How To Cure Concrete Faster
by TRP Ready Mix on December 11, 2021
And How To Avoid The Slow Drying
There’s nothing more frustrating than something that takes what seems like forever to dry. And when it comes to ready mixed concrete, this can be particularly gruelling when you need to use your driveway, walkway, patio, or stairs.
Freshly poured concrete needs time to cure so it can solidify and form the chemical bonds that are strong enough to support heavy loads, like vehicles, furniture, and foot traffic. If concrete dries too quickly, it will lose its strength and quality.
However, if the concrete dries too slowly, it can also be at risk of damage, along with being downright frustrating.
Since concrete is still pliable when drying, it’s important to have it dry fast enough (but not too fast) to avoid damage. While structural damage is of the utmost concern, wet concrete is also prone to less threatening but equally frustrating damage, like that pesky footprint or hand-carved inscription left by a passerby.
To avoid such damage and have your new concrete slab ready to use sooner than later, consider the following tips to help your concrete cure faster.
The Difference Between Curing and Drying
Even though these two terms are often used in the same way and refer to moisture, they do not mean the same thing. Curing concrete means providing adequate moisture, temperature and time that would help the concrete get the properties for the intended use. Drying, on the other hand, means providing the proper conditions to allow the concrete to achieve the appropriate moisture. So, in order to have a concrete floor you can easily walk on, you must both cure it and dry it.
How Long Does It Take for Concrete to Cure?
The general rule of thumb for concrete curing time is 28 days. More specifically, it can take 28 days for each inch of thickness and only under ideal curing and drying conditions—such as an enclosed area with low humidity, proper air circulation, and the HVAC system on.
But more often than not, the curing and drying conditions are not always ideal, and project deadlines make that 28-day wait seem unbearable. But there are ways to speed up the curing process. First and foremost, it’s essential to understand what slows down the drying process.
READ MORE: HOW CONCRETE CURING, TEMPERATURE AND STRENGTHS ARE RELATED
What Causes Slow Drying?
Concrete releases moisture from the slab’s surface as it dries. But if there is too much moisture in the air—also known as high humidity—the moisture from the concrete won’t evaporate quickly. And instead, too much moisture in the air will slow down the drying process of concrete.
The same goes for cooler weather. If the air temperature is too cold, the concrete curing process will slow down or stop altogether. Concrete needs to stay warm to cure properly, so cold damp weather or interior conditions will slow down the curing and drying process.
The effects of moisture and temperature on curing concrete make warm, dry weather the best time to pour concrete, especially if there is no rain in the forecast.
Pre-Pour Steps to Speed Up the Drying Process
The amount of water added during the initial mix can help reduce drying times. But too low of a water-cement ratio will also slow drying times since there are fewer capillaries in these types of mixes. So finding the right balance between water content and drying conditions is important.
Chemical admixtures that promote self-desiccation, like silica fume, also help to speed up the drying process. These admixtures absorb the concrete moisture content quickly, reducing the drying time the volume of water in the mix would typically need.
Placing a vapour retarder underneath or behind the concrete slab can help speed up the concrete drying time by preventing ground moisture from entering the concrete slab.
Post-Pour Steps to Speed Up the Drying Process
Avoid hard troweling or troweling to a burnished finish. This type of finishing seals off the natural capillaries between the elements of the mix and the concrete surface will lose its ability to let moisture pass through.
Dehumidification can speed up the natural drying process of concrete. By reducing the dew point in the air around the concrete, more moisture within the concrete slab will evaporate from the surface.
For successful dehumidification, the concrete slab must be completely enclosed to prevent the removed moisture from re-entering the concrete’s environment. The ideal concrete enclosures are surface-ready indoor conditions.
Otherwise, concrete poured outdoors should have a proper barrier built to keep the moisture out.
The most common types of dehumidification include:
Ideal for use in enclosed areas, desiccant dehumidifiers remove moisture from the air using a chemical attraction. As humid air moves across a desiccant material, the desiccant absorbs the moisture. A hot air stream will vent this moisture away from the room or area of the concrete slab enclosure.
The dried desiccant will continue the process of binding and holding moisture from the air until it is released through the vent. This drying process can be used year-round for curing concrete since the indoor concrete is not affected by weather conditions.
This type of dehumidification uses cooling-based dehumidifiers. These dehumidifiers cool the air to drop the dew point and then collect and draw away the moisture.
This dehumidification process heats the air to raise the dew point and absorb more moisture from the concrete slab’s surface. The moisture-saturated air is circulated through a collection system or to the outside air so it can release moisture as it cools.
Tips to Ensure the Concrete Dries as Fast as Possible
Along with pouring the concrete during warm, sunny weather, or in a stable indoor enclosure, consider these other tips for helping your concrete dry faster.
Add an accelerating compound, such as calcium chloride, to the concrete mix before pouring. This accelerant will help the concrete solidify much faster.
Since heat speeds up the drying process for concrete, consider placing a heater near the freshly poured concrete.
Cover the concrete with a plastic sheet to trap moisture escaping from the concrete. This moisture helps the concrete to cure faster without drying out too quickly.
READ MORE: TIPS FOR POURING CONCRETE IN COLD WEATHER
While concrete may not dry as quickly as you’d like, it’s still possible to speed up the drying process. And remember, when it comes to drying concrete, it’s better to be safe than sorry. If it dries too quickly, it will also be at risk of damage. So speak with your ready mixed concrete suppliers to find the right concrete mix for your job, timeline, and conditions so you can start enjoying your new concrete sooner than later.