Maya Ellison
Concrete has three states, and the first of these is the plastic state, which refers to the concrete when it is wet and malleable. In this state, concrete can be transported, moulded, or poured into any required shape. This is because concrete in the plastic state is soft, like bread dough, and has good workability and cohesiveness. However, if concrete is too wet, it may be difficult to finish, and it may separate and bleed.
| Characteristics | Values |
|---|---|
| State of Concrete | First of three states |
| Concrete Composition | Aggregate, water, and cement |
| Plastic State | Wet, soft, and mouldable |
| Transportability | Can be transported, moulded, and poured easily |
| Workability | Ease of mixing, transporting, placing, and compacting |
| Cohesiveness | How well concrete holds together |
| Bleeding | Appearance of water and particles on the surface |
| Segregation | Separation of coarse aggregates from concrete |
| Curing | Controlled moisture and temperature |
| Hardened State | Concrete has developed specified strength for intended use |
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What You'll Learn
- Concrete in the plastic state is mouldable and can be poured or transported easily
- Workability and cohesiveness are important properties of concrete in the plastic state
- Concrete in the plastic state should be free from segregation and bleeding
- A harsh mix of concrete will not give a smooth surface
- Concrete in the plastic state is soft and similar to bread dough
Concrete in the plastic state is mouldable and can be poured or transported easily
Concrete in the plastic state is soft and malleable, much like bread dough. This is the first of three states of concrete, the others being curing and hardened. In this state, concrete can be easily transported, moulded, or poured into any required space. It is highly workable, which means it can be easily mixed, transported, placed, and compacted.
The ease with which concrete can be worked in its plastic state is known as workability, and it is the most important property of concrete. A highly workable concrete mix will not result in segregation or bleeding. Segregation occurs when the coarse aggregates separate from the concrete, and bleeding is when water and fine particles of cement and sand appear on the surface of the freshly laid concrete. A harsh mix will not give a smooth surface with trowelling.
The plastic state of concrete is achieved when the ingredients of aggregate, water, and cement are first mixed together. In this state, concrete is dense and reasonably watertight, and it can resist changes in temperature as well as wear and tear from weathering.
Concrete in the plastic state is also cohesive, which means it holds together well. The cohesiveness of concrete is affected by the size of the aggregates used. A well-graded mix of aggregates, ranging from large rocks to small sands, will result in a more cohesive mix. However, if there is too much coarse aggregate, the mix will be boney.
After the plastic state, concrete begins to stiffen and set. This happens after compaction and during finishing. A sloppy or wet mix of concrete may be easy to place but will be more difficult to finish. Once concrete has set, it will begin to gain strength and harden.
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Workability and cohesiveness are important properties of concrete in the plastic state
Concrete in the plastic state is soft and can be moulded or poured into place. Workability and cohesiveness are important properties of concrete in this state. Workability is defined as the ease with which concrete can be mixed, transported, placed, and compacted. It is the most important property of concrete in the plastic state. A workable concrete mix does not result in bleeding or segregation. Bleeding is the appearance of water and some particles of cement and fine sand on the surface of freshly placed concrete. Segregation is the separation of coarse aggregates from concrete in the plastic stage. A workable concrete mix can be achieved by adding more cement paste, using well-graded aggregates, and employing admixtures. However, adding more water to increase workability decreases the strength and durability of concrete.
Cohesiveness refers to how well concrete holds together in the plastic state. It is affected by the grading, size, shape, and surface texture of aggregates, as well as the optimum quantity of water. Well-graded aggregates, which include a range of aggregate sizes from large rocks to small sands, result in a more cohesive mix. Conversely, too much coarse aggregate results in a boney mix that lacks cohesiveness. A cohesive mix will not exhibit any tendency for segregation. Additionally, air entrainment can be used to increase cohesion and reduce bleeding and segregation in plastic concrete.
The workability of concrete is important during the mixing, transporting, placing, and compacting stages. Fresh concrete, also known as green concrete, is in the plastic state and can be easily handled and flow into formwork and around reinforcement with the assistance of compacting equipment. It is important to ensure that air entrapped during mixing and handling is removed by compaction equipment. Higher workability concretes are easier to place and handle but can be weaker due to the increased water content.
After the plastic state, concrete begins to stiffen and set. Setting takes place after compaction and during finishing. Concrete that is too wet may be easy to place but will be more difficult to finish. Once concrete has set, it gains strength and hardens. The properties of hardened concrete are strength and durability.
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Concrete in the plastic state should be free from segregation and bleeding
Concrete in the plastic state is easily transportable, mouldable, and pourable. This state is also referred to as the "fresh concrete" or "green concrete" stage. Concrete in this state should be free from segregation and bleeding, which can compromise the quality and performance of concrete structures.
Segregation in concrete refers to the breakdown of the uniform distribution of aggregates, cement, and water, resulting in a non-homogeneous mixture. It occurs due to differences in the densities and sizes of concrete constituents, with heavier aggregates settling at the bottom and lighter cement paste floating upwards. Segregation can be caused by improper mixing, transportation, and placement techniques, such as dropping concrete from a significant height.
Bleeding in concrete is a type of segregation where water, due to its low specific gravity, migrates upwards, carrying some cement particles to the surface. While moderate bleeding can enhance the workability of concrete, it can also lead to the formation of laitance and channels, compromising stability and reducing wearing capacity and bond strength.
To prevent segregation and bleeding, proper mixing, transportation, and placement techniques must be employed. Controlled vibration and revibration techniques can also be used to counteract the adverse effects of bleeding. Air entrainment is another method to reduce bleeding and segregation by decreasing the density of the concrete.
In summary, concrete in the plastic state should be free from segregation and bleeding to ensure the structural integrity, strength, and durability of the final product. Preventative measures and mitigation strategies are crucial to addressing these issues and ensuring the high quality of the concrete.
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A harsh mix of concrete will not give a smooth surface
Concrete in its plastic state is easily transportable and can be moulded or poured into any place. Workability is the most important property of concrete in its plastic state. Workability refers to the ease with which the concrete can be mixed, transported, placed, and compacted.
A harsh mix of concrete refers to a concrete mix that does not provide a smooth surface with a certain amount of trowelling. A harsh mix of concrete lacks plasticity and its ingredients may tend to separate. This separation is known as segregation, which is when the coarse aggregates separate from the concrete in its plastic state.
There are several reasons why a harsh mix of concrete will not give a smooth surface. Firstly, a harsh mix of concrete may be caused by a deficiency of mixing water. Water acts as a lubricant for the fine and coarse aggregates and makes the mixture workable. Therefore, a lack of water can result in a harsh mix that is difficult to work with and does not produce a smooth surface.
Secondly, a harsh mix of concrete can also be caused by an excess of rough, angular, flat, or elongated aggregate particles. When there are too many of these particles in the mix, it can be challenging to achieve a smooth surface due to the uneven distribution of the aggregates.
Additionally, the technique used to mix and apply the concrete can also impact the smoothness of the surface. For example, if the concrete is not mixed thoroughly, it may result in a lumpy mixture that does not spread evenly and, consequently, does not produce a smooth surface.
Furthermore, the concrete must be sufficiently liquid for the aggregates to settle and create a smooth surface. If the concrete is too dry, the aggregates will not settle properly, resulting in a rough finish. However, it is important to note that adding too much water to the concrete can also cause problems such as cracks.
To achieve a smooth surface with a harsh mix of concrete, additional steps may be required. One possible solution is to use a soft topper or a grinder to smooth out the surface after the concrete has been applied. Alternatively, if the concrete will be covered, such as with tiles, there may be no need to worry about the smoothness as the rough surface will be concealed.
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Concrete in the plastic state is soft and similar to bread dough
Concrete in its plastic state is soft and pliable, much like bread dough. This is the first of three states of concrete, and it occurs when concrete is freshly mixed and wet. In this state, concrete is easily transportable and can be moulded, worked, or poured into any desired shape. It is highly manoeuvrable, allowing it to be placed into position for a variety of projects, such as sidewalks, high-rise walls, or foundation footings.
The workability of concrete is a critical aspect of this state. Workability refers to how easily concrete can be mixed, transported, placed, and compacted. A highly workable concrete mix will not result in segregation or bleeding. Segregation occurs when coarse aggregates separate from the concrete, while bleeding refers to the appearance of water and fine particles on the surface of freshly placed concrete.
To achieve good cohesiveness, or the ability for concrete to hold together when plastic, the ratio of water to cement is important. Too much water can lead to a lack of cohesiveness and potential separation or bleeding. Therefore, a well-graded aggregate, with a range of aggregate sizes, is essential for a cohesive mix.
During the plastic state, concrete begins to stiffen through a process called setting. This occurs after compaction and during finishing. As concrete sets, it becomes less soft and gains strength, transitioning into the second state of concrete, known as curing. Proper curing, which involves controlling moisture and temperature, is crucial for concrete to develop its full strength and durability.
Overall, the plastic state of concrete is a crucial phase in the material's lifecycle, allowing it to be shaped and placed with ease before it hardens and gains strength. This state is characterised by the concrete's softness and dough-like consistency, making it highly workable and mouldable for a wide range of applications.
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Frequently asked questions
The plastic state is the first state of concrete, when it is wet and malleable. At this stage, concrete can be transported, moulded, or poured into any shape or space.
The most important property of concrete in the plastic state is workability, or how easily it can be mixed, transported, placed, and compacted. Concrete in this state should also be cohesive, or able to hold together well.
The second state of concrete is the curing process, where the concrete develops strength and durability.
