Can you asphalt over cement

Take a look below. Concrete is not usually a compacted surface because it hardens no matter what it is poured over. Asphalt, on the other hand, has to be compacted to get longevity and strength. If the concrete has been poured over an unstable base, the slabs, once they crack at the expansion joints, can pivot slightly with traffic. Think of a time when you have driven down a bumpy concrete road where the bumps are rhythmic.

Those slabs have pivoted slightly from where they were originally poured. Chances are these slabs weren't poured over an unstable base, but rather, frost heaving moved them. Each individual slab can move at the expansion joints, and if you have an unstable base, the condition can occur more often. A concrete pavement that moves will damage any asphalt overlay over time. If you are looking to add asphalt over concrete, you will need to make sure you have a stable concrete surface below, with no expannsion joint shifting, to make a proper base for overlay.

Concrete has expansion joints where asphalt does not. Over time, the expansion joints will shift the concrete surface and wherever your concrete has a crack, the asphalt will eventually crack there as well. The expansion joint in the concrete is a designed area to allow for a crack, and while there are special reinforcing fabric strips that can be applied prior to overlay, over time, there is a very good chance that the cracks will eventually crack in the same spot on the asphalt.

This is not considered pavement failure, but it is just a result of ongoing heat and cold expanding and contracting. Concrete is smooth and solid and can therefore provide an excellent base for an asphalt driveway. But there is much more to it.

These issues are going to affect the asphalt layer. The strength of the upper layer of asphalt comes from the strength of the base layer of concrete. If there are any issues with the lower layer, it will show on the upper layer.

The main way this happens is through water getting into the concrete layer. Asphalt is permeable; therefore, water will seep through it. This water will then reach the concrete layer, and seep into any cracks that are there — even very tiny imperceptible cracks. Due to the freeze and thaw cycle, the water in these cracks will expand making the the cracks larger. The movement of the concrete base will soon start to affect the asphalt layer and the cracks will start to show on the surface.

Even a perfect concrete driveway can cause problems. A concrete driveway is usually laid with expansion joints every few metres. These are designed to allow movement of the concrete surface to allow for weather changes, and water freezing and thawing. Laying asphalt directly over these gaps can mean that you are introducing weak areas to the upper surface. As the concrete layer continues to move, it will affect the asphalt layer as well. Your contractor may be able to work around this by tapering the edges , but the driveway will always be higher than it was.

You also need a good depth of asphalt to ensure it will last and not start to crumble; reducing the amount of asphalt used is not an option. Your concrete driveway may be a few centimetre deep already, and when you add another layer of asphalt, you are adding a few centimetres more. Before you know it, you will have a lip or edge that runs all the way around the perimeter. This may be an issue where the driveway meets the road or pavement edge, and where it meets the steps into your home.

While you may be adding asphalt to your driveway to improve how it looks and performs, you need to bear in mind that the surface will require ongoing maintenance. The fact it is installed over concrete is likely to mean it is prone to cracks. These can be repaired relatively easily, but should be done as soon as they appear. You may also choose to seal the driveway; this needs to be repeated every years. If you want asphalt, you should dig up the old the driveway, and start afresh. But if you are doing that, you might want to consider resin bound as it will last even longer and give you plenty more options when it comes to the look you want to achieve.

Switching From Concrete to Asphalt The first thing to consider is whether you need to remove the concrete driveway or if you can simply pave over it. The determining factor here is what lies underneath. Concrete itself is very stable and strong, so no matter what it is poured over, the slab is going to be solid when it hardens. Therefore, concrete is often used as a bridge over unstable ground.

Asphalt requires a well-prepared, stable subbase, otherwise the resulting pavement will be subject to instability and cracking.