No matter how old we get, we’ll always be like little kids. When we get something new, we would like to try it out as soon as possible. Be it brand-new clothes, shoes, and home improvements (yeah, new driveway!) we’d like to imprint ourselves on it! But unlike new clothes and shoes, we can’t simply roll our heavy cars over newly installed concrete driveway. That is, unless we want our tire tracks permanently stamped on concrete - or worse cause it to become unleveled. So, no matter how tempted you are, reign in your excitement and let concrete to be fully cured before driving over it. But for how long?
Think of concrete as a hot air balloon that you get on during the annual balloon fest in October. As much as you want to get it up in the air and flying, it won’t until it’s fully inflated. With concrete, you have to wait until it is fully cured to gain it’s full strength and carry heavier loads without setting. It has to undergo a full chemical procedure called hydration to harden completely and gain durability.
Let’s talk about concrete hydration and curing to better understand how it works. Anyways, it is what’s preventing you from trying to park in your driveway, right?
Chemical Reaction
When you mix water with cement, a chemical reaction is triggered. You’ll notice particles dissolving as they react together.
As the chemical reaction advances, hydration products are created, including Calcium-silicate-hydrate that forms a gel-like substance binding aggregates together. It is what makes concrete strong and durable. There’s also calcium hydroxide. This alkali in concrete helps with setting and compacted strength. Lastly, there is the ettringite that helps with concrete setting.
Hydration of a Newly Poured Concrete
There’s a lot going on during this phase. It’s not just water+cement mixture that influences the hydration progression.
- Water+Cement ratio: The ratio of water+cement mixture affects the rate of hydration and the final strength of the concrete. This means the more water you use, the more it becomes prone to cracking as it becomes less dense. Meanwhile, when there is less, it won’t go through the proper hydration. Expect uneven, weak surfaces riddled with air pockets. The more air-pockets there are, the less durable the concrete becomes.
- Temperature: Lower temperatures slow down the hydration process. With curing still in progress, concrete is more susceptible to cracking when freeze sets in. On the other hand, high temperature means faster and uneven dehydration. When concrete dehydrates too fast, the surface cracks.
- Admixtures: Chemical additives can affect the hydration process . There are two types of admixtures used to help with curing. During cold months, accelerators are used to hasten curing. Meanwhile, to slow down hydration during hotter months, retarders are used.
- Curing: This is like spa-day for concrete. It is when concrete is pampered to make sure there is enough moisture during the early stages of hydration. This determines the strength development of concrete.
Concrete Curing Process
- Setting time: This is the initial phase when the concrete transitions from a liquid to a solid state. Though it looks solid and can bear some weight, do not walk over it.
- Hardening: Following the setting time, the concrete enters a hardening phase. While it may appear solid, it's still susceptible to damage. Leave it alone for 24 to 48 hours to harden completely before attempting to walk on it.
- Strength gain: This is the final stage where the concrete gradually reaches its maximum strength. This is when it is safe to be walked and parked on.
The arid desert climate, with dramatic weather changes in Albuquerque directly affects the curing process of concrete. Here’s how:
- High temperatures: Albuquerque's infamous summer heat with 91°F temp can cause the moisture in concrete to evaporate faster. Though it seems good, too much heat and too fast evaporation leads to cracking.
- Low humidity: The desert is dry, which is bad since we need to keep a certain level of moisture in concrete during curing.
Patience is a virtue! Don’t let the waiting game get to you. So you don’t get bored waiting for your concrete driveways to be ready, here’s the usual timeline when concrete is ready to use:
- General guideline: It usually takes 24 to 48 hours for fresh concrete to initially set. After this time, you can start walking on newly laid concrete.
- Light vehicles: It may take at least seven days after the crew laid the concrete before you can start driving or parking lightweight cars on newly laid concrete. Make sure to ease up and monitor the concrete. If you notice any setting or dents, move your car away from the concrete and inform your contractor.
- Heavy vehicles: For heavier trucks or RVs, you should wait until the concrete has fully cured. This usually takes 28 days or so, depending on the thickness of the base and slab.
Take note that this timeline is just an estimate. It is still best to check with your concrete contractor who best knows the specifics of your project on when you can park on your newly poured concrete paving.
Concrete Care Tips
You already spent a lot of time and money getting your new concrete driveway laid. Add to that the time you spent waiting for it to cure. With that in mind, there is no reason to hasten its demise! Here are a few tips you can follow to make sure your concrete stays in good shape for a long time:
- Heavy loads like cars, heavy machinery, and large pieces of furniture should not be placed on newly installed concrete surfaces.
- Cover the concrete with a curing blanket or tarp to prevent moisture evaporation. You can also do this to protect concrete when it rains.
- Use curing compound to help promote proper hydration.
- Do not power wash or use harsh chemicals on concrete.
