A mortar for self-compacting concrete consists of the following components (per 1 m3): water (170 -180 kg); Portland cement (530 kg); sand (650 kg); fine crushed stone (950 kg); plasticizer (3-4 kg); fly ash (aggregate) (200 kg). This is a standard calculation of the composition of concrete. However, in addition to these components, various chemical modifiers and fillers can be added to it, which increase adhesion and reduce the risk of cracking during shrinkage.

Application and styling

features SCC is used in the construction of various objects, in particular for the construction of hydraulic structures (piers, port buildings, breakwaters, dams of hydroelectric power plants). This material is also widely used in the following areas: In the production of prefabricated reinforced concrete elements and structures. For the construction of monolithic screed floors. For strengthening and strengthening buildings and supporting structures. When erecting objects for which an initially high-quality flat surface is required that does not require additional processing (for example, a runway). When building from concrete of various structures with a high content of reinforcing elements. For the construction of fences or thin-walled rooms (for example, when the building requires a minimum weight of load-bearing and supporting floors). When laying self-compacting concrete, it is worth remembering some of the features and nuances of using this material. So, for example, due to the increased content of superplasticizers, the setting time of the concrete mixture is significantly increased. Self-compacting concrete, when transported in a concrete mixer for more than one hour, begins to lose its self-compacting property, plasticizers also negatively perceive long-term transportation and, as a result, the mobility of the solution is lost. Professionals recommend not to save money and produce SMS directly at the construction site.

When transporting concrete through a pipeline with a length of more than 200 meters to the working area, delamination may appear and, as a result, heterogeneity of the mass. This point should also be taken into account especially carefully and try, if possible, to avoid using long supply pipelines when filling. The presence of a heterogeneous composition and layering can adversely affect the final result and significantly reduce the physical and mechanical properties of the finished structure.

Before pouring the self-compacting concrete into the formwork, make sure that there is no liquid, as even a small amount of water can disturb the composition. If there is water, then it is worth removing it, and it is desirable that the surface be dry at all, this will significantly improve the adhesion coefficient. When pouring the SCC, it is important that all components are fed continuously, otherwise the homogeneity may be disturbed and the quality of the final result may be reduced. For some time, the solution should not be touched, since it does not need to be compacted, and any manipulations can disrupt the uniformity and create surface irregularities after solidification.

Important: If during transportation or storage the self-compacting mixture has lost some of its quality characteristics and thickened, they can be restored with special chemical thinners, which are fed directly into the concrete mixer and mixed until the mass is homogeneous and its original properties are restored. To improve the quality characteristics of class-B15 concrete in the process of preparing the working mixture, the following additives can be used: sand and crushed stone of smaller fractions - when using them, the strength increases significantly, but the viscosity also increases (since the surface area of ​​the particles of the fine fraction in the total amount is much larger than that of the coarse one; the addition of micro- and ultradispersed filler to the mixture also significantly increases the strength and reduces the risk of corrosion on the reinforcement and the appearance of cracks during shrinkage and subsequent operation.
To improve the quality characteristics of class-B15 concrete in the process of preparing the working mixture, the following additives can be used: sand and crushed stone of smaller fractions - when using them, the strength increases significantly, but the viscosity also increases (since the surface area of ​​the particles of the fine fraction in the total amount is much larger than that of the coarse one; the addition of micro- and ultradispersed filler to the mixture also significantly increases the strength and reduces the risk of corrosion on the reinforcement and the appearance of cracks during shrinkage and subsequent operation.

Diagnostics

Regulatory data, strict requirements for manufacturing conditions and diagnostics of self-compacting concrete mixtures during construction are used only in the EU countries. To assess the workability and flowability of a concrete solution, a "rheological" method of analysis is used, based on hydrodynamics and rheology. Analysis and diagnostics are carried out according to the following quality indicators: Strength characteristics. Viscosity of the mixture. The degree of drainage. Separation coefficient of the medium. Mobility (determined in centimeters by the amount of draft of a standard cone). Workability (assessed by indicators of mobility). For More Details Visit : https://www.contractorsconcrete.com/