جستجوی مقالات مرتبط با کلیدواژه « بتن الیافی » در نشریات گروه « عمران »

Concretes have different behavior in the tensile and compressive loading. Concretes have a strong compressive strength, but the tensile strength of them is weak. To compensate for this weak tensile strength, it is necessary to use materials with high tensile strength. Steel fibers have been widely used in recent years because of their high energy absorbing capacity, scientific improvement of the concrete behavior after the creation of the first crack, and improvement of the bending and impact strength. Fiber concretes are a type of composite materials. In this concrete, fibers were used in the concrete mix design and increased significantly the tensile and compressive strength of the concrete. In this paper, the combination of steel fibers and polyolefin fiber in the construction of the concrete cube specimens was used. The steel fibers with a volume percentage of 1% and polyolefin with a volume percentage of 1% and 2% were used in the concrete mix design. Also, pumice powder and feldspar with a weight percentage of 10% and 20% individually and in combination with the same proportion were used. The 19th concrete mix design was constructed and experimental tests were performed on them to investigate the mechanical properties of the specimens. The compressive test on the 100 ×100 mm cubic specimens according to ASTM C109 and the three -point flexural test according to ASTM C348 at the age of 7 and 28 days of the specimens were conducted. The results exhibited that the combination of the steel fibers and polyolefin fibers led to an increase in the 28 -day concrete compression strength test of the specimens with pumice powder and feldspar. The optimal percentage of the combination is the steel fiber with 1% and polyolefin with 1%. Also, the use of fiber and polyolefin fibers improved the flexural strength of the specimens with pumice powder. It should be mentioned that a combination of the steel fiber and polyolefin with 1% in the specimens with 10% pumice powder achieves the best flexural strength at the age of 28 days. Also, the combination of the steel fibers and polyolefin fibers improved the compressive strength of the specimens with pumice powder and feldspar at the age of 7 days, but they resulted the lower compressive strength in comparison with the control specimen. Also, the use of these fibers led to an increase in the energy -absorbing capacity and the ductility of the specimens by increasing the fracture strain of the concrete. Depending on the amount of the pumice powder and feldspar in the concrete mix design, increasing the volume percentage of the fibers has a positive or negative effect on the ductility of the specimens. Also, increasing the weight percentage of the pumice powder and feldspar reduced the electrical resistance of the specimens. It should be noted that a combination of steel fibers and polyolefin fibers has a significant effect on the decrease of the electrical resistance. The use of the pumice powder and feldspar increased the water -absorbing capacity of the specimens and it intensified due to the use of the fibers.

Concrete is one of the widely consumed building materials in the construction industry, Among the specifications of the concrete which have been paid attention to by the researchers are compressive strength and tensile strength. So, to attain this goal, in the recent years, using a less ratio of water to cement with superplasticizers and natural and or synthetic pozzolans and also with fibers of different materials and specifications in the concrete mixture is a normal method. In this research, the effect of the combined use of fibre microgels and steel fibres on the mechanical properties and durability of concrete has been studied in a laboratory. Fiber microgels include micro-silica (silica fume), polypropylene fibers (pp fibers) and superplasticizers. Consumable steel fibers are 5 cm long and 0.8 mm in diameter with a hooked end. The effect of microgels and steel fibers were each compared and evaluated in five ratios of fibrous microgels 0, 0.5, 1, 2, 5% and steel fibers in ratios of 0, 05, 1, 1.5, 2%. A total of 25 mixing designs were tested for compressive and flexural strength to evaluate mechanical properties. The results of compressive and bending strength tests have shown that by adding different percentages of fibers, the percentage of increase in compressive strength in most of the 7-day samples has improved more than the 28-day samples. The highest resistance growth was related to the samples containing 5% fibrous microgel and 2% steel fibers.

Concrete is the most used construction material in the world. Today, there are various concretes with different applications in the industry. One of the types of concrete is fiber concrete. In this study, several concrete samples were made with steel, glass and polypropylene fibers and the effect of the volume and weight percentages of each of the fibers in improving the compressive strength of the samples at temperatures Different has been checked. In order to check the results and the possibility of comparing it with the behavior of normal concrete, a type of concrete without fibers was also made using common materials and similar tests were performed on it. Based on the investigations, the results showed that the concrete samples with steel fibers tolerated higher temperature levels and had higher resistance compared to other samples. In the samples, by adding 0.25% and 0.5% by volume of steel fibers to concrete, respectively, the compressive strength of the sample at high temperatures was improved. The strength of concrete samples with 3400 Kg/m was slightly decreased by increasing the percentage of fibers from 0.5% to 0.75%. The compressive strength of concrete containing steel fibers is 20% higher than that of concrete containing propylene fibers.

The use of fiber concrete technology in the form of flooring to remove thermal rebars and reduce the consumption of structural rebars is popular in the world today. Therefore, it is necessary to evaluate the properties of fibers such as their mechanical properties in concrete, to provide a fiber-concrete mixture design suitable for each project. The mechanical properties of fiber concrete are influenced by various parameters such as the type of fibers, the amount of fiber consumption, the dimensional characteristics, and the physical and mechanical characteristics of the fibers. The main parameter in determining the performance of fiber-reinforced concrete is the ability to provide bending strength after cracking. The purpose of this research is to investigate the effect of different amounts of macro synthetic fibers on the residual strength of concrete. For this purpose, eight concrete mix designs were used with amounts of 2, 4, and 6 kg per cubic meter and a control sample without fibers in two different compressive strengths of 25 and 35 MPa. The method of performing the test is based on the ASTM-C1609. Moreover,, to test the residual strength of fiber-reinforced concrete, the properties of fresh concrete and compressive strength testing were also done. The results of the residual strength test show that the use of macro synthetic fibers increases the load-carrying capacity after cracking, In the compressive strength test, the use of fibers, although it has no effect on the compressive strength value, changes the type of fracture from brittle to ductile.

One of the crises facing humanity is damage to the environment. Inadequate management and attention to greenhouse gas emissions threaten human life on Earth. Given the CO2 emissions from cement production, finding a way to reduce cement consumption in concrete as the most widely used building material is a priority. In this paper, a natural pozzolan from Iran with suitable physical and chemical properties for replacing part of cement in concrete was introduced and its engineering properties were investigated. To strengthen its strength, steel and polypropylene fibers were used separately and hybrids with new mineral pozzolans were used in concrete. According to previous studies and optimizations, mineral pozzolan with a weight fraction of 15% cement in concrete was used. A comparison of the strength of local mineral pozzolan samples with other famous pozzolanic concretes showed that concrete with local pozzolan is more resistant than ordinary cement concrete. Also, concrete containing steel fibers and local pozzolan has higher compressive strength than other samples. Pozzolanic concrete samples containing a combination of steel fibers and polypropylene had better performance in flexural strength than other samples and the impact toughness of these samples was better than other samples. Investigations showed that the impact resistance of samples containing local mineral pozzolans was 3.75 and 8.33% higher than conventional cement concrete at 28 and 90 days, respectively. The test results generally indicate that the local mineral pozzolans studied can be a good option to replace part of the cement in concrete and while improving the engineering properties of concrete, not only greatly reduce cement consumption but also a valuable finding for environmental protection. Biology, construction, and production of green concrete.

The use of fiber-reinforced concrete in various industries is developing due to the desired mechanical properties, light weight of the structure, good energy absorption capacity and high initial strength under impact loads. a new generation of fiber-reinforced concrete with excellent ductility and exceptional crack control capability. Although fibre concrete is suitable for structures exposed to impacts and other extreme loads, In this study, the energy absorption and initial strength of reinforced concrete with Forta, basalt and barchip fibers under penetration impact loading were investigated. To investigate the effect of fiber percentage on impact properties, 8 specimens were subjected to experimental tests hybrid groups. Also, the fracture surface and the adhesion of fibers to fiber-reinforced concrete with degradation modes were evaluated. The results showed that the initial strength and energy absorption in hybrid-fiber reinforced concrete increased by 292.8% and 212.3%, respectively, compared to Net conceret. Also, by examining the fracture surface of the specimens, it was found that the adhesion between the two basalt and forta fibers to the base concrete is very desirable. However, the separation between barchip fibers and concrete is high and reduces the efficiency of these fibers in reinforcing concrete.

Nowadays, concrete has received special attention due to reasons such as the ease of preparation of constituent components, low costs compared to other materials, favorable engineering properties, extraordinary durability, formability, and most importantly, positive interaction with the environment. Although the construction of concrete with the main components of cement, aggregate and water is very simple and conventional, but the addition of new materials such as fibers causes the fragility of concrete to be significantly reduced and it shows ductile behavior under different loads. Fibrous concrete is actually a type of composite that, with the use of reinforcing fibers in the concrete mixture, does not easily fall apart under the impact of impact loads, and its tensile strength increases above normal.Concrete gains very little strength at very low temperatures, so when the degree of saturation of the concrete is not sufficiently reduced by the dewatering action, it is necessary to protect the concrete against damage caused by freezing. The use of polyolefin fibers and the effect of appropriate granulation in the concrete mixing plan is one of the effective factors in reducing the effect of freezing. In this article, the reason for the use of polyolefin fibers, the manufacturing method, mechanical properties, fiber concrete applications, and the effect of mixing design granulation on the compressive strength and abrasion percentage of fiber concrete samples in the normal environment and freezing, according to the results of applications and researches has been discussed.

With the increasing development of concrete structures, properties such as strength and durability of concrete have become particularly important. Therefore, it is necessary to use special concretes and obtain new combinations. Ordinary concrete is brittle and frangible, and if rebar is not used, other materials such as fibers should be added to the mixture to remove the brittleness of the concrete. Fiber is used to control cracks in concrete, which in addition to controlling cracks, improves impact resistance, fatigue, shear, bending, as well as energy absorption of concrete. In this research, fiber concrete made of steel, barchip, and macro synthetic fibers and the combination of each fiber with different volume ratios is subjected to explosive load and the failure rate of each sample and the resistance of fiber concrete with hybrid fibers to explosion have been investigated in laboratory and field. Also, the special electrical resistance of hybrid fiber concrete against the electric current has been evaluated, which can be considered as a measure to evaluate the permeability and parallel absorption of concrete water. The results showed that concrete with macro synthetic fibers had greater explosion resistance than other samples. Also, the electrical resistance of concrete with macro-synthetic fibers has been higher than that of other samples, which will have special applications in corrosive areas with high penetration of chloride ions due to higher electrical resistance and consequently lower permeability. Also, for estimating the cost of fiber performance in concrete, the lowest excess cost of using fibers in concrete was related to the use of 1.5% of the concrete volume of macro synthetic fibers due to the low cost of these fibers and its high resistance to electrical resistance and resistance to explosive load. The use of these fibers in concrete to withstand explosion and electric current has been cost effective.

This research was aimed to evaluate the effect of the recycled waste carpet fiber on the mechanical properties of self-compacting concrete (SCC). Waste carpet fibers in 0, 0.5, 1.0 and 1.5% of volumes fraction of SCC were added. SCC samples have two different curing procedure; normal curing and curing at relative humidity of 30 %. For fresh stage, slump flow test, j-ring, V funnel and L box were done and for hardened stage, compressive and flexural tests were performed at the age of 28 days. The load–deflection curves were extracted from flexural test data to calculate the flexural toughness. Results show that by increasing fiber from 0 to 1.5%, the workability of SCC and compressive strength significantly decreases. However, reduction in workability for fibers up to 1% is still in the acceptable limits of EFNARC. From 0 to 1.5% waste fiber in flexural test, significant increases in energy absorption and toughness index were observed. The major increase in toughness index were observed from 0 to 0.5 % and after that does not change considerably.

Nowadays, the use of recycled concrete has increased significantly for economic and environmental reasons. Increasing the replacement percentages of recycled aggregates change the mechanical properties of concrete. In this research, the mechanical properties of concrete containing recycled aggregates with different percentages of steel fibers and polypropylene fiber has been investigated in the structural laboratory. A total of 36 cylindrical compression specimens, 36 cylindrical tensile specimens with dimensions of 20 * 10 cm and 36 flexural specimens with dimensions of 10 * 10 * 35 cm were tested. Recycled aggregates (coarse aggregates) in ratios of 25 and 50% (weight ratio) replaced with natural materials (coarse aggregates). Also, steel and polypropylene fibers were added to recycled concrete samples in ratios of 0%, 0.5%, 1% and 0%, 0.4%, respectively. Fiber concrete samples containing recycled aggregates under compressive force, indirect tension and three-point bending are tested and factors such as compressive strength, tensile fracture toughness, modulus of elasticity, flexural strength and fracture energy were investigated. The results show that the increase in porosity in recycled concrete is affected by the increase in the percentage of replacement of recycled aggregates and reduces the specific gravity of concrete. Increasing the composition of 1% steel fibers with polypropylene fibers without the presence of recycled aggregate has a greater effect on increasing the specific gravity of concrete than polypropylene fibers (alone). By increasing 25 and 50% replacement of recycled aggregate, 0.8% and 2.5% of specific gravity of concrete were reduced, respectively. Compressive strength decreases with increasing replacement percentage of recycled aggregate. Increasing the percentage of replacement of recycled aggregate due to poor transmission area reduces the amount of energy absorption. So that by replacing 25% and 50% of recycled aggregate, the energy absorption rate decreases by 21.7% and 26%, respectively, compared to the control samples. Polypropylene fibers have a positive effect on increasing compressive strength and combination of polypropylene fibers with 0.5 and 1% steel fibers increases the energy absorption. Also, increasing the replacement percentage of recycled aggregates reduces the hardness. Maximum tensile strength decreases by 3% and 13% with 25 and 50% increase in replacement of recycled aggregate, respectively. The results of flexural strength test show that increasing the replacement percentage of recycled aggregate has a negative effect on reducing the final load and reduces the final load in flexural specimens. Also, polypropylene fibers have a positive effect on increasing the loads and preventing the collapse of concrete, and combining polypropylene fibers with 0.5 and 1% steel fibers, respectively, increases the final load by 20% and 95% in 25%, replacing recycled aggregates and increasing 19% and 21% of rainfall in 50% recycled aggregate replacement. Increasing the percentage of steel fibers, the amount of deformation in the area after cracking and the amount of energy absorption increases, so that by increasing the amount of steel fibers to 0.5% and 1% by volume of concrete, the amount of energy absorption to 2 and it increases 3 times. The use of polypropylene fibers in the area after cracking has little effect and increases the load capacity.

In recent years, the use of synthetic fibers to improve mechanical properties and reduce the shrinkage of fresh and hardened concrete, increase energy absorption and impact resistance of concrete, and replace thermal reinforcement with fibers have greatly expanded. The use of various types of fiber has led to the improvement of some properties and the weakening of other properties. Simultaneous use of several types of fibers with designed ratios can enhance the mentioned properties simultaneously and prevent possible weaknesses. In this study, the effect of fibers with various volumetric percentages on compressive, flexural and tensile strength of the samples at different ages compared to the control sample has been measured. The simultaneous combination of steel, barchip and macro-synthetics fibers with different ratios, compressive performance, flexural and tensile performance of concrete has been tested. Among the constructed concretes, the best performance of reinforced concrete with steel fibers in different tensile, compressive, and bending strengths has shown that these fibers perform better than other constructed samples. In hybrid fiber concrete, the best performance in bending and compressive strength and tensile strength has been related to hybrid fiber concrete consisting of macrosynthetics fibers and steel fibers.

According to increasing the use of PET products, the present study aimed to the use of PET fibers in the concrete industries. Moreover, the behavior of normal concrete contained recycled fibers is not studied and the guidelines aren’t published yet. The aim of this study was to determine the effect of polyethylene terephthalate fibers on the mechanical properties of hardened concrete. Fibers were used in three volumetric percentages of 0.15%, 0.30%, and 0.45% with the lengths of 1, 2, and 3 centimeters, separately. So, 10 combinations of specimens including the control specimen and 9 combinations of PET fiber reinforced concrete were made. All mixtures were examined for compressive strength, tensile strength, flexural strength, shrinkage, durability, and impact loading.The results showed that by adding the PET fibers, the compressive strength, the bending strength, and energy absorption increase 5 to 18 percent, 6 to 30 percent, and 30 to 156 percent, respectively. However, no noticeable change was observed in tensile strength , while even a reduction in tensile strength is monitored. The impact strength of the fiber concrete was increased two to seven times in comparison with the control concrete. By comparing the experimental results it was determined that the combinations that contained 2 cm fibers with 0.45% volume had the best performance compared with the other mixtures.

In the present study, the effects of glass and basalt fibers (GF and BF) and temperature on the properties of self-compacting lightweight concrete (SCLC) has been investigated. For this aim, the fresh and hardened properties of 12 SCLC mixes have been investigated that contained monotype and hybrid fibers. The volume of the monotype fibers were 0.25%, 0.5%, 0.75% and 1% of the concrete volume. The hybrid fibers had volume fractions of BF/GF= 0.25%/0.75%, 0.5%/0.5%, and 0.75%/0.25%. The self-compacting properties of SCLC was assessed by means of slump flow, T500, V-funnel and J-ring. After 28 days of curing, the compressive, splitting tensile and flexural strengths tests were performed to characterize the mechanical properties of SCLC at room temperature of 20 °C and high temperatures of 100 and 300 °C. The test results of fresh concrete showed that all the mixes could be defined as SCLC with good flowability, viscosity and passing ability. Hardened test results indicated that the addition of the fibers reduced the compressive strength and increased the tensile strength, flexural strength and fracture energy. Moreover, compared to monotype fibers, the hybrid ones formed effectively enhanced mechanical behaviors of SCLC. The mixes containing 0.75% GF and 0.25% BF was the optimum one and determined acceptable fresh and hardened properties as well as high temperature resistance.

Today, concrete is regarded as one of the main materials in the construction industry, but besides its advantages, it is brittle and fragile and its tensile strength is lower than compressive strength. Due to the development of science and technology, the use of metal, polymer, glass and natural fibers in the construction industry is considered as an effective step in eliminating the poor tensile strength of ordinary concrete. Thus, in this research, the effect of steel and macro synthetic fibers on the behavioral model of concrete and mechanical properties (compressive and tensile strength, modulus of elasticity) and durability (electrical resistance, water permeability of concrete) have been investigated. Hence, in this research, 10 mixing designs with three different types of fibers, including steel, macro synthetic, polyolefin, and polypropylene fibers with 0.5, 1, 1.5 vol% were tested, and the results show that the steel fibers have no considerable effect on the compressive strength at a percentage higher than 0.5 and significantly increase the tensile strength and reduce the electrical resistance. The macro synthetic fibers of polyolefin and polypropylene have insignificant effect on compressive strength and even reduced compressive strength at high percentages and have a positive effect on tensile strength, electrical resistance, and water permeability, and the fibers can be used to increase the area under the stress-strain curve.

One of the undesirable modes of failure in reinforced concrete (RC) beams is the shear failure prior to bending one. One of the methods to prevent the occurrence of shear failure at a low level of shear forces is to provide the minimum shear reinforcement in RC beams. This paper investigates the effect of crimped end-hooked steel and modified polymeric fibers on the shear behavior of RC beams with normal strength. The experimental results of this study are then compared whit the shear behavior of the cross-section having the minimum shear reinforcement under similar conditions and the possibility to replace the minimum shear reinforcement by the fibers according to ASTM C1609 along with the fiber acceptance requirements based on ACI 318-2011, is evaluated. For this purpose, 16 half-scale reinforced concrete beam specimens with the shear span-to-effective depth ratio of 2.6 were made in three groups. The first four specimens were without the shear reinforcement and fibers, the other four specimens were without the fibers and reinforced with the minimum shear reinforcement and, eight other specimens were without shear reinforcement containing a hybrid of steel fiber (0.75%, 1%) and polypropylene fiber (0.25%). Moreover, the effect of longitudinal reinforcement ratio (2.5%, 4%) on the shear behavior of the beam specimens was investigated. After using the four-point loading test, it was observed that the combination of the crimped end-hooked steel and modified polymeric fibers would improve the shear behavior of RC beams and could be a good substitute for the minimum shear reinforcement.

Concrete and steel are materials with extensive use in human construction activities. Concrete is a material with high stiffness which is less expensive than other available construction materials, and steel is a material with high strength and ductility. Steel-concrete composite structural systems have been utilized in the construction of high-rise buildings due to their superior structural behavior. Fibrous concrete-encased steel columns are one of the most important composite structural members in which the axial load is carried by the steel and concrete at the same time. These columns are attracting the interest of many researchers due to their excellent structural performance under both static and seismic loading conditions. The steel-concrete interaction enhances the performance when carrying monotonous and earthquake loading. Reinforcing steel fibers help control crack propagation and prevent brittle failure in concrete through improving aggregate interlocking and thus enhance the properties of concrete including the tensile strength and ductility. This paper aims to investigate the axial capacity of fibrous concrete-encased steel composite stub columns. A total of 36 specimens with different cross-sectional shapes of steel profiles, including H-shaped and C-shaped, were tested, and axial parameters and compressive behavior were investigated. The variables of the research included the shape of the steel profile (H-shaped and C-shaped), steel fiber volume ratio (0%, 0.75%, and 1.25%), and the stirrup spacing (40, 65, and 130 mm). The results showed that the loading capacity of fibrous concrete-encased steel columns was affected by the shape of the steel profile inside. In this regard, the use of the H-shaped steel profile in the columns led to a higher axial loading capacity than the use of the C-shaped steel profile, due to greater confinement provided by concrete in columns with this section type (H-shape). Moreover, the addition of fibers significantly increased the ductility of these columns in comparison with those without fibers, and also, the addition of fibers increased the axial capacity of the steel-concrete composite columns by 6%. On the other hand, given the results, it is found that the stirrup spacing had a considerable effect on the load-carrying capacity of these columns, in that by increasing the stirrup spacing, due to the lower confinement of the column, the axial load-carrying capacity declined. In this regard, as the stirrup spacing increased, the decline in this parameter reached up to 11% for the columns with the H-shaped profile and 9% for the columns with the C-shaped profiles. Furthermore, the results of this study showed that the specimen with the H-shaped steel sections, 1.25% fibers, and the stirrup spacing of 40 mm generally were the optimal specimens in terms of the axial load-carrying capacity and ductility in comparison with the other specimens under study. All the specimens had almost similar damage patterns up to their failure. The difference was that the specimens containing fibers experienced failure mainly in the form of the crushing of concrete cover and its breakage from the middle of the column height, due to greater integrity of the concrete structure in these specimens. However, in the specimens without fibers, a considerable portion of the concrete cover was completely detached from the column.

Application of the concrete segments used in tunneling always lead to extensive cracks due to the impact of trust jack or forces created in the transportation stage. On the other hand, use of fiber reinforced concrete is of great interest because of reducing labor costs. Inclusion of fibers in concrete segments improves the mechanical properties and results in resisting high tensile stress. The purpose of this investigation is analysis of the replacement effect of steel fibers with bars in reinforced concrete segments applied in tunneling by using DBA method. Firstly, requirements and standards of fiber reinforced concrete segments were studied. Then, reinforced concrete segments simulated by ABAQUS finite element software were loaded. One of the reinforced concrete segments included reinforced concrete segment with steel bars. Also, to evaluate the replacement effect of steel fibers with bars, two steel fiber reinforced concrete segments with 0.5 and 1.0 percentage of volume content were simulated. Finally, the results obtained from DBA method considering compressive, tensile, and flexural capacity and cost showed that the reinforced concrete segment with 1.0% volume content of steel fiber was the most optimal among all reinforced concrete segments.

In this research, efforts were made to study the effects of water to cement ratio (W/C) and steel fiber volume fraction (V_f (%)) on the fracture parameters of self-compacting steel fiber-reinforced concrete using both Work Fracture and Size Effect Methods. In an experimental program, a variety of water to cement ratio and volume of steel fibers were considered and five mix designs were prepared in two series. In the first, water to cement ratio were altered (Includes values :W/C=0.42, 0.52, and 0.62) with a constant volume of steel fiber (V_f=0.3%), and in the second, varied volume of steel fibers (Includes values: V_f=0.1, 0.3, and 0.5%) with a constant water to cement ratio (0.52) were considered. Results have shown that an increase in the water to cement ratio reduces the fracture energy, However, we see a different behavior in the lower water to cement ratio, while an increase in the volume of steel fiber not only increases the fracture energy causing the concrete to become more ductile, but it can also reduce the size effect greatly. G_F⁄G_f has been found for all mix designs about 11.81 and it has been concluded that the work fracture method yields more fracture energy than the Size effect method.

Due to shrinkage, evaporation, or atmospheric conditions, small cracks appear in the outer concrete surfaces. These cracks can be repaired by using additives, which may also affect the structure and strengthening process. Concrete hydration may partially contribute to concrete repair. Repair usually occurs in small cracks. If concrete cracks were controlled, ordinary concrete would have somewhat of self-healing characteristic. This study investigated the self-healing effect of concrete at different ages by adding fiber (0%, 1%, and 2% of cement weight) to decrease the crack width, and micro silica (0%, 5%, and 10% of cement weight) to affect hydration. Due to the self-healing characteristic of concrete, compressive strength of concrete is a concern of this study. In fact, this study set out to investigate the self-healing effect on compressive strength recovery after the development of structural cracks. Results suggest that adding micro silica can enhance the rate and degree of self-healing in concrete. However, high micro silica content results in relative reduction of concrete strength as compared to the baseline. Moreover, adding fiber imposes crack closure and enhances self-healing characteristic of concrete. Adding these materials may improve the self-healing compressive strength of concrete, which is induced by compressive strength recovery of concrete.

In the last two decades, the increase in quality and strength in new concrete technology has grown significantly. One of the new generation concretes that is considered as a powerful and efficient concrete in the construction industry today is fiber concrete, which has improved mechanical properties such as higher tensile strength and even improved compressive strength. This concrete, which has a compressive strength in a range of 15 to 200 MPa, is mainly used in the construction of structures resistant to dynamic loads and thin walls, and its use in new construction projects has a high potential. In the present study, the role of human hair as fibers in reinforcing concrete and the characteristics of hardened concrete have been investigated and its details have been studied from the point of view of mechanical characteristics. For this purpose, 6 types of mixing schemes with different percentages of crushed hair (0-1-2-3-4 and 5% by volume) were considered and the desired mixtures were reached and molded with the help of lubricant. Tests of compressive strength, tensile strength, modulus of elasticity, and water absorption were performed to evaluate the mechanical and physical properties of concrete. The results of compressive strength of the samples showed that 2% of the consumed hair caused a 9.8% increase in compressive strength compared to the control design. Tensile strength also increased by 34.3% in the same percentage of consumption compared to the control design. The modulus of elasticity increased by 8.65% in 1% of hair consumed and then decreased. Water absorption had an increasing trend and in 2% consumption, showed a 24.2% increase compared to the control.