Whether you are building a house or an airplane hangar, laying the concrete floor is an essential step. Before finishing the concrete slab, the working team levels and marks the area, installs utility lines and prepares the foundation. Most buildings cannot move on until all stages of concrete paving have been completed. This article will walk you through these steps.
Step 1. Prepare the area for work
Heavy equipment may be needed to clear the site. All debris must be removed, then the soil must be checked. The soil must be sufficiently elastic, because it serves as a support not only for the concrete slab, but also for the entire structure.
- Call a geological exploration service or mark the building lines yourself. To make a marking of the territory (for its further cleaning and leveling), castoff is used or pegs are hammered in the corners of the future building.
- Trees, bushes and other plants should be uprooted along with roots. Otherwise, the roots remaining in the ground will begin to rot over time, voids will form, which will damage the base.
- Clear the ground from various foreign materials.
- Use a construction roller (or other tool) to compact the disturbed parent soil.
Step 2. Make a shape and lay a concrete base under the foundation on which the concrete slab will lie
A monolithic slab can be poured onto a natural base, deepening at the edges. But for many structures, a foundation cushion is poured, on which foundation concrete blocks (FBS) are then laid out, building a basement.
Step 3. Fix the casting formwork
Construction markings, the pegs of which are taken out beyond the boundaries of the future monolithic slab, and a stretched thread at a well-defined level, will allow you to set the formwork at the desired height along the boundary lines.
Step 4. Install water and sewer pipes according to the project diagram, as well as sleeves for future ventilation ducts and electrical networks
Drainpipes are often fitted with plugs to prevent debris from entering the pipes.
Step 5. Cover the area surrounded by formwork with suitable material
Use capillary filler in case of high moisture content of soils.
- Use lime or other non-metallic materials of similar properties if the board will be subjected to heavy loads. For example, a foundation for a warehouse or an aircraft hangar.
- Use binding materials such as clay if the substrate (soil) is naturally not sufficiently stable and the soil surface cannot be fixed with traditional materials.
Step 6. Final filling and compaction of the filler
For production buildings, the density of the backfill material must meet the specifications. Compliance testing is often done by geotechnical engineering laboratories.
Step 7. Pre-clean the litter and soil from insects using a proven proprietary termite control product
Usually cleaning companies provide pest control services - contact them.
Step 8. Apply a layer of waterproofing or waterproof membrane immediately after cleaning the area from insects
This will allow the chemicals to last longer as they will not evaporate and dry out.
Step 9. Place the associated slab reinforcement in accordance with the architectural / engineering requirements
Make sure the reinforcement is locked and positioned at the correct height. For this, concrete rebar clamps are ideal.
Step 10. Think about what method to use to level the surface of the poured concrete
In the case of a large area, you will need to install certain beacons that workers will be guided by when pouring concrete. Thus, specialists can pour the concrete base horizontally or at a specific angle. To level the surface, you can use pipes, profiles, columns with marks, laser levels.
Step 11. Determine the equipment and tools that you will use to place the concrete
The truck and equipment available on the day you want may not always be found right away. Therefore, you should think about this in advance.
- Articulated boom air pumps with a collection hose are used to pour concrete into various areas of the slab up to a height of 36.5 m (from the concrete pump truck). They are often used when pouring concrete at heights and in hard-to-reach places.
- A pipe and hose can also be attached to the concrete pump to move the concrete from the truck to the placement site. But moving the hose around the area requires a lot of effort.
- Concrete buckets can be used to move concrete to great heights or into hard-to-reach areas using a crane or forklift.
- Self-propelled trolleys can maneuver in narrow spaces and are used for transporting concrete.
- In case of a convenient arrival of a concrete truck, concrete can be unloaded directly into the mold through the tailgate of the machine.
Step 12. Make sure the formwork is level and that the reinforcement is well tensioned and secured
The rods must not be allowed to bend, break or displace during pouring.
Step 13. Calculate the amount of concrete needed to fill your slab
Multiply the measured length of the slab to be poured by the width and height. Remember that all three parameters must be in a single measurement system (meters, for example). Thus, you will get the amount of required material in cubic meters. It is advisable to order a little more concrete in case of bent forms, formwork, unaccounted for cavities, which also need to be poured.
Step 14. Order a ready-made mortar from a concrete supplier for a specific date when you plan to pour the base
Specify the time, delivery period, unloading time. If multiple concrete machines are expected, plan their arrival so that there is no downtime, and the workers have time to unload the concrete.
Step 15. Check the quality of concrete in a special testing laboratory, if required by the technical design
Testing laboratories usually check the following:
- Shrinkage. The plasticity of the concrete is checked. Concrete is poured into the vertical conical shape and the shrinkage is measured. This makes it possible to determine if the concrete is too wet and meets the technical specifications.
- Temperature. Concrete loses its properties at very high temperatures, therefore the temperature of the concrete must be controlled during pouring.
- Air penetration. Certain chemicals are added to the concrete to make the air escape from the concrete. The presence of air in concrete leads to small voids, which in turn lead to expansion and disintegration of the concrete, especially if the floor will be exposed to high temperatures in the future. The permissible amount of air in the concrete pavement is no more than 3-5%.
- Compressive strength. The strength of concrete is measured in kg / cm2, and special plastic forms are used to collect the poured solution for analysis, which will be further studied in laboratory conditions.
Step 16. Plan the installation of large slabs as early as possible
In this case, the following points are important:
- Make sure you have enough workforce to get the job done.
Watch out for weather conditions. These factors play an important role when pouring concrete:
- Temperature. The higher the air temperature, the faster the concrete will thicken; but very hot weather affects the ability of workers to work.
- Humidity. Reduced humidity promotes rapid evaporation of moisture from the solution.
- Wind, which can increase the speed at which the concrete surface dries.
- Cold weather can significantly slow down the curing time of concrete. Concrete work at a temperature of about 0 degrees, or when frost is expected within 48 hours after pouring, is highly discouraged.
- Bright sun. Concrete hardens much faster in sunny weather.
Step 17. On the day of pouring, all the necessary equipment should be prepared
If a concrete pump will be used, make sure it arrives an hour early and is in a convenient location.
- Check the trowel, in particular: the panel is working, the blades are present, the level of gasoline and engine oil.
- Check for a ruler, concrete leveling tool, mechanical vibrating screed, long-handled trowel and make sure they are in good condition.
- If using a concrete vibrator, make sure it is working properly.
- Prepare personal protective equipment: gloves, rubber boots, eye mask.
- Clean and tidy up all hand tools.
Step 18 Start pouring concrete from the corner and continue along the line of the formwork
Concrete can be poured in parallel sections. In this case, the next section should be poured when the previous one is finished; otherwise, a cold joint will form between the fill layers, which will negatively affect the quality of the base.
Step 19. When pouring the slab, make sure that the reinforcement does not bend to the very bottom
If necessary, ask one or two workers to use the hooks to lift the reinforcement. Keeping the reinforcement in proper position is essential for a solid concrete floor.
Step 20. Lay the cement strictly level and level with a trowel or vibrating screed
Use hand tools to smooth out the cement around electrical wiring and water pipes.
Step 21. After the first leveling of the concrete, one or two finishers should go over the surface with a long-handled trowel
The workers may need an assistant who will pour the concrete mixture to the places where there is a shortage.
Step 22. After smoothing the concrete with a long-handled trowel or a hand-held concrete trowel, check the edges of the slab
To do this, we go through the edges of the slab with a hand trowel along the entire perimeter. This must be done to ensure that the surface is even and that the cement is poured to the correct level.
Step 23. When the entire section of the slab is closed, beacons, pipes with a level mark are removed
If there are voids or pits where there were pegs or other guides, fill them with the remaining concrete.
Step 24. Concrete is poured until the form is filled to the brim
When the concrete is completely flattened, wash the pouring tools, including pipes, trowels, hooks, and shovels.
Step 25 Let the concrete harden
Do not start the next stage of finishing work until the cement has set well enough to support the weight of a person. Test the firmness by pressing a gloved finger against the surface. If the surface is dense and unyielding, you can start sanding.
Step 26. In hard-to-reach places where the trowel cannot get through, the worker needs to sand the surface by hand with his knees resting on the board
The process of grinding grooves, surfaces around pipes, and released fittings requires significant human effort.
Step 27. You can start sanding the concrete floor with a trowel when the floor can support the weight of a person, without leaving dents or marks on the surface
Waiting too long will result in very hard floor finishing work. But if you start work before the concrete has hardened enough, the blades of the machine can pierce the floor, leaving furrows, bumps and other defects.
Step 28. Use the hand float to walk over the concrete slab, running the tool parallel to the floor
Thus, the trowel will not sink into the concrete due to the larger support plane. In the early stages of concrete setting, this is the best way to grind.
Step 29Spray a small amount of water on areas that cannot be trowelled
This will allow the mortar to swell somewhat and fill in the many voids left after sanding with a long-handled trowel.
Step 30. Let the concrete harden for a while after the first plaster
If the surface is flat and free from defects, you can leave it to cure until the final grouting. Since the concrete is poured in several stages, the sections poured first will harden faster. However, it should be remembered that concrete in an open area, under the influence of sunlight and wind, will set faster than concrete, which hardens indoors or in a place protected from precipitation.
Step 31. Trowel over the surface for finishing
If the surface is too hard to finish, increase the number of working blades for more effective grouting.
Step 32. In case of hot dry weather, it is necessary to protect the plate from drying out too quickly
To do this, it is advisable to add plasticizing additives to the concrete composition or use various techniques that prevent the rapid evaporation of moisture from the slab.
Step 33. Check all concrete section joints required by construction drawings
34 Remove the formwork from the slab and clean it for next use
Make sure the formwork boards are free of nails and screws to protect workers from the risk of injury in the future.
- If possible, schedule the pouring work on warm, dry days.
- Clean tools immediately after use.
- Make sure you have all the tools you need for the job.
- Make sure there are enough workers for each step of the job.
- Keep all tools in working order.
- Pouring concrete is a process that requires a lot of effort. Therefore, you and your workers should sleep well before doing this, and drink water during work.
- Concrete contains alkali metal salts and chemical additives that are harmful to humans. Avoid skin contact and wear a mask when pouring.