The definition of concrete This adhesive is generally the interaction of hydraulic cement and water. Even such a definition of concrete includes a wide range of products. Concrete may be made from a variety of cement as well as pozzolans, kiln slag, aggregates, sulfur, concrete admixtures, concrete polymers, concrete fibers, and so on. Also, heat, steam, autoclave, vacuum, hydraulic pressures, and various compressors may be used in its construction. Due to the development of science and the emergence of various technologies over the centuries, knowledge of concrete and its properties, so that it can have different applications of concrete with different materials. Has its own. Currently, different types of cement are produced, including pozzolans, sulfurs, polymers, different fibers, and different additives. It can also be noted that the production of various types of concrete is done using heat, steam, autoclave, air cooling, hydraulic vibration pressure, and mold. Concrete is generally a product that results from mixing water with aqueous cement and various aggregates due to the reaction of water with cement in environmental conditions and has special properties. Concrete Now, more than 170 years after the founding of Portland Cement, a Lindsay building has undergone dramatic changes and improvements. The availability of its materials, relatively durability, and the need for numerous constructions of concrete structures such as buildings, structures, dams, bridges, tunnels, and roads, make this material very widely used. For about three to four decades now, the use of this substance in special circumstances has been welcomed by its users. Planned With the advancement of science and technology, it is clear that simply considering the strength as a feature for the design of dry concrete for different environments and different applications can not answer the problems that arise in the long run in concrete structures. The issue of concrete durability in different environments has been considered for several years. Observing the breakdowns with chemical and chemical agents in concretes in most parts of the world and with more intensity in the country now has led the thoughts and minds to design concretes with special characteristics and necessary durability. In this regard, some of the instructions and standards for high-performance concrete design have been prepared and designers and implementers in this case of this advanced requirement to comply with these instructions. For information on the purchase and price of different types of concrete, you can contact the technical equipment of Iran Concrete Clinic.
Concrete ingredients
Concrete materials from aggregates make up about three-quarters of its volume, and cement mortar and water make up a quarter.
1. Cement (cement)
Cement mortar is a constituent of concrete.
2. Water (water)
Water quality is important because the impurities in it may affect the setting of the cement and there is an obstacle. Inadequate water can also adversely affect the strength of concrete, causing stains on concrete surfaces and even rusting of the reinforcement. In water, most mixtures are suitable for drinking concrete that is suitable for drinking. Such aqueous solids will rarely be more than 2000 parts per million ppm, typically less than 1000 ppm. This amount is equal to 0.05 weight of cement in relation to water to cement 0.5. Drinking water is not for absolute mixing, and drinking water may not be suitable for concrete due to its high percentage of sodium and potassium ions, which poses a risk of alkaline reaction of rock aggregates. As a general rule, any water that (acidity) is between 6 and 8 and does not taste salty can be consumed. Dark colors and odors do not necessarily prove the presence of harmful substances in water.
3. The amount of water used in cement
The amount of water consumed inside the concrete is very important. In order to perform the process of cement reaction with water, a certain amount of water is required. If this amount is less than that, part of the cement will not receive enough water to react and will react and remain. If more than the required amount of water is added to the concrete mix, after completing the reaction, the amount of water remains freely inside the concrete, which after the concrete hardens, causing it to become hollow and consequently reduced. For this reason, care should be taken not to consume too much water inside the concrete in order to achieve high strength.
The amount of water required to perform the reaction is defined as the ratio of water to cement. This ratio is about 25% for ordinary Portland cement. With this amount of water, concrete will be required without efficiency and is usually more than this amount compared to water to cement used in construction workshops. In determining the mixing ratio of concrete, it is theoretically considered that some aggregates should be considered before adding water, which is required in determining the amount of water. This is the excess (or excess) amount of excess moisture (lack of surface area) of the aggregates from the saturated state with SSD or (Saturated Surface Dry).
✔ Concrete curing (concrete curing)
With continued hydration, the strength of concrete increases, and this reaction increases the strength of concrete or the setting of cement. The relative humidity must be at least 80% to process or find the Hydration process. If it is less than this value, the action starts and if it increases more than 80%, it starts to increase hydration or hydration again. Due to the evaporation of a part of the water required before completing the reaction between water and cement (which takes a few days) parts of the hair cement June remains unreacted in the concrete mix. After concreting, the necessary attention should be paid to the curing process immediately. Curing is the retention of concrete moisture until the reaction between cement and water is complete. This can be done by temporarily insulating, spraying water or producing steam. From a practical point of view, it is recommended to keep the concrete moist for 7 days. In cases where this is not possible, the minimum concrete curing time should not be less than 2 days.
Aggregates: Aggregates in concrete make up about three-quarters of its volume, so their quality is of particular importance. In fact, their physical, thermal, and sometimes chemical properties affect the performance of concrete. Natural stone grains are usually formed by weathering and erosion or by artificially crushing mother rocks.
Size of stone aggregates: Concrete is generally made of aggregates of different sizes with a maximum diameter of between 10 mm and 50 mm. On average, aggregates with a diameter of 20 mm are used. Particle size distribution is commonly known as “aggregate granulation”. In general, grains with a diameter of more than four or five millimeters are called sand and smaller ones are called sand, which is determined by a 4.75 mm sieve or a score of four. The lower limit of sand is usually 0.07 mm or slightly less. Materials with a diameter between 0.06 mm and 0.02 mm are called silt and finer clay materials. Flower is a soft substance that contains relatively equal amounts of sand, silt and clay.
Important minerals: Important and common minerals of aggregates in the field of use in concrete are: Siliceous minerals (quartz, opal, calcine, trimetite, cristobalite), feldspars, mica minerals, carbonate minerals, sulfate minerals, minerals Iron sulfide, ferromanganese minerals, iron oxide minerals, zeolites and clay minerals.
Classification based on appearance: In ASTM standard, stones are divided into five groups in terms of appearance: perfectly rounded corner, rounded corner, relatively rounded corner, relatively sharp corner and sharp corner. In the BS standard, this designation is rounded, amorphous and irregular, flaky, sharp, long, flaky.
Concrete Admixtures
Usually, instead of using a particular cement, it is possible to change some of the properties of the commonly used cements by combining it with an additive. It should be noted that the terms “composite materials” and “concrete admixtures” should not be used interchangeably, because composite materials are materials that are added to cement during the production phase, while concrete additives are added to concrete during the mixing stage. To be. Chemical additives are essentially: water reducers, retarders, and accelerators, which are classified as C, B, and A in the ASTM Code, respectively. The category of additives in the BS standard is similar. There are also other additives whose main purpose is to protect concrete from the harmful effects of freezing and thawing.
Concrete accelerators
There are additives that accelerate the hardening of concrete and increase the initial strength of concrete. Some examples of accelerators include sodium carbonate, aluminum chloride, potassium carbonate, sodium fluoride, sodium aluminate, iron salts, and calcium chloride.
Concrete retarders
There are additives that delay the setting time of concrete. These materials are very useful in very hot weather, which shortens the normal setting time of concrete, and also to prevent the formation of cracks due to setting in successive concreting. Examples of retarders include sugar, hydrocarbon derivatives, soluble zinc salts, and soluble brats. [11] For example, if we add the weight of sugar cement to concrete with a precise control of 0.05, it will delay setting for about four hours. Consumption of 0.2 to 1% by weight of cement prevents the cement from setting.
✔ Water reducers (lubricants)
These add-ons are used for three purposes:
Achieve higher strength by reducing the ratio of water to cement
Achieve a certain efficiency by reducing the amount of cement used and consequently reducing the hydration temperature in the concrete mass.
Simplicity of concreting by increasing efficiency in formwork with massive reinforcement and inaccessible positions for viewing water reducers with descriptions and performance diagrams in full detail, see here.
Water reducing additives are classified as Type A; However, if additives delay clotting while reducing water requirements, they are classified as type D. If these lubricants accelerate the setting, they are called type E.
✔ Concrete superplasticizers
These materials are among the strongest types of water reducers, which in the United States are named as strong concrete lubricants and in ASTM as type F. There are additives that, while drastically reducing water, also cause some delay in setting and are classified as Type G. Two examples of strong lubricants are concentrated sulfated melamine formaldehyde or [[condensed sulfated formaldehyde naphthalene]]. Basically, the use of sulfated acids accelerates the dispersion process. Because cement is absorbed on the surface of the particles and gives them a negative charge, and this causes the particles to repel each other. This process increases the efficiency in a certain ratio of water to cement.
Types of concrete
The use of building concrete is divided into the following types according to its type:
Normal
The most common type of concrete is a mixture of Portland cement, sand, gravel and water, this concrete is used with or without reinforcement in structures, roads and foundations. The ratio of sand, cement and cement mixture of this concrete varies from 1: 1: 2 (for the strongest mixture) to 1: 3: 6 (concrete except or as bed concrete). Made with ordinary aggregates and cements of type one to five Portland and with a specific weight of 2200 to 2500 kg per cubic meter.
Bulk plain concrete
Plain concrete is called reinforced concrete. This concrete is used in bulk concreting such as building dams, weight retaining walls, etc.
✔ Bed concrete (except megr)
Concrete is a simple concrete bed with a higher percentage of sand compared to cement compared to structural concrete. This concrete is used as a filler in non-structural works or as a protective layer of structural concrete against the penetration of solutes and materials in the bed soil, which is harmful to concrete. Concrete, except for cleaning concrete or the same as concrete for regulating the foundation formwork floor, is in fact a low-grade concrete (between 100 and 150 kg of cement per cubic meter) that is used to prepare the excavated bed for reinforcement and paving. To be.
Structural concrete
Structural concrete is concrete that can be used for structural load-bearing members. The weight of this concrete while compacted is about 2400 kg / m3 and should have high strength. If this concrete is made of lightweight stone materials, it can have high strength by observing special criteria in its design.
Reinforced concrete — reinforced concrete
Reinforced concrete or reinforced concrete is called reinforced concrete with rebar (reinforcement). Reinforcing rebars, reinforcing mesh, metal plates or reinforcing fibers are used to reinforce concrete. The main purpose of using reinforced concrete is to transfer the tensile forces created in the concrete to the rebars (due to the high tensile strength of the rebar) to Do not enter the concrete by tensile forces and do not cause cracking and eventually cracking of the concrete.
Prestressed concrete
Prestressed concrete is a structure in which the parts of the member that are affected by tensile stress during operation are pressed from the beginning. Therefore, under the load of concrete, it never falls into tension. Hypersensitivity is the creation of a constant and permanent stress in a concrete member in an arbitrary and sufficient way, so that due to this stress, some of the stresses caused by dead and live loads in this member are neutralized and as a result, the bearing strength It increases. The main purpose is to limit the tensile stresses and cracks caused by bending anchors under the influence of loads on that member. Concrete is physically resistant to pressure, but its resistance to tension is very low, so by applying pressure to the concrete, the tension created by the dead and live load in the concrete member can be reduced and thus its strength can be increased. Dad.
What is in-situ concrete?
It is concrete that is poured and hardened at the place of its permanent use. This method is the most common method of execution in concrete structures.
Prefabricated concrete
It is concrete that is poured in separate molds in the concrete factory and is done in a controlled way and hardens and is transported to the workshop site when necessary for final installation. In this process, concrete can be made with high quality formwork and strength and relatively low price. This method is used to produce floor slabs, blocks, road construction tables, fence railings, bridge beams and walls, etc. Prefabricated parts can have reinforcement and engineered steel parts can be embedded and installed in it.
Vacuum concrete
It is a concrete that has a high percentage of water to provide the necessary performance and the strength of the concrete is poured into complex molds or around compacted reinforcement. The concrete is then vacuumed and most of the water is removed, giving the concrete more strength as it hardens.
Pump concrete
Pump concrete is concrete that is transferred from the mixer to the discharge point by a pipe. The concrete is discharged from the mixer into a funnel and enters the pump from there, which causes a force to be applied to move the concrete forward in the pipe. The diameter of the pipe is 100–150 mm and with this method, the concrete can be pumped up to a horizontal distance of about 650 m or a vertical distance of about 50 m or a combination of these two sizes. Pumped concrete needs to have a higher percentage of water to improve the psychological properties of concrete. If high strength concrete is required, special additives should be used instead of excess water.
Stressed concrete
This method is used in the production of concrete springs and pipes. The production process involves pouring relatively dry concrete into a rotating cylindrical mold. The concrete is poured into the mold wall by centrifugation, creating a dense, impenetrable hard wall.
✔ Concrete present
It is concrete that is made in a concrete factory and transported to the workshop by a mixer truck. In this transfer, the cylindrical source in which the fresh concrete is poured is rotating continuously from the time of loading to unloading the concrete. The specifications of the concrete mix are agreed between the manufacturer and the consumer before construction and are usually of high quality.
Water resistant concrete can be waterproof or sealed.
Waterproof concrete consists of a surface with a water resistant layer while the internal volume of concrete is ordinary concrete. The waterproof layer can be created by applying a spray of varnish or by applying a layer of bitumen or asphalt coating on the concrete surface or by applying a solution of sodium carbonate (baking soda) or sodium silicate.
Sealed concrete can be produced by making dense concrete with a strict quality control method to prevent water or air from entering. Concrete that bن Normal
The most common type of concrete is a mixture of Portland cement, sand, gravel and water, this concrete is used with or without reinforcement in structures, roads and foundations. The ratio of sand, cement and cement mixture of this concrete varies from 1: 1: 2 (for the strongest mixture) to 1: 3: 6 (concrete except or as bed concrete). Made with ordinary aggregates and cements of type one to five Portland and with a specific weight of 2200 to 2500 kg per cubic meter.
Bulk plain concrete
Plain concrete is called reinforced concrete. This concrete is used in bulk concreting such as building dams, weight retaining walls, etc.
✔ Bed concrete (except megr)
Concrete is a simple concrete bed with a higher percentage of sand compared to cement compared to structural concrete. This concrete is used as a filler in non-structural works or as a protective layer of structural concrete against the penetration of solutes and materials in the bed soil, which is harmful to concrete. Concrete, except for cleaning concrete or the same as concrete for regulating the foundation formwork floor, is in fact a low-grade concrete (between 100 and 150 kg of cement per cubic meter) that is used to prepare the excavated bed for reinforcement and paving. To be.
Structural concrete
Structural concrete is concrete that can be used for structural load-bearing members. The weight of this concrete while compacted is about 2400 kg / m3 and should have high strength. If this concrete is made of lightweight stone materials, it can have high strength by observing special criteria in its design.
Reinforced concrete — reinforced concrete
Reinforced concrete or reinforced concrete is called reinforced concrete with rebar (reinforcement). Reinforcing rebars, reinforcing mesh, metal plates or reinforcing fibers are used to reinforce concrete. The main purpose of using reinforced concrete is to transfer the tensile forces created in the concrete to the rebars (due to the high tensile strength of the rebar) to Do not enter the concrete by tensile forces and do not cause cracking and eventually cracking of the concrete.
Prestressed concrete
Prestressed concrete is a structure in which the parts of the member that are affected by tensile stress during operation are pressed from the beginning. Therefore, under the load of concrete, it never falls into tension. Hypersensitivity is the creation of a constant and permanent stress in a concrete member in an arbitrary and sufficient way, so that due to this stress, some of the stresses caused by dead and live loads in this member are neutralized and as a result, the bearing strength It increases. The main purpose is to limit the tensile stresses and cracks caused by bending anchors under the influence of loads on that member. Concrete is physically resistant to pressure, but its resistance to tension is very low, so by applying pressure to the concrete, the tension created by the dead and live load in the concrete member can be reduced and thus its strength can be increased. Dad.
What is in-situ concrete?
It is concrete that is poured and hardened at the place of its permanent use. This method is the most common method of execution in concrete structures.
Prefabricated concrete
It is concrete that is poured in separate molds in the concrete factory and is done in a controlled way and hardens and is transported to the workshop site when necessary for final installation. In this process, concrete can be made with high quality formwork and strength and relatively low price. This method is used to produce floor slabs, blocks, road construction tables, fence railings, bridge beams and walls, etc. Prefabricated parts can have reinforcement and engineered steel parts can be embedded and installed in it.
Vacuum concrete
It is a concrete that has a high percentage of water to provide the necessary performance and the strength of the concrete is poured into complex molds or around compacted reinforcement. The concrete is then vacuumed and most of the water is removed, giving the concrete more strength as it hardens.
✔ Pump concrete
Pump concrete is concrete that is transferred from the mixer to the discharge point by a pipe. The concrete is discharged from the mixer into a funnel and enters the pump from there, which causes a force to be applied to move the concrete forward in the pipe. The diameter of the pipe is 100–150 mm and with this method, the concrete can be pumped up to a horizontal distance of about 650 m or a vertical distance of about 50 m or a combination of these two sizes. Pumped concrete needs to have a higher percentage of water to improve the psychological properties of concrete. If high strength concrete is required, special additives should be used instead of excess water.
Stressed concrete
This method is used in the production of concrete springs and pipes. The production process involves pouring relatively dry concrete into a rotating cylindrical mold. The concrete is poured into the mold wall by centrifugation, creating a dense, impenetrable hard wall.
✔ Concrete present
It is concrete that is made in a concrete factory and transported to the workshop by a mixer truck. In this transfer, the cylindrical source in which the fresh concrete is poured is rotating continuously from the time of loading to unloading the concrete. The specifications of the concrete mix are agreed between the manufacturer and the consumer before construction and are usually of high quality.
Water resistant concrete can be waterproof or sealed.
Waterproof concrete consists of a surface with a water resistant layer while the internal volume of concrete is ordinary concrete. The waterproof layer can be created by applying a spray of varnish or by applying a layer of bitumen or asphalt coating on the concrete surface or by applying a solution of sodium carbonate (baking soda) or sodium silicate.
Sealed concrete can be produced by making dense concrete with a strict quality control method to prevent water or air from entering. Concrete that bن Normal
The most common type of concrete is a mixture of Portland cement, sand, gravel and water, this concrete is used with or without reinforcement in structures, roads and foundations. The ratio of sand, cement and cement mixture of this concrete varies from 1: 1: 2 (for the strongest mixture) to 1: 3: 6 (concrete except or as bed concrete). Made with ordinary aggregates and cements of type one to five Portland and with a specific weight of 2200 to 2500 kg per cubic meter.
Bulk plain concrete
Plain concrete is called reinforced concrete. This concrete is used in bulk concreting such as building dams, weight retaining walls, etc.
✔ Bed concrete (except megr)
Concrete is a simple concrete bed with a higher percentage of sand compared to cement compared to structural concrete. This concrete is used as a filler in non-structural works or as a protective layer of structural concrete against the penetration of solutes and materials in the bed soil, which is harmful to concrete. Concrete, except for cleaning concrete or the same as concrete for regulating the foundation formwork floor, is in fact a low-grade concrete (between 100 and 150 kg of cement per cubic meter) that is used to prepare the excavated bed for reinforcement and paving. To be.
Structural concrete
Structural concrete is concrete that can be used for structural load-bearing members. The weight of this concrete while compacted is about 2400 kg / m3 and should have high strength. If this concrete is made of lightweight stone materials, it can have high strength by observing special criteria in its design.
Reinforced concrete — reinforced concrete
Reinforced concrete or reinforced concrete is called reinforced concrete with rebar (reinforcement). Reinforcing rebars, reinforcing mesh, metal plates or reinforcing fibers are used to reinforce concrete. The main purpose of using reinforced concrete is to transfer the tensile forces created in the concrete to the rebars (due to the high tensile strength of the rebar) to Do not enter the concrete by tensile forces and do not cause cracking and eventually cracking of the concrete.
Prestressed concrete
Prestressed concrete is a structure in which the parts of the member that are affected by tensile stress during operation are pressed from the beginning. Therefore, under the load of concrete, it never falls into tension. Hypersensitivity is the creation of a constant and permanent stress in a concrete member in an arbitrary and sufficient way, so that due to this stress, some of the stresses caused by dead and live loads in this member are neutralized and as a result, the bearing strength It increases. The main purpose is to limit the tensile stresses and cracks caused by bending anchors under the influence of loads on that member. Concrete is physically resistant to pressure, but its resistance to tension is very low, so by applying pressure to the concrete, the tension created by the dead and live load in the concrete member can be reduced and thus its strength can be increased. Dad.
What is in-situ concrete?
It is concrete that is poured and hardened at the place of its permanent use. This method is the most common method of execution in concrete structures.
Prefabricated concrete
It is concrete that is poured in separate molds in the concrete factory and is done in a controlled way and hardens and is transported to the workshop site when necessary for final installation. In this process, concrete can be made with high quality formwork and strength and relatively low price. This method is used to produce floor slabs, blocks, road construction tables, fence railings, bridge beams and walls, etc. Prefabricated parts can have reinforcement and engineered steel parts can be embedded and installed in it.
Vacuum concrete
It is a concrete that has a high percentage of water to provide the necessary performance and the strength of the concrete is poured into complex molds or around compacted reinforcement. The concrete is then vacuumed and most of the water is removed, giving the concrete more strength as it hardens.
Pump concrete
Pump concrete is concrete that is transferred from the mixer to the discharge point by a pipe. The concrete is discharged from the mixer into a funnel and enters the pump from there, which causes a force to be applied to move the concrete forward in the pipe. The diameter of the pipe is 100–150 mm and with this method, the concrete can be pumped up to a horizontal distance of about 650 m or a vertical distance of about 50 m or a combination of these two sizes. Pumped concrete needs to have a higher percentage of water to improve the psychological properties of concrete. If high strength concrete is required, special additives should be used instead of excess water.
Stressed concrete
This method is used in the production of concrete springs and pipes. The production process involves pouring relatively dry concrete into a rotating cylindrical mold. The concrete is poured into the mold wall by centrifugation, creating a dense, impenetrable hard wall.
✔ Concrete present
It is concrete that is made in a concrete factory and transported to the workshop by a mixer truck. In this transfer, the cylindrical source in which the fresh concrete is poured is rotating continuously from the time of loading to unloading the concrete. The specifications of the concrete mix are agreed between the manufacturer and the consumer before construction and are usually of high quality.
Water resistant concrete can be waterproof or sealed.
Waterproof concrete consists of a surface with a water resistant layer while the internal volume of concrete is ordinary concrete. The waterproof layer can be created by applying a spray of varnish or by applying a layer of bitumen or asphalt coating on the concrete surface or by applying a solution of sodium carbonate (baking soda) or sodium silicate.
Sealed concrete can be produced by making dense concrete with a strict quality control method to prevent water or air from entering.