Although it may not receive as much attention as mixes with higher strengths, lean concrete is still very important in construction projects. In essence, it’s a less expensive, less dense mix that offers a solid foundation for additional concrete work. Getting lean concrete just right is essential to making sure everything holds up well, whether you’re laying the groundwork for a driveway or getting ready for a more significant structural project.
Lean concrete preparation consists of a few simple steps. Specific ratios of cement, sand, and gravel are mixed; typically, more aggregate and less cement are used than in regular concrete. Although less expensive, this mixture is nevertheless durable enough to act as a base layer or a strong foundation.
The proper ratio of materials is one of the most important things to remember. Lean concrete usually contains less cement than richer mixes, so you have to be careful to make sure it’s the proper strength and consistency. For the concrete to work as well and last as long as possible, it must also be mixed and cured correctly.
We’ll take you step-by-step through the steps of making lean concrete in this guide, from assembling the components to mixing and curing. These steps will help you create a solid foundation for your building requirements without going over budget.
Step | Description |
1. Gather Materials | Collect cement, sand, and aggregate. You"ll also need water and tools for mixing. |
2. Mix Ingredients | Combine the cement, sand, and aggregate in the right proportions. A common mix ratio is 1 part cement, 2 parts sand, and 3 parts aggregate. |
3. Add Water | Slowly add water to the mix while stirring until the mixture reaches a workable consistency. It should be moist but not too runny. |
4. Mix Thoroughly | Ensure all materials are well blended. The mix should be uniform without lumps. |
5. Pour and Spread | Pour the mixture into the prepared area and spread it evenly. Use tools to level and smooth the surface. |
6. Let It Cure | Allow the concrete to set and cure for at least 24 hours. Keep it moist to prevent cracking. |
- Scope of application
- Composition and grades of lean concrete
- Properties and classes of lean concrete
- Cost of lean concrete
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Scope of application
Lean concrete is typically utilized as an auxiliary component because of its low strength, such as when:
- construction of bases for road surfaces, sidewalks and other asphalt areas;
- construction of foundation bases;
- processing of foundation joints;
- construction of preparation (layer up to 10 cm) for pile foundations;
- arrangement of screeds and concrete pads up to 9 cm high;
- preparation of foundations for swimming pools;
- installation of floors in the soil.
It is important to remember, though, that the ratio of its constituent parts dictates the range of applications for lean concrete.
Composition and grades of lean concrete
GOST 10178-85 guidelines state that a binder for "thin" concrete can be Portland cement M300–M400 or less expensive cinder block cement. On the other hand, when weak concrete is being prepared, less binder is needed when comparing the lean mixture to a standard solution.
Wholesome Cement should make up no less than 5% of the lean mortar (of the total volume of the dry mixture), according to SNiP.
When discussing lean concrete, it is important to take into account the aggregate that was used in its creation. There are two possible types of solutions depending on the filler type:
- fine-grained – in this case crushed stone with a fraction of no more than 5 mm is used;
- coarse – filler diameter is about 40 mm.
Additionally, plasticizers and other additives may be included in the composition of lean, low-strength concrete; however, the dosage of these additives should be somewhat higher than in building mixtures with greater durability.
You need to combine 170 kg of Portland cement, 831 kg of sand, roughly 1300 kg of crushed stone, and 140 liters of water to make lean concrete M100 for a 1 m3 area. The mixture in this instance shouldn’t be creamy. The consistency of "lean" cement should be similar to that of semi-dry soil. The amount of water needed is determined by the percentage of crushed stone; if the stone is finer, then a little more water is needed.
Practical! The maximum amount of water that you can add is 85% of the Portland cement’s volume.
You must use different amounts of sand, gravel, and Portland cement (ideally M400) to create concrete of different grades.
The component ratio will alter if PC M500 is added.
Of all "lean" materials, lean concrete M200 has the highest plasticity. The mixture itself will be harder the lower the grade of the solution. Large-area concrete mass laying is the most common application for these solutions. Select a more plastic material if you intend to pour the solution into a mold.
Properties and classes of lean concrete
SNiP also controls the solution’s characteristics. These specifications dictate that lean concrete needs to have the following qualities:
- grade from M75 (almost never used) to M200;
- frost resistance class from F50 to F100;
- water resistance class W2-W4.
Moreover, lean materials with grades M75–200 have a respective load tolerance of 5–15 MPa. This indicates that a pressure of between 50 and 150 kg/cm2 can be applied to the hardened structure.
In terms of lean mixture strength class, SNiP states that they should range from B5 to B15. Using concrete M100 class B7.5 (strength 98 kg/cm2) or mortar M150 (B10 – 131 98 kg/cm2) is the best combination for pouring the ground-leveling rough layer of the floor, which is approximately 4.5 cm high. You can obtain a solid and long-lasting base by applying hot bitumen or another waterproofing material to such a surface.
Furthermore, the soil beneath home foundations is stabilized with class B7.5 compositions.
More plastic concrete, or M200, has a strength class of B15 (196 kg/cm^2, which makes it appropriate for building stairs, monolithic lintels, ceilings, crowns, and many other things. However, the price of the material will increase with its grade.
A solid and long-lasting foundation can be achieved with lean concrete preparation, which also helps to keep material costs down. You can make a low-cement concrete mix that’s perfect for sub-base layers and non-structural applications by carefully balancing the mixture of cement, sand, and aggregate and making sure that the right mixing and placement procedures are followed. This approach guarantees long-lasting performance in a variety of construction projects while also increasing efficiency.
Cost of lean concrete
Making the solution yourself will save the most money. The price of PC M400 is approximately 230–250 rubles per package (50 kg), while the price of 50 kg of fine-grained crushed granite is approximately 300 rubles. If you do need to use modifying additives, you will have to pay more money for them. Buying a premade dry mixture makes sense in this scenario.
One cubic meter of building material will cost more if granite is used as a filler. M100, M150, and M2000 will cost at least 3000 rubles.
A practical skill that can be applied to a range of construction projects is the preparation of lean concrete. When you need a sturdy foundation but don’t need the high strength of regular concrete, it’s an affordable option. Understanding the fundamentals, such as the appropriate mix ratio and mixing methods, will help you guarantee that your lean concrete works efficiently and supports your project.
A crucial lesson to remember is how crucial it is to get the mix just right. Generally speaking, lean concrete is less expensive than standard concrete but still durable for a variety of uses because it contains less cement. It’s critical to make sure the cement, sand, and aggregate are balanced properly. One part cement to six or eight parts sand and aggregate is a typical mixture, but you should always adjust for your unique needs and the conditions in your area.
Placement and mixing are also crucial. For the mixture to have a consistent consistency, it must be blended evenly. Pour and spread it right away after mixing to avoid it setting too soon. Properly compacting the concrete will lessen the chance of uneven surfaces or cracks and help it set firmly.
Lastly, don’t forget about curing. Lean concrete still requires proper curing to reach its maximum strength, even with less cement in it. After pouring, leave the surface damp and covered for at least a week. This small action can have a significant impact on your concrete’s longevity and toughness.
You can easily prepare lean concrete that satisfies your needs and endures over time by adhering to these guidelines. An attention to detail goes a long way, whether you’re building a base or laying the groundwork for a more intricate project.