جستجوی مقالات مرتبط با کلیدواژه « nano silica » در نشریات گروه « فنی و مهندسی »

Using recycled asphalt mixtures, which are made by waste materials, have attracted attentions due to their environmental and economical benefits. However, challenges exist with the performance of the recycled mixtures. In this study, the effect of using nano-silica on the behavior of non-rejuvenated and rejuvenated recycled asphalt concrete has been investigated. Penetration grade asphalt binder modified by 5% of nano-silica has been used in recycled asphalt concrete containing 60% of reclaimed asphalt pavement (RAP). The mixture without rejuvenation and rejuvenated by a constant percentage of waste cooking oil and waste engine oil has been evaluated by indirect tensile strength test on dry and moisture conditioned samples, dynamic creep test and stress controlled fatigue test. The properties of the mixtures have been compared with each other and with the control mixture made by neat binder and aggregates. The tests have been conducted on the samples before aging and after undergoing long term aging condition to investigate the effect of aging on the properties. Results reveal that incorporating RAP into the mixture increases the tensile strength, resistance against creep and fatigue and decreases the moisture resistance of the mixture. Nano-silica modification increases the dry and conditioned tensile strength, resistance against permanent deformation and fatigue. Nano-silica also improves aging resistance of the recycled mixtures. Furthermore, results reveal that waste oils as rejuvenator improves moisture resistance of the mixtures with more improvement for waste cooking oil. In addition, the effect of aging on the properties of the mixture rejuvenated by waste cooking oil is higher than those rejuvenated by waste engine oil.

The aim of this study was to compare the effect of nanocellulose and nanosilica on the properties of packaging cardboard made from waste white pulp. In this study, waste pulp was transferred to the laboratory. Handsheet cardboard was made of 60 g.m-2 with 4 and 8% nano-silica condition, and nanocellulose and cationic starch at 1.5% level. Finally, the physical, mechanical and morphological properties of the prepared cardboard were tested according to the TAPPI standards and compared with each other. The results showed that 4% cellulose nanofibers and 1.5% cationic starch had 2.5, 14.1, 46.9, 35.9, 9.5, 8.9, 20.5 and 5.1%, respectively, water absorption, surface smoothness, tensile strength index, burst resistance index, tensile strength index, brightness, whiteness and opacity more than 4% cellulosic nanofibers and have 30.9%, 19.3% of air resistance, and fewer yellowness than 4% cellulose nanofibers. 8% cellulose nanofibers and 1.5% cationic starch have 16.1%, 43.7%, 7.6%, 21.3%, 10.7%, 6.1%, 1.1%, 6.6% of water absorption, air resistance, tensile strength index, burst strength index, tear strength index, brightness, whiteness and opacity are higher than 8% cellulose nanofibers and have 36.2 and 23.1% surface fines, respectively, and fewer yellowness than 4% of cellulosic nanofibers. 4% nano-silica and 1.5% cationic starch have 8.1%, 18.3%, 34.1% and 6.9% surface smoothness, whiteness and opacity, more than 4% nano-silica, respectively, with 10.1% 13.1, 10.8, 1.5, 9.9 and 75.2% water absorption, tensile strength index, burst strength index, tear strength index, brightness and fewer yellowness than 4% nano-silica. 8% nanosilica and 1.5% cationic starch have 1, 14.7, 40.2 and 6.7% water absorption, air resistance, whiteness and opacity are more than 8% nano-silica, respectively, and have 5.2, 36.3, 69.3, 74.5, 5.1, and 14.8 percent surface smoothness, tensile strength index, burst strength index, tear strength index, brightness and fewer yellowness than 8% nano-silica. The results showed that the use of cellulose nanofibers is more preferable, and it can be important because it leads to a decrease in imports.

Although bitumen makes up only a small portion of asphalt mixtures, it significantly impacts their performance. Over the past few decades, bitumen modifier additives, such as nano-silica, have been utilized to enhance asphalt performance. This research aims to investigate the influence of nano-silica on the mechanical properties of asphalt and bitumen mixtures. The study utilized crushed stone materials with grading No. 4 of the Iran Road Pavement code, 70-60 pure bitumen, and nano-silica in varying amounts (2%, 4%, and 6% by weight of bitumen). Marshall and resilient modulus tests were employed to evaluate the mechanical properties of asphalt mixtures, while Marshall's resistance ratio was used to assess moisture sensitivity. Additionally, tests on penetration degree, softening point, and elasticity were conducted to evaluate the effect of nanosilica on bitumen properties. The findings revealed that modification of bitumen with nanosilica led to decreased penetration, increased softening point, and reduced plasticity. Furthermore, the use of nano-silica improved Marshall strength and reduced Marshall's flow in asphalt mixtures, with a 6% addition of nano-silica increasing strength by 41% compared to the control sample. The addition of nano-silica also enhanced the moisture sensitivity of the mixtures and increased the resilient modulus by 95% compared to control asphalt samples.

The primary goal of engineering design of buildings is to reduce the weight of the structure and its resistance to earthquakes and explosions because the occurrence of these events is inevitable. In this research, lightweight concrete has been used due to its unique advantages in weight reduction, and attention has also been paid to increasing the resistance and behavior of this concrete in the face of any type of accident and investigating its static and dynamic behavior. The dynamic behavior of concrete has been studied by using Hopkinson compression machine at three strain rates of 100, 200 and 300/s. Static and dynamic properties of concrete include compressive strength, modulus of elasticity, and dynamic increase modulus. For this purpose, a study has been conducted on 8 mixing designs for samples without metal fibers and nanosilica and samples containing different percentages of nanosilica and metal fibers. The results have shown that nanosilica and metal fibers play a role in improving compressive strength and the best results are obtained by adding 3% nanosilica and 1% metal fibers. Nanoparticles are more effective in static loads because the pozzolanic interactions of nanosilica improves the microstructure, and in dynamic loads, nanoparticles are less efficient due to nano's sensitivity to high loads, and also metal fibers prevent cracks in concrete. In this study, a mathematical relationship for the dynamic increase coefficient has also been extracted and compared with the experimental results.

Repairing and Strengthening of concrete structures is of special importance and the mechanical properties of repair mortars and their compatibility with the base concrete are significant aspects in the field of repairing of damaged concrete structures. The bond strength parameter of materials is one of the important properties in the selection of repair mortars. In the current Experimental studies, the bond strength of 7 types of cement base mortars consisting Nano-Silica (NS), Micro-Silica (SF) and Polyvinyl Alcohol (PVA) fibers have been tested on base concrete according to ASTM C882 standard. The base concrete is made of fiber concrete with a target compressive strength of 45 MPa and consisting macrosynthetic fibers. The workability of fiber concrete was 120 mm, and the method of curing the samples was done as the wet method. The obtained results indicate that all 7 types of repair materials of this research were compatible with the base concrete and the sample with the combination of PVA fibers and Nano-Silica in cement-based mortars has increased the bond strength of the samples by 85% compared to the samples without fibers. The highest bond strength among the samples was related to cement based mortar containing PVA fibers and Nano-silica (PVA0.75NS6) with bond strength equal to 21.83 MPa.

This research was conducted with the aim of investigating the compatibilizer of methyl diphenyl diisocyanate and maleic anhydride polypropylene on the morphology and physical-mechanical properties of wood-plastic composite containing nanosilica and nanoclay, high density polyethylene, wood flour. For this purpose, 3% compatibilizer along with nano particles at 3 levels of 0%, 2%, 4% were mixed with an internal mixer and test samples were prepared using the injection molding method. Then, the physical and mechanical properties of the samples such as water absorption and thickness swelling, modulus and tensile and bending resistances and impact resistance were performed on the samples. The results showed that the increase of nano particles had a positive effect on the physical and mechanical properties except impact resistance and improved them. However, the presence of nano-silica has led to an increase in the water absorption of composites. Examining the FTIR spectra and XRD patterns, the distribution of nanoclay in the field of polymer is of interlayer type, and in nanosilica, there is the accumulation of nano particles and the increase in the dimensions of the crystals in the composite. The results of bending and tensile strength were confirmed by scanning electric microscope.

Collapsibility is the sudden volume change of the soil due to the increase degree of saturation. This phenomenon occurs in sands due to the grains sliding on each other and in clays due to the loss of electron bonds between particles. The percentage of soil collapsibility depends on various conditions such as soil type, mineral composition, moisture percentage, dry weight, stress applied during wetting, and the amount of initial soil moisture increase. This paper has been conducted to investigate the effect of nanomaterials on soil collapsibility potential. The soil was selected from the Allahabad region of Kerman in south east of Iran with a high loamy index. For this purpose, Nano-silica, Nano-clay, aluminum Nano-oxide, and Calcium-Nano-Carbonated additives with percentages of 0.5, 1, 1.5, and 2% were used to improve the soil. Double consolidation and direct shear tests were the two main criteria for evaluating the performance of nanomaterials. The results showed that the collapsibility index of the desired soil due to the addition of Nan- clay compared to the addition of calcium Nano-Carbonate, Nano silica, and aluminum oxide causes a greater decrease in the collapsibility index. Furthermore, the results obtained from the SEM images indicate that the collapsible soil has microscopic and macroscopic holes, which the addition of an additive destroys larger holes and creates a correlation between soil particles. This problem reduces the amount of collapsibility index.

Self-compacting concrete (SCC) is known for its outstanding characteristics such as superior mechanical and durability properties. Corrosion of rebar due to penetration of chloride ions in the reinforced concrete elements is of particular importance. Therefore, this issue in the SCC must be investigated. Pozzolanic materials could be used in the SCC to increase the resistance of concrete against chlorine ion penetration. In this research, effects of pozzolanic materials including micro silica, nano silica, fly ash, rice husk ash, as well as limestone powder on the mechanical and durability characteristics of self-compacting concrete placed in chloride environment have been studied. The results show that nano-silica increases the mechanical and durability characteristics of self-compacting concrete. Moreover, the SCC containing combination of nano-silica and pozzolanic materials has better properties than the one containing nano-silica.

Due to the problems of high cost, difficult processing and unfavorable storage stability of bitumen modified with 1SBS, a lot of research has been done on composite bitumen to achieve superior pavement performance. In this study, the asphalt mixture was modified by nanosilica, gilsonite and SBS. Asphalt binder main performance tests, rutting tests, low temperature bending tests, moisture sensitivity tests, fatigue tests, and durability tests of asphalt mixture modified with SBS, gilsonite, nanosilica/rock asphalt, and nanosilica/ gilsonite/SBS were conducted to determine the performance Their structure should be evaluated. By comparing the results of the tests with the properties of the unmodified asphalt mixture, nano-silica and stone asphalt led to the improvement of the structure performance. The modified asphalt mixture with nanosilica/gilsonite/SBS had higher stability temperature, low temperature cracking resistance, lower moisture sensitivity, and longer durability than asphalt binder modified with 5% SBS, except for similar fatigue life.

The current study examined the properties of warm mixture asphalt (WMA), which contains nano- and polypropylene polymer (PP) polymers. Unmodified WMA and modified WMA both include 3% PP and NS (2–5%) by weight of asphalt respectively. The tests used to assess performance include the tests for fatigue resistance, rutting resistance, and moisture resistance. The results show that adding Nano-silica and Polypropylene enhances WMA performance. The results also show that adding polypropylene and nano-silica to asphalt as modifiers increases the asphalt's performance and durability.

Today, the use of nanomaterials in various sciences has found a wide perspective. In this regard, nanoscale additives in the concrete industry with the aim of improving the mechanical properties and durability of concrete, have been considered by researchers. In the preparation of geopolymer concrete, materials containing abundant aluminosilicate materials are combined with alkaline solution. In this laboratory study, a mixing design was made of control concrete containing Portland cement. Then, slag geopolymer concrete was made in three mixing designs containing 0, 4 and 8% nanosilica (4 mixing designs in total). Then, SEM test at 90 days of curing age and tests of water permeability, compressive strength and modulus of elasticity at 7 and 28 days of curing at room temperature were performed on concrete samples. Laboratory results indicate that increasing the curing age of concrete has improved the results of compressive strength, modulus of elasticity and water permeability. In the test of water permeability, modulus of elasticity and compressive strength, the addition of 8% nanosilica to geopolymer concrete improved the results by 26, 13 and 19%, respectively, compared to the design of nanosilica-free geopolymer concrete at 28 days after curing.

Today, the construction of highly critical structures (such as military and nuclear structures, hospitals and infrastructures), with high resistance to impact loads and high temperatures, is of particular importance in the field of passive defense. In this regard, the production of high-strength and nature-friendly concrete as the main material used in these types of structures plays a significant role. In this paper, the laboratory properties of the slag geopolymer concrete containing 0 to 8% nanosilica and 1 to 2% polyalphin fibers have been investigated. The concrete samples made at 90 days of curing age at 25 and 500 °C Celsius underwent weightlifting, weight loss, scanning electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy, and X-ray fluorescence (XRF) at 25 °C. At the age of seven days, the processing was performed on the concrete samples. The results indicate the weakening of the microstructure of concrete exposed to high temperatures. Also, the improvement of test results in the geopolymer concrete compared to ordinary concrete is evident. The best and worst performance in the weight loss test of the samples belonged to the geopolymer concrete containing 8% nanosilica and the geopolymer concrete containing 8% nanosilica and 2% fibers, by 0.061% and 0.12% weight loss of the sample, respectively. The best performance in the energy absorption of falling weight at 25 and 500 degrees Celsius belongs to the geopolymer concrete (containing 8% nanosilica and 2% fiber) at 2928.25 and 773.44 joules, respectively. The highest and lowest energy loss of concrete samples at 500 °C compared to 25 °C belong to the ordinary concrete and the geopolymer concrete (containing 8% nanosilica) by 83.33% and 53.33%, respectively.

The present research investigates the effects of nano-silica on strength parameters of sand-cement mortar at high temperatures. For this, sand cement mortar replacing 5, 10 and 15 wt% of cement with nano-silica was prepared. The mortar, having been processed at 3, 28 and 90-day ages, was subjected to 25, 100, 200, 400, 600 and 800 ºC, respectively. Effects of high-temperature rates on the physical and mechanical properties of the sand-cement mortar were examined by macrostructural experiments of compressive strength, weight loss and water uptake, as well as microstructural experiments using XRD and SEM. The research found that the macrostructural behavior of sand-cement mortar was highly dependent on microstructures and nanostructure cementitious changes when subjected to heat. At 600 ºC, the initial portlandite was fully degraded, which caused the CaO to form as water exited. At 800 ºC, in addition to alite (C3S) and Belite (C2S), β- Wollastonite was formed from the degradation of the C-S-H nanostructure. The addition of nano-silica improved the strength properties of the sand cement mortar against heat, with the compressive strength of the 28-day samples without nano-silica experiencing a 57% weight loss as the temperature rose to 800 ºC, decreasing from 31.1 MPa to 13.3 MPa. On the other hand, the compressive strength of the sand cement mortar samples containing 15% nano-silica experienced lesser strength loss (52%) at 800 ºC, decreasing from 40.2 MPa to 19.2 MPa.

Today, with advances, researchers are looking for a way to prevent human and financial damage from collisions. In this research, the energy absorption of nanocomposite structures with different percentages of clay and nan osilica nanoparticles along with diethylene triamine has been investigated using epoxy resin polymer and nanoparticles. And the samples under compressive axial loading have absorbed different amounts of energy. Therefore, the purpose of this study is to investigate the different effects of nanomaterials and different percentages. The design of this experiment has been done by Design-Expert software with a parametric study and Box Behnken Design (BBD). The range of changes in nanomaterials was 0-0.4 % and also diethylene triamine with weight percentages of 1, 3, and 5 % was used. The results show that the materials used in the study had a positive effect on energy absorption and the failure of the structure and the sample with weight percentages of 0.4% nano clay, 0.4% nano-silica, and 3% diethylenetriamine is the most optimal energy absorption mode. Has had a special.

Due to the increasing development of fiber-reinforced cementitious composites, studying their fracture behavior is necessary for the possibility of widespread use in the construction industry. In the present study, a new cementitious composite with strain hardening behavior has been fabricated. To reduce the adverse environmental problems, part of the cement has been replaced with pozzolanic materials such as blast furnace slag. Due to the fact that composites with high pozzolanic materials have lower strength at early ages than composites produced with ordinary cement, nano-silica has been used to solve this problem. Therefore, in this study, the effect of adding nano-silica on the fracture behavior of cementitious composites has been discovered. The double-k fracture method (DKFM) has been used to analyze the fracture behavior at different stages of specimen failure, i.e., crack initiation and stable and unstable crack propagation. In addition, the digital image correlation technique has been used to find the initial crack load and the crack opening displacement at different loading stages. The results show that the addition of 3% nano-silica positively affects compressive and flexural strength. In addition, it increases the toughness of the fiber bridging and reduces the brittleness of the composite.

In this paper, the effect of various parameters on the shear strength parameters of soil reinforced with ceramic fibers coated with nano-silica and kaolin particles has been investigated using the results of direct shear tests. The effect of the ceramic fiber content, fiber length, the nano-silica and kaolin contents and the content of fibers coated with nano-silica and kaolin on the shear strength parameters of reinforced silty sand has been investigated. The microscopic structure of the samples and the interaction of nano-silica, kaolin and fibers have also been examined with Scanning Electron Microscope (SEM). The results show that the shear strength parameters of the samples increase by adding ceramic fiber, nano-silica or kaolin particles to the natural soil. The length of ceramic fibers does not have a significant effect on the shear strength parameters of fiber-reinforced specimens, and 0.5% fiber content was recognized as the optimal fiber content. The samples containing kaolin particles have a higher shear strength than those containing nano-silica particles for a constant content of additive. The coating of fibers with kaolin has a greater effect on increasing the shear strength parameters of the samples.