- Concrete types
- Percentage composition
- Concrete mixing
- Pouring concrete
After reading this article, you will learn how to make good concrete with your own hands, what characteristics good concrete should have, what is included in the composition and in what proportion, the advantages of manual and mechanical technology for mixing concrete and pouring it.
Concrete is often referred to as the main building material. Foundations, walls, roofs, screeds, claddings, paving slabs, balusters, vases – unlike granite or marble, it is easy to make concrete yourself and in the required quantity. Depending on the area of application, good concrete can be heavy or light, strong or frost-resistant, set quickly or for a long time, be more or less mobile.
Usually concrete is a mixture of cement, water and sand. To increase the strength of concrete, large aggregates in the form of crushed stone and gravel are used, and to give additional properties and ease of manufacture and pouring, various reinforcing substances and plasticizers are added. The heaviest concrete is used in underground bunkers as a reliable radioactive barrier.
To obtain good concrete, you must carefully consider the selection of all components.
The main link in concrete, a single bundle of all components and the most expensive element. For good durable concrete, you will need Portland cement of the M500 brand, and if the preparation of concrete is carried out at temperatures above 30 degrees, then slag cement is needed. If we are talking about paving a bright garden path, it is better to take white cement, gray Portland cement will drown out any pigment paint. Lime cement has a low setting speed and is ideal for small decorative elements.
The cement must be dry and crumbly, free from lumps and moisture. If the packaging is torn or the cement was stored on the street – just walk by. The first cement in terms of importance is the last in terms, it is better to buy it no earlier than a few days before the start of concrete production.
The main characteristic is the absence of impurities, which negatively affects the strength of concrete and its durability. By types, sand is usually divided into river, ravine and artificial sand, obtained by processing rocks. Gully sand is cheaper than river sand, but it contains much more silt and clay, and stone sand gives additional weight to the concrete composition in the interfloor screeds.
You can buy ready-made washed sand or drive to the nearest quarry, and then at home using a sieve to get a homogeneous product.
To understand how clean the sand is, you need to pour it into a hot water bottle, stir it and let it stand for several hours. If the water becomes cloudy, this indicates a high clay content. Concrete from such sand will become loose and crumble.
Coarse aggregate is indispensable to obtain durable concrete. For high-strength concrete, crushed stone is preferable, and for medium-sized concrete, much cheaper gravel is suitable. The type of crushing affects the cost of the material – crushed stone is obtained mechanically, it is distinguished by its roughness and the presence of sharp corners. Naturally, gravel has a more rounded shape. You cannot use river or sea gravel polished by the current, it will not give the desired adhesion to the mortar. For the foundation, it is better to take gravel of different sizes – from medium to large (with elements from 10 to 35 mm), this will give the particles the opportunity to create a more uniform base. For stairs and decorative elements, you need fine gravel with a diameter of no more than 7 mm.
Expert tip: Store crushed stone and gravel on tarps to prevent natural contamination and moisture from soil.
The main rule is to use drinking water. You can safely take water from a sewer or a column, but it is not recommended from a well or a river, its composition can bring many unpleasant surprises.
Expert tip: Add liquid soap to the water to increase the elasticity of the solution.
To make it easier to lay concrete, lime is usually added. It is sold slaked in bags or buckets as a lime dough. Sometimes it comes across under the name “fluff”. When working with lime, it is better to wear not only gloves, but also a mask, as it has strong corrosive properties.
If the foundation or concrete product is of complex shape, then plasticizers will need to be added to the solution, which affect the viscosity and fluidity. They will help to quickly fill the most difficult-to-reach places and significantly speed up the process..
When forming a thin screed or unstable soil, special reinforcing substances will be needed. Such substances prevent the formation of shrinkage microcracks and increase the impact strength of concrete several times..
Expert advice: additives should not exceed 2 percent in the solution of the mass fraction of cement. PAt subzero temperatures during kneading add potash.
To form the main part of the foundation for the house, you will need strong concrete with the inclusion of large gravel and high fluidity for compaction. A lighter concrete made of sand and cement is used to equip the substrate for the foundation. To achieve the best value for money, it is necessary to understand for what purpose the concrete is made. Depending on the composition of the brands, concrete is divided into three groups:
- Lightweight concrete (M100 and M150) – a wooden house, garage, curbs, screeds, stairs. The main plus is that crushed stone can be replaced with gravel, especially if you have a farm and have a stone crushing machine.
- Medium concrete (M200, M250, M300) – reinforced concrete products, piles, good solid houses with 2–3 floors. This concrete can be used to build walls and cast monolithic foundations..
- Heavy concrete (M400, M500 and above) – withstands 5 or more floors. Used in the construction of swimming pools, water parks and bank vaults, it sets quickly and is expensive.
Most often, when pouring a foundation, a ratio of one part water to one part cement, three parts sand and six parts aggregate is used. For an accurate calculation, it is better to use a table based on M500 cement, sand and aggregate:
Concrete type Composition C-P-Z,% one hundred 6-36-52 150 8–34–50 200 9–32–50 250 11-28.5-49.5 300 11.5-27.5-49.5 400 15-23-47 450 16-22-46
If you need to make a foundation for a house of about 100 squares, then you can’t do without a concrete mixer. The expense for its purchase (10,000–20,000 rubles) will be justified by the ease of mixing. It will be difficult to manually mix all the ingredients without adding a lot of water, which, in turn, will affect the consumption of expensive cement. On the market today, you can buy mechanical concrete mixers so as not to be tied to the power grid. If we are talking about paving a path or making a concrete staircase, then improvised means are also quite suitable..
To prepare the mixture by hand, we need:
- Kneading container – trays or old tub.
- Weight measure – metal bucket.
- A pair of mixing shovels.
Add the ingredients in turn, stirring constantly:
Expert advice: we do not spend all of the water at once, but divide it into 2 parts. 80% – first, the rest – after adding all the ingredients.
The mixing time should take no more than half an hour, otherwise the cement will begin to set. It is better to prepare concrete in small portions for transportation by wheelbarrow to the place of laying.
The main danger when pouring concrete is uneven distribution over the surface and the formation of air voids. For this purpose, you can make a homemade vibrator from a hammer drill or drill. Depending on the thickness of the concrete pavement, you will need a reinforcing bar of various lengths and a rubber hose to prevent the mortar from reaching the bar. Pouring should be done gradually, in layers of no more than 10 cm.If the aggregate is well compacted, then cement milk should appear on the surface.
Expert advice: the drill should be designed for long-term use, it is better to take a device with a power of 650 W or more.
For protection from the external environment and uniform drying, the concrete is covered with a film. The approximate drying time is 36 hours to 2 weeks, and the strength of the concrete will build up over time and reach a maximum after one year.
Expert advice: for the concrete hardness, it is recommended to pour water over it after 3-4 hours and not leave it exposed to direct sunlight.