Characteristics Of Cement Research Articles

Sewage sludge ash for soil stabilization: A review

Rapid industrialization leads to an increase in the quantity of combustion deposits like ashes. Currently, most of these ashes are disposed of in landfills. However, in India, the facilities for disposing these waste is very limited. Many states in India doesn’t have a proper disposal mechanism for such wastes, and thus the improper dumping of waste will affect the natural ecosystem. The waste management by reuse or recycling is crucial in the present-day scenario. With the fast growth in the volume of sewage sludge obtained from sewage treatment plants, it is crucial to reuse and reduce sludge. Sewage sludge ash (SSA) obtained from the burning of sewage sludge has significant dissimilarities with the fly ash/bottom ash in terms of chemical, physical and cementitious characteristics. Soil stabilization is indispensable due to the increase in the construction of structures. The studies dealing with soil stabilization has more focus on the use of chemical additives which are expensive and unsafe. Improving the ground using waste materials is one of the most essential and cost-effective methods. The commonly used additives such as cement and lime for stabilizing poor ground can be replaced with waste material, leading to a sustainable and environment friendly approach for discarding the industrial waste. This paper briefly describes the production, properties and application of SSA in civil engineering even though the focus was on the utilization of SSA for soil stabilization. Studies have already reported that SSA possesses pozzolanic properties and has the potential to stabilize the soft ground. This paper also addresses a broad review of the index and engineering properties of soil improved with SSA.

Study on the Optimization of Filling Ratio and Strength Variation Characteristics of Cemented Backfills Containing Fly Ash

The fly ash for underground filling can effectively utilize solid waste, improve the strength of the backfill, and reduce the cost, thus creating good social and economic benefits. Relying on the filling requirements of a gold mine in Jilin, this paper carried out the filling ratio experiments containing fly ash and analyzed the reasons for the variation of the backfill strength based on the hydration characteristics of cement and fly ash and scanning electron microscope. The results show that fly ash has an overall effect on the strength of the backfill, and the strength development is mainly concentrated in the period of 28–56 d; when the filling slurry contains tailings, the excessive amount of fly ash is likely to cause a large number of fine particles to obstruct the hydration of cementitious materials; when the concentration of the filling slurry is 74%, the cement content is 5%, the mass ratio of waste rock-tailings-fly ash is 6:2:3, and the CaO content is 6:3, the strength of the backfill is significantly higher than the current strength of the backfill of the mine, and the cost can be saved by RMB 0.56 per cubic meter; the strength characteristics of the backfill mainly depend on the pore structure; when the filling slurry is better matched, the cement and fly ash hydration generates a large number of C-S-H gel particles, which wraps the aggregate to form a dense structure with less pore structure, and the strength of the backfill increases; the strength variation process of backfill containing cement and fly ash is divided into cement hydration period, fly ash infiltration period, and slurry hardening period. To enhance the strength of the backfill, it is necessary to determine the appropriate cementitious material ratio to maximize the excitation of fly ash hydration during the fly ash infiltration period, and the hydration produces a gel structure with an excellent aggregate ratio. In addition, the slurry hardening reduces the porosity of the backfill. The results can provide basic data and theoretical guidance for further promotion and application of fly ash in mine filling.

Preliminary Research On Waste Rubber Application In Cement Bound Base Layer

Besides all the positive characteristics of cement bound courses (CBC), it has some detrimental effects on the pavement wearing courses. Due to cement hydration, this mixture is affected by shrinkage. Shrinkage induces cracks in the whole layer which along with weather conditions propagate through asphalt layers in a short period. Also, it’s stiffness negatively affects cracks propagation without providing elastic support for upper layers. As a result, roads are covered with various damages which reduces driving comfort and safety and demand new financial investments. The focus is on reducing the detrimental effect of CBC on the pavement. Nowadays, large quantities of recycled rubber can be found on the market. Wasted rubber is a large ecological problem due to its long decomposition period. On the other hand, by mechanical grinding and separation process, suitable fractions of rubber can be obtained for use in construction. Consequently, the replacement of conventional material by crumb rubber reduces the consumption of natural material and energy for its exploitation. Appropriate amounts and fractions of recycled rubber have the potential to reduce shrinkage and increase the elasticity of CBC. Within this paper, preliminary research results will be presented on the possibilities of crumb rubber implementation in CBC and its effects on mechanical characteristics. By using recycled materials in construction processes we undertake a major step in the sustainable management of natural resources.

A Study on the Characteristics of Clinker and Cement as Chlorine Content

A Study on the Characteristics of Clinker and Cement as Chlorine Content

The mechanism of pores enhancing the deformation of completion cement under confining pressure

As a porous material, the strength and deformation characteristics of cement after well-completion are related to internal pores. This article describes a damage law of cement with pores. The damage law was applied to a damage response analysis of a gas storage salt cavern wellbore during the service period. The damage is caused by two aspects: the initial isotropic damage caused by the primary pores, and the subsequent anisotropic damage caused by the secondary micro-cracks in the matrix. It is necessary to establish a damage evolution model including the effects of pores and micro-cracks. Triaxial compression tests are performed on two sets of cement samples with and without pores to verify the model. By user programmable features (UPFs) in the finite element software ANSYS, the damage constitutive equation is embedded in a numerical calculation. According to the structure and load parameters of a salt cavern in Jintan, a wellbore model with porous cement sheath was established for engineering application. The following conclusions are obtained through experiments and numerical calculations: the pores reduce the strength of cement under low confining pressure but increase the deformability under high confining pressure. If there are no pores in the cement sheath, high damage areas are easily formed at the internal interface. When the porosity becomes 5%, the radial deformation ability is enhanced, and the interface is not easy to debond. However, when the porosity increases to 7.5%, the radial micro-cracks between the pores are formed, resulting in radial destruction.

Spatial Variation of the Chemical Properties of Rice Husk ASH

Pollution and waste management and control are global issues, particularly in the industrial and agricultural sectors. Pollution and health dangers, particularly those linked with the cement and clay-brick industries, are concerning and demand immediate action from authorities. One method of addressing the pollution problem associated with these sectors is the possible use of some agricultural waste that has pozzolanic properties. Based on available literature, RHA is widely accessible and has a great potential as a pozzolanic material. As a result, the current study was performed to examine in depth the chemical composition of non-ground RHA collected from various rice mills in Nigeria using X-ray fluorescence (XRF) technology. The RHs were collected from four (4) separate places in Nigeria, comprising seven (7) samples. In this study, Portland limestone cement of the UNICEM brand was used as a control sample and was acquired at a cement merchant store in Nsukka, Enugu State. The husks were carefully separated from the bran before being burned in the open air. Following that, the ashes were collected and stored in a dry area of the laboratory for analysis. Chemical analysis of the ashes and cement was performed to identify the elemental composition of each ash. This study also looked at the physical characteristics of RHA and cement, such as density, specific gravity, and particle size distribution. Non-ground RHA particle size distribution findings were comparable to cement. The ashes produced by open-air burning were milky-white in color, with a percentage difference in chemical composition. These compositional differences may be due to differences in soil chemistry at the sampling sites, paddy types, and the type of chemical fertilizers used. Finally, the findings indicated that the pozzolanic properties of RHA vary based on where they are located.

Triaxial Mechanical Characteristics and Microscopic Mechanism of Graphene-Modified Cement Stabilized Expansive Soil

To investigate the effect of graphene (G) on the triaxial mechanical characteristics of cement stabilized soil, a triaxial unconsolidated and undrained (UU) test was conducted on cement stabilized expansive soil (CES) and graphene-modified cement stabilized expansive soil (GCES) with 0.05%, 0.1%, 0.15%, and 0.2%G content, respectively. The experimental results showed that compared with CES, the deviatoric stress-strain curve of GCES showed a more obvious softening characteristic. The addition of G had a good modification effect on the triaxial mechanical characteristics of CES, and with the increase of the content of G, the compressive strength and shear strength of CES increased first and then decreased, and reached the best value when the G content was 0.1%. The failure angle predicted by the Mohr-Coulomb failure angle formula had a good correlation with the measured failure angle of soil specimens, so it could provide help for the prediction of soil failure surface in practical engineering. Besides, the scanning electron microscope (SEM) analysis indicated that the internal structure of CES was improved due to G addition.

Enunciation of size effect of sustainable palm oil clinker sand on the characteristics of cement and geopolymer mortars

Palm oil clinker (POC), a by-product from palm oil industry, has gained attention as a potential sand replacement in concrete. This study focuses on the grading of palm oil clinker sand (POCS) as a whole replacement of conventional sand in cement and geopolymer mortars. Fly ash (FA) and ground-granulated blast-furnace slag (GGBS) were used as binders and activated with a Na2SiO3/NaOH ratio of 1.5 in geopolymer mixes. Four different gradings of POCS with a maximum size of 4.75, 2.36, 1.18, and 0.60 mm, along with a control mix with the utilization of Mining sand (MS), were used to cast a total of 10 mixes for cement and geopolymer mortars. The microstructure of the POCS was analysed, and engineering properties of mortars were investigated through flow table test, compressive and flexural strengths, density, drying shrinkage, water absorption and sorptivity tests, and SEM images. The results revealed that mixes with the incorporation of finer POCS particles produced better compressive, flexural, and water absorption values, while the opposite was experienced in terms of drying shrinkage. Overall, the density of the mixes incorporating POCS was reduced by up to 20% and POCS geopolymer mortars produced higher strengths than those of cement. A 28-day compressive strength of 55–65 MPa was produced with the utilization of POCS in geopolymer mortar under the ambient temperature of 26–28 °C.

Microstructural and Strength Characteristics of Cement Treated Clay Stabilized with Zeolite for Road Base Application

The stabilization of clay soils with cement has been identified to be uneconomical, and its production is not environmentally friendly. The addition of pozzolanic material to cut down on the use of cement is very pertinent. Clayey soil was stabilized with 0, 2, 4, and 6% cement admixed with 0, 3, 6, 9, 12, and 15% zeolite. Index properties tests were conducted on the clay, while the unconfined compressive strength (UCS) test was carried out on the clay soil and clay treated with the selected composition of cement and zeolite. Tests including X-ray fluorescence (XRF) were conducted on the clay, cement, and zeolite. X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests were conducted on the clay and clay mixed with the selected composition of cement and zeolite. The objective of this study is to investigate the effect of zeolite on the strength and microstructure of cement stabilized clay soil. Index properties result in the group the clay as A-7-6 and clay of high plasticity (CH) based on AASHTO and Unified Soil Classification Systems, respectively. The (UCS) increased from 62kN/m2 for untreated clay to a maximum of 1552 kN/m2 for clay treated with 6% cement and 6% zeolite after 60 days of curing. The (XRF) test revealed major oxide compositions of the clay as silica, alumina, and iron; that of cement was quicklime and silica, while that of zeolite is silica, alumina, and sodium. The (XRD) result showed that the clay contained active montmorillonite along with other minerals. The addition of 6% cement disintegrates the montmorillonite minerals to less active kaolinite minerals with the introduction of calcite minerals. The addition of 6% cement and 6% zeolite further converted the montmorillonite mineral to kaolinite minerals with the introduction of calcite and zeolite. The (SEM) result of the clay mixed with cement and zeolite revealed a smooth, compact structure without pores which justifies the highest UCS value recorded in this mixture. 6% zeolite was observed to be the optimal zeolite that gave the highest UCS for each cement addition.

Characteristics of experimental resin-modified glass-ionomer cements, containing alternate monomers to HEMA

ObjectiveResin-modified glass ionomer cements (RMGICs) present several advantages (e.g. fluoride release), but their reported cytotoxicity has been associated with hydroxyethyl methacrylate (HEMA) monomer release. Therefore, different monomers were tested for use in RMGICs in order to improve their biocompatibility and reduce monomer release. MethodsEight experimental liquid compositions were prepared replacing different percentages of HEMA (conventional monomer used in commercial RMGICs) with hydroxypropyl-methacrylate (HPM) and/or tetrahydrofurfuryl-methacrylate (THFM), which are known to have better biocompatibility. Moreover, two commercial materials (Fuji-Plus and RelyX) and two compositions, based on these (home), were included as controls. Monomer release of all materials (commercial, home and experimental) were tested using high-performance liquid chromatography (HPLC) methods after immersing discs in deionized-water (DW) or ethanol:DW. Cytotoxicity of the materials extracts was tested on normal human oral fibroblast line (NHOF-1) using 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay. ResultsThree experimental materials containing THFM (F3, R3 and R4) showed less or similar monomer release compared to corresponding commercial products. Furthermore, two experimental materials (F3 and F4) showed similar effects on NHOF-1 cells compared to the negative control medium. SignificanceThe lower monomer release and higher cell viability of some experimental THFM compositions are encouraging. THFM partially replacing HEMA is potentially a suitable alternative for producing biocompatible RMGICs.

A comparative study on solidification/stabilization characteristics of coal fly ash-based geopolymer and Portland cement on heavy metals in MSWI fly ash

Cement-based solidification/stabilization (S/S) is a widely approach applied for municipal solid waste incineration (MSWI) fly ash. Although Portland cement on MSWI fly ash S/S has been widely developed, the economical and environment-friendly binders should be explored to reduce the energy and improve MSWI fly ash S/S performances. A comparative study about MSWI fly ash S/S treatment with coal fly ash-based geopolymer and Portland cement was carried out in this work. Specifically, physical and chemical characteristics of MSWI fly ash, compressive strength, leachability and chemical speciation transformation of heavy metals, microstructures and morphology of S/S samples were investigated. Results showed that leaching concentration of Pb, Cd and Zn in MSWI fly ash was 5.36 mg/L, 40.3 mg/L and 129.0 mg/L respectively. It was 34.7, 160.2 and 0.29 times higher than Standard GB16889, far exceeding the requirements for municipal solid waste landfill. Leaching tests indicated that immobilization rates of Pb, Zn and Cd with geopolymer S/S treatment were exceeding 99%. Compressive strength of geopolymer and Portland cement S/S samples curing for 28 days varied from 14.3 to 22.4 MPa and 2.5–10.8 MPa, respectively. In summary, geopolymer exhibited better immobilization performances on MSWI fly ash than Portland cement. In geopolymer S/S samples, active aluminosilicate in MSWI fly ash participated the geopolymerization reaction and generated new phases such as Friedel’ salts (3CaO•Al2O3•CaCl2•10H2O) and hydrocalumite (Ca2Al(OH)6Cl2H2O). It not only promoted the bulk resource utilization and disposal of fly ash, but also realized the effective encapsulation of heavy metals and chloride ions. Therefore, geopolymer is a more promising candidate for MSWI fly ash S/S treatment.

Influence of intracoronal bleaching agents on the bond strength of MTA cements to composite resin and their surface morphology.

The objective of the present in vitro study was to evaluate micro-tensile bond strength (µSBS) of MTA cements to composite resin using a universal adhesive after internal bleaching procedure, and to examine surface characteristics of MTA cements exposed to bleaching agents. MTA specimens were divided into three subgroups according to the bleaching agent used which were, 37% carbamide peroxide (CP), 35% hydrogen peroxide (HP), and no exposure as a control group (n = 12). After exposure to bleaching agent, composite resins were applied to MTA surfaces using a universal adhesive in self-etch mode. The specimens were exposed to a shear force until failure to evaluate bond strength. MTA surfaces were investigated using scanning electron microscopy (SEM) to observe the effects of the bleaching agents. Differences between groups were analyzed using two-way ANOVA test and intergroup comparisons were assessed with Tukey test (p < 0.05). Although there was a slight difference in bond strength between bleaching agents (CP and HP), no significant difference was found, irrespective of MTA cement. After the HP application, the bond strength values decreased approximately by half compared with the controls. SEM results demonstrated distinct morphological differences between the intact MTA surface (control) and treated MTA surface. Distinct micro-cracks, surface irregularities, and capillary voids formed due to the superficial dissolution caused by peroxides. Exposure to the intra-coronal bleaching agents had a negative influence on the surface morphology of MTA cements and their bond strength to composite resin.

Structural characteristics of soil-rock mixtures based on electrochemical impedance spectroscopy

Geotechnical problems in extremely complex environments have become increasingly prominent, which raises the need to explore more efficient solutions. Multidisciplinary approaches show a new perspective to deal with these problems. In this study, the electrochemical impedance spectroscopy (EIS) was introduced to illustrate the structural characteristics of soil-rock mixtures (SRM), aiming at deducing the relationship between physical property indices such as the mass ratio indices (e.g., water content, soil-rock ratio, and stone particle size) and volume ratio indices (e.g., porosity and saturation) and equivalent circuit at the macro and micro levels. A three-level equivalent circuit corresponding with the physical characteristic of SRM was established to describe the cementation state. It shows that the degree of cementation of SRM increases with increasing water content, rock content, and median size of block stone; meanwhile, the real impedance coefficient of the non-cemented part is lower than that of the cemented part. The corresponding relationship between the imaginary impedance and the specific gravity has segmental characteristics. The density first increases and then decreases with the increase of water content; the water content and saturation threshold are 16% and 80 ± 2%, respectively. Moreover, the saturation (Sr and n∙Sr) decreases with the increase in the real impedance coefficient. In addition, the characteristics of the propagation mode and interfacial contact characteristics of the charged material inside SRM were examined, and the macro and micro mapping of the cementation state of SRM and the basic mass transfer mode (i.e., migration, diffusion, and convection) were obtained. The mapping relationship proposed in this study reflects the micro-scale cementation characteristics and the macro-scale physical characteristics of the SRM system, which provides new insight into the multi-scale research of SRM.

Characteristics of dissolved pores and dissolution mechanism of zeolite-rich reservoirs in the Wuerhe Formation in Mahu area, Junggar Basin

The reservoir in the Wuerhe Formation in the Mahu Sag, northwestern Junggar Basin, China, exhibits complex dissolution and cementation related to zeolite. The source and mechanism of diagenetic fluids are crucial in studying the reservoir genesis. Thus we investigated the key reservoirs fluids related to the zeolite and discussed their significance in the zeolite-rich reservoir of the Permian Wuerhe Formation in the Mahu Sag. Based on thin sections and electron microscope observations of rock samples and analyses of physical properties, C-O isotopes, and major elements, it is found that the reservoir underwent mainly two stages of fluid-related dissolution and cementation processes, in which the hydrocarbon-bearing fluid played the primary role in forming the high-quality reservoir. Dissolution pores are the most important storage space, and zeolite cement is the most important dissolution mineral. The geochemical characteristics of zeolite and calcite cement indicate the presence of two diagenetic fluids. The iron-rich calcite and orange-red heulandite is related to early diagenetic fluids with high iron content and higher carbon isotope values, whereas the calcites, with high manganese content and lower carbon isotope values, are formed by late acidic organic diagenetic fluids related to oil and gas activities. The hydrocarbon-bearing fluids form different spatial diagenetic zones, including the dissolution zone, buffer zone, and cementation zone, and the dissolution zone near the oil source fault is the main site of zeolite dissolution. The late fluid has the characteristics of multi-stage activity, which makes the spatial zoning expand gradually, resulting in multiple superpositions of dissolution and cementation and increasing the complexity and heterogeneity of the reservoir diagenesis. This study expands the understandings of the dissolution activities of different fluids in zeolite-rich reservoirs and also has reference significance for dissolution activity of hydrocarbon fluid in other types of reservoirs.

ВЛИЯНИЕ АГЛОМЕРАТОВ НАНОПОРОШКА КАРБИДА ВОЛЬФРАМА НА СВОЙСТВА ЦЕМЕНТА

The object of the research is cement samples modified by agglomerates of tungsten carbide nanopowders obtained from carbide waste. The paper considers the influence of tungsten carbide nanopowder on the change in the main cement characteristics (density, water demand, setting time, kinetics of strength gain, compressive strength, bending strength). The optimum additive content in cement materials is 3%. This parameter is estimated by the maximum growth of compressive and flexural strength at all stages of hardening. The effect of WC powder additive on the structure of the cement matrix has been shown. Due to the high dispersibility of WC nanopowder, its particles act as additional crystallization centers, fill in the micropores of the cement stone and create a denser and stronger structure. The results of studying the microstructure of the cement stone with additions of WC powder indirectly confirm the results of strength characteristics. The cement-sand samples with the modifier are found to have a denser crystallized cement-sand stone compared to the control sample (without WC powder addition). The conducted researches have shown perspectivity of application of WC nanoparticles agglomerates as modifying additives for cement materials, which can be used in production of special purpose concrete (hydraulic, radioprotective, etc.). The economic effect of the use of WC nanoadditives obtained from hard-alloy production wastes can be obtained due to a reduction in costs at the stages of construction and operation of structures, buildings, structures based on it.

Studies on computing compressive strength of zeolite blended concrete using multiple regression analysis

Concrete is most extensively adopted materials for construction, due to its high ration of durability to cost. The important factor on which concrete performance depends is characteristics of cement consumed during concrete production. Greater the environmental and economic profits can be achieved when addition of Pozzolanic mineral additives such as fly ash, GGBFS in Concrete production. It is normally accepted that adding of pozzolan decreases the amount of calcium hydroxide in paste of cement and raises the perviousness of concrete.Zeolites are alumina silicates having crystalline properties with even pores and hollows. They hold exceptional characteristics, such as molecular sieves, ion exchange, a huge area of Surface, and catalytic action, which mark them as anticipated ingredient for numerous industrial uses. The Pozzolanic features of Zeolite are largely due of their volatile content of SiO2 and Al2O3. This content reacts with calcium hydroxide (CaOH2) which is generated in the procedure the Cement hydration, and transforms it into Calcium silicate hydrate (CSH) gel. Hence, the microstructure of concrete is enhanced and the concrete turn out to be impermeable.Additives of zeolite concrete implants have been attempted to advertise hazardous substances, especially those contained in car extinguishing. It can be believed that the estimation regarding CO2 absorption of concrete with added zeolite has not been tested, yet zeolite displays a very good adsorption property for CO2 and NOx.In this study, it is proposed to examine the influence of blending of Natural Zeolite on strength properties of Concrete. Statistical Package for the Social Sciences (SPSS) package is used for multiple regression Analysis to suggest a formulae for strength forecast. The predicted result is validated with the test results conducted in Laboratory on Zeolite blended Concrete.

Experimental Study of the Mechanical and Microstructure Characteristics of Coal Gangue Road Stabilization Materials Based on Alkali Slag Cementation.

To accelerate the resource utilization of coal gangue and meet the strategic requirements of carbon neutralization, alkali-activated, slag-cemented coal gangue is applied in the preparation of solid waste-based road stabilization materials. Here, the cementation characteristics and microstructure characteristics of alkali-activated, slag-cemented coal gangue road stabilization materials are studied using the alkali equivalent and coal gangue aggregate ratio as experimental variables. The results show that with the increase in alkali equivalent from 1% to 7%, the unconfined compressive strength of the alkali-activated coal gangue road stabilization material initially increases and then decreases, with 3% being the optimal group in terms of stabilization, the aggregate ratio of coal gangue increases from 70% to 85%, and the 7-day unconfined compressive strength of the stabilized material decreases approximately linearly from 8.16 to 1.68 MPa. At the same time, the porosity gradually increases but still meets the requirements of the specification. With the increase in hydration time, a large number of hydration products are formed in the alkali slag cementation system, and they are closely attached to the surface of and interweave with the coal gangue to fill the pores, resulting in the alkali slag slurry and coal gangue being brought closer together.

Mechanical and Microstructural Characteristics of Calcium Sulfoaluminate Cement Exposed to Early-Age Carbonation Curing.

The early-age carbonation curing technique is an effective way to improve the performance of cement-based materials and reduce their carbon footprint. This work investigates the early mechanical properties and microstructure of calcium sulfoaluminate (CSA) cement specimens under early-age carbonation curing, considering five factors: briquetting pressure, water–binder (w/b) ratio, starting point of carbonation curing, carbonation curing time, and carbonation curing pressure. The carbonization process and performance enhancement mechanism of CSA cement are analyzed by mercury intrusion porosimetry (MIP), thermogravimetry and derivative thermogravimetry (TG-DTG) analysis, X-ray diffraction (XRD), and scanning electron microscope (SEM). The results show that early-age carbonation curing can accelerate the hardening speed of CSA cement paste, reduce the cumulative porosity of the cement paste, refine the pore diameter distribution, and make the pore diameter distribution more uniform, thus greatly improving the early compressive strength of the paste. The most favorable w/b ratio for the carbonization reaction of CSA cement paste is between 0.15 and 0.2; the most suitable carbonation curing starting time point is 4 h after initial hydration; the carbonation curing pressure should be between 3 and 4 bar; and the most appropriate time for carbonation curing is between 6 and 12 h.

The Effect of Vancomycin and Silver Combination on the Duration of Antibacterial Activity of Bone Cement and Methicillin-Resistant Staphylococcus aureusBiofilm Formation

Background.Local prevention of periprosthetic infection and treatment of infectious complications after various joints arthroplasties includes the use of polymethylmethacrylate-based spacers impregnated with antimicrobial agents. At the same time, the added components are able to change the bone cement characteristics and have variable antimicrobial effect duration. The aim of the studywas to evaluate the duration of antimicrobial activity and the effect on the MRSA ATCC 43300 biofilm formation on bone cement samples with gentamycin impregnated with vancomycin and/or highly dispersed silver.Materials and Methods.Samples were made from bone cement DePuy CMW 1 Gentamicin and mixed with vancomycin and/or highly dispersed silver. The elemental composition was studied by scanning electron microscopy and micro-x-ray spectral analysis. The study of the antimicrobial activity duration was performed by daily applying an incubation solution with samples to the bacterial lawn surface. The effect on biofilm formation was evaluated by immersing the test samples in LB-broth with MRSA.Results.The control samples did not have antimicrobial activity (AMA) against MRSA ATCC 43300. Test samples, additionally containing 10 wt.% of vancomycin was effective for 9 days. When adding highly dispersed silver, the lengthening of the samples activity time was recorded. So, when applying 2.5 wt.% of highly dispersed silver, the duration of AMA was 21 days, and when increased to 10 wt.% — 34 days. Energydispersion analysis of the sample surface with 10 wt.% of vancomycin and highly dispersed silver showed that the skeletal structure type contains matrix component based on barium sulfate with silver inclusions. During the study of the samples effect on a typical strain biofilm formation, no statistically significant differences were found between the optical density of gentian violet extracts in the negative control and in the medium with MRSA.Conclusion. The vancomycin with highly dispersed silver combination prolonged the antimicrobial activity of the samples against MRSA ATCC 43300 and effectively prevented the formation of microbial biofilms on its surface. Despite the fact that the conditions of the conducted experiment in vitro are not identical to the conditions of bone cement antimicrobial spacers clinical use, our results indicate the need to use spacers with a known duration of antimicrobial activity and to comply with the terms of temporary structures replacement.

Effect of Polypropylene Fibers on moisture Susceptibility of Warm Mix Asphalt

Warm Mix Asphalt (WMA) is a modern energy-saving process that uses environmentally friendly materials, has lower mixing and compaction temperatures, and uses less energy and releases less contaminants than conventional hot mix asphalt. Moisture damage poses one of the main challenges of the material design in asphalt pavements. During its design life, the asphalt pavement is exposed to the effect of moisture from the surrounding environment. This research intends to investigate the role of the polypropylene fibres for modifying the moisture susceptibility for the WMA by using different percentages of polypropylene (namely 2, 4, and 6%) by weight of the binder of the control mixture (WMA). In this paper, the physical characteristics of the asphalt cement, Marshall properties, Tensile Strength Ratio (TSR) and Index of Retained Strength (IRS) were determined to establish the effect of the polypropylene on the moisture susceptibility of the WMA. The results displayed that the modification of the AC with polypropylene caused an increase in the optimum asphalt content by 1.03, 3.09, and 11.3%, with the addition of 2, 4 and 6% of the P.P., respectively. The moisture resistance of the asphalt mixture was enhanced by adding the P.P., according to the rise in the Tensile Strength Ratio (TSR) and Index of Retained Strength (IRS) values. The TSR value showed 9.4, 18.2 and 19.5% increase when the P.P. increased from 0.00 to 0.02, 0.04, and 0.06, respectively; besides, the IRS showed improvement with the addition of the P.P. to the WMA. Doi: 10.28991/cej-2021-03091704 Full Text: PDF