Loss Of Mechanical Strength Research Articles

Characterization of Tannic Acid-Coated AZ31 Mg Alloy for Biomedical Application and Comparison with AZ91.

Magnesium alloys are promising materials for bioresorbable implants that will improve patient life and reduce healthcare costs. However, their clinical use is prevented by the rapid degradation and corrosion of magnesium, which leads to a fast loss of mechanical strength and the formation of by-products that can trigger tissue inflammation. Here, a tannic acid coating is proposed to control the degradation of AZ31 and AZ91 alloys, starting from a previous study by the authors on AZ91. The coatings on the two materials were characterized both by the chemical (EDS, FTIR, XPS) and the morphological (SEM, confocal profilometry) point of view. Static degradation tests in PBS and electrochemical measurements in different solutions showed that the protective performances of the tannic acid coatings are strongly affected by the presence of cracks. The presence of fractures in the protective layer generates galvanic couples between the coating scales and the metal, worsening the corrosion resistance. Although degradation control was not achieved, useful insights on the degradation mechanisms of coated Mg surfaces were obtained, as well as key points for future studies: it resulted that the absence of cracks in protective coatings is of uttermost importance for novel biodegradable implants with proper degradation kinetics.

Evaluation of coating mortars with addition of açaí seed (Euterpe oleracea Mart.) in different processing conditions

The açaizeiro is a palm tree found in large scale in the northern region of Brazil and one of its main non-timber forest products, with great economic potential. However, the wastes, which represent about 85% of the total fruit, are an environmental problem, since about 365 tonnes of seeds are discarded daily, without any reuse. The objective of this research is to evaluate the potential of reuse of the açaí seed as partial replacement by mass (10%) of the fine aggregate in mortars for coating (1:3 vol ratio). The seeds were crushed and divided into groups to be subjected to different types of treatment, namely calcination and liquid paraffin. Four samples were studied, R1 (reference - without seeds), R2 (calcined seeds), R3 (untreated crushed seeds) and R4 (paraffin treated seeds). The samples were subjected to fresh state tests, hardened state tests and microstructural analyses. The results show that in the fresh state sample R2 shows the best indexes when compared to the reference mix, with only a small improvement in consistency and water retention. In the hardened state, all compositions showed a significant loss of mechanical strength, demonstrating the weakness caused by the waste in the matrix. The microstructural analyses show a slight increase in porosity and amorphism in the sample due to the presence of the waste. For the mixes, substitution ratios, water/cement ratio and treatments adopted, the characteristics of the mortars do not meet the intended use.

Physical, Mechanical, and Durability Properties of Concrete with Class F Fly Ash

Concrete is one of the most used manufactured materials in the world. Fly ash (FA) is a byproduct produced from pulverized coal combustion in power generation. A total of 0.08 million tons of class F fly ash is produced from a coal-based power plant yearly in Barapukuria, Bangladesh, whose disposal is of a great issue. Therefore, this study aims to explore the possibility of using class F FA in concrete construction as a supplementary cementitious material. In this study, two different water-to-cement ratios (0.4 and 0.5), each with five cement replacement levels numerically, 0%, 10%, 20%, 30%, and 40% with FA are used. Various tests are performed on cylinder and beam specimens to assess physical, mechanical, and durability properties, such as workability, density, compressive strength (CS), splitting tensile strength (STS), flexural strength (FS), chloride ion penetrability (CIP), and shrinkage. Analyzing the results, it is reported that workability increases and density decreases with the increasing FA replacement. Mechanical properties mostly decrease with increasing FA content. However, the strength gained with age is higher for concrete with FA compared to the control concrete. The CIP reduces with FA replacement, especially at 56 days of age. Shrinkage value reduces 82% at 40% replacement FA replacement and w/c ratio 0.4. However, at 10% FA replacement and concrete age of 56 days, mechanical strength loss is infinitesimal or even better compared to the control concrete. Thus, a low replacement percentage of FA with a high curing period is a suitable concrete cement alternative.

Influence of hydrothermal conditions on the mechanical properties of hybrid composite pipes

Composite materials are becoming widespread in many sectors today, especially in the defence and space industry. Composite materials can be exposed to significant temperature changes and various environmental conditions depending on their usage areas. Therefore, composite materials with high resistance to high temperatures and harsh environmental conditions are being studied today. In this study, four types of 6-layer composite pipes with glass/glass/glass, basalt/basalt/basalt, glass/basalt/glass and basalt/glass/basalt stacking sequences were fabricated with filament wound method. In order to simulate the behavior of composite materials under environmental conditions, specimens were subjected to hydrothermal aging in pure water at 70°C for three different periods of 500, 1000 and 1500 hours. During the aging process, the mass changes of the pipes were measured regularly, and the water absorption behavior was determined with reference to ASTM D5229 standard. Hardness tests were carried out with Rockwell hardness tester based on ASTM D785 standard. As a result of the study, it was determined that the mechanical performance of hybrid specimens was higher than that of non-hybrid specimens. It was observed that the hydrothermal aging process caused a loss of mechanical strength in all specimens. It was concluded that the hybrid composite specimen with basalt/glass/basalt stacking order had the highest resistance to hydrothermal aging.

Integrated Hemicellulose Extraction and Papermaking Fiber Production from Agro-Waste Biomass.

The present study deals with the valorization of corn stalks in an integrated processing strategy targeting two products: extracted hemicelluloses (HC) and papermaking fibers. Preliminary trials were conducted to assess the individual or the combined effects of biomass treatment on the quality of the obtained hemicelluloses and papermaking fibers. Depending on the hot alkaline extraction (HAE) conditions, the extracted HC had a xylan content between 44-63%. The xylan removal yield ranged between 19-35%. The recovery of HC from the extraction liquor and final black liquor was significantly affected by process conditions. The experimental approach continued with the study of HAE conditions on the obtained paper's mechanical properties. The optimization approach considered conserving paper strength properties while achieving an equilibrium with the highest possible HC extraction yield. The optimal values are sodium hydroxide concentration (1%), process time (33 min), and temperature (100 °C). The xylan content in the separated HC sample was ~55%. An extended extraction of HC from the resulting pulp under hot alkaline conditions with 5% NaOH was performed to prove the HC influence on paper strength. The xylan content in HC samples was 65%. The consequence of xylan content reduction in pulp leads to 30-50% mechanical strength loss.

Crosslinked polymer-in-salt solid electrolyte with multiple ion transport paths for solid-state lithium metal batteries

Low ionic conductivity and unsatisfactory mechanical properties of the solid polymer electrolytes hinder their applications of in solid-state lithium metal batteries. Herein, we design a polymer-in-salt solid electrolyte (PISSE) with multiple Li+ transport paths and crosslinked polymer chain networks, endowing the PISSE with both high mechanical strength and high ionic conductivity. The optimized PISSE can therefore reach ionic conductivity of 3.03×10−4 S cm−1 (25 °C) and the mechanical strength of 0.811MPa. The percolation model explains that the salt-rich clusters account for the extra fast ion transfer paths; whereas, the crosslinking structure compensates the loss of mechanical strength at high salt concentration. Finally, the in situ polymerization of PISSE promotes the electrode-electrolyte interface compatibility, resulting in the Li//PISSE60%@LiFePO4 cells with 71% (initial capacity: 111.8 mAh g−1) of capacity retention after 800 cycles at 0.5 C. Moreover, the PISSE also exhibits compatibility with high voltage cathode LiFe0.2Mn0.8PO4 cells up to 4.3V. Therefore, this work provides a practical strategy to fabricate stable solid electrolytes for next-generation lithium metal batteries.

Silane-modified bentonite clay-coated membrane development on ceramic support for oil/water emulsion separation using tuning of hydrophobicity

Bentonite clay-coated and silane-modified hydrophobic composite membranes were prepared on the ceramic support by facile sol-gel deposition route to effectively separate various oil-water colloidal solutions. This study explores the correlation of silane content involved in optimizing and modifying surface hydrophobicity, membrane pore characteristics, and the solvent permeation properties in terms of oil permeation rate and water rejection (%) in oil-water emulsion solutions. Membrane surface modifications with relatively higher silane content (∼15%) reduced the membrane pores extensively, increasing the water rejection properties but the oil flux was reduced modestly. The oil flux increases with the introduction of reduced silane content (∼2%) but the water rejection properties were compromised. Silane: solvent ratio of 1:100 (silane loading ∼10%) proved to be efficient for the separation (94–99%) of various hydrocarbons such as hexane, toluene, cyclohexane, and heptane from emulsified solutions with permeate flux of 25–40 Lm−2h−1. Cake filtration model was found suitable to explain the membrane fouling. The optimized membrane also recorded a minimal loss of hydrophobicity and mechanical strength enduring oil atmosphere and corrosive environments. The overall study supported by suitable physicochemical material characterizing techniques reveals that optimizing silane concentration in bentonite-based clay composite membrane surface modification can be an effective oil/water separation strategy.

Synergistic coating strategy combining photodynamic and photothermal properties along with reinforcing corrosion protection fabricated on magnesium alloys

Postoperative infections of bone implants and loss of mechanical strength due to the corrosion are two major obstacles in the pathway for the magnesium alloys applications in biomedical region. To resolve above issues, a novel hybrid coating, MAO/EPR/Gel, is prepared on AZ31B magnesium alloys, in which the photodynamic therapy (PDT) and photothermal therapy (PTT) agents are combined together to form Er@PDA-RB and they are inserted in the micropores of micro-arc oxidation (MAO) coating rather than doping in it. The gelatin is utilized to prevent the leaking of Er@PDA-RB and it would be decomposed spontaneously in the human body. The |Z|0.01Hz of MAO/EPR and MAO/EPR/Gel are 4.35 × 104 Ω cm2 and 6.99 × 104 Ω cm2, which is much larger than that of MAO coating and bare AZ31B Mg alloy with the values of 3.70 × 104 Ω cm2 and 1.50 × 103 Ω cm2, respectively. The antibacterial ratio for E. coli reaches 93.9% under 980nm near-infrared (NIR) irradiation within 60min. Moreover, the MAO/EPR/Gel coating displays the excellent cytocompatibility with the HL-7702 cell viability > 75% with or without 980nm NIR irradiation. This multifunctional integrated coating accomplishes both PDT and PTT functions with only one NIR irradiation without sacrificing the anti-corrosion feature, which exhibits a promising application for magnesium alloys in biomedical applications.

Enhancing water resistance of regenerated cellulose films with organosilanes and cellulose nanocrystals for food packaging

Cellulose has been explored as potential alternative to traditional petroleum-based packaging materials, but its hygroscopic features lead to fast penetration of water and reduced mechanical properties of cellulose-based materials under humid and wet conditions. Chemical vapor deposition of organosilanes can incorporate hydrophobic moieties to overcome water sensitivity, but also decrease the strength of cellulose films. Herein, two commonly used organosilanes were selected to improve the water resistance of cellulose films, and cellulose nanocrystals were incorporated to compensate for the loss in mechanical strength. The results revealed that the films with dual modifications showed the unchanged tensile strength of around 57MPa when the environmental relative humidity increased from 0 to 60% and the highest wet strength of about 12MPa compared to the original and singly modified cellulose films. The water vapor permeability significantly decreased from 4.07 × 10−7 to about 3.3 × 10−7g·m−1·h−1·Pa−1 after the modification, and all the films could completely disintegrate within 14 days. Moreover, the cookies preserved by the modified cellulose films for 100 days showed similar weight gain (∼1.2%) and lower peroxide value (∼5.6meq/kg) than the ones covered by commercial plastic wrap. Therefore, this study presents a promising approach to develop cellulose films with enhanced water resistance for food packaging applications.

Influence of surface polishing on the degradation behavior of biodegradable Magnesium alloy

Mechanical polishing can significantly improve the surface integrity of Mg alloys to reduce the corrosion rate (CR) by minimizing the galvanic corrosion sites. In this study, an emery-polishing attachment on a lathe machine has been used for surface polishing of as-turned cylindrical ZM21 Mg alloy. Using Taguchi’s L9 orthogonal array, three process variables with three levels were investigated and optimized for minimum surface roughness (Ra and Rz values) of Mg-alloy samples. The minimum surface roughness values of Ra; 195 nm and Rz; 1481 nm were obtained corresponding to emery paper (EP) grade; 2000, rotational speed; 250 rpm, and polishing time; 2 min. An in-vitro immersion study was conducted in simulated body fluid (SBF) for up to 28 days to investigate the degradation behavior of as-turned and as-polished Mg alloy samples. In-vitro study showed that the as-turned samples (surface roughness; Ra: 640 nm, Rz: 4640 nm) had a higher degradation rate (CR: 3.9 mm year−1 after 28 days) with a higher volume of H2 evolution rate, whereas the polished sample with the minimum surface roughness (Ra: 195 nm, Rz: 1481 nm) exhibited lower weight loss, H2 release rate, degradation rate (CR: 0.95 mm year−1 after 28 days) and minimum loss of mechanical strength. Based on the present study, polishing is recommended as a secondary operation after machining of Mg alloy to reduce the corrosion rate for biodegradable implant applications.

Aging Mechanism and Lifetime Prediction of Glass Fiber Reinforced Liquid Crystal Polymer Composite under Thermal and Oxidative Conditions

AbstractDevelopment of fifth‐generation technology leads to a growing demand for materials with exceptional thermal property, mechanical strength, and low dielectric loss. However, ensuring the broad application of such materials by comprehensively investigating their aging mechanisms and service lifetimes remains a challenge. In this work, we have developed a glass fiber (GF) reinforced liquid crystal polymer composite (GF/LCP) and conducted a thorough exploration of its aging mechanism, behavior, and service lifetime under thermal and oxidative conditions. On the basis of the general Arrhenius model, the composite maintains a high level of functionality for a remarkable 18 years at 150 °C and 1.5 years at 200 °C. Despite the extremely high thermal resistance of GF/LCP composite, the LCP matrix exhibits localized brittle fracture, and the main chains still undergo gradual degradation to generate phenolic groups, which ultimately leads to severe pulverization and mass loss. However, a high degree of connection maintenance between GF and LCP components is still reserved. This work provides a valuable reference for the reliable application of 5G materials under thermal and oxidative conditions.

Corrosion studies of various salt solutions on metals and alloys

Corrosion studies of various salt solutions on metals and alloys

Mathematical modeling of cross-corrugated waveguide shell formation

Flexible cross-corrugated shells are used to create flexible waveguides that connect rigid waveguides. They compensate for mounting stresses during assembly, provide temperature compensation and vibration damping. These waveguides are widely used in spacecraft communication systems, they are required – flexibility, mechanical strength, geometric accuracy and minimal energy loss when connected to the transmission line. In this paper, the process of corrugating rectangular profile pipes made of BrB 2 bronze to create transversely corrugated shells is investigated. Objectives of the work: 1) analysis of technological processes of corrugation of waveguide pipes to select the most accurate method; 2) conducting a numerical experiment to determine technological parameters. Based on the analysis of the methods of transverse corrugation, the most rational method of corrugation with a liquid punch on a solid matrix has been incorporated. The scientific novelty lies in the creation of a mathematical model based on the theory of bending moments and beam stretching. With its help, a mathematical experiment was carried out, which has an applied benefit for the calculations of technological operations, for the corrugation of a waveguide. The pressures necessary for corrugation for different corrugation geometries are found and patterns are revealed. The mathematical model has an applied use for preliminary calculations of technological operations of corrugation of rectangular pipes. The calculation allows you to choose the most optimal mode of the technological process: fluid pressure, deformation, change in yield strength, allowing you to produce a flexible waveguide qualitatively. The result of the calculations is useful in preliminary design to determine the size of the corrugating equipment and the effort required to implement the technological process of forming the corrugations of rectangular pipes.

TRPV4 Activation and its Intracellular Modulation Mediated by Kinin Receptors Contribute to Painful Symptoms Induced by Anastrozole.

Anastrozole, an aromatase inhibitor, induces painful musculoskeletal symptoms, which affect patients' quality of life and lead to therapy discontinuation. Efforts have been made to understand the mechanisms involved in these painful symptoms to manage them better. In this context, we explored the role of the Transient Receptor Potential Vanilloid 4 (TRPV4), a potential transducer of several nociceptive mechanisms, in anastrozole-induced musculoskeletal pain in mice. Besides, we evaluated the possible sensibilization of TRPV4 by signalling pathways downstream, PLC, PKC and PKCε from kinin B2 (B2R) and B1 (B1R) receptors activation in anastrozole-induced pain. Anastrozole caused mechanical allodynia and muscle strength loss in mice. HC067047, TRPV4 antagonist, reduced the anastrozole-induced mechanical allodynia and muscle strength loss. In animals previously treated with anastrozole, the local administration of sub-nociceptive doses of the TRPV4 (4α-PDD or hypotonic solution), B2R (Bradykinin) or B1R (DABk) agonists enhanced the anastrozole-induced pain behaviours. The sensitizing effects induced by local injection of the TRPV4, B2R and B1R agonists in animals previously treated with anastrozole were reduced by pre-treatment with TRPV4 antagonist. Furthermore, inhibition of PLC, PKC or PKCε attenuated the mechanical allodynia and muscle strength loss induced by TRPV4, B2R and B1R agonists. The generation of painful conditions caused by anastrozole depends on direct TRPV4 activation or indirect, e.g., PLC, PKC and PKCε pathways downstream from B2R and B1R activation. Thus, the TRPV4 channels act as sensors of extracellular and intracellular changes, making them potential therapeutic targets for alleviating pain related to aromatase inhibitors use, such as anastrozole.

EFFECTS OF MODIFIERS ON MAGNESIUM OXYCHLORIDE CEMENT DOPED WITH PAPER MILL SLUDGE

To apply the composite material of magnesium oxychloride cement (MOC) doped with paper mill sludge (PMS) to engineering, the four modifiers such as phenylacrylic emulsion (PE), sodium methyl silicate (SMS), sodium phosphate monobasic (SPM), and citric acid (CA) were used to explore their effects on the composite material. The effects of these modifiers on the setting time, flowability, mechanical strength, softening coefficient, and strength loss coefficient of the composites were analyzed by physical properties, mechanical strength, water resistance, and resistance to sulfate attack, as well as by XRD. Results show that all four different modifiers can delay the setting time of the slurry and increase the fluidity of the mortar. With the increase of modifier dosage, the strength of mortar modified by different modifiers is lower than that of the control group, and the softening coefficient and sulfate erosion resistance coefficient of the modified mortar are significantly improved. At 2% and 1.5%, respectively, SPM and CA have the best modification effects, but PE integration decreases the softening coefficient of the mortar and only increases it by 47.30% at 0.5%. The obtained conclusions can provide a reference for the engineering application of PMS-MOC. Keywords: Magnesium oxychloride cement, Paper mill sludge, Composite materials, Modification, Softening coefficient.

Effect of ceramic waste powder content and sodium hydroxide molarity on the residual mechanical strength of alkali-activated mortars

In the study, the effects of various ceramic waste powder (CWP) additions (5, 10, and 15%) and sodium hydroxide (SH) molarity (8 M and 16 M) on the residual mechanical properties of different ambient-cured alkali-activated mortar (AAM) samples were investigated under the elevated temperatures (300, 600, and 900 °C) and freeze-thaw (100 cycles) attacks. The fresh (flowability, initial and final setting time, water absorption, and void ratio) and hardened (compressive and flexural strength, ultrasonic pulse velocity, and weight loss) state performances were evaluated. Also, XRD and SEM analyses were carried out. The findings pointed out that flowability enhanced up to 15% of CWP replacements. The initial and final setting time was reduced with higher molarity, while improved with further CWP incorporations. The water absorption and void ratio decreased with higher CWP incorporations and SH molarity. Moreover, mechanical strengths increased with time, which were found to be more with a higher CWP replacement ratio and SH molarity. After elevated temperature, the average compressive strength losses were about 50% at 600 °C and 85% at 900 °C, while average flexural strength losses were about 70% at 600 °C and 85% at 900 °C. Meanwhile, similar residual compressive strengths were obtained at elevated temperatures, irrespective of the SH molarity and CWP incorporations. However, both CWP incorporation and high SH molarity slightly enhanced the residual flexural strengths. After freeze-thaw attacks, an average of 23% compressive strength loss and 29% flexural strength loss was obtained, and almost similar mechanical strength losses were observed with varying SH molarity and CWP replacement ratio.

Performance evaluation of structurally modified wellbore cement with graphene nanoplatelets undergone thermal cyclic loading

Geothermal energy is identified as one of the alternatives to fossil fuels in global climate crisis and the effective efforts for net-zero carbon emissions by 2050. The potential of geothermal heat at high temperatures is yet to be unlatched thus requiring a novel approach in all aspects of wellbore technology including cementing. Understanding the characteristics of the geothermal system is critical as we aim to develop wellbore materials for these thermally and chemically challenged wells. Materials used require stability at high temperatures and chemical resilience in contact with geofluids, where ordinary Portland cement (OPC) is deteriorating due to low pH that leads to loss in overall mechanical strength. Recent studies have shown that adding graphene nanoplatelets (GNP) to OPC based materials can improve properties and reduce risks from mechanical failures. GNP effect on overall cement properties has been studied and experimental results show promising outcomes at very low concentrations (<1% bwoc), significantly impacting strength and stiffness of the cement. The Class-H cement is hydrated with and without, liquid and powdered GNP at 0.008% and 0.1% concentrations each and cured in approximately pH 13 Ca(OH)2 solution to examine the influence of GNP on cement hydration. All the samples were subjected to cyclic temperature loading between 20 °C and 110 °C at 95% RH following an 8-hour cycle for 7 and 28 days in an environmental chamber. These temperature cycles help us evaluate close to the subsurface conditions where enhanced geothermal systems undergo thermal changes over tens of thousands of times during a lifetime of a well. Following API RP-10B specifications, GNP in the powdered form (PG) prepared from environmental waste and a 99.5% carbon purity lab grade liquid dispersion GNP (LG) were used. 0% GNP (neat) control, 0.008%, 0.1% of PG and LG mix design cement samples were prepared. Results show that 0.1%LG samples hydrated for 28 days had greater dispersion of GNP with a notable increase in the ductile behavior out of all the designs tested. There is a 13.21% decrease in permeability, 27.77% decrease in hardness and 50.71% decrease in elastic modulus when compared to neat sample hydrated for 28 days thus proving its effectiveness for wellbore integrity with increase in hydration time.

Effects of synthesis parameters on the performance of crosslinked Co-polymers with clays for conformance control

Conformance control or water shut-off is a technique used to improve oil recovery. During conformance control, polymers block high permeability water areas and redistribute water drive toward unswept oil zones. In this study, co-polymers (denoted ATP-PGV/AM-co-AMPS) were synthesized using acrylamide (AM) and 2-acrylamide-2-methylpropane sulfonic acid (AMPS) as the monomers, polyethylene glycol (PEG)-200 and methylenebisacrylamide (MBA) as the crosslinkers, attapulgite (ATP) and bentonite (PGV) as the clay types, and ammonium persulfate (APS) as the initiator, in addition to paraffin oil and surfactants. Samples were synthesized using inverse emulsion polymerization with different concentrations of monomers, crosslinkers, and clays, and they were characterized using Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). FTIR spectra of the samples confirmed the existence of sulfonate and hydroxyl groups, which are important for polymer swelling. SEM-EDX images indicated that the morphology and elemental composition were different before and after swelling, confirming the occurrence of swelling. Moreover, samples were placed in sodium chloride solution (20,000 ppm) for 7 days to evaluate swelling at both room temperature and 90 °C. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to determine the thermal characteristics of the microparticles. Finally, rheological measurements were used to assess the deformation and rheological behavior of the hydrogels. The results showed that after 1 day, good swelling without loss of mechanical strength was achieved with the composite synthesized using 10% AM, 15% AMPS, 6% PGV, and 10% ATP.

ADDITION OF BACTERIOLOGICAL ADDITIVES IN THE PRODUCTION OF SELFHEALING CONCRETE

Self-repairing concrete is a product in which microorganisms will be used to produce limestone to fill cracks appearing on the surface of concrete structures. It is presented by the author that specially selected types of bacteria of the genus Bacillus, a calcium-based nutrient known as calcium lactate, and nitrogen and phosphorus are added to the ingredients of concrete when it is mixed. These self-healing agents can remain dormant within concrete for up to 200 years. Self-repairing materials are a special type of materials that regenerate their strength properties after minor damage caused to the material during its service life. Self-repair technology is particularly useful in the case of composite materials because composites have low damage detection capability and are susceptible to sudden and brittle failure. Modern man-made materials have excellent mechanical properties. However, they lack the ability to self-repair. Therefore, in the event of damage, there is the possibility of loss of mechanical strength and, over time, a gradual loss of functional strength in the absence of human intervention.Different bacterial species along with abiotic factors such as salinity, ambient pH value, temperature, nutrient availability and habitat composition play a significant role in the calcium carbonate precipitation process in a wide range of different environments. There are four key factors that determine the MICP process: (I) calcium concentration, (II) dissolved inorganic carbon concentration, (III) pH value and (IV) presence of nucleation centres.

On the Roles of Cellulose Nanocrystals in Fiber Cement: Implications for Rheology, Hydration Kinetics, and Mechanical Properties.

Fiber cement reinforced with pulp fibers is one of the key drivers for the decarbonization of nonstructural building materials, where the inclusion of sustainable pulp fibers at high proportions (i.e., > 8 wt %) renders poor workability of fiber-cement slurry with a concomitant loss in mechanical strength. Petrochemical-derived superplasticizers, i.e., polycarboxylates (PCEs), are predominantly used in fiber cement (including cement mortars) because they dramatically improve (content <0.5 wt %) the slurry rheology but reduce the rate of hydration and weaken the strength of the cured composite. Thus, it is crucial to explore renewable and bio-based superplasticizers devoid of any negative traits (if possible) of the conventional PCEs. In this study, we examined wood-derived cellulose nanocrystals (CNCs) as a multifunctional additive in fiber cement (bleached pulp fiber content: 8 wt %). In fiber cement, variation of the content (0.02-4 wt %) of CNCs resulted in improvement in the shear thinning behavior of the fiber-cement slurry and thereafter increased the hydration kinetics at high CNC contents (2-4 wt %). Notably, the flexural strength of the composite also exhibited improvement upon the addition of CNCs; the maximum strength was observed at 4 wt % of CNCs. Overall, the beneficial roles of CNCs afforded >10 wt % (in-total) bio-based content in fiber cement without compromising the mechanical strength and curing time (compared to PCEs); hence, the findings of this study could unravel new avenues in interface engineering of cement composites leveraging the multifunctional features of biomaterials, thus enhancing sustainability.