Alkaline Attack Research Articles

Cesium stabilization by engineered alkaline attack of glass for pharmaceutical containers

An innovative method for immobilizing cesium has been developed through the alkali activation of boro-alumino-silicate glass. Glass powders from discarded pharmaceutical vials, suspended in CsOH-based activating solutions yield cementitious matrices upon drying at nearly room temperature. Solid blocks are formed through bridging of adjacent particles by condensation reactions in hydrated surface layers. Silicates, borates, and aluminates released into the solution, along with atmospheric CO2 interact with Cs+ and NH4+ ions, forming additional phases, with various chemical stability. When exposed to boiling water the blocks are stable. Boro-pollucite (CsBSi2O6) formed as the result of chemical reactions in the system is stable and does not dissolve. However, boiling results in dissolution of cesium carbonate. A mixed attack by CsOH-NH4OH instead of CsOH reduces the formation of cesium carbonate, maximizing the immobilization of cesium in a stable matrix.

Enhancing Concrete Durability: Sustainable Ternary Blends Incorporating Agricultural and Industrial Wastes

<p>The demand for sustainable concrete in civil infrastructure operations grows by the day, resulting in the use of agricultural and industrial byproducts and controlling high-cost nanomaterials. Ternary blended concrete is an excellent alternative to conventional concrete for long-term development by lowering carbon footprint. Ternary blended concrete is a green and sustainable concrete made from three separate source components to make a binder. The fundamental benefit of ternary mixed concrete is its densely packed particles of various shapes and sizes, resulting in superior characteristics. This study discusses experimental studies that were conducted to assess the durability properties of regular ordinary Portland cement (OPC) concrete and ternary blended concrete containing 1% nano-SiO2 and industrial or agricultural byproducts. Concrete durability is defined as its capacity to sustain a safe degree of serviceability and various environmental exposure circumstances without requiring considerable repair or rehabilitation during its service life. Conventional concrete is prone to cracking because of its low tensile and durability properties. Six potential mixes were investigated in this work: three blends based on industrial byproducts (fly ash, ground granulated blast furnace slag, and metakaolin) and three mixes based on agricultural byproducts (rice husk ash, corncob ash, and sugarcane bagasse ash). This study investigated the durability characteristics such as water permeability, sorptivity, resistance to sulphate, acid attack, and alkaline attack. The experimental test findings were determined to be well within limitations when compared to the requirements specified in the standard/literature. The study also shows that ternary blended concrete with regulated nano-SiO2 enhances durability metrics significantly. Furthermore, energy dispersive spectrophotometry (EDS) measurements show dense phases with high proportions of Si atoms in the substrate's penetration layer. As a result, ternary mixed concrete is strongly advised in structural repair works.</p>

Enhancing alkaline resistance of concrete using alccofine and metakaolin in mineral admixtures of sustainable development

Addressing the need for sustainable construction materials that minimize environmental impact and reduce CO2 emissions, particularly in OPC compositions. Assessing alccofine and metakaolin in OPC compositions to determine their impact on concrete strength, durability, and microstructure in alkaline environments for sustainable material development. Experimental investigation involved incorporating alccofine and metakaolin into OPC concrete mixes, creating binary and ternary blended systems. Modified concrete specimens were subjected to various alkaline attacks using diluted solutions of magnesium sulfate (MgSO4), sodium sulfate (Na2SO4), and sodium chloride (NaCl) both individually (5%) and in combination (2.5%), resulting in significant improvements in concrete strength and durability. The modified concrete exhibits enhanced resistance to alkaline attacks, reduced weight and compression strength loss, and superior performance in Base Durability Factor (BDF) and Base Attack Factor (BAF) compared to conventional specimens. Scanning electron microscopy (SEM) study of the altered concrete’s microstructure shows that it has a densely packed microstructure, which increases its load-bearing capability. Mineral admixtures aid pore clogging, leading to denser, more alkali-resistant concrete due to finer particles. Notably, Alccofine and metakaolin offer effective solutions for sustainable construction materials, aiding in the decrease of CO2 releases during cement production and addressing critical gaps in sustainable material development.

Durability studies on concrete with partial replacement of cement and coarse aggregate by seashell waste

A sea animal creates a hard, protective outer layer called a seashell. Empty seashells frequently wash ashore, and beachcombers find them. This marine byproduct can be used in concrete as a replacement for cement or aggregate. This study describes the use of seashell products as a partial substitute for cement and coarse aggregate in the production of sustainable concrete to evaluate the durability characteristic of concrete. Various percentages of seashell trash were substituted for the cement and coarse aggregate by weight of the concrete. Water absorption, sorptivity and rapid chloride permeability on the seashell concrete were performed experimentally. Additionally, sulphate and alkaline attack as marine environment were studied for seashell concrete specimens immersed in chemical solution for 90 days. The seashell concrete's durability traits were contrasted with those of a control specimen. It is concluded that the optimum percentage of replacement of cement and coarse aggregate by seashell powder (SP) and seashell aggregate (SA) are 10% and 20% respectively to obtain durable concrete.

Influence of nano zirconia on the mechanical and durability properties of high-performance concrete containing nano-silica

High Performance Concrete (HPC) was prepared by reinforcing with hybrid nanoparticles such as nano-SiO2 and nano-ZrO2 and the flowability, strength and durability of the concrete was investigated. Slump study showed that the prepared HPC displayed a slump loss with the addition of hybrid nanoparticles due to the absorption of water by hybrid nanoparticles. Experimental results showed that the inclusion of 10% nano-SiO2 and 5% nano-ZrO2 hybrid nanoparticles (mix code M5) enhanced the compressive strength of concrete and exhibited a maximum of 50.12 MPa and 76.4 MPa at 7 days and 28 days of curing due to the reduction of pore volume. Split tensile strength followed the same trend of variation as compressive strength and the mix code M5 showed the maximum split tensile strength of 5.33 MPa and 7.08 MPa cured at 7 days and 28 days respectively. Flexural study resulted that the mix code M5 exhibited a maximum flexural strength of 5.73 MPa and 7.38 MPa cured at 7 days and 28 days respectively owing to the restriction of crack ignition by reinforced hybrid nanoparticles. Rheological study reported that all the prepared concretes lost the weight by less than 1% and the chloride attack displayed maximum weight loss of 4% whereas alkaline attack showed less weight of concrete.

Application of Coffee Husk Ash as Partial Replacement of Fine Aggregate in Concrete

The task of turning agricultural waste into practical construction and building materials has been placed before civil engineers. Coffee husk is produced in vast amounts due to the global commerce of coffee beans, which are incinerated into ash when used as fuel, producing coffee husk ash (CHA). Even though many researchers have worked on the utilization of CHA in concrete, they have been used as partial cement replacement but not as a replacement of aggregates. The experimental study of the performance of concrete on fine aggregate replaced partially with CHA is represented in this paper. The fine aggregate is replaced by 0%, 2%, 4%, 6%, and 8% by weight of CHA. The performance of the partially replaced fine aggregate with CHA is reviewed by considering the compressive strength and workability of fresh concrete and the splitting tensile strength, flexural strength, durability under acid and alkaline media, thermal conductivity, and rapid chloride permeability test of hardened concrete. The results indicate that the partial replacement of fine aggregate with 4% of CHA (CHA04) in concrete provides a positive impact to all the selected performance parameters. The compressive strength, flexural strength, and splitting tensile of the CHA04 mix were 43.4 MPa, 3.7 MPa, and 2.44 MPa, respectively, which were 28.4%, 19.35%, and 1.66%, respectively, greater than normal concrete mix (CHA00). Even the study of acid and alkaline attack on the CHA04 mix showed lesser strength reduction as compared to other mixes. The RCPT showed less chloride permeability, and the thermal conductivity is higher for CHA04, indicating lesser voids compared to other mixes. With the help of this investigation, it can be said that fine aggregate replacement with 4% CHA has the best strength and durability properties compared to regular concrete.

Fly-ash-based geopolymer modified by metakaolin for greener grouting material

Fly ash usually requires high-temperature maintenance owing to its low volcanic ash activity, which greatly limits its application. In this study, fly-ash-based geopolymer grouting materials were prepared by modifying them with suitable alkali activators and metakaolin at room temperature. The results of the orthogonal experiments showed that the content of metakaolin had the most significant effect on the 1-, 7- and 28-day mechanical properties of the material. The optimum mix proportion was determined as metakaolin content (m MK/m P) = 15%, sodium silicate modulus (M s) = 1.0 and sodium silicate content (m SS/m P) = 50%. The compressive strengths of the materials at 1, 7 and 28 days were 12.6, 24.9 and 36.3 MPa, respectively. The results of X-ray diffraction, Fourier transform infrared spectroscopy, mercury intrusion porosimetry and scanning electron microscopy showed that the reaction mechanism of fly ash was subject to a bidirectional alkaline attack. Meanwhile, the unreacted fly ash particles proved the inertness of fly ash, while metakaolin mostly dissolved and formed hydrated sodium aluminosilicate gel to increase the mechanical strength of the geopolymer. The material developed in this study can meet the specification requirements of inorganic cementitious material for road grouting in terms of compressive strength and fluidity, increasing the usage of fly ash and contributing to environmental protection.

An Experimental Study on Recycled Aggregate Concrete With Partial Replacement of Cement With Flyash and Alccofine

Recycled aggregates are the aggregates which are collected from the construction and demolition waste. Now a day the demolition waste production is more, due to this the environment gets polluted. So the use of recycled aggregates in the place of natural aggregates will decrease the waste accumulation. The scope of using recycled aggregates increasing day by day because of that the cost will decrease effectively. The main focus of this paper is to find the strength qualities of recycled aggregates so as to use it as an alternative for the natural aggregates and fly ash and alccofine are used for the partial replacement of the binding material for an M40 grade concrete. Here concrete is made with replacement of natural aggregates with recycled aggregates (25%, 50%, 75% and 100%), partial replacement of cement with a fly ash (25%) and alccofine (0%, 5%, 10% and 15%). Mix design of binary blended recycled aggregate concrete is done by using IS: 10262-2019. Workability is measured and mechanical properties like compressive strength, flexure and split tensile strength were determined for 7days and 28 days. Alkaline attack is evaluated after 28 days of NaOH solution curing. It is observed from the test results mechanical properties of the concrete is decreased if recycled aggregate & alccofine content.

Upcycling of Boro-Alumino-Silicate Pharmaceutical Glass in Sustainable Construction Materials

The present Covid-19 emergency has dramatically increased the demand for pharmaceutical containers and the amounts of related waste. This paper aims at presenting the upcycling of discarded pharmaceutical glass into various porous ceramics, starting from the activation of fine powders suspended in weakly alkaline solutions (2.5 M NaOH/KOH). The alkaline attack determines the gelation of glass suspensions, according to hydration of glass surfaces, followed by condensation starting from 40 °C (‘cold consolidation’). Alkali are mostly expelled from the gel, according to the formation of water-soluble hydrated carbonates. The mutual binding of activated powders was exploited for the encapsulation of waste-derived glass (from the plasma processing of municipal solid waste) and quartz sand as coarse aggregate. Moreover, industrial mud could be used instead of water in the preparation of alkaline solutions. Depending on the formulations, products comparable to facing bricks can be obtained directly after cold consolidation or after application of low temperature (700 °C) firing. In addition, selected formulations led to highly porous glass foams, to be used for thermal and acoustic insulation.

Engineering properties and microstructure of a sustainable roof tile manufactured with waste rice husk ash and ceramic sludge addition

Clay replacement with waste rice husk ash (RHA) and ceramic sludge (CS), helps to reduce the consumption of natural clay and solves the ecological issues created by waste disposal. In this study, properties of waste RHA and CS added fired clay tile were investigated, focusing on structural, durability, thermal performance as well as the water quality of the harvested run-off from fired clay roof tiles manufactured in an industrial scale plant. Tiles were cast by clay replacement with waste RHA and CS in four mixtures: 10 %RHA and 0 % CS, 10 % RHA and 10 % CS, 10 % RHA and 15 % CS, and 10 % RHA and 20 % CS (by weight). For 10 %RHA and 10 %CS tiles, dry mass was reduced by 4.9 %, compared with conventional roof tiles, promising a light weight roof tile. Roof tiles with 10 % RHA and 10 %CS showed a transverse breaking load of 1519 N, whereas that of 20 %CS tiles showed 1427 N, indicating that a further 6.5 % strength improvement can be achieved with clay replacement with a combination of two waste materials. Clay replacement with 10 % RHA and 10 % CS resulted in water absorption of 15.25 %. When increasing the clay replacement with combined waste from 10% (10 %RHA and 0%CS) to 30 % (10%RHA and 20 %CS), weight gain due to acid and alkaline attacks reduced from 3.5% to 3.0%, and from 2.2 % to 1.6 %, respectively, indicating enhanced durability performance by incorporating combined waste. High porosity, also confirmed by SEM, contributed to enhanced thermal performance: tile with 10 % RHA and 10 % CS achieved 4.4 °C temperature reduction, compared to the conventional tile. pH value and total solid concentration of run-off water were in the range of recommended values of water for agricultural purposes, ensuring that the collected run-off can be utilized as an alternative water source for potable activities.

Highly aligned growth of carbon nanotube forests with in-situ catalyst generation: A route to multifunctional basalt fibres

Hierarchical fabrics are gaining ever-growing practical interest, thanks to the possibility of combining different properties into a single textile, particularly useful for applications such as high-performance composites showing in situ structural health monitoring capabilities. In this study, homogeneously aligned carbon nanotube forests are directly grown on basalt fabrics by a fast (∼15 min) chemical vapour deposition process without any external catalyst addition providing, for the first time, a highly dense coverage of the underlying substrate. It is demonstrated by transmission electron microscopy that the direct growth of nanotubes on basalt fibres is catalysed by the microstructural segregation of ferrous iron and its subsequent reduction in hydrogen atmosphere to nanocrystalline metallic iron. It is shown that in situ growth requires a pre-treatment etching which can be conducted in mild basic or acidic conditions, achieving optimum performance with an alkaline attack, without compromising the tensile strength of the fibres. Post-growth Raman analysis shows characteristic features associated with high graphitic ordering which turn an intrinsically insulating substrate into an electrically conductive (∼260 S/m) fabric, thus suggesting the possibility to employ the newly engineered hierarchical fabric in all those applications where the combination of good mechanical properties and electrical conductivity is a key requirement.

Influence of natural fiber in the mechanical and durability behaviour of hybrid fiber-reinforced concrete

ABSTRACT Cracks developed due to drying and shrinkage in plain cement concrete can be overcome by introducing discreet and randomly oriented fibrous material as a reinforcing agent. Researchers focused only on synthetic fiber-reinforced concrete (FRC) most of the time while neglecting natural FRC. Previously, researchers focused on double hybrid FRC, whereas triple hybrid FRC required a further behavioral study on FRC’s mechanical characteristics. The primary objective of this study is to enhance mechanical properties of matrix due to the effect of short fiber in randomly oriented without changing their individual identity. Here, sisal fiber (SF), banana fiber (BF), and human hair fiber (HH) are used as reinforcing agents with varying volume fractions ( from 0.5% to 2% and a hybrid of 1% with concrete matrix. This investigation found that BF 0.5%, SF 1.5%, HH 1%, and H6 (SF0.25BF0.5HH0.25) % showed the optimum volume fraction, which improved mechanical properties and resisted sulfate and alkaline attack on the concrete matrix. Product from individual and combined natural FRC could be a sustainable building material that is economical, eco-friendly, and durable.

Mechanical performance and durability of banana fibre and coconut coir reinforced cement stabilized soil blocks

Agricultural waste disposal is said to be amongst one of the pressing environmental problems in many countries. Finding economical usage for this waste by incorporating it in a product is the approach often used to overcome associated environmental issues. Banana fibre and coconut coir are major agricultural waste products in Sri Lanka and fewer amounts of these are converted into usable products. Manufacturing cement-stabilized soil blocks incorporating these waste materials is envisaged to reduce environmental impact. The present study focused on the post-peak behaviour and durability of banana fibre and coconut coir-strengthened cement-stabilized soil blocks. Banana fibre and coconut coir reinforced cement-stabilized soil blocks were tested for compression, flexural bending, water absorption, sorptivity, resistance against chemicals, wet-dry weathering and freeze-thaw weathering. The banana fibre showed better post-peak behaviour in compression and coconut coir showed better post-peak behaviour in flexural. Both fibre reinforcements improved durability of cement block against acid attack, alkaline attack, wet-dry weathering and freeze-thaw weathering. Moreover, the specimen reinforced with coconut coir was found to exhibit better durability compared to the specimen reinforced with banana fibres.

Durability studies on ready mix concrete using mineral admixtures and manufactured sand

To meet the intensifying demand of fine aggregate in construction sector, manufactured sand has become a viable alternative to the river sand. Ready mix concrete (RMC) is playing vital role in fast-track construction particularly in Tire-II cities in India. The strength and durability concerns about using 100% manufactured sand along with mineral admixtures in RMC plant needs to be addressed through suitable experimental demonstrations. This research gives the experimental results on strength and durability studies of concrete carried out on samples obtained from RMC Plant by making use of manufactured sand containing (50% of crushed sand and 50% of the crushed rock fines) as replacement for natural sand. Trials on partial replacing cement with fly ash content of 33% and GGBS of 40% has also been carried out. Compressive and split-tensile strength studies were conducted on cubes (150mmx150mmx150mm) and cylinders (150mmx300mm) at 7, 14 & 28 days of curing. Non-Destructive tests such as Ultra Sonic Pulse Velocity (UPV) and rebound hammer tests were conducted to assess the quality of these mixes. Durability tests were conducted and comparison of the % of loss in mass and % of loss in strength for concrete samples subjected to acid attack, sulphate attack, alkaline attack tests were also carried out. Rapid chloride permeability test (RCPT) was conducted to check the concrete resistance against chloride ions penetration. The experimental results revealed that the use of 100% manufactured sand along with mineral admixtures in producing ready mix concrete is a good choice in view of the non-availability of river sand to meet the demands of fast-track construction projects.

Accelerated Alkaline Attack of 3D Printing Polymers to Assess Their Durability in Geopolymer-Based Matrices

Geopolymers exhibit high mechanical performance and low CO2 emissions, and have garnered interest in the construction sector. The brittleness of geopolymer matrices has led to a demand for materials to reinforce them and make them suitable for applications involving tensile or dynamic loading, such as reinforcements produced with 3D printing. However, the durability of polymers currently used in 3D printing in geopolymer matrices is unknown. The properties of polylactic acid (PLA) and poly(ethylene terephthalate)-glycol (PETG), when immersed in an alkaline solution that simulates the pore water of geopolymer matrices, were assessed with weight monitoring, Fourier transform infrared spectroscopy, thermal analysis, and direct tensile tests. The results showed that new carbonyl compounds are formed in the extension of the polymeric chains, which could be associated with the oxidation of the chains. PLA presented a weight loss of 35.83% and a decrease in tensile strength of 45.62%. PETG showed no significant changes in properties, indicating its good durability in geopolymer matrices.

Natural resources derived biocomposites as potential carriers of green pesticides in agricultural field: Designing and fabrication of a pot‐like device

AbstractHemp fibers (HF) are used as filler in pectin to produce biocomposites. To improve the compatibility of the filler with the polymeric matrix, HF are treated through mechanochemically assisted alkaline attack. The effect of the treatment time on the morphology of HF is investigated through atomic force microscopy and infrared spectroscopy. Cinnamic acid, a green pesticide, is added to the composites in order to test the capability of such materials to act as potential devices in the agricultural field. Analysis of thermal, mechanical, barrier properties and surface energy are evaluated on biocomposites and compared either to unfilled pectin or to composites filled with untreated HF. The release of cinnamic acid is evaluated and found to be dependent on the fibers' treatment time. The design and the fabrication of a pot prototype is also reported. The manufacture appears promising as green functional container for plants to be implanted in the ground.

A novel approach to design sustainable fiber reinforced materials from renewable sources: mathematical modeling for the evaluation of the effect of fiber content on biocomposite properties

The paper reports a sustainable, fast and efficient methodology to treat natural hemp fibers (HF) using a mechanochemical approach. Mechanical milling was used to carry out an alkaline attack on HFs for 30 min at ambient temperature. Composites HF/pectins were prepared by varying the fiber weight fraction (3%; 7.5%; 10%; 20% w/w by weight). The improvement in thermal degradation, mechanical and barrier properties to water vapor was correlated with the fiber volume fraction and mainly due to the improved fiber-matrix adhesion. The fibers–matrix interaction was then evaluated by analyzing and modeling the mechanical properties using several mathematical models: a modified Nielsen and Pukànszky and Smith models. Sorption isotherms to water vapor were analyzed through a modified Guggenheim, Anderson, de Boer (GAB) model where a new parameter, α, was introduced to consider the heterogeneity of the system. Finally, a modified Burgemman model was used to fit the experimental data and support the improvement in water diffusion with fiber loading.

Optical Fiber Waste Used as Reinforcement for Concrete with Recycled Marble Aggregate

Sustainable development in the 21st century depends on the reuse of materials and products, as well as on economic and environmental incentives for recycling. Several studies have sought to improve the quality of concrete, as well as its durability and strength, by adding fibers (metallic, polypropylene, carbon, vegetables) or by replacing the aggregate. The use of optical fiber waste in concrete is still incipient and few studies address the use of marble aggregate to be used in concrete. This research assesses the behavior of the mixture composed of: Portland cement + fine aggregate (sand from crushed marble waste) + coarse aggregate (gneiss) + optical fiber waste and water. The compressive strength, the tensile strength and the modulus of elasticity of concrete and the durability of optical fiber waste in alkaline composite were tested through microstructural evaluation. The results present an increase of about 20% in the mechanical properties and a reduction in the rigidity of the mixture, making the material more ductile. The superficial protection of the fibers made them more resistant to the alkaline attack of the cement. The knowledge acquired would allow the creation of sustainable concrete reinforced with optical fiber in a much more efficient way.

Mechanical Performance and Durability of Banana Fibre and Coconut Coir Reinforced Cement Stabilized Earth Blocks

Agricultural waste disposal is among the environmental problem in many countries. Finding economical uses for this waste by incorporating it in a product is the approach often used to overcome the environmental issue. Banana fibre and coconut coir are major agricultural waste products in Sri Lanka and fewer amounts of these are converted into usable products. Manufacturing cement-stabilized earth blocks incorporating these waste materials can reduce the environmental impact. The present study focuses on the post-peak behavior and durability of banana fibre and coconut coir-strengthened cement-stabilized earth blocks. Banana fibre and coconut coir reinforced cement-stabilized earth blocks are tested for compression, flexural bending, water absorption, sorptivity and resistance against chemicals, wet-dry weathering and freeze-thaw weathering. The banana fibre is shown better post-peak behavior in compression and coconut coir shown better post-peak behavior in flexural. Both fibre reinforcements improved the block’s durability against the acid attack, alkaline attack, wet-dry weathering and freeze-thaw weathering. Moreover, the specimen reinforced with coconut coir was found to exhibit better durability compared to the specimen reinforced with banana fibres.

Mechanical Damage Assessment of GFRP Rebars with Different Resins due to Hydrothermal Aging

Abstract This study investigates the effect of hydrothermal aging on the properties of glass fiber reinforced polymer (GFRP) rebars manufactured with isophthalic polyester or vinylester resin and glass fiber type E. The GFRP rebars were immersed in an alkaline solution (pH 12.6) for 1000 h at different temperatures (23 and 60 oC), and their deterioration was evaluated based on microstructural and chemical changes (using SEM, DSC, XRF, and FTIR techniques), moisture absorption, and variation in mechanical properties. The results indicated an increase in the presence of voids and water absorption of the rebars with accelerated aging, with a reduction in the glass transition temperature of the resin and alteration of the chemical composition of the glass fiber. The comparison between the experimental results indicates that the rebars with matrix in vinylester resin present greater chemical resistance than the rebars with a polyester matrix. The degradation of the rebar also resulted in a reduction of approximately 6% in the tensile strength of the rebar and 2% in the modulus of elasticity. Using the damage model, it was possible to identify that the reduction in mechanical strength was associated with the simultaneous degradation of the resin and glass fiber due to the alkaline attack.