Construction sites
CONSTRUCTION SITES
Concrete is the most widely used construction material in the industry. We find concrete on almost all construction sites. It is an artificial material that has many of the external properties of stone. When you want to give concrete extra strength, you can choose to reinforce it. Concrete is a very durable and hard building material and is also favourably priced.
Instead of consisting of a single material, it is a mixture of water, with cement as binder, and aggregates such as sand, gravel, crushed stone or granules.
In addition to precast concrete products, large quantities of in-situ concrete, or ready-mixed concrete, are used on construction sites. In-situ concrete is a product produced in concrete plants. Concrete can be produced and delivered ready-mixed in large quantities to quickly finish even the largest projects.
In-situ or ready-mixed concrete is used in concrete structures for:
- Motorways
- Railways
- Walkways
- Car parks (parking decks and basements)
- Canals
- Bridges
- Tunnels
- Flood defences and dams
- Bank protection
- Artworks
- Foundations of wind turbines
- Foundations of heavy machinery
- Foundations
- Retaining walls
- Houses
- Office buildings
- Commercial Buildings
In-situ concrete or ready-mixed concrete is transported to the construction site using truck mixers or pump mixers. It is important that the customer informs the concrete plant about the requirements the delivered concrete must meet. This includes requirements for the hardened concrete, as included in the project specification, but also requirements for the workability of the concrete.
At the construction site, the concrete is then used to make:
POURING FOUNDATIONS
Foundations ensure that the weight of a structure or heavy machinery is transferred to the underlying soil. In weak soils, the required foundations are supported by piles, which are driven into the ground to reach firm soil layers. Normally, the next step is digging foundation trenches. In those trenches, shuttering is placed. After that, the concrete can be poured.
Shuttering is used to keep the concrete of the foundation neatly in place. It functions as a mould to make the concrete take its proper shape. Once the concrete has cured, the shuttering is removed.
POURING WALLS, FLOORS, COLUMNS AND BEAMS
Concrete structures are poured “in situ” and shaped by using shuttering. In serial construction or project-specific construction, in-situ concrete is used to make concrete walls, columns, bearing floors and beams.
In-situ concrete floors consist of standard layers, each with its own function. A subfloor, intermediate layer or bearing floor, for example. For intermediate floors, construction companies use wide slab flooring. These floors consist of a reinforced concrete shell with top reinforcement. After installing the piping and ventilation ducts, the floor is covered with a layer of ready-mixed concrete. The result is a neatly finished floor that incorporates drainage, water, electrical and air-control ducts. The floor also has good acoustic properties and high fire resistance.
Solid walls are poured to ensure high rigidity of the shell structure of houses and buildings. In most cases, reinforcement is not needed or is limited because the strength of unreinforced walls is great enough for the required stability.
RESIDUAL CONCRETE ON CONSTRUCTION SITES
Surveys from various international industry associations estimate that 3-5% of deliveries of ready-mixed concrete are rejected at construction sites. Rejection occurs for various reasons, such as the concrete not meeting specifications, or because a project simply has leftover ready-mixed concrete. The concrete industry produces a high percentage of waste material. This costs a lot of money and is bad for the environment.
Causes of residual concrete on construction sites:
1. Shuttering problems
Shuttering material is severely tested when pouring concrete, and placing it is done manually. If the shuttering is faulty, leakage may occur or the shuttering may even collapse. In situations where the concrete mixer has already started pouring, operations will have to be aborted. The remaining quantity in the truck’s concrete mixer should be processed as soon as possible, as it is bound to a limited unloading time and workability. If the shuttering material is badly damaged, the concrete is dumped into a waste container or disposed of at waste processing plants.
2. Surplus quantities of in-situ concrete
When using ready-mixed concrete on building sites, a proper calculation of the required quantity must be made in advance. If the calculation is incorrect or does not reflect the actual situation, there may be residue left in the concrete mixer after the concrete has been poured.
In large construction projects, a margin is maintained to ensure sufficient ready-mixed concrete is delivered to the site. This can easily amount to an extra 5-10% ready-mixed concrete. After processing the ready-mixed concrete from the concrete mixer, there may be residual concrete left that cannot be processed in the structure. This creates waste that is dumped on the construction site.
3. Quality problems in-situ concrete
When ready-mixed concrete is delivered to the construction site, the workability of the concrete may not be up to par or the concrete may not meet the performance requirements. This may be concluded from the concrete’s viscosity or a visual inspection of the composition on site, or based on the documentation of the order deviating from the actual delivery.
If the concrete is rejected, the concrete is disposed of to a waste disposal company if no immediate alternative use can be found for it.
THE SOLUTION FOR SMART HANDLING OF RESIDUAL CONCRETE ON CONSTRUCTION SITES
Residual concrete increases project costs and can have a negative effect on construction progress. More importantly, it has a negative impact on the environment.
The concrete industry emits a large amount of CO2 and consumes a lot of water. The impact of residual concrete on the environment negatively affects the public opinion of the concrete industry.
A solution to this situation is to turn residual concrete into a valuable product directly on site. Valuable construction products, like stackable concrete blocks or concrete slabs, can be made using professional moulds. These construction products are widely used for paving sites and building walls. For moving and transporting the concrete blocks, matching accessories are available.
In some countries, there is now a market for the buying and selling stackable concrete blocks. Dealers collect the concrete blocks by driving past construction sites. The construction company that produced the blocks receives compensation for them. In this way, the construction company contributes to circularity without having to pay disposal fees and benefits from extra income. The traders then sell the concrete blocks and concrete slabs in larger batches to buyers who can use the building materials.
For example, constructing retaining walls or storage boxes for bulk dry goods, trench silos and site paving in the industrial and agricultural sectors.
A set of moulds is easily placed on a pallet in storage and can be transported to the construction site when work starts. Providing construction sites with concrete moulds for stackable blocks and concrete slabs is a simple method of dealing with residual concrete in a circular way and making disposal costs a thing of the past.