In concrete construction, curing is one of the most important steps in making strong, durable projects. Letting the material cure increases its durability, making it less susceptible to cracking and spalling. However, curing can take a long time – 24 hours before a surface is usable, and as many as 28 days to fully cure. Believe it or not, the concrete in the Hoover Dam is still going through the curing process. Are there ways to speed up this process?
There are, and for many jobs, we would use quick performing concrete. It’s a type that can be ready to handle traffic after as little as two hours. How does it work, and when would we use quick performance concrete?
What Is Quick Performance Concrete?
Quick performance concrete uses similar raw materials, equipment, and processes that other types of concrete use – cement, water and an aggregate like gravel or sand – but like the other options, the mix is key. Accelerating concrete’s curing time is most commonly done using fast-setting cement or chemical additives.
When a project calls for quick performance concrete, it’s best to use a mix blended in the factory and laboratory tested for long-term durability. It gives the mix a consistency that is ideal for projects requiring fast return to service time and high final strength.
The chemicals used in quick performance concrete can generate excess heat, making it necessary to hydrate the materials. If enough water evaporates to interfere with the hydration process needed to build strength, the concrete won’t be as strong.
When Would We Use Quick Performance Concrete?
Quick performance concrete has many advantages, including the ability for concrete contractors to remove formworks early to advance the building process when time is of the essence. We can also use it to repair concrete works in ways that don’t disturb the structure, making it ideal for restoration work. Road surfaces can become fully operational in just a few hours, reducing the disruption of traffic.
Ultimately, the strength and durability can vary from standard concrete, depending on compositional details. The most convenient curing method is to cover the concrete with plastic.
Why Not Only Use Quick Performance Concrete?
You might be asking yourself, “why not use quick performance concrete for the entire structure?” It’s a good question; after all, both quick performance and standard concrete have similar strength profiles. The question can be answered by looking at the cost: a bag of fast-setting concrete costs more than regular concrete (though prices vary by supplier and location). The added expense might not seem like much for a job like fitting a fence post, but not all jobs are that small.
Quick performance concrete is also not always fitting for the climate conditions. The chemical additives can create extra heat that keeps the concrete above 10°C, letting it hydrate in colder climates and develop long-term durability. When it’s hot out, though, accelerated evaporation can severely reduce the hydration process, harming the strength of the concrete.