Pros and Cons of Pouring Concrete Over Your Asphalt

Can you pour concrete over asphalt? This is a common question for homeowners looking to update their exterior spaces. While it is possible to pour concrete over existing asphalt, there are several factors to consider first.

By the end, you'll know if this project is right for your property.

Pros of Pouring Concrete Over Asphalt

Let's start with the potential benefits:

• Less prep work required. Unlike removing the old asphalt completely, pouring concrete over asphalt involves less labor and costs.
• Lower cost overall. Preparing the solid asphalt base is cheaper than other driveway base materials.
• Faster installation. With minimal asphalt patching required beforehand, it takes less time to complete the concrete pour.
• Easier to achieve smooth surface. The existing asphalt provides a more uniform surface for the concrete to bond to.

Yes, you can pour concrete over asphalt , but there are conditions that must be met. The asphalt base must be stable and free from defects caused by frost heave or shifting. If the asphalt surface is still structurally sound or has remained intact for years, it is acceptable to use as a base for a concrete garage floor or driveway.

Cons of Pouring Concrete Over Asphalt

However, there are also some potential downsides:

• Cracking and crumbling. Temperature changes may cause the concrete to crack due to differing expansion rates.
• Drainage issues. Water can get trapped between the concrete and asphalt, leading to damage.
• Uneven settling. If the subsurface has soft spots, it can settle unevenly under the new concrete's weight.
• Lack of long-term durability. The concrete may deteriorate quicker than expected.

There are instances when you should not pour concrete over asphalt . If the asphalt is severely heaving or has large chunks missing, then it is recommended that you not pour concrete over it. The asphalt walls in a garage should also be high enough to accept the new depth of the concrete .

Assessing Existing Asphalt Condition

Before deciding whether to pour concrete over asphalt, carefully inspect the existing asphalt surface. Look for:

• Cracks and potholes. Mark areas needing repair.
• Smoothness and levelness. Check for depressions or uneven sections.
• Drainage capacity. See if water pools on the surface after rains.

When pouring concrete over asphalt , it is essential to mechanically fasten the concrete to the asphalt surface to prevent movement. This can be done by securing vertical rebar to the asphalt or drilling holes through the asphalt for drainage.

Preparation for Pouring Concrete

Proper prep work is crucial when pouring concrete over asphalt. This includes:

• Thorough cleaning of asphalt. Sweep and pressure wash surface beforehand.
• Apply bonding agent. This helps concrete adhere to the asphalt.
• Install rebar reinforcement. Add rebar for stability and to minimize cracking.

Pouring concrete over asphalt is not ideal because the two surfaces have different thermal expansion rates. This can cause the pavement to buckle and crack over time.

How to Pour Concrete Over Asphalt

The process of pouring concrete over an asphalt base includes:

1. Form setting. Build formwork around area, allowing for proper depth.
2. Mix concrete. Prepare it to correct consistency in mixer.
3. Transport and place concrete. Shovel inside forms.
4. Float, trowel and edge concrete. Smooth and level surface.

If your driveway is in poor condition, it may be better to go with asphalt crack filler instead of pouring concrete over it. It's also advisable to inspect your pavement regularly to prevent further damage.

Curing and Sealing Concrete

Allowing the poured concrete to cure properly ensures durability:

• Wet curing with moisture. Spray surface with water for several days.
• Apply curing compounds. Liquid membranes slow moisture loss.
• Control temperature changes. Prevent rapid heating or cooling.
• Seal surface from elements. Apply sealants to protect from weathering.

If you have to fill cracks and potholes in winter, it's best to use infrared asphalt patching instead of concrete or asphalt crack filler.

Troubleshooting Common Problems

Sometimes issues come up after installation:

• Preventing cracks. Control curing temperatures and add control joints.
• Fixing uneven sections. Grind down high spots.
• Improving drainage. Clean weep holes and use drain tile.
• Repairing deteriorated areas. Patch with additional concrete.

To summarize, while it's possible to pour concrete over asphalt , it's crucial to ensure the asphalt base is stable, the concrete is mechanically fastened to the asphalt surface, and the thermal expansion rates are considered. In some cases, it may be better to use alternative solutions such as asphalt crack filler or infrared asphalt patching.

Alternative Options to Consider

Instead of pouring concrete over asphalt, some other options include:

• Asphalt resurfacing. Mill down high spots and overlay new asphalt.
• Paver installation. Interlocking pavers may last longer than concrete.
• Gravel or stone driveway. Cheaper and easier to repair.

FAQs About Pouring Concrete Over Asphalt

Is pouring concrete over asphalt recommended?

It depends on the existing asphalt's condition. For stable, intact asphalt, pouring concrete over it is acceptable. However, badly damaged or shifting asphalt is not a good base.

What thickness of concrete should be poured?

Typically 4-6 inches of concrete is ideal when poured over asphalt. The asphalt base should be able to support the weight and depth.

How long does concrete take to cure when poured over asphalt?

Allow at least 5-7 days of curing time before driving or parking vehicles on new concrete poured over asphalt. Longer curing times are better to ensure proper strength gain.

Pouring concrete over existing asphalt can be an affordable and fast way to update exterior concrete surfaces. However, the success depends greatly on the asphalt's current condition, proper preparation, quality concrete materials, experienced contractors, and suitable curing conditions.

Weigh your specific project's pros and cons to decide if this solution makes sense, or if you would be better served choosing other approaches. Be sure to take measures to prevent typical problems like cracking and uneven settling too. With the right approach, pouring concrete over asphalt can turn out great.