Fine-grained concrete and its composition: what is it, where is it used in construction

Because of its precise strength and smooth finish, fine-grained concrete is a unique kind of concrete that is frequently used in construction. Fine-grained concrete depends on smaller aggregates, such as sand or finely crushed stone, as opposed to regular concrete, which mixes a variety of aggregate sizes. This produces a more consistent texture and appearance, which can be important in some applications where durability is not as important as appearance.

In actuality, projects requiring a high-quality finish frequently use fine-grained concrete. This covers things like exposed surfaces, ornamental concrete elements, and even some kinds of architectural elements. It is also utilized in precast concrete products, which are manufactured in a factory and assembled on location, due to its smoother consistency. This can include ornamental elements or concrete panels that must have an impeccable appearance from the start.

The ease with which fine-grained concrete can fill complex molds and details is another benefit. Because of this, it is perfect for casting intricate patterns and shapes that could be challenging to accomplish with coarser mixtures. Fine-grained concrete provides the accuracy and polish required for these specialized tasks, whether you’re working on intricate sculptures, a decorative facade, or high-quality flooring.

Concept of the material

Artificial concrete stones, known as fine-grained concrete, are made of cement, various fractions of sand, and water. We also call this type of concrete sand. The filler that is a part of the composition typically has a size of no more than two millimeters. A chemical reaction starts when sand, cement, and water are mixed together, resulting in the formation of a sturdy monolith.

• High tensile/flexural strength coefficient.
• The ability to change different properties of the material – increase strength, frost resistance, water resistance.
• Good resistance to vibration loads.
• Excellent transformation capacity of the finished solution.
• Maximum homogeneous structure due to the selection of filler.
• Wide choice of methods for creating a concrete structure/product.
• Frost resistance index is 2 times higher compared to conventional concrete.
• High water resistance, provided that the composition is selected correctly for fine-grained concrete.
• Ease of transportation, no likelihood of peeling.
• High density of stone due to the specific structure of the components.
• The product is suitable for products of any strength, various shapes.

The following drawbacks should be noted: shrinkage during product pouring or casting; high coefficient of hardness and complexity in mechanical processing; and increased binder consumption.

Features

Three ingredients are used to prepare heavy and fine-grained concretes: water, cement, and fillers. Fillers can vary in size; for regular concrete, small fillers (sand) and large fillers (crushed stone, gravel) are used. Nevertheless, only sand with fractions up to 2 is selected for a fine-grained solution. five millimeters. To enhance particular qualities, the composition can also contain a variety of additives.

• Uniformity of composition and maximum density, which affects strength (it is at least 30% higher in comparison with similar brands of conventional concrete).
• The solution is mobile due to the absence of large fractions, so it can easily be poured into hard-to-reach places, cast complex shapes, etc.d.
• To prevent air from getting into the mass, it is not recommended to vibrate this type of concrete. When exposed to a vibropress, air enters the solution, causing bubbles to appear, reducing the strength.
• Due to its porosity, concrete retains heat well.
• The cost of the material is relatively low.

To get the best option for a fine-grained concrete solution, you can adjust the composition, proportions, and other factors (this applies to home pouring of certain products, structures). GOST 26633-91 regulates the composition and component ratios in mixtures used in construction. In order to increase strength, plasticizers, ash, and other finely dispersed additives are permitted to be added to the composition.

Sand concrete’s characteristics are quite similar to those of regular concrete. Of the variations, the following are the only ones that merit attention: the presence of filler with fine grains, the total lack of large particles, and a cement content that is doubled.

Concrete is labeled in accordance with standards; the strength level falls between B3.5 and B80, and the qualities and proportions of the constituents used influence the characteristics.

Connection of components

Every element that makes up the fine-grained concrete has been chosen in compliance with the standard. Three different kinds of sieves are used to filter sand in the fraction selection process. To obtain the first fraction, it is first sifted through a mesh that has 2.5 millimeter cells. After that, strain using 1-cell cells through a sieve. Take a sieve with even smaller cells—0.135 millimeters—after 2 millimeters.

Take 20–60% of the first group’s total weight of sand when mixing fine-grained concrete, and then fill the remaining space with the second and third (smallest) fractions. Strong binding of the sand fractions is facilitated by the cement in the mixture, which serves as a binder and a supporting element. In this case, grades M400 and M500 are the better options because more cement is required than is typically the case. In addition, additives are used to boost strength and quality.

A specific kind of concrete known as fine-grained concrete has a mix that contains smaller aggregate particles, giving it a smoother texture and more application precision. Because of its distinctive composition, it is perfect for applications where precise craftsmanship and a high-quality finish are crucial, like elaborate molds, decorative surfaces, and upscale architectural elements. The definition of fine-grained concrete, its distinctions from regular concrete, and its optimal applications in construction projects are all covered in this article.

Application area

For the most part, reinforced products and structures are made of fine-grained concrete. The classic solution is unable to reach all areas due to the frequency of the bars located reinforcement; therefore, fine-grained concrete is poured into all areas that are difficult to access.

Because fine-grained concrete is so mobile, it’s frequently used to seal various deformations, repair joints, and cracks. The screed is frequently prepared by adding a fine-grained solution prior to waterproofing work. In the process of building roads, fine-grained solutions are also employed; this is important when creating curbs and paving slabs.

• Creation of concrete products by casting (arches, curbs, paving stones, etc.).d.).
• Production of thin-walled structures with dense or complex reinforcement.
• Preparation of solutions for sealing various types of cracks and joints in monolithic concrete.
• Construction of structures and buildings on sand quarries, crushed stone.
• Laying road surfaces – the high frost resistance, strength, and water resistance of fine-grained concrete are relevant here.
• A wide variety of reinforced cement structures.
• Production of small/large diameter concrete pipes, including pipes for the drainage of aggressive waters.
• Creation of elements for the installation of hydraulic structures.
• Pour the floor slabs for the installation of awnings in agricultural structures (where it is important to cover large spans).
• Arched structures for covering impressive spaces (in the equipment of exhibition pavilions, for example).

Large casting containers for the storage of liquid or bulk materials are known as bunker structures.

Cooking process

You can get such a mixture at any plant, regardless of whether a fine-grained solution is required in Moscow or throughout the region. You can also make it yourself; there are a few subtleties to the procedure, but nothing too complicated.

• The cement must be as fresh as possible to preserve all the characteristics.
• There should be no hardened pieces in the solution.
• All fillers are thoroughly cleaned of dirt, clay, impurities.

Distribution of sand into fractions

First, all of the dry components are ready, with the sand receiving special attention. The sand needs to be thoroughly cleaned, then sifted through three sieves and mixed in a way that distributes the volume evenly between large and medium fractions (50–60% of the total volume) and smaller fractions.

• Large fraction – 5-1.25 millimeters.
• Medium fraction – 1.25-0.3 millimeters.
• Small fraction – 0.3-0.15 millimeters.

Combination with a binder

Next, combine cement and sand. Use Portland cement grades M400/M500, as these are typically corrosion-resistant, sulfate-resistant, and pozzolanic cements. The components’ proportions may change based on the concrete’s intended use, operating circumstances, additional specifications, and anticipated qualities. Sand and cement are combined in a ratio of 1:1.5, while weaker is obtained in a ratio of 1:1.35 to create durable concrete.

There simply won’t be enough cement to completely encase each particle in the fine sand, so the standard recipe (1:3) is inappropriate. As a result, the mixture won’t be robust enough or fulfill the specifications.

Measuring water

There may be variations in the water and additive volumes. Plasticizers are added to the measured water if they are included in the composition. Enough water should be present in the mixture to guarantee the solution’s strength, density, and fluidity when it solidifies into a monolith. The rheological characteristics of the working solution serve as the decisive factor in this instance.

Connection of components

In a concrete mixer, all the ingredients are well combined. This is the prepared and compacted solution. It is crucial to observe the properties of the mixture, adhere to the ratios, and add extra water if the cement volume rises.

However, you shouldn’t stray too far from the technology because these kinds of experiments can lead to a decrease in strength and an increase in density. Insufficient cement in the mixture can compromise the structural integrity of the masonry and cause discomfort.

Pneumatic spray

This technology is growing in popularity every day because of its effectiveness, simplicity, speed, and high-quality output. Concrete with fine grains is ideal for the particular laying technique.

Applying a solution with a specialized gun and solution (cement, sand, fiberglass) is known as pneumatic spraying. All parts are simultaneously fed into the device’s container, blended inside, and routed through a pipe into which compressed air is used to force a mixture of fiber and solution out. This material is put into a form that has already been prepared, and a roller is used to roll the material.

One aspect of the process is that, even in transit, the mixture is continuously exposed to compressed air. By displacing water, this technology enhances the quality of concrete, producing a monolith with better qualities than sand-cement.

In the construction industry, fine-grained concrete is distinguished by its special qualities and broad range of uses. Because of the higher proportion of fine aggregates, such as sand, in its composition, it has a dense, smooth finish that is both aesthetically pleasing and practical. Highly regarded for its capacity to fill complex molds and produce a superior surface, this kind of concrete is perfect for intricate architectural details and ornamental accents.

Fine-grained concrete is applied in a variety of contexts in real life. It is frequently found in ornamental components like exposed aggregate finishes, floor tiles, and countertops. In addition, its polished look and silky texture make it a well-liked option for sculpture and artistic uses. It also performs exceptionally well in settings where a smooth surface is crucial, like upscale residential and commercial projects.

Gaining an appreciation of the advantages of fine-grained concrete requires an understanding of its composition. In addition to being more aesthetically pleasing, the concrete mix with a higher proportion of fine aggregates has better workability and finish. This results in fewer flaws and a neater appearance, which is crucial for construction for both practical and aesthetic reasons.

In the end, fine-grained concrete is a useful material in contemporary construction because it has both aesthetic and functional benefits. Its special qualities offer the quality and flexibility required to produce exceptional results, whether you’re working on a decorative element or a complex architectural project.

Video on the topic

Lecture 3 Testing filler in concrete.Influence of fillers on the properties of concrete mix