Weight Loss Of Specimens Research Articles

Application of Celtis Zenkeri Exudates as Corrosion Inhibition for Galvanised Steel Exposed to Acidic Media

This study investigated the performance of Celtis zenkeri exudates in preventing galvanised steel exposed to acid concentrated water and soil. The study was performed in order to find an alternative coating substance that can reduce the corrosion of galvanised steel pipes exposed to corrosive water and soil media. Various steel specimens were cut into portions and coated with the exudates at 25 - 50µm thickness. To accelerate the rate of corrosion, 0.5M hydrochloric acid (HCl) was added to tap water in a container. Also, the same concentration of HCl was equally added to soil samples. Uncoated steel specimens were immersed in the acid concentrated water and soil, servicing as control sample. The rate of corrosion was monitored for 30 days (720 hours). The inhibition efficiency of the exudates for both corrosive media was compared. Results showed that the weight loss and corrosion rate of galvanised steel decreased with increase in coating thickness. Comparatively, the weight loss and corrosion rate in the uncoated specimens were higher than the coated specimens. With 25 - 50µm coating thickness, the decrease in corrosion rate ranged from 0.01272 to 0.0027mm/yr for specimens immersed in water and from 0.2226 to 0.0185mm/yr for specimens buried in soil, while for uncoated specimens, the corrosion rate was 0.2793mm/yr and 0.4150mm/yr for specimen immersed in water and soil respectively. The inhibition efficiency of Celtis zenkeri exudates increased with coating thickness, which ranged from 54.46 – 99.03% for specimens immersed in water and 46.36 – 95.54% for specimens buried in soil at 25µm – 50µm coating thickness. The results demonstrated that Celtis zenkeri exudates can be used as corrosion inhibitor for steel exposed to corrosive media.

Comparative Analysis of Various Irrigation Solutions in Root Canal Treatment.

"Root canal treatment (RCT)" is essential in preserving natural dentition by eliminating infection within the root canal system. Irrigation solutions play a crucial role in achieving successful RCT outcomes by facilitating disinfection and debris removal. An in vitro experimental design was employed to evaluate the irrigation solutions. Antimicrobial efficacy was assessed using agar diffusion assays against Enterococcus faecalis and Candida albicans. Tissue dissolution ability was evaluated by measuring the weight loss of dentin specimens. Cytotoxicity was assessed using cell viability assays with human periodontal ligament fibroblasts. NaOCl demonstrated the highest antimicrobial efficacy, while EDTA exhibited superior tissue dissolution ability. CHX and QMix displayed lower cytotoxicity compared to NaOCl and EDTA. The choice of irrigation solution in RCT should consider factors such as antimicrobial efficacy, tissue dissolution ability, and cytotoxicity. NaOCl remains effective but has high cytotoxicity, whereas CHX and QMix offer alternatives with lower cytotoxicity. EDTA is effective in tissue dissolution but should be used cautiously due to cytotoxic potential. Clinicians should weigh the benefits and limitations of each solution for optimal treatment outcomes.

EFFECT OF CEREAL SEED CONTRIBUTION TO THE WEAROF SELECTED MATERIALS USED TO PRODUCE SCREWCONVEYOR BLADES

This paper presents the analysis of the process of structural material wear by cereal seeds. Two steel gradeswere subjected to testing: C45 and low-alloy steel with a micro-addition of boron. The experiment wasconducted under laboratory conditions by the “rotating bowl” method. Wheat and maize seeds were usedas an abrasive. During the testing, analyses of specimen weight and volume loss as a function of the frictiondistance were carried out. An analysis of the test material surface was conducted as well.The study results show that the C45 steel worn in maize grains exhibited a weight loss greater by 20% thanthat for the wear in wheat grains. For the abrasion-resistant steel, the difference was 22%. In both abrasivemediums, the C45 steel wore to a greater extent than the abrasion-resistant steel. For the maize grain abrasive,the weight loss value was approx. 1.5 times higher than that for the C45 steel. Similar correlations were notedfor the wheat abrasive. The abrasion-resistant steel had a wear rate approx. 1.6 times lower than the C45 steel.The dominant wear types observed on the surfaces of the test steels include ridging and micro-cutting.

Mechanical Properties of Geopolymer Concrete Subjected to Elevated Temperature

Abstract: The present study is to examine the influence of the sustained elevated temperature on hardened properties of the Geopolymer concrete (GPC), achieved by complete replacement of cement by GGBS and SCBA in the proportion of 70:30 andmixing with the sodium based alkaline activators with varying molar concentration of NaOH (4M,8M,12M). After completion of 28 days curing the specimens were kept inside the electric oven , capable of attaining a maximum temperature of 10000C and the required temperature of 2000C, 4000C, 6000C and 8000C was set. After a steady state is reached the specimens were sustained for a predetermined duration of 2 hours. After attaining the 2 hours sustained temperature specimens are set aside to cool to room temperature and tests are conducted to measure the residual strength of the specimens using proper experiment setup. The outcomes revealed that with increase of temperature the weight loss of specimens is increased and the residual compressive strength of the specimens is decreased, GPC has a better resistance against cracking and spalling up to 600 0C

Experimental Investigation on Color Change and Weight Loss of Steel Fibre Reinforced Concrete when Exposed to Elevated Temperature

Objectives: This study mainly focuses on different steel fibres content behaviour, when exposed to various temperature. Methods: In this experimental investigation, the prism specimen of size 500 x 100 x 100 mm with steel fibre content of 0% and 1.5% were exposed to temperature of 100 °C, 300ºC, 500 °C and 700 °C. The Temperature-Time graph was obtained as an outcome of the experiment. Color change and weight loss of specimens at different temperatures was assessed. Findings: The RSM weight loss prediction model has been proposed for specimen before and after exposure of temperature. Color changes at 100 °C, 300 °C, 500 °C and 700 °C was observed to be no color change, red, grey and whitish grey respectively. Mass loss of 0% steel fibre concrete prism at 100 °C, 300 °C, 500 °C and 700 °C was found to be 2.17%, 4.33%, 4.24% and 6.55% respectively. Mass loss of 0% steel fibre concrete prism at 100 °C, 300 °C, 500 °C and 700 °C was found to be 0.61%, 4.51%, 5.66%, and 6.27% respectively. Novelty: Very few studies have been conducted on the combination of color change and weight loss of the specimen. Weight loss prediction model is the novelty of this study. The RSM prediction model clearly indicates that the response values are 97.21% and 96.12%, where the model is fit for weight of specimen before and after exposure to temperature respectively. Keywords: SFRC, Color change, weight loss, RSM, Temperature

Study of corrosion properties of carbon steel, 304 and 316L stainless steels in sulfuric acid and their degradation products

In this study, corrosion properties of carbon steel and stainless steels, and degradation of sulfuric acid by the corrosion mechanism are presented. Carbon steel (CS), 304 stainless steel (SS304), and 316L stainless steel (SS316L) specimens were analyzed through their electrochemical response by using a potentiostat measurement. The specimens were submerged in concentrated 98 wt.% of H2SO4 acid for 0 day to 60 day. The degradation of H2SO4 was determined by its volume change, turbidity, and color due to the corrosion mechanism. Corrosion rate of CS, SS304 and SS316L specimens are 43.237 mm/year, 0.420 mm/year and 0.086 mm/year, respectively. After 60 days, the weight-loss of CS, SS304 and SS316L specimens are 48 wt%, 33 wt% and 0.1 wt%, respectively. Corrosion resistance of the materials are influenced by the passive oxide layer that forms on its surface and associated with electrochemical activity or semiconductive composition. The degradation of H2SO4 acid was observed due to the corrosion process of specimens and related to the turbidity and volume increase while the wt% concentration of H2SO4 acid decreases. In order to make material choices that enable continuous and safe operation of the process, it is important to understand the corrosion mechanism changes.

Investigation on residual bond strength and microstructure characteristics of fiber-reinforced geopolymer concrete at elevated temperature

Fiber-reinforced geopolymer concrete has been attracting attention and interest worldwide due to its sustainable properties. However, few studies have reported the pull-out behaviour of fiber-reinforced geopolymer concrete (GPC) at elevated temperatures. In order to bridge this knowledge gap, a series of detailed investigations aimed to investigate the effect of elevated temperatures on the mechanical and microstructure properties of fiber-reinforced geopolymer concrete. In the present investigation, crimped steel fibers (SF), polypropylene fibers (PF), basalt (BF), and hybrid fibers such as SF:PF and PF:BF is employed to develop the GPC. Alkaline activators such as sodium hydroxide (NaOH) of 8 M and 10 M and Na2SiO3/NaOH ratios of 2.5 are used in the production of M35 and M40 grade GPC. Compressive strength, weight loss, crack pattern, bond strength, and microstructure of fiber-reinforced GPC specimens have been evaluated, after exposing to higher temperature following ISO 834 standard fire curve. Results from the conducted tests show that adding various types of fibers improves the compressive strength and bond strength of the GPC specimens. More specifically, amongst all tested specimens, the exposed GPC-BF shows lesser weight loss and higher residual compressive strength with fewer cracks on the surface of the specimens. on the other hand, GPC with SF shows higher residual bond strength than other fiber-reinforced GPC specimens. Microstructure analysis (SEM/EDAX) confirms the extent of damage and contribution of fiber in the temperature-exposed GPC. A statistical relationship and correlation has been obtained between compressive and bond strength.

Impact of glazing on wear, fracture load, and optical properties of a new fully crystallized lithium disilicate ceramic material

ObjectivesLithium disilicate (LDS) based glass ceramics are indispensable materials in the field of prosthetic dentistry due to their strength and excellent esthetics. Recently, novel fully crystallized LDS for the milling process have been introduced to the market, requiring only chairside polishing before delivery. Since limited data is available about subjecting this material to glazing, this study aimed to evaluate the wear properties, fracture resistance, and optical properties of the newly introduced fully crystallized LDS after glazing. MethodsLithium disilicate glass-ceramics (fully crystallized (LiSiCAD) and partially crystallized types (EmaxCAD), of shade A3, were used in the present study. The fully crystallized specimens were subjected to a glazing firing cycle in a furnace (LiSiCAD-G) and compared to a polished fully crystallized counterpart (LiSiCAD-P, negative control) and a glazed partially crystallized LDS (EmaxCAD, positive control). Rectangular-shaped ceramic specimens (n = 10, 12 × 6.5 × 1.5 mm) and enamel antagonists were used to test the wear resistance in a specially designed wear machine built at the Department of Oral Technology, University of Bonn, Germany. The volumetric enamel loss of antagonists was measured by means of overlapping virtual 3D models derived from micro-CT scans for the teeth before and after the wear test. The weight loss of ceramic specimens in milligrams was measured after 100,000 and 200,000 wear cycles. A spectrophotometer was used to calculate the CIELAB color parameters of the ceramic specimens against black and white backgrounds to measure the translucency. Fracture resistance was also assessed after thermodynamic fatigue using a universal testing machine until fracture at a 1 mm/min crosshead speed. Statistical analysis was performed using one-way ANOVA and the significance level was set at α = 0.05. ResultsEmaxCAD and LisiCAD-G groups showed significantly higher mean ceramic weight loss after 100,000 cycles (2 ± 0.3 mg and 1.93 ± 0.2 mg, respectively) than LisiCAD-P group (0.78 ± 0.19 mg). Glazed LiSiCAD specimens demonstrated significantly higher ΔE values from shade A3 compared to polished LiSiCAD. There was no significant difference in ΔE between LiSiCAD-G and EmaxCAD. For fracture resistance, no significant difference was observed between LiSiCAD-G and LiSiCAD-P before or after aging. ConclusionsThe glazed fully crystallized LDS was superior to the partially crystallized one with regard to wear resistance but showed more color changes than the polished fully crystallized one. Furthermore, polishing of fully crystallized LDS could still be considered a better option than glazing when aesthetics is a primary prerequisite.

Behavior evaluation of concrete made with waste rubber and waste glass after elevated temperatures

The re-use of solid wastes (waste rubber and waste glass) to make green concrete is very important towards sustainable buildings. In this work, a novel efficient solution of replacing natural fine and coarse aggregate with waste rubber (WR) and waste glass (WG) respectively was adopted to analyze the performance of WR and WG as well as their combinations in mixtures when subjected to elevated temperatures. In present research, the river sand was replaced by WR particles at varied volume ratios from 10% to 30% and WG was used as gravels at 10%, on volume basis. These specimens were heated to 200 °C, 400 °C, 600 °C, 700 °C and 800 °C, and then they were kept for 2 h and subjected to air-cooling regime naturally. To this end, the appearance change, mass loss rate, volume change, compressive strength, split-tensile strength, and ultrasonic pulse velocity (UPV) were evaluated through a series of tests at ambient and after exposure to elevated temperatures. Also, water absorption and sorptivity tests were conducted to assess porosity as well. In addition, the scanning electron microscopy (SEM) was used to understand the influence of this two wastes on the microstructure evolution under various temperatures. According to experimental results, the compressive strength of mixtures presented a 4.32%–8.53% increasement in temperature between 20 °C and 200 °C, followed by a gradual decrease in the strength values. While split-tensile strength showed a decline at each temperature level, with a strength reduction of 60%-70% at 700 °C. On the other hand, the combined mixture mitigated damage of rubber concrete and improved its mechanical behaviors. Particularly, when the volume fractions of both WR and WG aggregates were 10% respectively, the mixture outperformed the other combination mixes concerning mechanical and durability performance of heated and unheated samples. Furthermore, the water absorption and weight loss of specimens were found to increase with temperatures, with water absorption exceeding 10% and mass loss varying from 7.88% to 9.44% at 700 °C. Whereas the ultrasonic velocity values gradually decreased. To sum up, the combination of WR and WG was proved as a promising option to enhance the performance of rubberized concrete under high temperatures.

Microhardness and dry sliding wear behaviour of HVOF sprayed WC-Co-Cr+ graphene nanoplatelets coating

In this study, coating of WC-10Co-4Cr with the incorporation of 2 wt%, 3 wt%, and 4 wt% graphene nano-platelets (GNPs) were created on an IS-2062 steel substrate by employing high-velocity oxy-fuel (HVOF) technique. Cross-sectional Vickers' microhardness and dry siding wear of coated substrate against hardened EN32 steel disc were investigated after successful coating deposition in the range 220–230 µm. Furthermore, the worn-out surface was characterised using optical images, weight loss, and the coefficient of friction. The experimental results show that the hardness of IS-2062 steel has been increased by a factor of 5. The weight loss of specimens during dry sliding wear is primarily caused by micro-ploughing, lips formation, and breaking, as observed from the optical images.Weight loss during sliding wear was found to decrease as the percentage of GNPs increases in WC-10Co-4Cr feedstock powder. In terms of higher microhardness and low wear rate, the coating configuration WC-10Co-4Cr+ 3% GNPs provides the best results for practical applications.

Granite powder as partial replacement of cement in M30 grade concrete mix using IS 10262:2019

PurposeThis study aims at designing consistent and durable concrete by making use of waste materials. An investigation has been carried out to evaluate the performance of conventional and optimal concrete (including 5% GP) at high temperatures for different exposure times.Design/methodology/approachAn experimental work is carried out to compare the conventional and optimal concrete with respect to weight loss, mechanical strength characteristics (compressive, tensile and flexural) after exposed to 100, 200 and 300 °C with 1, 2 and 3 h duration of exposure followed by cooling in furnace for 24 h and then air cooling.FindingsThe workability of granite powder modified concrete decreases as percentage of replacement increases. Compressive, tensile and flexural strengths all increased at 100 °C when compared to strength characteristics at normal temperature, regardless of the exposure conditions, and there was no weight loss noticed. For 200 and 300 °C, the strengths were decreased compared to normal temperature and an elevated temperature of 100 °C, as weight loss of concrete specimens are observed to be decreased at these temperatures. So, the optimum elevated temperature can be concluded as 100 °C.Originality/valueIncorporating pozzolanic binder (granite powder) as cement replacement subjecting to elevated temperatures in an electric furnace is the research gap in this area. Many of the works were carried out replacing GP for fine aggregate at normal temperatures and not at elevated temperatures.

Utilization of Chitosan as an Inhibitor to Improve the Corrosion Resistance of Low-Carbon Steel

The Batam industry materials are steel, an alloy material between iron and carbon, and a few other elements. Low-carbon steel is one type of metal. However, this low-carbon steel has the disadvantage of corrosion resistance, mainly if applied to corrosive environments. In the utilization of Low carbon steel in the industry, corrosion can cause problems and cost a lot of money in its maintenance. Chitosan contained in invertebrate animals is predicted to be able to prevent corrosion as an inhibitor. This study aims to analyze the optimal conditions of chitosan inhibitors against the corrosion rate of low-carbon steel in environments with variations in the length of immersion of specimens in corrosive media. This study is a true-experimental study with a pre-post-test design. The determination of the optimal conditions of corrosion inhibition of low-carbon steel plate specimens by chitosan was carried out with variations in the parameters of HCl concentration, specimen immersion time, and chitosan concentration. The analysis carried out is the measurement of specimen weight loss in each parameter by determining the difference in weight before and after the experiment and determining the efficiency of the inhibitor. The experiment’s results showed that the optimal conditions of inhibition of corrosion were at 1M HCl, 400ppm chitosan, and a soaking time of 3 days with an efficiency of 48%. The efficiency value of this optimum corrosion inhibition of chitosan in low-carbon steel is 48%. To improve the efficiency of corrosion inhibition, it is necessary to further research with higher accuracyTo determine the effect of inhibition of corrosion using chitosan on the quality of steel surfaces, it is necessary to analyze the steel surface structure using ultrasonic testing or using XRD Analysis.

Residual Durability Performance of Glass Fiber Reinforced Concrete Damaged by Compressive Stress Loads

Concrete is exposed to a variety of stresses throughout its service life, which can result in cracks and damage. The use of fibers in concrete mixtures is known to improve the mechanical and durability properties of the concrete. In this study, glass fiber-reinforced concrete cube specimens were produced and stressed at 70 and 90 percent of their maximum compressive strength. The effects of stress loading-induced cracks and glass fiber reinforcements on mechanical and durability properties of concrete specimens were investigated using UPV, capillary water absorption, acid effect, and high-temperature effect tests. Glass fibers increased compressive strength and reduced water absorption in specimens that were not stressed. On the other hand, glass fibers increased the durability of stressed specimens at both degrees of compressive load stress. The bridging effects of glass fibers reduced crack creation, resulting in improved UPV test results. Glass fibers did not dissolve in acid solution due to their chemical resistance, resulting in less weight loss and higher compressive strength in concrete specimens. In the high-temperature effect tests, decreasing compressive strength values were observed as the stress load and temperature levels increased. However, such reductions were lower for glass fiber reinforced concrete than for control concrete without glass fiber. As a result of the present findings, glass fiber reinforcements prevent stress-induced cracks, making the concrete more durable and stronger against external forces.

Corrosion Rate and Weight Loss of Geopolymer Mortar Coated Concrete Specimens with Different Thicknesses

This study is about the use of geopolymer mortar as an alternative repair material to reduce the corrosion rate of building structures. The experiment was conducted by comparing the corrosion rate and weight loss of concrete specimens with different thicknesses of geopolymer mortar coating with concrete specimens coated with Sikagrout 215M. Observations showed that the specimens with 2.5 cm thick geopolymer mortar coating cracked faster and had higher current values than the others. Corrosion rate measurements showed that the specimen with 4 cm thickness geopolymer mortar coating had the lowest corrosion rate, while the specimen with Sikagrout 215M coating had a higher corrosion rate. Visualization of the cracked specimens shows that the geopolymer mortar layer’s thickness affects the reinforcement’s rust formation. Geopolymer concrete with proper coating thickness can reduce the corrosion rate and weight loss of concrete structures. This research further explains the effect of coating thickness and coating type in protecting steel in concrete from corrosion.

Wear Behavior Prediction for Cu/TiO2 Nanocomposite Based on Optimal Regression Methods

The present study investigated the effects of the addition of the TiO2 nanoparticles with different weight percent on the copper nanocomposites' abrasive wear behavior. In addition, optimal machine learning regression (OMLR) methods are used to detect the copper nanocomposites' abrasive wear behavior. The powder metallurgy method is used to fabricate the Cu/TiO2 nanocomposite specimens with 0, 4, 8, 12 wt% TiO2. The abrasive wear behavior of fabricated specimens is evaluated experimentally using a pin on the desk apparatus. The abrasive wear results are used to predict the abrasive wear behavior of the fabricated composites using OMLR methods. OMLR methods are implemented and carried out using MATLAB/software. The OMLR methods use the input parameters of TiO2, sliding distance and load, and the weight loss due to abrasive wear as an output to build their optimal models. OMLR methods were successfully detected with small errors, especially GPR methods. The results of the proposed GPR were compared with those obtained from the ANN model with the efficacy of the GPR model. The experimental results demonstrated that the weight loss in test specimens decreased with increasing wt% of TiO2 addition. This reflected improvements in the wear resistance of copper nanocomposites compared to pure copper.

Improvement of Fire Resistance and Mechanical Properties of Glass Fiber Reinforced Plastic (GFRP) Composite Prepared from Combination of Active Nano Filler of Modified Pumice and Commercial Active Fillers

Glass fiber reinforced plastic (GFRP) composites have great potential to replace metal components in vehicles by maintaining their mechanical properties and improving fire resistance. Ease of form, anti-corrosion, lightweight, fast production cycle, durability and high strength-to-weight ratio are the advantages of GFRP compared to conventional materials. The transition to the use of plastic materials can be performed by increasing their mechanical, thermal and fire resistance properties. This research aims to improve the fire resistance of GFRP composite and maintain its strength by a combination of pumice-based active nano filler and commercial active filler. The nano active filler of pumice particle (nAFPP) was obtained by the sol-gel method. Aluminum trihydroxide (ATH), sodium silicate (SS) and boric acid (BA) were commercial active fillers that were used in this study. The GFRP composite was prepared by a combination of woven roving (WR) and chopped strand mat (CSM) glass fibers with an unsaturated polyester matrix. The composite specimens were produced using a press mold method for controlling the thickness of specimens. Composites were tested with a burning test apparatus, flexural bending machine and Izod impact tester. Composites were also analyzed by SEM, TGA, DSC, FT-IR spectroscopy and macro photographs. The addition of nAFPP and reducing the amount of ATH increased ignition time significantly and decreased the burning rate of specimens. The higher content of nAFPP significantly increased the flexural and impact strength. TGA analysis shows that higher ATH content had a good contribution to reducing specimen weight loss. It is also strengthened by the lower exothermic of the specimen with higher ATH content. The use of SS and BA inhibited combustion by forming charcoal or protective film; however, excessive use of them produced porosity and lowered mechanical properties.

Oral Administration of the Antimicrobial Peptide Mastoparan X Alleviates Enterohemorrhagic Escherichia coli-Induced Intestinal Inflammation and Regulates the Gut Microbiota.

The gut microbiota plays an important role in intestinal immune system development and in driving inflammation. Antibiotic administration for therapeutic purposes causes an imbalance in the gut microbiota. Antimicrobial peptides can regulate the gut microbiota and maintain intestinal homeostasis. The aim of this study was to investigate the anti-inflammatory effects and regulation of the gut microbiota by the orally administered antimicrobial peptide mastoparan X (MPX). In this study, Escherichia coli was used to induce intestinal inflammation, and the results showed that MPX+ E. coli alleviated weight loss and intestinal pathological changes in necropsy specimens of E. coli-infected mice. MPX+ E. coli reduced the serum levels of the inflammation-related proteins interleukin-2, interleukin-6, tumour necrosis factor-α, myeloperoxidase, and lactate dehydrogenase on days 7 and 28. Furthermore, MPX+ E. coli increased the length of villi and reduced the infiltration of inflammatory cells into the jejunum and colon post infection. Scanning electron microscopy and transmission electron microscopy results showed that MPX could improve the morphology of jejunum villi and microvilli and increase tight junction protein levels. 16S rRNA sequencing analysis of caecal content samples showed that the species diversity and richness were lower in the E. coli-infected group. At the genus level, MPX+ E. coli significantly reduced the abundance of Bacteroidales and Alistipes and enhanced the relative abundance of Muribaculaceae. Alpha-diversity analyses (Shannon index) showed that MPX significantly increased the microbial diversity of mice. Overall, this study is the first to investigate the effects of oral administration of MPX on intestinal inflammation and the gut microbiota, providing a new perspective regarding the prevention of enteritis and maintenance of intestinal homeostasis.

Influence of Optiglaze Material on Wear Resistance of Thermoplastic Resin

Statement of problem: The wear resistance for flexible denture base material.
 Purpose: The purpose of the study was to measure the wear resistance, of flexible acrylic denture base material; after being coated with light-polymerized glaze material.
 Materials and methods: A total of (30) Thermoplastic resin specimens were divided into three groups according to the tests, each group consisted of 10 specimens (A) control group had no surface treatment, group (B) specimens surface was treated with Optiglaze materials after finishing and polishing; group (C) specimens was treated with Optiglaze materials after finishing only without polishing. Each specimen's weight loss was measured by comparing the weights before and after the wear test. Collected data were statistically analyzed using SPSS.
 Results: The results of this study showed the higher mean values for wear resistance was registered by (C) group which was 8.7420,followed by (B) group which was 7.3210,while the lowest mean value related to the (A) group which was 7.0907.
 Conclusion: Statistically wear values were lower for groups C & D and higher in group A.
 Clinical implications: This study may be useful in assisting dental professionals and technicians in selecting the best polishing and coating material for dentures. Coating flexible acrylic resin denture materials with an Optiglaze to improve wear resistance.

Evaluating the pH of Various Commercially Available Beverages in Pakistan: Impact of Highly Acidic Beverages on the Surface Hardness and Weight Loss of Human Teeth.

The objectives of this study were to investigate the pH of common beverages and to evaluate the effects of common acidic beverages on the surface hardness and weight loss of human tooth specimens. A total of 106 beverages were conveniently purchased from supermarkets in Karachi, Pakistan. Prior to evaluation, beverages were refrigerated or stored at room temperature in accordance with the manufacturers’ recommendations. Beverages were categorized into six groups: ‘Sports and Energy drinks’, ‘Water’, ‘Fruit Juices and Drinks’, ‘Sodas’, ‘Milk and Flavored Milk’ and ‘Teas and Coffee’. Using a pH meter, the pH of each beverage was measured in triplicate at room temperature. In addition, the influence of five highly acidic beverages on the weight loss and surface hardness of human tooth specimens was evaluated using gravimetric analysis and the Vickers hardness tester, respectively. ‘Sports and Energy drinks’, ‘Fruits Juices and Drinks’ and ‘Sodas’ were the most acidic beverage categories, with a pH range of 3.00–5.00. A total of 33% of beverages tested in this study were highly acidic (pH less than 4.00), 29% of beverages were moderately acidic (pH 4.00–4.99) and 31% were mildly acidic (pH 5.00–6.99). Significant weight loss was observed in all immersed specimens compared to control counterparts (p < 0.05). Similarly, for surface hardness, five highly acidic beverages (Red Bull, Pepsi, Apple Cidra, Tang Mosambi and Tang Orange) significantly decreased the surface hardness of specimens (p < 0.05). The pH levels of commonly available beverages in Pakistan are highly acidic, which may encourage loss of minerals from teeth; hence, affecting their surface hardness.

Sulfate Freeze–Thaw Resistance of Magnesium Potassium Phosphate Cement Mortar

Concrete facilities in the severe-cold areas of western China (salt lake environments and heavy saline soils) are seriously damaged by the multiple corrosion effects of freeze–thaw cycles and sulfate corrosion. Magnesium phosphate cement (MPC) cement-based material has become an ideal concrete structural component because of its superior performance. Because concrete structural repair materials are used in heavy-corrosion environments, their durability in those environments should also be considered. Regarding the salt-freezing resistance of MPC, the existing studies have all used a NaCl solution as the heat transfer medium. In addition to chlorine salt, sulfate, especially Na2SO4, is also common in typical use environments such as oceans, salt lakes, and groundwater. To evaluate the sulfate freeze–thaw resistance of potassium magnesium phosphate cement (MKPC) mortar, in this study the strength development, weight loss, and water absorption of MKPC mortar specimens subjected to different freeze–thaw cycles were tested and compared with those for Portland cement (P.O) mortar specimens of the same strength grade. The results showed that the P.O mortar specimen completely lost its strength after 75 cycles of rapid water freezing and thawing and 50 cycles of sodium sulfate solution (5%) freezing and thawing. However, the residual strength rating of the MKPC mortar specimen after 75 cycles of water freezing and thawing and 100 cycles of sodium sulfate solution freezing and thawing was higher than 75%. After 50 rapid freeze–thaw cycles in water and a 5% Na2SO4 solution, the P.O mortar specimen’s mass loss exceeded the 5% failure standard, whereas the mass loss of the MKPC mortar specimens was much less than 5%. Before the freeze–thaw cycles, the water absorption of the P.O mortar specimen was close to 8 times that of the MKPC mortar specimen, and after 50 water freeze–thaw cycles and 25 sulfate solution freeze–thaw cycles, the water absorption reached 4.88% and 5.68%, respectively. However, after 225 freeze–thaw cycles in water and the sulfate solution, the water absorption rates of MKPC mortar specimens were 2.91% and 2.51% respectively. The test and analysis results show that the freeze–thaw resistance of MKPC mortar was much higher than that of Portland cement mortar specimens. Those results provide a prerequisite for applying and expanding the use of MKPC-based materials in severe-cold areas of western China (salt lake and heavily saline soil environments).