and applications

Here, we have demonstrated an innovative decontamination strategy using molten salts as a solvent to clean stubborn uranium contaminants on stainless steel surfaces. The aim of this work was to investigate the evolutionary path of contaminants in molten salts to reveal the decontamination mechanism, thus providing a basis for the practical application of the method. Thermodynamic analysis revealed that alkali metal hydroxides, carbonates, chlorides and nitrates can react with uranium oxides (UO3 and U3O8) to form various uranates. Notably, the decontamination mechanism was elucidated by analyzing the chemical composition of the contaminants in the molten salts and the surface morphology of the specimens considering NaOH–Na2CO3–NaCl melt as the decontaminant. The decontamination process involved two stages: a rapid decontamination stage dominated by the thermal effect of molten salt, and a stable decontamination stage governed by the chemical reactions and diffusion of molten salt. Subsequently, a multiple decontamination strategy was implemented to achieve high decontamination rates and low residual radioactivity. Within the actual cleaning time of 30 min, the decontamination efficiency (DE) of UO3-contaminated specimens reached 97.8% and 93.0% for U3O8-contaminated specimens. Simultaneously, the radioactivity levels of all specimens were reduced to below the control level for reuse in the nuclear domain. Particularly, the actual radioactive waste from the nuclear industry reached a reusable level of radioactivity after decontamination. The NaOH–Na2CO3–NaCl melt outperforms conventional chemical solvents and may be one of the most rapid and efficient decontaminants for stubborn uranium contamination of metal surfaces, which provides insights in regard to handling nuclear waste.

Corrosion Inhibition of Aluminum Alloy (R408, R613) in Sodium Hydroxide Alkali Medium by Expired Drug of Ketoprofen

Corrosion Inhibition of Aluminum Alloy (R408, R613) in Sodium Hydroxide Alkali Medium by Expired Drug of Ketoprofen

Influence of Chemical Pretreatment on the Mechanical, Chemical, and Interfacial Properties of 3D-Printed, Rice-Husk-Fiber-Reinforced Composites

This article explores using biomass, namely rice husks, as a reinforcement material in thermoplastic copolyester (TPC) composites. Rice husks were subjected to three chemical pretreatments: single-stage sulfuric acid hydrolysis, first-stage sulfuric acid hydrolysis followed by a second-stage methanesulfonic acid (MSA) treatment, and first-stage sulfuric acid hydrolysis followed by a second-stage sodium hydroxide alkali treatment. We studied the effects of these treatments on the rheological, thermal, interfacial, and mechanical properties of composites. The fibers were mixed with polymers at high shear rates and temperatures, and 3D-printed filaments were produced using a desktop 3D printer. The printed parts were analyzed using tensile tests, torque and viscosity measurements, and thermogravimetric analysis to obtain their mechanical, rheological, and thermal properties. SEM imaging was performed to understand the fiber–polymer interface and how it affects the other properties. The results showed that first-stage sulfuric acid hydrolysis followed by a second-stage pretreatment of the fibers with MSA showed better fiber–polymer adhesion and a 20.4% increase in stress at 5% strain, a 30% increase in stress at 50% strain, and a 22.6% increase in the elastic modulus as compared to untreated rice husk composites. These findings indicate that readily available and inexpensive rice husks have significant potential for use in natural fiber-reinforced composites when pretreated using dilute sulfuric acid followed by methane sulfonic acid hydrolysis.

Activated Carbon as an Adsorbent: A Review

Activated carbon is highly porous with a large surface area for activity, thus making it highly adsorption efficient, and is usually derived from waste products. The proximate and ultimate analysis of agricultural waste material and chemical compositions such as hemicelluloses, cellulose, and lignin contents were also discussed. The authors reviewed chemical activators such as alkali hydroxides, KOH, phosphoric acid, zinc chloride, potassium carbonate, and NaOH used to produce activated carbon. A detailed explanation of the characterization techniques (SEM, FTIR, EDAX, BET, XRD etc.) for precursors and activated carbons are discussed. The effect of various parameters on adsorption efficiency of activated carbon is discussed. Wastewater containing different toxic dye contaminants causes serious environmental problems. Removal of various pollutants (SO2, NO2, H2S, CO2 etc.) using activated carbon were reviewed. In addition, the equilibrium adsorption data were fitted to Isotherm models for the determination of constants correlated to the adsorption phenomena was reviewed.

Hydroxylation-Depolymerization of Oxyphenylene-Based Super Engineering Plastics To Regenerate Arenols.

Super engineering plastics, high-performance thermoplastic resins, show high thermal stability and mechanical strength as well as chemical resistance. On the other hand, chemical recycling for these plastics has not been developed due to their stability. This study describes depolymerization of oxyphenylene super engineering plastics via carbon-oxygen main chain cleaving hydroxylation reaction with an alkali hydroxide nucleophile. This method is conducted with cesium hydroxide as a hydroxy source and calcium hydride as a dehydration agent in 1,3-dimethyl-2-imidazolidinone, which provides hydroxylated monomers effectively. In the case of polysulfone, both 4,4'-sulfonyldiphenol (bisphenol S) and 4,4'-(propane-2,2-diyl)diphenol (bisphenol A) were obtained in high yields. Other super engineering plastics such as polyethersulfone, polyphenylsulfone, and polyetheretherketone were also applicable to this depolymerization.

Hydrothermal Synthesis and Crystal Structure of Vesuvianite Compounds, Ca19Al13Si18O71(OH)7 and Sr19Fe12Ge19O72(OH)6

New compositions of synthetic vesuvianite were investigated using hydrothermal synthesis. High quality single crystals with the formula Ca19Al13Si18O71(OH)7 (I) having the vesuvianite-type structure were crystallized during a high temperature hydrothermal growth reaction. Starting materials of Al2O3 and CaSiO3 reacted at 670 °C and 2 kbar in 0.5 M aqueous alkali hydroxide mineralizer to form single crystals up to 0.25 mm per edge. Similar reactions employing SrO, Fe2O3, and GeO2 reacting at 580 °C and 2 kbar in 6 M aqueous alkali hydroxide mineralizers led to the formation of the analogous Sr19Fe12Ge19O72(OH)6 (II). These crystals were obtained in sizes up to 0.5 mm per edge. The structures of both compounds were refined in space group P4/nnc after careful evaluation of the diffraction data and subsequent test refinements. Elemental analysis indicated only the presence of Ca2+, Al3+, and Si4+ cations in I and only the presence of Sr2+, Fe3+, and Ge4+ cations in II, representing synthetic vesuvianite comprising the minimum number of unique cations. The use of larger cations than are typically found in natural vesuvianite, such as Sr2+, Fe3+, and Ge4+, resulted in an expanded crystalline lattice and extended the vesuvianite analogs to include an increasing variety of elements.

Phase-Engineering of Layered Nickel Hydroxide for Synthesizing High-Quality NiOx Nanocrystals for Efficient Inverted Flexible Perovskite Solar Cells.

Nickel oxide (NiOx) nanocrystals have been widely used in inverted (p-i-n) flexible perovskite solar cells (fPSCs) due to their remarkable advantages of low cost and outstanding stability. However, anion and cation impurities such as NO3- widely exist in the NiOx nanocrystals obtained from calcinated nickel hydroxide (Ni(OH)2). The impurities impair the photovoltaic performance of fPSCs. In this work, we report a facile but effective way to reduce the impurities within the NiOx nanocrystals by regulating the Ni(OH)2 crystal phase. We add different alkalis, such as organic ammonium hydroxide and alkali metal hydroxides, to nickel nitrate solutions to precipitate layered Ni(OH)2 with different crystalline phase compositions (α and β mixtures). Especially, Ni(OH)2 with a high β-phase content (such as from KOH) has a narrower crystal plane spacing, resulting in fewer residual impurity ions. Thus, the NiOx nanocrystals, by calcinating the Ni(OH)x with excess β phase from KOH, show improved performance in inverted fPSCs. A champion power conversion efficiency (PCE) of 20.42% has been achieved, which is among the state-of-art inverted fPSCs based on the NiOx hole transport material. Moreover, the reduced impurities are beneficial for enhancing the fPSCs' stability. This work provides an essential but facile strategy for developing high-performance inverted fPSCs.

Numerical Study of CO2 Removal from Inhalational Anesthesia System by Using Gas-Ionic Liquid Membrane

Inhalational anesthesia is supplied through an assisted ventilation system. It is mostly composed of xenon or nitrous oxide, halogenated hydrocarbons (HHCs), and oxygen. In order to reduce costs of the anesthesia compounds, the remaining anesthetics present in exhalation are recycled and reused, in order to minimize the amount of fresh anesthesia. An alkali hydroxide mixture (called soda lime) is employed in order to remove CO2 from the exhalation. However toxic compounds may be formed during the reaction of soda lime with halogenated hydrocarbons. Ionic liquids (ILs) have several advantages such as non-volatility, functionality, high carbon solubility, and low energy requirements for regeneration. In the framework of this research, carbon dioxide removal with ionic liquids has been numerically studied. COMSOL multi-physics finite element software has been applied. It solves the continuity, fluid flow, and diffusion equations. A new algorithm has been developed for calculating the infrared (IR) radiation absorption of CO2. Its absorption coefficient has wavelength-dependent properties. The gaseous absorption coefficient has been calculated by using HITRAN spectral database. It has been found that the CO2 is absorbed almost completely by the 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]) ionic liquid after a period of 1000 s. It has been shown that the absorption coefficient of CO2 can be neglected in the interval below 1.565 μm, and then at 1.6 μm, it increases to the same order as that for CO. Thus, it is possible to detect CO2 by applying a laser diode which is capable to transmit IR radiation at a wavelength of 1.6 μm. This time period is a function of the diffusion coefficient of the CO2 in the membrane and in the ionic liquid.

Mitigation of efflorescence, drying shrinkage and water demand of calcined clay-based geopolymers with biological waste ashes as activator and hardener

Uncertainties associated with durability and sustainability of geopolymer due to formation of efflorescence, shrinkage and activator cost are setbacks for its real-life applications. Therefore, the aim of this study was to produce geopolymers with improved durability and sustainability using local kaolin clay as precursor, cocoa-pods-ash (CPA) as alternative alkali hydroxide activator, periwinkle-shells-ash (PSA) as hardener and quarry-dust (QD) as filler. Local kaolin clay calcined at 700 °C (M7C), was replaced with some fractions of CPA and activated with only Na2SiO3 to produce binders (CPAG). The PSA was added to the best fit of M7C/CPA as fast-setting-agent, while QD was added to the best fit of M7C/CPA/PSA to produce mortars. 100% kaolin clay activated with 8MNaOH/Na2SiO3 was used as reference geopolymer. The geopolymers were cured at R.T for 7 and 28 days and characterised for physical, mechanical and durability properties. Clay, CPA, PSA, QD and geopolymers were characterised using XRF, ATR-FTIR and XRD. Reactivity was studied using isothermal conduction calorimetry. The ATR-FTIR and XRD results indicated transformation of kaolinite to metakaolinite in the clay, presence of K-C-O bond in CPA and O-C-O bond in PSA. Reference geopolymers set at 4 h while CPAG ranged from 14 to 19 h. With the addition of PSA, setting time reduced to values between 4 and 11 h. The compressive strength of reference geopolymer was 18.1 ± 0.3 MPa at 28 days, while CPAGs values ranged from 23.5 ± 0.3 to 35.6 ± 0.3 MPa. Best compressive strength was achieved with 2% PSA addition. No shrinkage in CPA-containing geopolymers while reference geopolymer had value of 0.03%. Efflorescence tendencies of the CPA-containing geopolymers reduced by 25–75% when compared with reference. Application of CPA as alternative activator improved the mechanical property, durability and sustainability of geopolymers.

Highly Utilized Active Sites on Pt@Cu/C for Ethanol Electrocatalytic Oxidation in Alkali Metal Hydroxide Solutions

AbstractUsing ethanol electrocatalytic oxidation reaction (EOR) with a lower reaction potential to replace oxygen evolution reaction (OER) and integrating hydrogen evolution reaction (HER) have a promising development prospect for more energy‐saving electrolytic hydrogen production. However, the main challenges of EOR are insufficient catalytic activity, high overpotential, and slow kinetics. Active sites on the electrocatalysts surface are occupied by alkali metal ion hydrate clusters by noncovalent interactions, which is considered to be one of the major causes of these challenges. To reduce the effect of the noncovalent interactions on the catalytic activity of the electrocatalyst, copper is chosen and doped in the form of a single atom in the electrocatalyst (Pt@Cu/C) to increase the electrocatalyst conductivity and make the anode contain more positive charge in this study. Then, alkali metal ion hydrate clusters are difficult to adsorb at the active site of Pt@Cu/C. The EOR electrocatalytic activity of Pt@Cu/C is up to 8184 mA mgPt−1, which is ≈4.8 times as high as that of Pt/C. The two‐electrode hydrogen production device using Pt@Cu/C as anode for coupled EOR&HER requires a smaller voltage of 0.60 V to reach 10 mA cm−2compared with that of Pt/C (0.76 V).

Analyzing the bleaching effects of activated carbon produced from natural coal on soyabean oil and Goya olive oil

Many contaminants, such as phosphatides, mucins, free fatty acids, dyes, and compounds that impact the color and odor, are present in crude fats and oils in variable concentrations. The standard chemical refining process removes these contaminants at numerous stages, including activation, carbonization, filtration, absorption, degumming, neutralization, and bleaching. While degumming is done to remove phosphatides so that hydratable phosphatides can be precipitated by adding water to the oil, non-hydrated phosphatides must be eliminated by adding acids, activation is done to open up the pore structure of the activated carbon. Additionally, free fatty acids are eliminated through neutralization with alkali hydroxides, producing soaps that can be eliminated, and undesirable colored impurities are eliminated through bleaching with an adsorptive reagent. Subsequently, the unwanted compounds are adsorbed and can be eliminated along with the adsorbent through filtration. Then, bleaching is done to get rid of color and unwelcome volatile and odiferous elements because bleaching removes numerous antioxidants. The equilibrium concentration, values for Ce/qc, b, and slopes for soybean oil and goya olive oil were calculated using the Langmuir isotherm equation. Ce/Qc = 1.Ce/Qo + 1/bQo, Ce = equilibrium concentration, Qc = percent absorption, 1/Qo = slope, Qo = adsorption capacity, and b = Langmuir constant. The results of % absorption obtained for soyabean oil are as follows; 86.90, 85.90, 86.90, 79.70, 78.40 and 29.60 while the results % absorption obtained for goya olive oil are 86.10, 84.10, 82.90, 81.80, 77.70, and 77.50 respectively. Based on their near range of adsorption capacities, it was concluded that activated coal was successful in bleaching both soyabean oil and goya olive oil. However, the activated coal had a little higher adsorption capacity on goya olive oil than soya bean oil.

Kinetics of base-promoted transformation of berberrubine-cucurbit[7]uril inclusion complex: Active role of alkali cations

A pH-responsive inclusion complex was created from berberrubine, a pharmacological active natural isoquinoline alkaloid and cucurbit[7]uril (CB7) macrocycle exploiting the more than four orders of magnitude larger binding affinity of the cationic guest (BOH+) compared to the deprotonated uncharged conjugate base (BO). Since only the CB7-encapsulated BOH+ emitted strong fluorescence, the transformation of this host–guest complex could be selectively monitored in real time by stopped-flow measurements. Alkali cations accelerated the exit of BOH+ from the CB7 cavity in a pseudo-first order reaction and their impact grew with the ion radius. In contrast, the gradual rise of alkali hydroxide concentration brought about parabolic increase in the apparent rate constant of the deprotonation of the CB7-embedded BOH+ and the reaction had the partial order of 1 with respect to alkali and hydroxide ions alike. LiOH induced the proton loss of the BOH+-CB7 complex much more efficiently than NaOH or KOH. These unexpected findings highlight the active role of alkali cations in the control of the kinetics of pH-responsive guest release from CB7 and provide a new way for the tuning of the temporal behavior of base-induced transformations of host–guest complexes.

CO2 electroreduction to multicarbon products from carbonate capture liquid

CO2 electroreduction to multicarbon products from carbonate capture liquid

Guest Editorial: Is CO2 Removal Technology Key to a Sustainable Future?

_ The urgent need to address climate change has unleashed a wave of innovative ideas on how to mitigate the greenhouse gas (GHG) emissions that are driving the problem. Among the approaches considered to hold great promise is carbon dioxide removal, or what some call negative emissions technologies. These strategies have attracted significant attention in recent years and involve removing carbon dioxide (CO2) from the atmosphere and storing it in long-term sinks such as oceans, forests, and underground geological formations. What follows is a closer look at how these strategies work, their potential to address the global climate crisis, and the challenges they currently face. Direct Air Capture (DAC) This technology captures CO2 directly from the air using chemical reactions and/or physical processes. The captured CO2 can then be stored in a long-term sink, used for food processing and cement manufacturing, or combined with hydrogen to create synthetic fuel. There are currently about 20 direct air capture plants operating worldwide. Climeworks’ Orca plant in Iceland, the largest operating DAC plant in the world, has the capacity to remove 4,000 tons of CO2 per year and store it deep underground. The majority of commercial direct air carbon capture techniques utilize large fans to force ambient air through a filter, with a liquid solvent, often amine-based or caustic, being used to absorb CO2 from the gas. There are three chemical processes that are being studied extensively for purposes of DAC: causticization using alkali and alkali-earth hydroxides, carbonation, and organic-inorganic hybrid sorbents consisting of amines supported in porous adsorbents. Additionally, others are exploring membrane separation methods based on semipermeable membranes to capture CO2, which require less water and a smaller footprint. Perhaps the biggest challenge facing this technology’s ability to scale up lies in its ability to be economically successful given current carbon credit pricing regimes balanced with the unknown amount of energy DAC units will need to achieve meaningful capture volumes. Ocean Fertilization The aim of ocean fertilization (OF) strategies is to enhance certain biological processes in the oceans that will lead to increased uptake of atmospheric CO2 followed by permanent storage in deep oceanic layers. The technique involves the addition of nutrients such as iron, phosphorus, and nitrogen to the ocean for stimulating the growth of phytoplankton that absorb CO2 from the atmosphere. When the marine species die, they sink to the ocean floor, taking the absorbed CO2 with them, where it is stored permanently. However, the implementation of OF has not been thoroughly studied and there are limited long-term experiments. Additionally, certain OF storage approaches are subject to reversibility. In other words, the stored carbon may not remain sequestered permanently and could be released back into the atmosphere due to the constant changes in ocean conditions such as temperature or nutrient availability. This issue highlights the need for caution and thorough study before implementing OF as a carbon dioxide removal strategy. The Convention on Biological Diversity and the London Protocol have called for appropriate regulations and assessments of risks and impacts related to climate-related geoengineering and OF.

Synthesis of 2-Amino-2-deoxy-β-d-mannosides via Stereoselective Anomeric O-Alkylation of 2N,3O-Oxazolidinone-Protected d-Mannosamine: Synthesis of the Trisaccharide Repeating Unit of Streptococcus pneumoniae 19F Polysaccharide.

Cesium carbonate-mediated stereoselective anomeric O-alkylation of a 2N,3O-oxazolidinone-protected d-mannosamine with sugar-derived primary or secondary alkyl triflates afforded the corresponding 2-amino-2-deoxy-β-d-mannosides in moderate to good yields and excellent stereoselectivity. The oxazolidinone ring can be opened with aqueous alkali hydroxide to liberate the amine functionality. This method has been successfully applied to the synthesis of the trisaccharide repeating unit of Streptococcus pneumoniae 19F polysaccharide.

Erratum: A new method for determining protein solubility index (PSI) based on extraction with 5 mM alkali hydroxide and its correlation with trypsin inhibitor activity in soybean products

Erratum: A new method for determining protein solubility index (PSI) based on extraction with 5 mM alkali hydroxide and its correlation with trypsin inhibitor activity in soybean products

Minimum flexural reinforcement of fly ash and GGBS based geopolymer concrete members

Geopolymer concrete is a relatively new binder material that can replace cement in concrete. Fly ash is activated in the presence of alkali activator (combination of alkali Silicate and alkali hydroxide) that binds the fine aggregate and coarse aggregate in geopolymer concrete. These concretes need temperature curing to the extent of 60 °C for about 24 h. The temperature curing to this extent is difficult in conventional construction practices. Many researchers have reported that fly ash and ground granulated blast furnace slag (GGBFS) based geopolymer concrete can be cured in the room temperature and can develop desired strength. With this advent, research in the direction of geopolymer concrete in respect of mechanical strength characteristics like tensile strength, compressive strength and modulus of elasticity, mix design and confinement aspects of geopolymer concrete, is increasing. This paper presents the behavioural aspects of reinforced geopolymer concrete members subjected to flexural loading. Three different proportions of geopolymer concrete with target 28-day compressive strength of 30 MPa, 45 MPa and 60 MPa were developed. The test results indicated that minimum flexural reinforcement is needed in geopolymer concrete beams to avoid brittle failure and controls the cracking. Minimum flexural reinforcement is needed to maintain the integrity of the reinforced concrete members even after the tensile resistance of concrete is exhausted. Thus, an expression for the minimum flexural reinforcement needed in beams is proposed.

Expandable Geopolymers Improve Zonal Isolation and Plugging

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 212493, “Expandable Geopolymers for Improved Zonal Isolation and Plugging,” by Foster D. Gomado, SPE, Mahmoud Khalifeh, SPE, and Jan A. Aasen, SPE, University of Stavanger. The paper has not been peer reviewed. _ The sealability performance of an expanding geopolymer (E-GP) is compared with that of an expansive commercial cement (EC) with regard to shear bond strength (SBS) and hydraulic bond strength (HBS) at curing conditions of 25°C and 34.5 bar. A neat Class G (NG) cement and a neat geopolymer (N-GP) were characterized alongside corresponding expansive versions. The effect of these expansive agents on cement and geopolymers was evaluated in terms of linear expansion using the annular ring test. The complete paper reveals that geopolymers can be deployed as an alternative to Portland cement upon optimization. Geopolymer Characteristics and Use In recent years, geopolymers have been receiving attention as a viable and environmentally friendly alternative for zonal isolation and plugging and abandonment (P&A) operations because of their robust features such as higher strength, lower permeability, and durability in high-pressure/high-temperature conditions. Geopolymers can be described as binders formed by a chemical reaction between aluminosilicate materials and alkali hydroxide or soluble silicates. In this study, cement/casing bonding properties are the primary focus. Greener options for cementing, zonal isolation, and P&A must meet acceptable criteria before mass adoption. Geopolymers, like Portland cement, experience shrinkage to some extent. To improve cement bonding, expansive agents are regarded as relevant additives, correlating volume changes to bonding properties, mostly SBS. In the case of geopolymers, few studies have been directed toward the study of volumetric changes with and without expansive additives. The current literature for geopolymers lacks correlation between the performance of expansive agents on geopolymers in terms of HBS, SBS, and load-to-displacement profile. Thus, the authors explored the effect of expansive agents on SBS and accompanying interfacial friction and hydraulic sealability for both NG and EC, as well as neat geopolymers and expansive versions at equal conditions. Experimental Procedures NG cement was used as a reference because it is the most widely used cement in the Norwegian North Sea. The EC was made by the addition of a commercially available expansive agent [made of a blend of calcium oxide (CaO) and quartz] to NG at a concentration of 5% by weight of cement (BWOC). The geopolymer deployed in this study was synthesized in house. The E-GP was synthesized by the addition of a calcium salt in a concentration of 1.1% of the solid precursors. The complete paper details slurry preparation and the methodology for linear-expansion (shrinkage) tests, SBS/bond slip tests, and HBS tests.