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Fire can not only lead to many human and financial losses, but also can cause structures to collapse and destroy them. For this reason, it is necessary and inevitable to protect buildings against fire and conduct more research in the field of better understanding the effects of combining different materials with each other and obtaining materials with greater resistance to fire. Concrete and concrete structures are always used by construction engineers due to their resistance, availability and resilience against fire. Ordinary concrete loses its strength at high temperatures, and the use of unreinforced concrete is not very useful due to its brittleness and weakness in tensile strength. In concrete, the tensile strength is lower than its compressive strength, and for this reason, researchers are trying to increase the resistance to fire and heating by improving the tensile strength of concrete. Reinforcing concrete with rebar is always a solution to increase the tensile strength in concrete parts, one of the most important weaknesses of using rebar in concrete is that the reinforcements form a small part of the concrete cross-section and actually cause the concrete to be inhomogeneous. In this research, double-bent steel fibers have been used to overcome the mentioned weakness and reinforce the concrete. It should be noted that concrete containing steel fibers has favorable compressive and tensile strength due to the high tensile strength of steel fibers. In order to achieve this goal and achieve fiber concrete that has good fire resistance, we defined seven different mixing plans with different percentages of steel fibers and lubricants. Concrete samples were produced using double-bent steel fibers in amounts of 0.5, 1, and 1.2 percent by volume of concrete and superlubricant in 0.5, 1, and 1.3 percent by weight of cement, and then in Cubic molds with dimensions of 10x10x10 cm and cylindrical ones were sampled as standard, and after setting the cement, the 28-day-old concrete samples, after heating and placing inside the electric heater with different temperatures, were divided into two The method of gradual cooling with ambient air and fog spraying (water spraying) is similar to what firefighters do when extinguishing a fire, after measuring the amount of weight loss of the heated samples, the weight loss values ​​were presented in the form of a diagram, then the samples were subjected to tests Compressive strength, tensile strength (Brazilian test) and ultrasonic wave speed (ultrasonic test) were placed, and the results and data of each of them for each mixing design were presented in the form of a diagram after examination and classification, so that the effect of high heat on Concrete containing steel fibers and super-lubricant should be determined. The results clearly showed the improvement of the tensile strength in three volume percentages of fibers by 14.6, 16.8 and 64.5%, respectively, compared to concrete without fibers, and also the compressive strength of concrete after bearing the heat of 250 degrees Celsius and cooling to the fogging method had 44.5, 31.6, and 9.3 percent, respectively, and in the gradual air cooling method, the compressive strength was 43.3, 44.9, and 50 percent, respectively.


 

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Reactive Powder Concrete (RPC) is recognized as one of the most innovative types of concrete, notable for its exceptional strength and durability. This type of concrete is composed of essential components such as cement, silica fume, quartz powder, silica sand, superplasticizer, and water. Due to its superior mechanical properties, RPC is widely utilized in specialized projects and structures that require outstanding strength and durability. However, the high cost of its components, particularly quartz powder, significantly increases the overall production cost, limiting its widespread application in larger, cost-sensitive projects. Quartz powder is scarce in the Azerbaijan region of Iran and is often sourced from mines in Hamedan and Isfahan. By replacing it with more locally available, affordable materials, final production costs can be reduced. To address this issue and optimize the use of available resources, the possibility of substituting quartz powder with local, cheaper, and more accessible materials has been explored. Micronized quartz powder is crystalline, though some of its finer particles have a minor pozzolanic effect. In contrast, diatomite powder, which contains both amorphous and crystalline particles with a high percentage of amorphous silica, exhibits significantly greater pozzolanic activity. These enhanced reactions contribute to the formation of a denser and stronger concrete matrix, improving its mechanical properties. The purpose of this study was to investigate the feasibility of replacing quartz powder with diatomite powder in different proportions—specifically 25%, 50%, 75%, and 100%. The goal was to evaluate how this substitution affects the concrete's strength while also reducing overall production costs. In this research, concrete samples were tested at various curing ages, including 7, 14, and 28 days. Mechanical tests such as compressive strength and tensile strength were conducted to assess the effects of the substitution on the concrete's performance. Additionally, parameters such as standard water absorption, water absorption during curing, density, and consistency were measured. To simulate real-world construction conditions and avoid the use of specialized equipment, the samples were cured in a water tank at 25°C. This curing method not only eliminated the need for expensive equipment like autoclaves but also made the concrete more applicable to typical site conditions, further lowering production costs. The test results were promising. The strength of the modified concrete mixtures improved significantly when diatomite powder replaced quartz powder. In samples where 100% of the quartz powder was substituted with diatomite, the compressive strength increased from 543 MPa to 806 MPa (approximately 49%), and the tensile strength increased from 543 MPa to 806 MPa (approximately 18%) at 28 days. In addition to the improvements in mechanical properties, the use of diatomite powder offers significant economic advantages. Diatomite is abundantly available in various regions, and its accessibility reduces both production and transportation costs. As a result, the overall production cost of the concrete is significantly lowered, which is especially beneficial for large-scale construction projects where cost efficiency is critical. In conclusion, replacing quartz powder with diatomite powder is a practical solution that brings both technical and economic benefits. The enhanced strength of the concrete, coupled with reduced production costs and the efficient utilization of local resources, makes this approach a practical and effective method for producing high-performance concrete.

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Research subject: External radiotherapy is a major method of treating cancer. For just hitting the cancer cells by emitting rays, masks are used to stabilize the patient's body in the right position during the radiotherapy, so that the rays are not emitted to the healthy tissues of the patient's body. Due to the unique properties of these masks, suitable polymeric materials must be used to produce them, which has initially been investigated using a variety of thermoplastic polymers.
Research approach: In the following, polycaprolactone is proposed as the main material for making the mask. Due to its low tensile strength, this material alone is not suitable for the intended use. Therefore, the material was cured with different percentages of benzoyl peroxide (BPO) to increase tensile strength by crosslinking of the polymer. The properties of the cured samples were investigated using the tests of gel content, shape memory, unidirectional tensile strength and, DSC diagrams.
Main results: With increasing BPO, the percentage of gel content and shape memory of the cured samples increased. All cured samples had a high percentage of shape recovery, the highest of which belonged to samples containing 2 and 3% by weight of BPO. By Examining the tensile strength test diagrams, it was observed that by increasing the amount of BPO from 0.5 to 2% by weight in the cured samples, the tensile strength at the breaking point increased to 10 MPa. Shape recovery and tensile strength at the breaking point were 94% and 10 MPa for both cured polycaprolactone samples with 2% by weight of BPO and the Orfit mask, which were very similar in this respect. Finally, a mixture of PCL with 2% by weight of BPO is proposed to make a radiotherapy mask.
 

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  Due to the environmental hazards of using plastic films, studies on the development of plant based films such as soy protein films, are receiving more attention.  In this research, edible films were prepared from soy protein isolate and the effect of glycerol as a plasticizer at three concentration levels of 0.4, 0.6 and 0.8 g/g of soy protein isolate on the properties of these films was investigated. Some Mechanical properties, i.e. tensile strength and extension, and physical properties, i.e. water vapor transmission rate, opacity, water adsorption and solubility were examined. Films prepared without glycerol were very brittle and could not be examined. Results showed that increasing the concentration of glycerol led to a significant (p<0.05) increase in extension rate and decrease in tensile strength of soy protein isolate films. Solubility percentage, water adsorption and water vapor transmission rate of the films were found to increase when the glycerol level increased.  Although glycerol addition reduced the opacity of the films, its concentration did not have a significant correlation with this parameter (p<0.05).

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The objective of this study was to investigate the effect of different glycerol concentrations (15, 30, 45, 60 & 75% w/w of methylcellulose) and film thickness (15, 30 & 60µm) on methylcellulose (MC) films water vapor permeability and mechanical properties. Finally, 15µm films containing 45% glycerol (the best conditions) were selected. Results showed the significant effect of glycerol concentration on films water vapor barrier and mechanical properties. Film thickness affected WVP and tensile strength but not elongation at break.  

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Abstract: Chloride penetration resistance of concrete is considered a key parameter affecting durability of structures exposed to marine environments. Chloride diffusivity of concrete can be determined by immersion or ponding tests. However such tests are time consuming and costly. These facts have lead researches to develop accelerated tests such as the rapid chloride penetration test RCPT (ASTM C1202). In the RCPT test, the electrical charge passing during six hours through a 50 mm concrete disc, under potential difference of 60 volts is measured. A main concern expressed for the RCPT test has been the rise in temperature of concrete specimens which results in a reduction in concrete resistivity. The other criticism towards the RCPT test is the role of ions other than chloride ion, particularly the (OH)^- ion in conductance of electrical charge. It has therefore been suggested that some complementary cementitous materials can cause a reduction in the electrical charge passed, by reducing the concentration of (OH)^- ions in pore solution. Another quick method for measuring chloride resistance of concrete is the Rapid Chloride Migration test RCMT (AASHTO TP64). This test is in general similar to the RCPT method. However for avoiding the heating of specimen, the applied voltage is adjusted in accordance with the initially passed charge. Also in the RCMT test, for avoiding the influence of other charge carrying ions, the actual chloride ion penetration into the specimen is determined. A further method proposed for appraisal of chloride resistance of concrete, is determination of electrical resistance. For avoidance of heating of concrete specimens, electrical conductivity measurements are carried out for short durations. This research was carried out with the aim of comparing the results of various quick methods for determination of chloride resistance of concretes containing various supplementary cementitous materials. In the experimental study the control mix had a water cement ratio of 0.38 and cement content of 420 Kg/m³. Mixes containing various amounts of supplementary cementitous materials including silica fume, fine fly ash, pumice, fly ash and slag were studied. For the RCPT test, the temperature effect resulted in considerable overestimation in the effect of using of supplementary cementitous materials in improving chloride resistance of concrete. Temperature rise did not occur during the RCMT test, and this test therefore does not suffer  In the case of optimum fiber value, the obtained results from laboratory tests have shown a reduction in compressive strength and value of ultrasonic test around 8.7% and 2.5% respectively. Moreover it has shown an increase in tensile strength, flexural strength, electrical resistance and value of VB test about 33%, 10%,11% and 51% respectively. Consequently utilizing such fibers in sleeper concrete could be suggested for practical applications.

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Pavement performance in Iran is not compatible with expectations and demands of contemporary society. The poor performance of pavement results in shortening country roadways lifetime and paying heavy cost. One of the pavement major problems particularly in wet conditions is stripping of aggregates. Stripping is a major distress occurring in hot mix asphalt (HMA) pavements in Iran and in various parts of the world The stripping of aggregates in hot mix asphalt not only is considered as an independent problem but also it may cause damages like cracking, rutting, raveling, fatigue cracking. The moisture first inflicts damage on the HMA mix by destroying the bond between the aggregate and the asphalt binder or by destroying the internal cohesive strength of the binder. This loss of adhesion causes the asphalt concrete to ravel under traffic loads. Stripping occurs in the presence of water, so it is often referred to as moisture damage. In this paper, the effective parameters causing stripping have been identified and the methods of increasing asphalt mixture durability have been investigated, focusing on the recognition of how stripping can be made. In this regard, limestone fillers and hydrated lime have been used in different amounts as antistripping agents (which can be found widely in the country) and the optimum resistant mixture against stripping have been prepared. In this thesis two kinds of aggregate from the east and west of Tehran and two kinds of bitumen (60/70) from Tehran and Isfahan refineries have been collected and the required experiment (on aggregates, bitumen and hot mix asphalt) have been carried out. Then according to marshal method and based on ASTM D6926 and ASTM D6927 standards, marshal specimen have been made and the optimum bitumen has been determined, using the required parameters by marshal method. Using indirect tensile strength and compressive strength tests over saturated and dry specimen, according to AASHTO T283 and ASTM D1075 standards, asphalt mixture stripping potential has been investigated. Since the resistance of asphalt mixture again moisture was not satisfactory, two kinds of limestone filler and hydrated lime were used for improving asphalt mixture resistance and their effect was investigated on asphalt mixture. Hydrated lime and limestone filler, when added to the asphalt prior to preparation of the mixtures, dramatically improved mixture resistance to moisture damage for both aggregates. The results obtained from indirect tensile strength and compressive strength tests over saturated and dry specimen, according to AASHTO T283 and ASTM D1075 standards show that using 1.5% hydrated lime or 4% limestone filler (by weight of aggregates) in asphalt concrete, significantly increased the asphalt mixture resistance against stripping. Also in this study the results obtained from two experiments methods (tensile strength and compressive strength tests) are compared.

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The main aim of this experiment is to investigate the effects of Nano-size Al2O3 on the mechanical properties and microstructure of multi-passes friction stir welding of Al 2024 lap joint. Nano particles were added into the joint line. A combination of rotational speed and travelling speeds were performed. Optical microscopy and scanning electron microscope were used to investigate the microstructure and fracture surface of samples respectively. Optimum condition (sample) was selected due to highest ultimate tensile strength (UTS). It was seen that sample which included Nano particles and fabricated by 1400 rev/min rotational speed and 16 mm/min travelling speed in second pass of continues welding had improvement in UTS in comparison to one pass welded sample of particle free and after that increasing the number of passes reduce the UTS. The average micro hardness of the sample which was particle rich were increased in comparison to particle free sample in nugget zone. Increasing the number of passes was not effect average micro hardness in nugget zone significantly. Grain sizes were reduced by 2 passes welding and after that no significant reduction has been seen.

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Since aircrafts are subjected to aerodynamic and structural loads; one common defect in the aircraft fuselage and its wings is crack criterion. In most of the cases, the service life of defective parts can be increased by some sort of repairs. One of the most common types of repairs in this field is using composite patches and pasting them on damaged parts. These patches have significant advantages such as high strength, corrosion and moisture resistance, low weight and also excellent fatigue properties. In this study, base notched plates were fabricated by using of 2024 T4 aluminum alloy. Fiber metal laminate (FML) patches were made of carbon-epoxy and Phosphor – Bronze layers. These patches were attached to the base notched plate by using adhesive Arldit 2011. Specimens were subjected to tensile test and results of the tests were compared. The tested variables were chosen as lay-up, metal layer thickness and composite patch length. The results of current study indicate a dramatic increase in tensile strength of repaired parts by using these patches compared with the repaired notched parts without patches so that tensile strength is increased up to 82.4 % in the best sort of repair.

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In recent years a high attention has been conducted to the structural application of wood plastic composites (WPCs). Regarding that the WPCs have lower mechanical strengths, fiber reinforcements have been applied for strengthening the WPCs. Hybrid wood plastic composites (HWPCs) include two types of reinforcements of glass fibers and wood flours that are added to a polymeric matrix. WPC pallets as an example can exploit the mechanical strength of HWPCs. In previous work, wood plastic composite was reinforced by continuous glass fibers by a unique extrusion process. Embedding the continuous glass fibers in WPC matrix resulted in significant improvements in mechanical properties such as tensile and impact strengths. In this paper, a model has been proposed to predict the tensile strength and modulus of the WPCs reinforced with unidirectional glass fibers. The methodology applied in this research considers the WPC as matrix and the glass fibers as reinforcements. Since WPC matrix is brittle, the rule of mixtures corresponding to the brittle matrix composites was used to predict the tensile strength. Results indicated that the predicted tensile properties were in good agreement with experimental data. The obtained mean errors between the experimental and theoretical results for tensile strength and modulus were 9.5% and 8.6% respectively.

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Premature failures are experienced in road pavements. Among the various failure modes, moisture damage is probably the most occurring distress in asphalt pavements. In fact, the continuous presence of water in asphalt layers weakens the bond between aggregate particles and bitumen, ending to stripping of mixes. With this regard, several parameters affect water damages to asphalt layers. Among these, aggregates type and source, bitumen type and grade, mixture design, construction practice, traffic volume, environment and the additive properties could be named as the most affecting parameters. In order to prevent stripping, one of the most effective methods is to use anti-stripping additives. Among the various additives, sulphur which is a byproduct of petroleum gas production industries, has been known to increase stiffness of bituminous mixes appreciably, provided that it is added properly and at right amounts. However, due to environmental drawbacks of this additive (i.e. emission of disturbing gases) and the too much stiffening effects that imparts to mixes, sulphur alone was banned to be used in road pavements for several decades. In the recent years, combined additives, consisting of sulphur and polymers have been produced and applied into asphalt mixes. These additives have shown to have less adverse environmental effects (i.e. reduced emission of gases such as ). The effects of these additive types is so that their sulphur component provides stiffness to mixes and their polymer portion imparts some flexibility to mixes and increase the adhesion properties of the mix binders. “ASTM D8” Standard Testing Method. In this research a locally produced sulphur polymer additive, named ‘Googas’, was used and applied in a continuously graded asphalt mix. This new product had lower emissions of gas, compared with the conventional sulphur mixes. In addition, it provided enhanced properties to mixes, compared with previously made sulphur alone containing mixes. In order to reduce the stiffness of mixes and provide these with more flexibility, CRM (Crumb Rubber Modifier) modified binders were used as the replacement of conventional penetration grade binder of mixes. CRM binders were prepared containing different amounts of crumb rubber. The preparation was carried out in the laboratory using a high shear rate mixer upon following The results showed that increased amounts of Googas sulphur polymer although resulted in increased compression strength, reduced the moisture resistance of mixes substantially. In fact, it was seen that when asphalt mixes were cooled to ambient temperatures, the sulphur tended to change from liquid into solid state, contributing little to bitumen adhesiveness. In contrast, mixes containing CRM binders alone, showed increased tensile properties, as indicated by increased ITS testing results. With analyzing the laboratory results, optimum amounts of the above two additives were determined. In fact, increased amounts of CRM resulted in increased tensile resistance of mixes (i.e. showing a gradual increasing trend). This was up to CRM’s of 18% to 20%. Further increases resulted in lower tensile strengths. Hence, optimized mixes were designed containing both CRM and sulphur polymer additives.

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In the case of presence of deep micro-cracks within the composite structures, they must be replaced. The self-healing phenomenon which is inspired from the biological systems such as vascular networks in plants or capillary networks in animals, is an appropriate strategy to control the defects and micro-cracks. In the present research, by taking accounts the advantages of self-healing concept, an attempt has been made to control the micro-cracks and damages which were created in composite structures. To do so, series of micro glass tubes were employed to provide a self-healing system. These micro-tubes were filled with epoxy resin/anhydride hardener as a healing agent. When the structure is subjected to loading conditions, some damages or micro-cracks are created. In this situation, the micro glass tubes will rupture and the healing agent flows in the damage area, leading to the elimination of the defects over a time span. The aim of this study is to find out the appropriate self-healing material volume fraction and healing time to obtain an efficient healing. For this purpose, glass micro-tubes containing various healing agent loadings of 0.75, 1.65 and 2.5 vol.% were incorporated in epoxy-carbon fibers composites and the tensile behavior of the specimens were assessed during different time span from defect creation. The highest tensile strength recovery of 89% was observed for the specimen with 1.65 vol.% healing agent. Also the results show presence of micro tube decrease the fracture strain and over the time span fracture strain recovered.

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In this research, 0, 5, 10, 15 and 20 percent of crumb rubber mix was used as a fine grained substitute for concrete pavement. Also, in another state, half percent of the steel fibers recovered from worn tires were added to these samples. The results of this study indicate that the compressive strength of samples with 5, 10, 15 and 20% crumb rubber in comparison with the control sample was reduced by 1.6, 36.9, 49.9% and 63.1%, and samples with 0, 5, 10, 15 and 20% crumb rubber and 0.5% steel fibers, respectively, decreased by 0.3, 11.2, 33.7, 5 / 41% and 44.3% respectively. Therefore, it is observed that the compressive strength of concrete containing crumb rubber and steel fibers is better than specimens with crumb rubber. Also, by replacing 5%, 10%, 15% and 20% of crumb rubber in concrete, its indirect tensile strength would be reduced by 7.5%, 15.3%, 41.4% and 31.2% , and by adding 0.5% of the steel fibers to the concrete by replacing 0, 5, 10, 15 and 20% of crumb rubber in concrete, Indirect tensile strength increased by 67.8%, 46.7%, 32.4%, 17.8% and 3.5%, respectively, and it is concluded that the tensile strength of concrete increases due to the addition of steel fibers. 

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With regard to the industry demand for welding dissimilar metals, which are not possible to be welded by conventional welding, friction welding process can be a proper approach. In this study, friction welding of two stainless steels, martensitic 410 to austenitic 304, with variable parameters of friction time (40, 50, and 40 s), friction force (90, 100, and 120 kN), and forging force (130, 150, and 180 kN), under the constant rotating speed (850 RPM) and forge time (60 s), was investigated. Microscopic characterization using optical and scanning electron microscopes, and elemental analysis using energy dispersive X-ray spectroscopy were carried out on the welds. Soundness of the weld joints was evaluated using tensile and microhardness tests. Fracture surfaces of the tensile specimens were examined as well. The structure of the welded samples composed of acicular and rough martensite and elongated grains adjacent to 410 and 304 stainless steels, respectively. Tempering heat treatment locally caused converting rough martensite to lath martensite. The results showed that the tensile strength of the samples was in the range of 400-520 MPa, and the fractography revealed the occurrence of a brittle fracture. Microhardness measurement revealed that the highest hardness value was obtained in 410 stainless steel, at the heat-affected zone close to the interface. An appropriate friction weld joint with a tensile strength of 751 MPa was obtained after heat treatment of the weld location, and with the aid of selecting optimal parameters of 50 s friction time, 120 kN friction force, 180 kN forging force.

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Increasing builders waste of autoclaved aerated concrete (AAC) require new concepts for future recovery processes. There are two main aspects, underlining this basic necessity for developing AAC recycling models. Environment protection ranks first because of the risk of groundwater pollution by compounds leached out from AAC waste during its deposition. The second aspect is raw materials preserving because of the high content of the valuable potential recyclable calcium- silicate-hydrate phase 11 Å tobermorite (5CaO 6SiO2 5H2O) besides pure quartz and minor aluminate. In general the main constituents of AAC amount around 40–50 wt-% for tobermorite and approx. 30–40 wt-% for quartz. The tobermorite phase is causing the AAC strength and forms hydrothermally at 180–200 °C and 10–12 bar pressure during autoclaving from the raw materials lime, quartz, and water. Minor parts of aluminum powder for pore-forming and small amounts of cement and anhydrite for better handling of the AAC-green bodies are the further additives of the AAC raw materials mixture. The high silicate content, as well as the valuable calcium parts, display AAC waste as an interesting raw material for zeolite formation as known from the treatment of fly ashes and slags. According to their outstanding properties zeolites are used in sorption techniques, catalysis, molecular sieving, and ion exchange processes, and in previous studies, we already could show zeolite hydro sodalite formation beside hydrogarnet and other valuable calcium- and sodium aluminosilicates applying NaAlO2 as an aluminum source in the reaction mixture. Those previous syntheses were performed in water and under low alkaline (1 m NaOH) and low acid (1 m citric acid) conditions. This mild reaction milieu was found to be responsible for relatively low AAC conversion rates and the formation of multiphase products. In reference, the aluminum source NaAlO2 was added to the AAC always before the leaching reactions were performed. In contrast, the presented study investigates leaching of pure AAC in stronger alkaline media of 4–8 m NaOH and the combination with acid treatment, before the aluminate is added for the final crystallization process. This procedure is expected to be much more effective to synthesize uniform zeolite products at 100% AAC conversion rates, as shown in the following experimental study. Autoclaved Aerated Concrete (AAC) used in low-rise buildings and infilled frames as a structural member. One of the weaknesses of AAC is low mechanical strength. In addition, AAC blocks absorb water of mortar which can lead to executive problems. In this paper, the effect of silica fume, zeolite and granulated blast furnace slag (7%, 14% and 21% by weight of cement) was investigated on improving mechanical properties and water absorption of AAC. The compressive and tensile strength tests and water absorption test was conducted on 10 x 20 cm cylindrical and 10 x 10 x10 cm cubical specimens. The results showed that pozzolanic materials can improve mechanical properties and water absorption of AAC. The compressive strength for AAC mixes containing silica fume, zeolite, and granulated blast furnace slag, increased up to 184%, 200%, and 172% compared with AAC control mix. In addition, the use of pozzolanic materials with the ratio of 21% by weight of cement improved tensile strength of AAC up to 25%. Generally, silica fume, zeolite and granulated blast furnace slag in different replacement levels decreased water absorption up to 50%, 45%, and 35%, respectively.

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In this study, an edible film based on gelatin-Persian gum was prepared and optimization of the edible film was done using Design Expert and Mixture Design. The resulting films were subjected to various physicochemical tests, including pH, total solid, heat seal ability, tensile strength, contact angle, calorimetric and moisture absorption. At first, modeling of responses was done using data regression analysis, and then 3D charts were drawn to show the effects of gelatin (0.5 -1), Persian gum (0.5 -1), and Glycerol (0-0.5) on the film characteristics. Finally, Numerical optimization based on optimization goals was performed and the optimal point with the highest desirability (0.78) was obtained. The ratio of each of the independent variables in the optimal formula was 0.5. Various properties of the optimal film including pH, total solid, heat seal ability, tensile strength, contact angle, moisture absorption, L*, a* and b* were obtained at 6.66, 95.61%, 84.45 N/M, 64.5 N, 77.34°, 4.5%, 70.98, 0.97 and 0.66 respectively. Generally, the findings proposed that the gelatin-persian gum-based edible film can be used as a food packaging material.

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Various fibers have been used by researchers to reinforce concrete and extend the service life of structures, also researchers are using different fibers to improve behavior of different concretes, especially high-strength concrete, against impact and dynamic loads. This study investigate the effect of different contents and lengths of steel fiber on the mechanical properties of high-strength concrete. In this study, wavy hooked-ended fibers of two length (30, 50 mm) with three volume fraction 0.5%, 1% and 1.5% were added to concrete mixes and 150×300 mm cylindrical specimens were made, then different tests were performed for determination of compressive strength, splitting tensile strength and impact resistance at 7 and 28 days, in accordance with standards and procedure proposed. The results indicated that the addition of different contents and lengths of steel fiber caused significant change in the mechanical properties of high-strength concrete. In the best case, using 1.5% of 50 mm long steel fibers, increased compressive strength and splitting tensile strength by 25% and 40%, respectively, compared to non-fibrous high-strength concrete. A remarkable improvement was observed in impact resistance of the fibrous concretes, as compared with the reference materials. By incorporating steel fibers into the mixtures, specially longer fibers, a conclusive increase in the number of blows required for first and final cracking (as compared to reference values) was observed, as well as the number of blows from the first cracks to the final failure in the high percentage of the fiber increased up to  80%. Moreover, it can be concluded that, by adding fiber, the failure crack pattern was changed from a single crack to a group of narrow crack, which demonstrate the beneficial effect of fiber reinforced concrete when subjected to impact loading.
 

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Concrete due to its special feature, is the most widely consumed material in the world, after water. But the production process of ordinary Portland cement as a main component of conventional concrete, has major disadvantages such as high amount of CO₂ emission and high energy consumption. Therefore, it seems necessary to find an alternative to ordinary Portland cement. In recent years, geopolymer has been introduced as a novel green cementing agent and environment-friendly alternative to the Portland cement which can eliminate the extensive negative of ordinary Portland cement production process. According to the needed engineering characteristics perspective in civil engineering, the geopolymer concretes have better chemical and mechanical properties than the ordinary ones such as high compressive, flexural and tensile strength, rapid hardening, resistance against high heat and firing, low penetration, resistance against salts and acids attacks, and low creep. On the other hand, in terms of technical characteristics, concrete has some disadvantages, most notably low tensile strength and consequently low ductility. Therefore, the use of different fibers in the concrete mixture and the manufacture of fiber reinforced concrete is considered as an appropriate solution to eliminate these defects. Also, fiber reinforced geopolymer concrete is known as a novel type of concretes with higher ductility than ordinary concretes. In this experimental study, two types of polymer fibers, including simple polypropylene fibers and 4-element polyolefin hybrid fibers, were used to manufacture fiber reinforced geopolymer concrete specimens. In this regard, fiber reinforced and non-fiber geopolymer concrete specimens were made and cured in 80 °C for 24 hours. After curing, specimens were placed in the ambient condition and associated tests including: density, 3-days water absorption, 7-and 28-days compressive, Brazilian indirect tensile and three point flexural strengths, were performed to study effect of fibers on metakaolin-based geopolymer concrete mechanical properties. Also, to study effect of fibers on high-temperature resistance of metakaolin-based geopolymer concrete, specimens weight and compressive strength loss percentage after exposure to high temperatures up to 800 °C, were measured. The obtained results indicated that using fibers in geopolymer concrete mixture, result in increasing compressive, indirect tensile and flexural strengths and also decreasing in density and 3-days water absorption. Further, the use of hybrid fibers due to their ability to inhibit the cracking process from both micro and macro levels, significantly improved compressive, indirect tensile and flexural strengths compared to simple fibers. The optimum amount of 4-element polyolefin fibers for compressive, tensile and flexural strength improvement was measured 0.2%, 0.2% and 0.15% (by volume), respectively. Also, the optimum amount of polypropylene fibers for compressive, tensile and flexural strengths improvement was measured 0.2% (by volume). In term of high-temperature resistance, although the polymer fibers reduced the risk of the explosive sapling of geopolymer concrete specimens due to generation micro channels which were randomly distributed in concrete because of melting of fibers, resulting in less weight loss than non-fiber specimen, but on the other hand, the compressive strength loss of polymer fiber reinforced specimens were higher than non-fiber one. Overall, it can be concluded that these fibers did not have a significant effect on the high-temperature resistance of geopolymer concrete.
 

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In this article, the effects of normalization heat treatment on girth weld with containing titanium oxide and titanium carbide microparticles (X-65 grade of the gas pipeline) were evaluated. The Charpy test results show that in the normalized sample containing titanium oxide microparticles and titanium carbide microparticles compared to the no heat treatment sample (containing titanium carbide microparticles and titanium carbide microparticles), has been respectively increased by 33% and 18%. Also, the ultimate strength of normalized samples containing titanium oxide microparticles and titanium carbide microparticles compared to the no heat treatment sample (containing titanium oxide microparticles and titanium carbide microparticles) has been increased by 9% and 11%, respectively. The results show that the fatigue life in both normalized micro-alloy samples has been increased. The fatigue life in the normalized sample of titanium carbide microparticles has increased more than the titanium oxide microparticles. The fatigue test results show that the fatigue life (150-N force) has been increased by 36% in the normalized sample containing titanium carbide microparticles compared to the normalized sample containing titanium oxide microparticles. In this loading, the fatigue life (normalized sample containing titanium carbide microparticles compared to the no heat treatment sample) has been increased by 27%. The hole-drilling strain-gage results show that in the normalized sample containing titanium oxide and titanium carbide microparticles, hoop residual stresses have been respectively decreased by 12% and 8%compared to the no heat treatment sample (containing titanium oxide microparticles and titanium carbide microparticles).