What is lean concrete: brand, composition, characteristics

A straightforward and affordable variety of concrete used in construction is called lean concrete. Lean concrete is less dense and robust than regular concrete because it contains less cement. It’s frequently applied as a foundation layer or in situations where strength isn’t as important. Because of this, it’s a cost-effective option for projects that need a solid foundation but don’t require a lot of support.

Lean concrete usually has a higher aggregate to cement ratio in its composition. This blend is referred to as "lean" because it produces a less binding material. Water, a tiny quantity of cement, fine aggregates like sand, and coarse aggregates like gravel are the main ingredients. This straightforward mixture is well-liked for a variety of construction tasks because it is simple to make and apply.

Workability is one of the key features of lean concrete. It is easily spread and leveled because it contains less cement. This makes it perfect for use as a filler, beneath footings, and in road construction. It might not be as strong as conventional concrete, but for many applications, its affordability and flexibility make it a good option.

What is it

The reduced cement content (binding component) of lean concrete sets it apart from standard and fatty concrete. Fillers, like crushed stone, are used more frequently at the same time. Since this combination produces a solution with a high degree of rigidity, there are a few guidelines that need to be followed when laying this kind of concrete.

Not all construction tasks are appropriate for concrete with a small amount of cement in it. It is crucial to take this into account because. If not, the construction project’s quality might decline.

Advantages and disadvantages

Now that you know what lean concrete is, you should explain why this mixture is so popular in the building industry.

1. Simple production cycle. Making this type of mixture requires less labor.
2. Financial savings. This is achieved due to the low concentration of cement.
3. Speed ​​of ​​construction operations. When using lean cements, the hardening rate of the composition is higher than when using fatty and standard mixtures.
4. High strength of the finished coating. It is achieved after compacting the solution with a roller.
5. Homogeneity of the composition. This feature is explained by the high content of crushed stone and a small amount of binders.
6. The ability to prepare the solution at the construction site. This reduces time costs and expenses for renting special equipment.

1. Relatively low strength (compared to the strength of fatty and standard compositions). This characteristic does not allow the use of lean concrete at those sites to which increased requirements are imposed.
2. High risk of cracking. In such cases, the performance indicators of the concrete coating are reduced.

When preparing the mixture, extra additives are added to extend the lean concrete coatings’ lifespan and strength. encompassing bitumen-containing emulsions.

Components

Lean concrete is composed of the following main ingredients:

1. Knitting elements. This group is represented by Portland slag cements and Portland cements of grades M300 and higher. These components are responsible for the adhesion of the components.
2. Aggregates (crushed stone).
3. Sand. Quarry or river material is used in construction. The fraction can be fine or medium (coarse sand is rarely used). The main purpose of using sand is to fill voids between coarse aggregates (crushed stone).
4. Water. The liquid must have a pH value of 4-12.5 units. The water should not contain petroleum products, fats, oils containing phenols.

Lean concrete is typically classified into two types based on the type of filler (crushed stone) used:

• fine-grained solution – it uses fine filler up to 5 mm in size;
• coarse-grained solution – the filler can have a size of up to 40 mm.

It is not advised to utilize fillers whose fraction is greater than 40 mm. This is explained by a compaction-related breach of the granulometric composition’s stability.

The mixture may vary in terms of the type of filler as well as its fraction.

• granite;
• gravel;
• lime.

The final coating’s strength and resistance to frost may be diminished if the fillers’ composition includes more than 10% clay dust particles.

Several indicators determine the mixture’s quantitative composition:

• cement grade;
• requirements for the strength of the coating;
• filler porosity index.

Building codes state that 1 m³ of lean concrete needs:

• from 120 to 145 liters of water (if the crushed stone filler has a water absorption level of 0.1-2%);
• from 145 to 165 liters (if the filler has a water absorption of 2-8%).

It is not advised to use more cement to water than is suggested. An excessive amount of liquid in the mixture causes the solution to shrink more and increases the chance of cracks.

Application

The most common use of concrete mixtures in construction is to strengthen the foundations on building sites.

• preparation of bases for foundations (prefabricated or monolithic);
• soil compaction for laying the road surface;
• laying of temporary roads;
• Black floor filling (such a mixture can be used in industrial and residential buildings);
• The initial stage of the improvement of the territory;
• Construction work when installing runways.

Road construction

A layer of 15-20 cm thick skinny (thin) concrete should be laid as the base for laying roads. These highways have a 25-year service life, depending on the technology. Its strength helps to explain why the concrete lasts so long. This layer is more resistant to subsidence, correctness, and crack formation.

Reduced cement mixtures have the benefit of being able to be assembled on site using locally available materials. This will shorten the technological gap between two masons and save costs.

Foundations for structures

There are multiple steps involved in the technology of installing a foundation substrate.

1. A layer of crushed stone or sand is poured onto the site of the foundation and compacted.
2. A reinforcing mesh is laid on a sand or gravel cushion.
3. Most often, M100 grade concrete is used. The mixture is evenly distributed over the site and compacted using vibration or mechanical rammers. The layer should be 10 cm thick.
4. The surface of the concrete is covered with waterproofing. Roll or coating materials can be used for this.
5. After complete hardening, a monolithic or prefabricated foundation of the building is laid.

The concrete substrate’s primary function is to keep the soil moisture out of the house’s later layers. As a result, the building’s service life is extended.

Floors paths

For laying subfloor screeds and path foundations, a lean solution is frequently employed. You may use concrete in class B7.5–10 for these purposes. The base is first covered with a layer of river sand and crushed stone (which needs to be free of clay).

When mixing concrete for uneven pathways and floors, it is preferable to use a filler whose percentage does not go above 20 mm. The solution needs to be applied evenly, with a layer no thicker than 40–50 mm. Insulation and waterproofing are applied to the screed following compaction.

Characteristics

It’s important to pay attention to the specifications when making mixtures with less cement. GOST 25192-2012 governs the final coating’s characteristics. Furthermore, on May 23, 2003, "Methodological recommendations" were adopted. The laying and preparation procedures need to adhere to SP 70.1330.2012.

1. The density should be in the range of 2450-2500 kg/m3.
2. Frost resistance indicator-at least 50-100 cycles.
3. The compression strength indicator should be from 75 MPa to 200 MPa.
4. The level of water resistance has an indicator of 6%.
5. The rigidity of the material can be 90-120 s.
6. The permissible indicator of the mobility of the mixture is 10-15 cm.

The amount of cement consumed is determined by brand. A concrete mixture weighing 100–240 kg per m³ is the most appropriate indicator.

Seal coefficient

Concrete that has been mined is not very strong. Resolving this issue permits compaction. According to this definition, it is typical to use a vibrating plate or roller to assess the impact on the concrete layer.

Air is eliminated, the coating density rises, and the mixture’s component adhesion increases as a result of their action. The indicator 0.98-1 is the ideal coefficient for sealing such concrete.

Brands

The following are the most well-known brands of concrete:

Although the manufacturers also provide concrete mixes M50 and M75, their applications are very restricted.

M150

A brand like this ought to be used for the fundamentals of roads, floors, pathways, and foundations. M150 is frequently selected in order to enhance the private sector.

M200

Based on the features, this brand is associated with more aggressive concrete. Its strength and operational term are also increased. It ought to be used on things with higher requirements (like building runways and foundations).

M100

Although this construction mixture brand has the lowest strength, it still has a number of benefits. Savings on construction work is possible because coatings are inexpensive. The layer also hardens gradually, giving the workers time to equalize.

A straightforward, low-cement mixture called "lean concrete" is used in construction to give buildings and roads a level, stable foundation. It is less expensive and less strong than regular concrete because it contains less cement, hence the name "lean." Usually, a mixture of cement, sand, water, and coarse aggregates make up the composition. Lean concrete is crucial for producing a smooth, compacted surface that aids in the even distribution of loads and serves as a strong foundation for more intricate concrete work, but it is not utilized for structural support.

Cooking

Such a mixture can be prepared on-site at the construction site or in BRU. The GOST has the consumption rates listed.

• cement grade M300 — 160 kg;
• fine crushed stone — 1300 kg;
• sand in the amount of 900 kg;
• water — about 60-70 liters.

Use a concrete mixer to ensure even mixing. Fill it with water and any required additives. Alternately add sand and cement. Mixing lasts for three minutes. Last, add the crushed stone. Ten more minutes are spent mixing. One can lay the completed mass.

Expert builders recommend mixing all the dry ingredients together first, then progressively adding water when mixing by hand. The mixture should have the consistency of slightly moist earth.

Transportation

Using a dump truck is the most straightforward and affordable method of delivery. The only concrete mixture types that can be transported in this manner are lean mixtures. A dump truck’s large size and poor maneuverability, however, are a major disadvantage. Not every time can such specialized machinery approach the construction site.

If you have the choice, it is better to order a finished product rather than prepare the mixture yourself. The manufacturer can supply the finished mixture in any quantity while adhering to manufacturing technology.

Laying

Following these guidelines is essential when applying the concrete mixture:

1. Preparing the base. The surface on which the concrete is laid must be carefully leveled and cleared of debris. If construction work is carried out in the cold season, there should be no snow or ice on the ground.
2. Laying. The mixture is distributed evenly over the surface. Most often, the concrete layer reaches a thickness of 10 cm.
3. Compaction. The use of vibratory tools or rollers is a prerequisite, since.. compaction increases the density and strength of the coating.
4. The surface of the concrete screed should not dry out, otherwise cracks will appear on it. To avoid drying out, the layer is regularly watered and covered with a film.
5. Formwork construction and further construction work can be continued after the solution hardens to a strength of 1.5 MPa.

Brand	Lean concrete typically has a low cement content, often around M5, M7.5, M10, or M15.
Composition	It"s made from cement, sand, coarse aggregates, and water, with a higher ratio of aggregates compared to cement.
Characteristics	Lean concrete has lower strength and is primarily used as a base layer or for non-structural purposes. It"s cost-effective and easy to work with.

Lean concrete is a common non-structural application that is both economical and versatile in construction. It is less robust than ordinary concrete due to its lower cement content, but it is more affordable. Because of this, it is a well-liked option for foundations and sub-bases where great strength is not necessary.

Lean concrete is made up primarily of aggregates, such as sand and gravel, along with a mixture of cement and water. It is "lean" in the way that is characteristic of reduced cement content. This mixture helps to level the ground and guarantees a smoother surface, giving other building layers a solid foundation.

Lean concrete is easily poured and spread due to its workability, which is one of its primary qualities. Moreover, it sets up more quickly, which is useful for accelerating building projects. However, it is not appropriate for load-bearing structures because of its reduced strength.

In conclusion, lean concrete is a useful and effective option for specific building requirements. It is a useful option for a variety of projects because it strikes a balance between affordability and utility. Comprehending its characteristics and uses can aid in making well-informed choices during the planning and implementation phases of construction.

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