The curing for pile foundations is not carried out in a conventional way. Using the right method of curing is essential for the concrete to support the structure in the way it needs to. This blog will discuss what curing is, the different methods and how it is done for a pile foundation.
What is curing?
Curing is a chemical process that is integral for concrete to have the required strength and durability. The purpose is to maintain the moisture and temperature of the concrete. The process takes place right after the concrete is poured.
Concrete that is not cured properly will most probably have a strength lower than the required design strength. This means it will not be able to support the building adequately which can result in cracking. Cracks can allow in humidity or water which results in many issues such as corrosion.
When setting concrete, there is a swift loss of moisture that takes place. The main aim of curing is to control this. As mentioned before the two main components measured are moisture and temperature.
Moisture
A lack of moisture in the concrete will result in it not developing properly and:
- Not reaching the required design strength
- An inadequate volume stability
- No resistance to freeze-thaw cycles
- Low resistance to abrasion and scaling
- Not have the target durability
Temperature
Maintaining temperature is critical for the curing process. The long-term stability of concrete is affected by it. The general rule is concrete temperature should be maintained above 10 degrees celsius for adequate strength. Issues that arise with high concrete temperatures during curing are:
- Higher chance of shrinkage, leading to cracking
- Decrease in concrete strength after 28 days
- Higher chance of corrosion
- Increased need for water, which raises costs
Issues that arise with low concrete temperatures during curing are:
- Water can freeze which then leads to cracking
- If the concrete freezes it can result in up to a 50% strength reduction
Common curing methods
The method used for curing is dependent on the concrete characteristics. The following are some common methods used:
- Water curing
Water curing consists of applying water so the concrete does not dry. This is usually used for thinner concrete.
- Wet covering
This method keeps the moisture in by covering the concrete with materials such as hessian. Water curing is only possible on horizontal surfaces, whereas wet covering can be used for vertical surfaces.
- Membrane curing
This method requires a liquid material to be sprayed over the concrete to solidify into a membrane. This avoids the evaporation of moisture. There are two types of membranes which can be used: water-based or oil-based.
- Sheet curing
Three different types of sheets can be used to cover the concrete for this method. Polythene sheets can be used for concrete that is not that important structurally. Plastic sheets can be used, they are watertight and easier to handle. Curing blankets are also used to avoid moisture evaporation.
- Curing by absorbing heat
Pipes can be set inside the concrete to absorb heat. This allows water to circulate in the concrete. This method is good for thick concrete however has to be carried out with care. The sudden temperature change can result in cracking.
- Hot mixing method
This method is not used often however can be used when concrete requires strength early. The temperature of the concrete is increased to raise its strength. Raising the temperature of the concrete up to 32 degrees celsius can enhance its strength by 10%-20%.
- Electrical curing
For electrical curing, there are three methods that can be used. The first is an electrical current that is passed through the freshly laid concrete. The second uses a high current with a low voltage through the reinforcement net. The third uses large electrical blankets.
Curing for pile foundations
The process of curing pile foundations is not the same as others, as it is not done manually. Pile foundations are underneath the earth’s surface, where there is a lot of moisture. This means there is a self-curing process. The moisture in cohesive soils and clay does the curing itself.
With the pile foundation being completely underground, there are also no effects from wind or the sun’s rays. So moisture is not lost from these external factors.
Curing is just one of the many aspects of construction. At Dart & Co we offer a range of piling contractor services to help you with your project. Our qualified engineers work to the highest quality to get the best results.
If you are looking for contractors for your project, get in touch with us today.