Self-compacting concrete (SCC) has transformed the building sector by providing a special blend of excellent performance and user-friendliness. With SCC, the concrete settles and flows naturally due to its own weight, as opposed to traditional concrete, which needs mechanical vibration for proper placement and compaction. Because of this, it’s perfect for intricate structures and difficult-to-reach places where other techniques might be ineffective.
SCC’s carefully designed composition is the key to its amazing qualities. SCC maintains its strength and durability by balancing the mixture of cement, aggregates, water, and chemical admixtures to allow for free flow. This mixture guarantees a high-quality finish with fewer voids and defects in addition to improving workability.
To choose the appropriate type of SCC for a given application, one must be aware of how SCC is classified. A number of factors, including flowability, viscosity, and resistance to segregation, can be used to classify SCC. Every variety is made to fulfill distinct construction requirements, ranging from big infrastructure projects to residential structures.
We will examine the constituents and categorization of self-compacting concrete in this piece, emphasizing the major elements that influence its functionality. Regardless of your level of experience, this guide will provide you important insights into this cutting-edge material that is reshaping the construction industry.
Classification | Composition |
High-Strength SCC | Cement, water, fine aggregates, superplasticizers, and sometimes fly ash or silica fume |
Moderate-Strength SCC | Cement, water, fine aggregates, superplasticizers, and a balance of normal aggregates |
Lightweight SCC | Cement, water, lightweight aggregates (like expanded clay), and superplasticizers |
Fiber-Reinforced SCC | Cement, water, fine and coarse aggregates, superplasticizers, and fibers (steel, glass, or synthetic) |
Advantages and disadvantages of SCC
Self-compacting concrete (SCC) has the following benefits when compared to conventional compositions:
- Installation of high-strength concrete structures is faster.
- Defects caused by improper sealing of the concrete mixture are reduced to zero.
- It becomes possible to install various structures of complex shape with any geometry.
- For SCC, less bulky and heavy formwork is used (no need to vibrate concrete).
- When using self-compacting concrete, the best adhesion of the mixture to the reinforcement is achieved.
- The solution does not delaminate.
- SCC has noise and vibration insulation properties.
- The compacting composition is able to penetrate into hard-to-reach areas of the structure.
- The cement-sand mixture can be supplied through the bottom of the formwork.
- The mixtures have a reduced water resistance ratio. According to GOST 7473-2010, this indicator is no more than 0.4.
- The workability index of the solution is 70 cm.
SCC’s increased creep coefficient and high cost are the only drawbacks that come to mind.
Understanding the various types of self-compacting concrete according to their intended use is essential for producing self-compacting concrete on your own.
Classification and areas of application of different types of SMS
Based on where they are used, contemporary concrete mixtures are categorized as follows:
- Highly mobile. Used for: non-reinforced or weakly reinforced structures (SF1); standard structures (SF2); vertical elements, heavily reinforced structures and for structures with complex geometry (SF3). This marking also indicates the degree of spreading of mixtures: SF1 – from 55 to 65 cm; SF2 – within 66-75 cm; SF3 – about 76-83 cm.
- Viscous. Such mixtures are marked with the letters VS/VF. The first parameter indicates the period of time during which the solution supplied from a standard cone spreads to 50 cm (VS1 – up to 2 seconds, VS2 – more than 2 seconds). VF – indicates the period during which the SCC passes through a V-shaped funnel (VF1 – less than 8 seconds, VF2 – 9-25 seconds). Based on this, there are mixtures that are suitable for structures that do not require finishing (VS1/VF1) and compounds that increase thixotropy, used in the construction of structures of low strength (VS2/VF2).
- Easy to form. These compositions are used for buildings with a reinforcement pitch of 80 ÷ 100 mm (PA1) and for concrete foundations with a pitch of 60 ÷ 80 mm (PA2).
- Resistant to delamination. SCC for vertical reinforced concrete structures with a pitch of less than 80 mm, as well as for high-rise elements and profiles (thin-walled) with a pitch of more than 80 mm. The homogeneity parameter is determined during the test of the mixture using a sieve (SR1 – up to 20%, SR2 – up to 15%).
Practical! Self-compacting concrete has the same strength indicators as a traditional mixture (B30, B40, etc.).
Transportation
Just like any cement mixture, self-compacting concrete needs to be transported under certain circumstances. The truth is that SCC is not an exception and is also vulnerable to segregation and delamination processes, which cause some of its properties to be lost and lower-quality final products to be obtained.
In order to stop this from occurring, you must consider that:
- When transporting for more than 1 hour without using a concrete mixer, sediment will form in the mixture. Therefore, SCC, like regular concrete, should be transported only by truck mixers.
- Weather conditions have a detrimental effect on the solution. If the concrete solution is exposed to direct sunlight for a long time, this will lead to an increase in the temperature of the mixture, which will ultimately affect the consistency of the concrete.
- After the solution is delivered to the construction site, a thinner must be added to the mixture, then the concrete will acquire an optimal consistency.
In the construction industry, self-compacting concrete (SCC) is a game-changer because it doesn’t require mechanical vibration to flow easily into intricate forms and around obstacles. Its performance and mix design—which includes variants like powder-type, VMA-type (viscosity modifying admixture), and combination-type SCC—are the basis for its classification. In order to achieve a smooth, dense, and flawless finish, SCC is usually composed of a mixture of cement, water, fine and coarse aggregates, and specific additives that improve flowability and stability. This innovative concrete enhances the quality and longevity of the structures built with it while also streamlining the construction process.
Features of laying SCC
When installing SCC, it’s important to consider the following details:
- Before pouring self-compacting concrete, make sure that there is no liquid in the formwork. If it contains even a small amount of water, the properties of the composition may change, which will lead to stratification of the concrete.
- During the laying process, it is necessary to constantly stir the SCC (if the composition has thickened, add a thinner).
- The length of the pipeline for supplying the solution to the workplace should not be more than 200 m. If the mixture goes on for too long, it may become heterogeneous.
- The concrete solution does not need to be additionally compacted.
- If you are pouring concrete mixture into a mold for a narrow column or into another formwork with poor air drainage, then it is not recommended to drop the solution from a great height. It is better to lower the construction sleeve as low as possible into the formwork and raise it as the form is filled. The lower the height, the less air will get into the concrete layer.
Self-compacting concrete (SCC) is a cutting-edge, contemporary material whose exceptional performance qualities and ease of use have revolutionized the construction sector. In contrast to conventional concrete, SCC flows readily into forms without the need for mechanical vibration, which ensures a high-quality finish while saving time and labor.
SCC is categorized according to a number of characteristics, such as its filling, passing, and viscosity. Superplasticizers and viscosity-modifying agents are examples of specialized admixtures that are used to modify these properties, along with carefully choosing the mix proportions. A balanced combination that satisfies the unique needs of every project is the aim.
Cement, water, fine and coarse aggregates, and chemical admixtures are the usual ingredients of SCC. It is essential to carefully balance these elements in order to obtain the appropriate strength and workability. SCC can be made to fit a variety of applications, from intricate architectural forms to substantial infrastructure projects, by optimizing the mix design.
All things considered, using self-compacting concrete has many benefits, such as quicker construction, higher-quality surfaces, and quieter construction sites. Its performance and adaptability make it a great option for contemporary building, offering a dependable way to create strong, long-lasting structures.