Pouring concrete is a fundamental process and acts as the backbone of a structure’s durability and resilience. Concrete pouring is also known as concrete placement. The process begins with the proper preparation of materials, ensuring the formwork is robust, levelled, and reinforced. Several factors directly influence its outcome. A technical challenge that arises in concrete pouring is timing.
Concrete is highly sensitive to various environmental factors, and therefore, the process is carried forward under controlled conditions to ensure quality. In today’s construction industry, various advancements have been made to improve the workability of concrete, shaping the future of this process. Facts reveal that the global concrete industry produces around 30 billion tons annually, with advances in technology like self-compacting concrete and high-performance concrete improving construction efficiency. Let’s get a detailed glimpse of concrete pouring in the following blog.
What is Concrete Pouring?
Concrete pouring is significant for creating a foundation that is strong and durable. Its attributes and versatility allow concrete to be molded into any required shape. It is a suitable and ideal choice for any construction project due to its wide range of beneficial features. Over time, concrete, with the incorporation of advances in technology, has greatly evolved. Such innovative solutions include the introduction of reinforced concrete and prestressed concrete. These contribute to improving strength and durability.
How to Pour Concrete: step-by-step process
Concrete pouring is considered a meticulous process, requiring proper planning and execution. As a fundamental task in any construction project, it involves several steps. These steps are followed to ensure the quality and structural integrity of the project to attain longevity. The process involved in the concrete pouring:
Site Work:
Site work or site preparation is an important phase in a construction project. Before pouring concrete, ensure proper cleaning of the area. It is essential to remove any debris, old concrete, or rocks. An unobstructed workspace is required before the excavation is performed on the site.
Secondly, maintain a proper level base. Excavate the area to the desired depth and prepare the subgrade by compacting the soil for stability.
Once a stable subgrade is established, the sub base is installed—a base composed of a layer of 4–8 inches of granular fill or road-based material.
The next step involves compacting the subbase using a hand tamper or plate compactor to ensure stability.
Finally, measures are implemented for moisture control. The damping of the sub-base prevents it from excessive water absorption.
Forming
Formwork plays a crucial role in achieving the precise shape of concrete structures. The process begins with meticulous planning and design of the form. Foam boards are cut to the required dimensions and carefully assembled using screws or nails before being secured in place with stakes. To ensure stability and prevent bowing under the weight of the concrete, it is essential to brace the formwork properly.
Mixing
Proper mixing of concrete provides uniform consistency, essential for strength, durability, and workability. The materials required for mixing include cement, sand, gravel, and water. Water and all ingredients are accurately measured. A concrete mixer is used where the water is added in measured portions, followed by cement and aggregates. Allow the mixer to run for 3 to 5 minutes to ensure proper mixing. Adjust the water content to obtain the desired consistency and texture.
Different Equipment Used for Mixing:
Concrete Mixer: A machine used to mix the ingredients uniformly.
Mixing Containers: If mixing by hand, use containers like wheelbarrows or mixing trays.
Shovels: For manually mixing and transferring materials.
Measurement Tools: Proper measuring tools are used to measure the ingredients.
Placement
Pour concrete into the form before it hardens and settles. Cover the edges using a shovel or rack to evenly spread the concrete. Enhance the concrete consistency by eliminating any void or air gaps. Often a vibrator is deployed to carry out this process. A screed board is then used to level the surface for a smoother finish.
Early Finishing
Early finishing is a technique that smooths and shapes the surface.
- Edging
Tool used: Edger
Edgers create round edges along the sides of the concrete slab, giving a finished look and preventing chipping.
- Jointing
Tool used: Groover tool or Saw
Joints are created in the slab to prevent cracking. A groover or saw is essential in creating them. The concrete further expands and contracts without cracking.
- Floating
Tool used: Bull float or hand float
Aggregate particles rising to the top are removed to smooth the surface. Move any type of float over the surface back and forth for levelling.
Troweling
Troweling of concrete is a step for refining the surface before it is fully set. This process is adopted before the concrete attains stiffness. When the concrete has hardened, begin the troweling process. Either a hand trowel or power trowel is used to continue with levelling. Finally, a steel trowel is used in the second troweling to achieve a smooth, strong finish. For larger areas, a power trowel is generally used.
Final Finishing
Several tools are used for the final finishing. A broom is commonly used to drag across the surface to facilitate a smooth finish. It creates slip resistance, providing a rough texture. Other equipment, such as a steel trowel, is employed to give a smooth finish. However, stamps and moulds are used for patterns and textures.
Curing
Curing is intended to improve the integrity, durability, and workability of the concrete. It aims to prevent early cracking, improving performance and lifespan. Concrete needs 24 to 48 hours to set initially.
Methods of Curing Process:
- The concrete is spread or covered with sponges to keep it moist. This process is called water curing.
- Use plastic sheets or a wet blanket to retain the moisture in the concrete.
- A liquid membrane compound is applied to the concrete surface to reduce evaporation.
Tips for Laying Concrete
- Plan with all necessary permits. Determine the area to be concreted and clear the place for a clean and stable base. This ensures proper ground levelling and soil compaction for laying the concrete.
- A wise selection of form boards, particularly straight ones, is required. Before nailing, the forms must be properly aligned and levelled. Secure the form by driving stakes into the ground.
- Prior calculation of concrete helps ensure the base is accurately levelled.
- For additional strength and to prevent cracking, reinforce the concrete using rebars or wire mesh.
- Be sure to wear gloves, safety glasses, and masks. Also, avoid excessive workability of concrete to prevent cracking.
- Use vibrators to spread the concrete evenly. Never add too much water to the mix, as this weakens the concrete over time and can lead to cracking or poor durability.
- Screed boards can remove excess concrete. During the curing process, protect the concrete from extreme weather conditions.
- Thoroughly mix the concrete to achieve a consistent texture and ensure an even distribution of materials throughout the slab.
Mistakes to Avoid While Pouring Concrete
- Concrete that is too wet or too dry compromises its strength, reduces workability, and creates a brittle structure.
- Improper reinforcement of concrete can affect structural integrity. When the reinforcing fibres and steel rods are misplaced, changes in the grid patterns occur.
- Poorly built forms will result in uneven slabs and affect the strength and appearance of the structure.
- Overwatering or underwatering of the concrete causes poor durability. This can affect the integrity of the structure.
- Concrete vibrators are essential for larger concrete pours. This helps avoid the existence of voids in the concrete.
- Failing to plan ahead is a common mistake. Before beginning, it is crucial to determine the thickness, size, and placement of the concrete pour.
- The compaction of the subgrade is often left unnoticed. However, it is crucial to prevent shifting and concrete slab settlement.
- When control joints are ignored in the concrete, it often creates random spaces and leads to cracking patterns.
- The curing process in concrete pouring must be done properly. Rushing can cause surface defects and reduced strength in the concrete.
Conclusion
Concrete pouring stands as the foundation of any construction project. It is a crucial factor that affects the durability, strength, and stability of the structure. There are no shortcuts to concrete pouring; all that matters is precision, patience, and attention. Every detail needs to be done properly with the right tools. Concrete pouring demands proper execution with attention to achieve the desired results.