In this article, we will discuss
Can you pour concrete over Asphalt | Pouring Concrete over Asphalt | Concrete Pouring Techniques Over Asphalt | The Advantages of pouring over concrete | Pouring a Concrete Driveway
Can you pour concrete over asphalt?
Concrete can be poured over asphalt, yes. For the concrete, an asphalt driveway provides a sturdy foundation. But to ensure proper bonding and reduce the chance of concrete cracking, the asphalt needs to be prepared."Whitetopping" refers to the application of concrete over an asphalt driveway. It is a typical and economical method of resurfacing damaged asphalt surfaces.
Whitetopping can reduce costs by up to 50% compared to resurfacing with a fresh asphalt layer. However, you might need to put in a little more effort to ensure the asphalt can support a concrete slab.
How to Pour Concrete Over Asphalt
Use the following steps to pour concrete over asphalt:- Survey the condition of the asphalt
- Drill holes to increase drainage
- Prepare the asphalt for proper bonding
- Build and brace a frame for the concrete
- Level the surface that you want to pave
- Pour and level the concrete
You can do these steps yourself or hire someone to do them. Hiring a pro guarantees that the job will be done right, but it will cost more. Keep in mind that if you make a mistake when you do it yourself, you may still end up paying more in the long run.
1. Survey the Condition of the Asphalt
- Large cracks
- Missing chunks of asphalt
- Buckling
- Thin asphalt
If the cracks are more than two inches deep and chunks of the asphalt are missing or buckling, it's best to remove the asphalt. The damage makes the baseless stable, which makes the concrete surface last less long.
Buckling is a sign that the surface beneath the asphalt wasn't prepared well enough. The ground is moving if there are cracks and pieces are missing. If you pour concrete over asphalt in these conditions, the concrete will eventually be affected by the same conditions.
Also, the asphalt has to be thick enough to hold up the concrete. The asphalt should be at least five inches wide for best results. It should also sit on at least eight inches of gravel.
Drill holes in the asphalt to determine how deep the asphalt and gravel beds are. If you drill and find that the layer of asphalt or gravel is too thin, you'll probably have to take the asphalt off.
Read More
2. Drill Holes for Better Drainage
To add drainage, drill holes in the asphalt. A concrete surface needs to drain water, so it doesn't settle, crack, or break down.
Most of the time, concrete is poured over a bed of gravel. The gravel gives the concrete the drainage it needs to stay safe. But asphalt doesn't have holes in it. It doesn't drain well enough for a driveway, patio, or walkway made of concrete.
Use drill bits for brick or stone at least 12 inches long. Make a grid of holes all over the surface. Put about a foot between each hole. You could add an extra row of holes to the asphalt's lowest sides, where more water drains since that's where it rains the most.
You can also add critical ways to help with drainage and bonding. You can cut small channels into the asphalt with a circular saw or an angle grinder to make keyways. The channels help move water around and keep the concrete in place.
3. Prepare the Asphalt for Effective Bonding
Concrete doesn't stick well to asphalt, so you must change the surface. You can mill the asphalt with a milling machine or attach rebar to the asphalt.
The top inch or two of asphalt can be taken off with an asphalt mixing machine. Milling gives the concrete a rough, even surface. You can hire someone to mill the asphalt for you or rent a machine to do it.
Putting up reinforcing bars is another way to prepare asphalt (rebar). Drill holes in the asphalt that are big enough for the rebar to fit through. Add rebar in a grid pattern every 18 inches, like how drainage holes are drilled.
The rebar should stand straight up and go at least two inches below the asphalt and a few inches above it. Add a horizontal piece of #4 rebar and use rebar ties to connect it to the vertical rebar.
If you don't put the rebar into the asphalt, you'll still have to use the rebar to build a frame before pouring the concrete. By securing the rebar to the asphalt, it will be able to hold the concrete in place even better.
4. Construct and brace a Concrete Frame
For concrete to stay in place, it needs a frame. Concrete forms are the sides of the frame. Each form is made with boards cut to two inches thick lengths.
Start by putting square posts in each corner of the area you want to pave. At least one foot of the posts should be in the ground.
5. Level the Surface That You Want to Pave
If your asphalt is in good shape, it should be flat and ready for concrete to be poured on it. But adding a few inches of granular fill helps the concrete get its shape and makes it more stable after it hardens.
Spread granular fill over the whole area. Let the fill slope down along the edges so the concrete can get thicker.
Reinforcing bars (rebar) are usually tied to the stakes at this point to make the concrete slab stronger. You can skip this step if you decide to secure a rebar grid to asphalt, as described in Step 3.
Place rebar with a thickness of 0.5 inches vertically around the inside of the frame. Tie two bands of rebar that is 0.5 inches thick around the outside. Add a rebar grid on top of the surface, with two feet between each bar in both directions.
6. Pour and Level the Concrete
If it looks like it might rain, don't pour concrete. Wait until things are clear. Let the concrete truck drive right up to the concrete frame if you can.
When the truck is done pouring the concrete, pull a straight 24 across the top. The 24 helps to make the concrete level. Keep going back and forth with the 24 until the concrete is level and filled evenly across the surface.
Smooth the top of the concrete with a bull float. The bull float should only be used three or four times. As you drag the float across the top, you may notice that water comes out of the concrete and sits on the surface. Wait for the water to go away before you use the bull float to smooth the surface.
Use an edging tool to round off the edges of the concrete. You should also cut control joints to make cracks less likely. A groover is used to cut a seam across the width or length of the concrete. This seam is called a "control joint."
Wait until the cement is strong enough to hold your weight. Use foam insulation such as knee boards and a steel trowel to smooth the surface. Let the concrete harden before taking the frame and braces off.
The question is, can concrete be poured over asphalt?
Check the asphalt for damage before you pour concrete over it. If the asphalt is badly broken, cracked, buckled, or too thin, it may need to be removed before you can pave. If the asphalt is in good shape, you can mill it or drill holes to make it stick better to the concrete. For the best results, you might want to hire a pro.
Steps for Pouring a Concrete Driveway
Step 1: Demo the driveway
- Before you do any serious digging, you need to call a utility locating service to ensure you don't hit any gas, water, or electric lines. Mark has already done this, so the demo can go as planned.
- They break up the driveway with a jackhammer and finish the job with picks and sledgehammers.
- Demolition is a lot of work for Emma and stark, but based on how old the house and driveway are, the base should be in good shape—settled and packed down. So, when the demolition is done, they shouldn't have to put down a new base. Instead, they should fix any problems and maybe spread a thin layer of gravel.
- Mark uses a compacter to level off the base. He wears ear and eye protection.
Step 2: Add mesh wire
- Stark says that before they pour the concrete, they will put mesh wire on top of the base. This mesh is used to make the concrete stronger. The wire should be raised above the base so the concrete can get under it.
- Stark and Emma did the measuring and laying of the mesh wire together.
- They must attach a thin strip of insulation to the driveway's sides before the concrete is delivered. This strip will serve as an expansion joint because they pour concrete up against stone rather than grass, allowing the stone and concrete to naturally expand and contract over time.
Read More
Step 3: Pouring the concrete
- According to Stark, there are several options available when choosing concrete: plain concrete, colored concrete, acid-stained concrete, and concrete with exposed aggregate. Because colored or acid-stained concrete doesn't fare well in cold weather, Mark explains that he chose plain concrete because it has a nice, clean appearance.
- Stark has scheduled the arrival of a ready-mix concrete truck at the residence to pour 5000 PSI (pounds per inch), 6 inches of concrete.
- Emma and stark are waiting with shovels and rakes to spread the concrete as it is poured by the truck.
- Stark uses a screed to level the surface after running 6 inches of concrete.
- Then, Emma and stark shape and smooth any edges or bumps using a hand
- trowel and an edging tool.
Step 4: Brushed finish
- Stark advises adding a brushed finish after the concrete has been poured and leveled. As with a walkway or patio, this will help the driveway look more natural and define it. In terms of functionality, it will aid in skid resistance.
- Emma and stark will add this brushed finish by hand with brooms.
Step 5: Setting the concrete
You cannot drive on the driveway for a week because it takes seven days to set concrete.