Presence Of Calcium Carbonate Research Articles

Preparation of microfibrillated cellulose by in situ and one step method using calcium hydroxide as swelling and grinding agent

Abstract Calcium hydroxide was used as a swelling agent and grinding aid to grind together with cellulose raw materials to prepare microfibrillated cellulose (MFC). Carbon dioxide was introduced to obtain MFC coated with calcium carbonate (CMFC). The effect of calcium hydroxide dosage on the fibrillation process of cellulose materials and the characteristics of MFCs and CMFCs were studied. Results show that when the dosage of calcium hydroxide was 5 % (based on cellulose materials), calcium hydroxide could be completely dissolved in water and had a swelling effect on cellulose materials. When the dosage reached 10 %, undissolved calcium hydroxide particles could serve as grinding media to assist in the fibrillation of cellulose materials. When the dosage exceeded 50 %, the auxiliary grinding effect of calcium hydroxide was more obvious. After accelerated carbonation, the generated calcium carbonate nanoparticles were coated on the surface of MFC, which increased its viscosity and decreased water retention value. The presence of calcium carbonate also facilitated the concentration, redispersion, and drying of MFC. The pretreatment, mechanical fibrillation, and accelerated carbonation were carried out in the same equipment without the need for heating or washing. Therefore, this study provides a in situ and one step method for the preparation of MFC.

Probing sediment burial age, provenance and geomorphic processes in dryland dunes and lake shorelines using portable luminescence data

Luminescence signals from portable optically-stimulated luminescence readers (POSL or port-OSL) can provide expedient insights into sample relative age, and under certain conditions can be simplistically calibrated against existing luminescence chronologies to provide first-order estimates of burial age. This is most straightforward in simple sedimentary systems where samples share a common provenance and geomorphic process history. The spatially extensive southern African dune and palaeolake shoreline luminescence database, for which hundreds of non-light exposed bulk sediments are available, offers a valuable test case to examine the conditions under which POSL-bulk sediment calibration approaches are feasible. To do this we combine measurements of inherent luminescence sensitivity of bulk sediment (BSS) with analysis of sedimentary composition (petrology and presence of calcium carbonate) and texture. We show that BSS, along with POSL IRSL:BSL ratios and petrological data, account for region-to-region variations, whilst internal variability (scatter) within the lake shorelines dataset relates to variations in BSS and sediment texture. At the scale of southern African subcontinent drylands, we see that provenance and geomorphological process history influence sample mineralogical composition and POSL signal characteristic, including BSS.

A sustainable synthesis, characterization of modified waste onion peels and its exploration in various applications

The modification of waste to a bio-based material that is economical, environmentally sustainable, and extremely effective is crucial for organic conversions. For bio waste, that doesn’t decompose easily and have bad impact on environment such as onion peels, a suitable method is introduced which focuses on utilizing onion peels, a commonly discarded agricultural waste, as a valuable resource for antibacterial studies and bio sensing of heavy metals. A comparative study to analyse these properties were done using onion peel extract and saponified onion peels. The saponified material was obtained by treating onion peels (Allium cepa) with sodium hydroxide in the presence of calcium carbonate. The popularity of saponification reaction and saponified material is rising because of their special qualities and uses as disinfectants, surfactants, antifungal agents, in drugs for target based delivery etc. The saponified onion peels was analyzed by FTIR (Fourier transform infrared spectroscopy), and XRD (X-ray diffraction), EDX (energy-dispersive X-ray), SEM (scanning electron microscopy). Furthermore, against Bacillus subtilis (Gram positive), antibacterial activity of onion extract and saponified onion peels were studied. In comparative study onion peel extract shows better inhibition zone then saponified onion peels. Bio sensing of heavy metals were done by using these materials, onion peel extract shows visual colour change with Nickel chloride (NiCl2), Cobalt chloride (CoCl2), Potassium bromide (KBr), Manganese sulphate (MnSO4), Mercury chloride (HgCl2) and Copper sulphate (CuSO4) metal salts.

Insights into bio-deterioration of concrete exposed to sewer environment: A case study

Microbial corrosion induced is considered to be the main cause of concrete deterioration in sewer systems. In this study, the corrosion depths and rates of concrete cores sampled from different sections of concrete sewer pipes exposed to real sewer environments were measured. The pH profile, phase assemblage, and microstructure of corroded concrete relative to depth were also determined. Results showed that after 32 years of exposure, the concrete sewer pipe suffered severe corrosion. Under the influence of water flow fluctuations, the concrete in the waterline region presented more serious thickness loss (up to 23.85mm) compared to the crown region, and the average corrosion rate of concrete in the waterline region and crown region was 0.71mm∙a−1 and 0.20mm∙a−1, respectively. The lowest pH level of concrete pore solution in the sewer was 5.74, observed in the layer close to the surface in the waterline region. The correlation and functional relation between the depth from the concrete surface, pH level, ions, and elemental concentrations in the concrete pore solution was obtain by Spearman correlation test and multivariate function nonlinear fitting. The presence of calcium carbonate behind gypsum and ettringite in inner concrete suggested potential carbonation due to the CO2 produced by heterotrophic bacteria in sewer environment. The results of this study suggest the contributions of flowing water and carbonation in the bio-deterioration of concrete under real sewer environment are non-negligible.

The Possible Use of Stable Carbon and Nitrogen Isotope Signal and Spectral Analysis to Identify Habitat Condition of Aquatic Plants

Many macrophyte species exhibit a high degree of plasticity, enabling them to thrive in various aquatic ecosystems. Identifying the growth conditions of individual aquatic plant species during research or specimen collection is not always possible. In many cases, the nature of the planned research does not necessitate recognizing environmental conditions. However, the scope of identifying the habitat parameters of the collections of submerged aquatic plant herbariums provides an opportunity for further research. This paper explores the possibilities of using isotopic signals of plants, supported by spectral analyses of powdered plant materials, to ascertain the environmental conditions from which the samples were collected. The results obtained from the stable carbon and nitrogen isotope compositions (δ13CORG and δ15NORG) and the analysis of spectral spectra via FTIR-ART (Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance) of plant material (Elodea canadensis Michx. species) collected from various habitat ecosystems, including rivers and both hard- and softwater lakes, exhibited significant distinctions between these habitats. Particularly high values of δ15NORG were recorded in the material from rivers. The stable carbon and nitrogen isotope compositions did not differentiate between the material collected from softwater and hardwater lakes. Nevertheless, when comparing the isotopic findings with the FTIR-ATR spectral analysis focused on identifying characteristic peaks associated with the presence of calcium carbonate, noticeable differences were observed in the presence and intensity of calcium carbonate peaks in the material. These differences were only evident when nondecarbonated plant material from hardwater lakes was used for the FTIR-ATR analysis. To the best of the author’s knowledge, the combination of methods applied in this study to identify the origin of E. canadensis from various freshwater environments is the first application of its kind that could enable the rapid identification of plant material origin. Such identification could prove useful in environmental, ecological, and paleoenvironmental research. The increased knowledge of macrophytes’ δ13CORG and δ15NORG values might also be essential in further tracking accelerated eutrophication based on aquatic vegetation’s isotopic signals. This might be important due to the assumption that the increased rate of eutrophication influences organic matter sedimentation in aquatic ecosystems, especially lakes.

Optimization of syngas production from co-gasification of palm oil decanter cake and alum sludge: An RSM approach with char characterization

The study explores co-gasification of palm oil decanter cake and alum sludge, investigating the correlation between input variables and syngas production. Operating variables, including temperature (700–900 °C), air flow rate (10–30 mL/min), and particle size (0.25–2 mm), were optimized to maximize syngas production using air as the gasification agent in a fixed bed horizontal tube furnace reactor. Response Surface Methodology with the Box-Behnken design was used employed for optimization. Fourier Transformed Infra-Red (FTIR) and Field Emission Scanning Electron Microscopic (FESEM) analyses were used to analyze the char residue. The results showed that temperature and particle size have positive effects, while air flow rate has a negative effect on the syngas yield. The optimal CO + H2 composition of 39.48 vol% was achieved at 900 °C, 10 mL/min air flow rate, and 2 mm particle size. FTIR analysis confirmed the absence of C─Cl bonds and the emergence of Si─O bonds in the optimized char residue, distinguishing it from the raw sample. FESEM analysis revealed a rich porous structure in the optimized char residue, with the presence of calcium carbonate (CaCO3) and aluminosilicates. These findings provide valuable insights for sustainable energy production from biomass wastes.

PROPERTIES OF EKRANOSEMS OF THE CITY OF LVIV

Ekranozems are urban soils that occupy a significant area of cities and play an important role in urban ecosystems, because they have a wide range of properties. One of the main features of ekranozems is the presence of a closed impermeable layer - a screen, that is, an artificial surface, which includes asphalt concrete, paving stones, sidewalks, etc. At the same time, thanks to the processing of scientific and literary sources, it should be noted that ekranozems are still little-studied and under-researched due to their inaccessibility. They are the result of a variegated relief, the influence of zonal and climatic conditions of soil formation and anthropogenic factors. It is clear that these interactions varied depending on the location and age characteristics of the city. The structure, composition and properties of ekranozems, as well as their functioning, are determined by the structural features of roads, driveways, footpaths, etc., as well as the features of anthropogenic impact (before sealing) on the soil, taking into account its natural features in certain conditions of soil formation. Ekranozems occupy a significant part of the territory of the city of Lviv and are characterized by a great variety of properties. As a result of their stay under asphalt concrete and pavement surfaces, such negative processes as a decrease in water permeability, a decrease in the concentration of oxygen in the soil, and a change in the water regime occur. There is also soil compaction and a decrease in general sparability during the improvement of the territory. These soils are united by their lack of humus throughout the profile. The studied ekranozems are characterized by the presence of calcium carbonates throughout the profile, which are brought, for the most part, during the construction and laying of networks, as well as various repair works on the road. The acid-base properties of ekranozems are represented by the alkaline reaction of the soil environment, which is caused by the presence of carbonate salts (pH ranges from 7.7 to 8.1), which causes a slowdown in soil-forming processes and, as a result, a change in soil quality. Keywords: ekranozem; urban soil; sealed soil; urban ecosystem; anthropogenic soil; Lviv plateau; cultural layer.

New insight into highly efficient removal of tetracycline by calcined hydroxyapatite activated peroxymonosulfate: The role of calcium carbonate and phosphate group

Tetracycline (TC) is an important antibiotic extensively used in livestock breeding and aquaculture, and so an effective removal strategy is urgently needed. This study explores the use of a series of hydroxyapatite calcinated at different temperatures (300, 400, 500, 600, and 700 °C) to activate peroxymonosulfate (PMS) for the removal of TC. The optimal conditions for the removal of 10 mg/L TC using hydroxyapatite calcinated at 600 °C (CHAP600) as a catalyst were determined to be: pH of 6.0, a catalyst dosage of 0.2 g/L and a PMS concentration of 0.3 mM. Under these conditions, the removal efficiency of TC reached 94 %. The potential degradation pathway of TC was proposed by identifying the intermediates using High Performance Liquid Chromatography/Triple Quad mass spectrometry. The characterization analysis revealed that the presence of calcium carbonate on the surface of CHAP600 promoted the generation of singlet oxygen (1O2). Additionally, the phosphate group in CHAP600 served as a catalyst for the production of sulfate radicals (SO4·−) from PMS, which subsequently react with hydroxyl or surface hydroxyl group to generate hydroxyl radicals (·OH). And the active species 1O2 is the most significant contributor to the catalytic degradation process of TC by CHAP600 activated PMS, followed by ·OH, and then SO4·−. This study provides new insight for the mechanism of removing organic contaminants using PMS activated with calcined hydroxyapatite.

Effect of CaCO3 on the Formation corrosion and sedimentation in Iron pipe Drinking water in Kufra- Libya

Corrosion phenomena means to the deterioration of metallic materials due to chemical and electrochemical reactions, because these materials are always trying to reach a state of lower energy potential. Groundwater is vital and the sole resource in most of the studied region in the city of Alkufra. In this study, The main objectives of this research are to further broaden the mechanistic understanding of CO2 corrosion of mild steel in the presence of high concentrations of calcium ions and evaluate the protectiveness of CaCO3 scale against further corrosion. The values of these concentrations in the studied water samples indicate that they constitute a chemically suitable environment for corrosion and precipitation reactions, additionally, the pH values for the studied water samples ranged between (7. 25 - 7.37), temperature values ranged from 35 ℃ to 37℃ . (95.64 F0 to 98.6 F) respectively,it was found that the Aggressiveness coefficient ranged between (0.25 – (-1.3) and this indicates that the water in this region is highly corrosive, and the Ryzner coefficient ranges between (6.7 - 9.7), which indicates the water condition is the cause of corrosion. The Langelier coefficient index shows that the negative values ​​are the cause of the increase in wear rate values from( -2.73 to -0.89) .Our results show that the presence of calcium carbonate and calcium sulfate as a scaling environment increases the corrosion rates for carbon steel.

Biomimetic mineralization of calcium carbonate under synergistic regulation of Sr2+ and egg-white proteins

The content of Sr in nacre is stable and second only to Mg, but its ability to induce aragonite is rarely reported. Therefore, the paper studied the effects of Sr2+ concentration, reaction rate and temperature on the biological mineralization of calcium carbonate in presence of egg-white proteins. The results show that Sr2+ could induce the formation of aragonite when coexisting with egg-white proteins as Mg2+. However, the large ion radius of Sr2+ makes it difficult to enter the calcite lattice, so its induction efficiency is much lower than Mg2+. Reducing the mineralization rate and increasing the mineralization temperature are beneficial to the formation of aragonite.

DIAMOND CRYSTALLIZATION AND PHASE COMPOSITION IN THE FeNi – GRAPHITE – CaCO3 SYSTEM AT 5.5 Gpa

An experimental simulation of diamond crystallization in the system FeNi - graphite - calcium carbonate at a pressure of 5.5 GPa and a temperature of 1400℃ was carried out. Two sample assembly configurations were used. In the first one – the starting materials were put layer by layer, and in the second one - the components were mixed. It has been established that calcium carbonate, when interacting with the FeNi-melt, decomposes with the formation of Ca,Fe oxides and the release of CO2. Magnetite may be present as an accessory phase. Due to the formation of solid reaction products (Ca,Fe oxides) during layer-by-layer filling of the growth volume, the presence of calcium carbonate between graphite and FeNi-melt prevents diamond crystallization in the graphite layer and carbon transport to diamond seed crystals. When the components are mixed in the growth volume, diamond synthesis and growth onto seed crystals occur. The phenomenon of segregation of diamond crystals together with calcium carbonate and oxide phases, the products of the reaction in the bulk of the metal, has been discovered. Aliphatic, cyclic, and oxygenated hydrocarbons, including heavy compounds (C13-C17), CO2, H2O, nitrogen- and sulfonated compounds, were identified in the fluid phase captured by diamonds in the form of inclusions during growth. The composition of the fluid phase in the studied diamonds is more oxidized compared to the composition of fluid inclusions in diamonds grown in the FeNi – graphite system without carbonate. The results obtained correlate with the data on natural diamonds, among which there are crystals with “essentially carbon dioxide” compositions of fluid inclusions, which indicates the possible participation of crustal carbonate matter in the processes of diamond formation during subduction into the deep mantle.

Chitosan-based mixed matrix membranes: effect of different fillers on membrane properties and performance in hydrophilic pervaporation

Pervaporation is still regarded as an emergent process, with a great potential to be an alternative to classical separation processes, with technical advantages. Chitosan is considered a promising material in next-generation pervaporation membranes, especially hybrid and mixed matrix membranes. This study aimed to evaluate the effect of fillers such as calcium carbonate, kaolinite, graphene, and graphene oxide, added separately at the concentration of 1 wt.%, on the mechanic and physical-chemical properties, microstructure, and hydrophilic pervaporation performance of chitosan membranes cross-linked with glutaraldehyde. The fillers influenced the mechanical and physicochemical properties of the membranes differently. Relative to the hydrophilic pervaporation tests, the presence of calcium carbonate and kaolinite increased membrane efficiency (αW/E of 1,777 and 1,225 against 611 in the control), whereas graphene reduced the permeate flux (0.341 kg·m−2·h−1 against 0.397 kg·m−2·h−1 in the control). The addition of graphene oxide increased the flux and permeability of ethanol (0.089 kg·m−2·h−1 and 8.66·10−14 kg·m−1·s−1·Pa−1 against 0.019 kg·m−2·h−1 and 1.74·10−14 kg·m−1·s−1·Pa−1 in the control), unlike the other fillers, which had no significant influence on this parameter. Thus, the membranes containing the fillers calcium carbonate and kaolinite were more suited for use in hydrophilic pervaporation (PSI of 842 and 561 against 228 in the control). Graphene did not affect membrane properties (αW/E of 398 and PSI of 127). Graphene oxide (αW/E of 174 and PSI of 72) may be considered as an alternative and starting point for the development and research of mixed matrix membranes based on chitosan to be used in target-organophilic pervaporation.

Study of Carbonated Clay-Based Phosphate Geopolymer: Effect of Calcite and Calcination Temperature

This study aims to use natural carbonated Tunisian clay as an aluminosilicate precursor for the elaboration of phosphate-based geopolymers, which yields to the valorization of this common material in Tunisia. In addition, the presence of calcium carbonate in this clay allows the investigation of this associated mineral’s effect on the properties of geopolymeric materials. To achieve these purposes, several experimental techniques were used, namely fluorescence (FX), particle size analysis, thermogravimetric analysis (TGA), differential thermal analysis (DTA), dilatometric analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The mechanical strength and the open porosity of the obtained geopolymeric samples were tested by the compression test and the standard test method for water absorption, respectively. The findings of this work show that the used Tunisian clay can present an attractive aluminosilicate precursor for the synthesis of phosphate-based geopolymers. It also shows that the chosen calcination temperature of the raw clay considerably modifies the reactivity of minerals during geopolymerization and, consequently, strongly affects the properties and structure of the geopolymeric samples. These effects were attributed essentially to the formation of new calcium crystalline phases in the obtained geopolymeric samples. In fact, the anorthite (CaAl2Si2O8) phase appears in all the samples but in greater abundance in those obtained from the clay calcined at 550 °C, and the brushite phase (CaHPO4·2H2O) appears only in the samples obtained from the clay calcined at 950 °C. All these new crystalline phases are strongly dependent on the state of the calcite present in the calcined clay.

Gypsiferous Gazha Soils of the Subboreal Zone of Eurasia

Gypsiferous soils (gazha soils – loose powdery gypsum) developed underdifferent bioclimatic conditions–forest-steppe, steppe, semidesert, and desertof the subboreal zone – are analyzed. Their morphological, micromorphological, mineralogical, and chemical properties are described. Gazha horizons of these soils may have different geneses: sedimentation, in situ weathering of hard gypsum rocks, and hydrogenic precipitation from groundwater. Despite the different origins of the gazhahorizon of these soils, its morphology and properties have much in common: the gypsum content of 50%, its powdery character with crystal size of 0.25 mm, the presence of calcium carbonates and soluble salts with a predominance of sodium and magnesium sulfates. However, in some cases, the field determination of the gazhahorizon and the chemical determination of gypsum give incorrect information about its presence; mineralogical analysis is necessary to determine the composition of the salts. An analysis of the micromorphological structure clearly demonstrates the genesis of gypsum: under hydrogenous conditions, when gypsum precipitates from groundwater or from lake and river water, the predominantly gypsum material with subparallel microstructure is formed, while in the in situ gazha or gazha originated from the lateral (colluvial) processes, gypsum is deposited together with plasmic material.

Phenomena of Bacillus sphaericus LMG 22257 Activity and Its Influence on Properties of Portland Cement Mortar Exposed to Different Curing Media

This study determined the influences of Bacillus sphaericus Laboratorium voor Microbiologie Gent (LMG) 22257 bacteria activity on mortar samples cured in various media regarding compressive strength, porosity, water absorption, and water permeability. Three types of curing media were utilized, namely distilled water (D.W.), deposition water (D.M.), and run-off water (R.W.). The compressive strength was measured using 100 mm mortar cubes. The water porosity, water absorption, and water permeability were analyzed using the Leeds permeability cell with dimensions of the mortar cylindrical specimens of 55 mm diameter and 40 mm thickness. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDX) were utilized, respectively, for microstructure analysis and quantifying the elements with atomic numbers. The results indicated the presence of calcium carbonate and more calcium silicate hydrate (CSH) depositions on bacterial mortars. The inclusion of Bacillus sphaericus LMG 22257 bacteria activity and curing media type affected mortar properties through compressive strength and durability improvements, as well as the reduction in water porosity, water absorption, and water permeability of mortar. The comparison of CaCO3 precipitation, such as a sufficient growth nutrient requirement and hostile bacteria environment, was observed. Curing in R.W. produced the most significant bio-based cement (BBC) mortar improvement, followed by D.M. BBC curing in runoff water had a 40% improvement in strength compared to normal curing. As a conclusion, runoff water is a highly promising sufficient nutrient to bacteria for the biomineralization process to produce CaCO3. This work also aims to apply this approach in the field, especially in sewerage and drainage systems.

Effect of Calcium Carbonate Content on Potential Pesticide Adsorption and Desorption in Calcareous Soil

ABSTRACT The presence of calcium carbonate (CaCO3) in soil plays an essential role in regulating many processes whether chemical, physical, or biological. The effect of calcium carbonate content on the adsorption and desorption characteristics of insecticides (chlorantraniliprole, CAP, dinotefuran, DNF) and herbicides (bispyribac-sodium, BPS, metribuzin, MBZ) in calcareous soil has been studied. Adsorption and desorption isotherms of tested pesticides were quantified using the batch equilibration technique. The data were modeled with the Freundlich model to obtain the adsorption parameters. The results showed that the adsorption of DNF and BPS was the highest in intact calcareous soil (IS), while the adsorption of CAP and MBZ was the highest in calcium carbonate free calcareous soil (FS). The desorption from IS and FS was highest for MBZ, whereas it was lowest for BPS. Therefore, we demonstrate that the soil calcium carbonate could block the adsorption sites available for certain pesticides like CAP and MBZ, while it could be shared in the adsorption of other pesticides like DNF and BPS.

Fabrication and characterization of three-dimensional polycaprolactone/sodium alginate and egg whites and eggshells hybrid scaffold in bone tissue engineering

Abstract The aim of this study was to fabricate three-dimensional bone scaffolds using polycaprolactone and egg shell powder. The scaffolds were coated with sodium alginate/egg white. SEM was used to investigate egg shell particles on the surface of each string of scaffolds. The presence of calcium carbonate in the scaffold structure was confirmed by microstructural analyses employing XRD. Egg shell-related functional groups were discovered using FTIR investigations. Bone cells were used to conduct biocompatibility tests on scaffolds (MG-63). Finally, scaffolds with the highest proportion of egg whites and eggshells have the best cell survival rate. It may be concluded that the PCL/7% Esh/15% Ew scaffold is a good option for application in bone tissue engineering.

Investigating the hydration characteristics of a new composite cementitious binder containing of slag and calcite

The influence of the filler content, filler fineness and water to powder ratio (W/P) on hydration kinetics and microstructure behaviour of a new clinker-free material made of calcium hydroxide, blast furnace slag (BFS), calcite and expansive agent are explored in this study. The hydration characteristics of the proposed material were investigated by multiple experimental programmes including X-ray diffraction (XRD), TG-differential thermal analysis (DTA), selective dissolution measurement and mercury intrusion porosimetry (MIP). The experimental results revealed that slag reaction degree is enhanced by increasing the filler content and fineness of the filler in high W/P ratio. However, the filler fineness does not show significant improvement in the hydration degree of slag with low W/P ratio in later curing period due to the reduced amount of available water for the hydration reaction. Another interesting finding of this study is that the hemicarboaluminate which is thermodynamically unstable than monocarboaluminate, stably formed even at the later age of hydration reaction in the presence of calcium carbonate. The amended thermodynamic model also well agreed with the tendency of the experimental results in terms of hydration products and porosity of the hardened matrix as a function of curing period.

Influence of Seawater Absorption on the Hardness of Glass Fiber/Polyester Composite

In the marine industry, glass fibers are commonly used to reinforce polyesters for ship hulls, submarine components, and other marine structures. Isophthalic polyesters are a feasible alternative due to their superior mechanical qualities and added end-of-life scenarios compared to orthophthalic polyesters. However, like other fiber composite systems, glass fiber reinforced polymer (GFRP) composites are also water sensitive. Here, GFRP composites of three different thicknesses are aged under three different immersion periods in seawater (20, 40 and 60 days). All samples are reconditioned and evaluated for hardness following aging. Significant emphasis is placed on the presence of calcium carbonate, over which increases in moisture content irrevocably reduce the composite’s hardness. Compared to untreated material, the hardness of 6, 8, and 10 mm composites decreased by 25.64, 10.92, and 4.63% after the 60-day aging period. This drop is mostly the result of microstructure evolution manifesting as an increase in porosity. Consequently, fiber deterioration, fiber cracks, and degradation of polymer-fiber bonding emerge in the composite, decreasing hardness.

Influence of Seawater Absorption on the Hardness of Glass Fiber/Polyester Composite

In the marine industry, glass fibers are commonly used to reinforce polyesters for ship hulls, submarine components, and other marine structures. Isophthalic polyesters are a feasible alternative due to their superior mechanical qualities and added end-of-life scenarios compared to orthophthalic polyesters. However, like other fiber composite systems, glass fiber reinforced polymer (GFRP) composites are also water sensitive. Here, GFRP composites of three different thicknesses are aged under three different immersion periods in seawater (20, 40 and 60 days). All samples are reconditioned and evaluated for hardness following aging. Significant emphasis is placed on the presence of calcium carbonate, over which increases in moisture content irrevocably reduce the composite’s hardness. Compared to untreated material, the hardness of 6, 8, and 10 mm composites decreased by 25.64, 10.92, and 4.63% after the 60-day aging period. This drop is mostly the result of microstructure evolution manifesting as an increase in porosity. Consequently, fiber deterioration, fiber cracks, and degradation of polymer-fiber bonding emerge in the composite, decreasing hardness.