How to choose the size of the workability of concrete

The workability of concrete refers to whether the composition of the concrete mixture can be kept uniform, and whether it is easy to pour and vibrate during production and operation.

The workability of concrete is a composite indicator. It includes three contents: fluidity, cohesion and water retention of concrete.

The fluidity of concrete refers to the ability of the concrete mixture to flow and evenly and densely fill the formwork under the action of manual insertion or mechanical vibration.

The cohesion of concrete refers to the fact that in the production process, between the materials that make up the concrete mixture, there will be no delamination and segregation, and there is a certain cohesion capacity.

The water retention of concrete means that in the production process, the concrete mixture will not produce serious water leakage, and has a certain water retention capacity.

At present, there is no method that can comprehensively determine the workability of concrete mixture, usually to determine its fluidity, and then empirically judge its cohesion and water retention.

The most commonly used method for determining the fluidity of concrete is the slump method. When measuring, the concrete mixture is loaded into the conical slump cylinder of standard size in three layers, each layer is loaded, with the ramming rod of diameter 16 vertically and evenly inserted from the outside to the inside 25 times, after the three layers are pounded, the cylinder mouth mixture is scraped flat, and then the cylinder is lifted vertically, put aside, then the mixture will collapse due to its own weight, and the size ( ) of the downward collapse is measured is called slump. The greater the slump, the more fluid the concrete.

After the slump test, the cohesion and water retention of the concrete can be observed at the same time. If there is no excessive moisture on the surface of the concrete, it means that the water retention is good. And you can use a tamper to gently knock the mixture from the side, and the concrete with good cohesion will not loosely collapse under the knocking.

The slump test is only applicable to plastic concrete and low plastic concrete; For dry and hard concrete, the method of measuring the degree of workability is often used. It is necessary to use a Viber consistency meter to determine its workability.

Generally, only the size of the slump is selected, and the size of the slump is determined by the laboratory, and the mix ratio of concrete construction is the best gradation made by the laboratory according to the materials contained in the concrete, and the construction party carries out the construction according to the batching table. The degree of collapse is mainly to control the water-cement ratio, which is given by the laboratory, and the construction site can also be adjusted in small quantities according to the actual situation. Commercial concrete is affected by factors such as cement manufacturers, grades, labels, transportation distances, temperatures, etc.

It's only up to experience.

Workability refers to the fact that freshly mixed cement concrete is easy to be operated in various processes (mixing, transportation, pouring, tamping, etc.) and can obtain uniform quality and dense forming, which includes fluidity, cohesion and water retention. It is also called the workability of concrete.

1.Fluidity refers to the performance of fresh concrete under the action of self-weight or mechanical vibration, which can produce flow and make the formwork evenly and densely filled. The fluidity reflects how thin the mixture is.

If the concrete mixture is too dry and too thick, the fluidity is poor, and it is not easy to vibrate and compact; If the mixture is too thin, it has good flowability, but it is prone to delamination and segregation. The main influencing factor is the water consumption of concrete.

2.Adhesion refers to the ability of the new concrete components to have a certain cohesion between them, and do not produce delamination and segregation during the construction process. The cohesion reflects the uniformity of the concrete mixture.

If the cohesiveness of the concrete mixture is not good, the aggregate and cement slurry in the concrete are easy to separate, resulting in uneven concrete, and honeycomb and cavities will appear after vibration. The main influencing factor is the mortar ratio.

3.Water retention refers to the performance of fresh concrete that has a certain water retention capacity during the construction process and does not cause serious water leakage. Water retention reflects the stability of the concrete mixture.

Concrete with poor water retention is easy to form permeable channels, which affects the compactness of concrete and reduces the strength and durability of concrete.

Workability refers to the ease of construction and operation of the concrete mixture, mixing, transporting, pouring, tamping) and can obtain uniform quality.

Uniform and dense performance, also known as workability. Workability is a comprehensive technical property, including fluidity and cohesion.

and water retention.

The workability of concrete refers to the performance of concrete that it is easy to construct and operate in various processes and can obtain uniform quality and dense concrete. It includes fluidity, water retention, cohesiveness, etc.

Workability is a comprehensive technical property, which is closely related to the construction process. It usually includes three meanings: fluidity, water retention and cohesion.

1. Fluidity refers to the performance of fresh concrete under the action of self-weight or mechanical vibration, which can produce flow and evenly and densely fill the formwork. The fluidity reflects the thickness of the mixture. If the concrete mixture is too dry and thick, the fluidity is poor, and it is difficult to vibrate and compact; If the mixture is too thin, it has good fluidity, but it is easy to appear stratified and segregated.

The main influencing factor is the water consumption of concrete.

2. Cohesiveness refers to the performance that there is a certain cohesion between the constituent materials of fresh concrete, and no delamination and segregation will occur during the construction process. Cohesiveness reflects the uniformity of the concrete mixture. If the cohesion of the concrete mixture is not good, the aggregate and the cement slurry in the concrete are easy to separate, resulting in uneven concrete, and honeycomb and cavities will appear after vibration.

The main influencing factor is the glue-to-sand ratio.

3. Water retention refers to the performance that the fresh concrete has a certain water retention capacity and will not produce serious water leakage during the construction process. Water retention reflects the stability of the concrete mixture. Permeable channels are easy to form inside the concrete with poor water retention, which affects the compactness of the concrete and reduces the strength and durability of the concrete.

The main influencing factors are cement variety, dosage and fineness.

The workability of freshly mixed concrete is a comprehensive embodiment of fluidity, cohesion and water retention, and the fluidity, cohesion and water retention of freshly mixed concrete are not only related to each other, but also often contradictory. Therefore, under the condition of certain construction technology, the workability of fresh concrete is the contradictory unity of the above three properties.

Influencing factors. 1.Quantity and consistency of cement slurry: The amount and consistency of cement slurry are determined by the amount of water used per unit volume, and it is the most important factor affecting the workability of concrete.

2.Sand rate: refers to the percentage of the total mass of sand and stone in concrete.

3.Cement varieties and aggregate properties: including the water demand and water secretion of cement and the properties of aggregates.

4.Admixtures improve the workability of concrete or mortar mixtures during construction.

5.Time and temperature.

Other information. At present, there is no simple determination method that can fully reflect the workability of concrete mixtures.

Typically, fluidity is determined experimentally to assess cohesion and water retention by visual and empirical measurements. The fluidity of concrete is expressed by consistency, and there are two methods for determining it: slump and slump propagation method and Vibo consistency method.

Workability: It means that the concrete mixture can keep its composition uniform, do not occur stratification and segregation, water leakage and other phenomena, is suitable for transportation, pouring, tamping and other construction operations, and can obtain the performance of uniform quality and dense concrete.

Workability is a comprehensive technical performance, including fluidity, cohesion and water retention.

1.Fluidity: refers to the performance that the concrete mixture can produce flow and evenly and densely fill the model under the action of self-weight or mechanical vibration force. The degree of thinness of the reaction mixture.

1) The mixture is too thick, and the concrete is difficult to vibrate, which is easy to cause internal pores;

2) If the mixture is too thin, it will be layered and segregated, which will affect the uniformity of the concrete.

2. Cohesiveness: It refers to the cohesiveness between the internal components of the concrete mixture, which will not cause segregation and stratification in the process of transportation and pouring, so that the concrete can maintain the overall uniform performance.

3. Water retention: refers to the concrete mixture has a certain ability to retain internal moisture, and will not produce serious water leakage during the construction process.

For example, when the fluidity is very large, the cohesion and water retention are often poor. Vice versa. Good cohesion, generally good water retention!

Mixing, transportation, watering, tamping, etc.), and can obtain uniform quality, forming dense performance. Workability is a comprehensive technical property, it is closely related to the construction process, usually, including fluidity, water retention and cohesion, water secretion and other four aspects of the meaning. The main factors affecting workability are the quantity and consistency of cement slurry, sand rate, cement variety and aggregate properties, admixtures, etc

Time and temperature.

Pumpability refers to the ability of the concrete mixture to pass through the pipe at pumping pressure.

Concrete with good pumpability should be:

1) The flow resistance between the conveying process and the pipeline is as small as possible.

2) There is enough cohesion to ensure that there is no water leakage and no segregation during the pumping process. Concrete pumpability and fluidity are two completely different concepts.

The workability of concrete refers to the fact that the concrete mixture is easy to operate (mixing, transporting, pouring, tamping) and can obtain uniform quality and dense forming, also known as workability.

It is a uniform mixture of concrete when mixing.

The workability of concrete includes three aspects: fluidity, cohesion and water retention.

Concrete and workability, do you really get it.

The dust-prone and workability of concrete refers to the fact that the freshly mixed cement concrete is easy to be operated in various processes (mixing, transportation, pouring, tamping, etc.) and can obtain the properties of uniform quality and dense molding.

Concrete refers to the general term for engineering composite materials that are cemented into aggregates by cementitious materials. The term concrete generally refers to the use of cement as cementitious material, sand and stone as aggregates; The cement concrete, also known as ordinary concrete, is widely used in civil engineering engineering by mixing with water (which can contain admixtures and admixtures) in a certain proportion.

Concrete has the characteristics of abundant raw materials, low cost and simple production process, so that the amount of concrete is getting larger and larger. At the same time, concrete also has the characteristics of high compressive strength, good durability and wide range of strength grades. These characteristics make it widely used, not only in various civil engineering projects, but also in shipbuilding, machinery industry, marine development, geothermal engineering, etc., and concrete is also an important material.

The workability of concrete refers to the ease of operation of freshly mixed cement concrete in various processes (mixing, transportation, pouring, tamping, etc.). And can obtain uniform quality and dense molding properties.

Concrete refers to the general term for engineering composite materials made of cementitious materials that bond aggregates into a whole. In general, the term concrete refers to cement as a cementitious material and sand and gravel as an aggregate. Cement concrete, also known as ordinary concrete, is made of water (including external cracking agent and admixture) mixed in a certain proportion, and is widely used in civil engineering.

Concrete has the characteristics of abundant raw materials, low quality, and simple production process, so its dosage is increasing. At the same time, concrete has the characteristics of high compressive strength, good durability and a wide range of strength grades. These characteristics make it widely used, not only in a variety of civil engineering, liquid resistance but also in shipbuilding, machinery industry, marine development, geothermal engineering and other acres of applications.

Concrete is also an important material.

Chemical admixtures used: superplasticizers, high-efficiency superplasticizers, air-entraining agents.

2.Increase the slurry content of concrete: increase the amount of cementitious materials (cement + mineral admixtures such as fly ash, mineral powder, silica fume, etc.).

3.Increasing the mortar content of concrete, that is, increasing the sand rate.

4.Reduce the maximum coarse aggregate particle size and use graded sand and gravel.

Concrete, abbreviated as "concrete (tóng)": refers to the general term of engineering composite materials that are cemented into a whole by cementitious materials. The word concrete usually refers to the use of cement as cementitious material, sand and stone as aggregate; Cement concrete, also known as ordinary concrete, is widely used in civil engineering engineering when it is mixed with water (which can contain admixtures and admixtures) in a certain proportion and is mixed to obtain cement concrete.