Our asphalt driveway is in need of repair or needs to be replaced. I don’t know a thing about asphalt and not handy, so please be kind in your reply. Does it matter if the ground is wet or gets wet while the asphalt driveway work is being done?
The surface under the asphalt is critical. It should consist of a sub base of compacted select material (no organics) that is sloped to carry moisture away from the driveway (down and to the sides). That should be capped with a base of aggregate (basically small rock) that should ideally be allowed to settle in for several days (but that rarely happens) before laying the asphalt on top. Asphalt has to be maintained between about 275 and 325F or it will be prone to fail. It also needs to be compacted (rolled) once in place. For a driveway, between 4" and 6" is ideal. Once that aggregate is laid down, any moisture will be wicked away and shouldn’t affect the asphalt topping.
Asphalt is essentially a very hot mix of gravel and tar. It comes from the plant hot, and needs to remain hot until leveled and compacted. I don’t think it matters if the ground is slightly damp, but you can’t pave in the rain.
You can’t? If it is drizzling, you can’t pave? Or are you talking downpour?
I’d think the only reason you wouldn’t want rain (or significant standing water) is because it would potentially lower the temperature of the asphalt to a point where it would not be viable, and fail.*
As always, the base is the key. As ChefGuy pointed out, the work under the driveway is critical for the longevity of a driveway.
The other thing about water is the outside temperature. If you are in an area where the temperature can dip below freezing, it is best to wait until that time of the year is over. If water is trapped, and then freezes, it will expand, causing the blacktop above it to potentially crack.
SFP
*I am not an expert. However, I play one on SDMB
Civil Engineer/Resident Engineer/Materials Engineer for road construction checking in here; moisture by itself is not an issue. The problem as mentioned above is the temperature of the hot mix asphalt. It needs to be over 250 to 275 degrees F to remain in a plastic state (so it can be properly compacted; 3% to 7% air voids is what we’re shooting for). Once it cools below that, rolling will no longer achieve compaction and can actually damage the mix by creating cracks. Rain/moisture can cause the mix to cool faster than it takes to achieve proper compaction. So… light rain is probably OK, downpour is worrisome.
BTW, the mix can get too hot also; which can cause the asphalt cement to become brittle so cranking up the heat on the mix must also be done with care.
If you are paving a road using a spreader box this is probably true. I worked for a paving company that patched parking lots and driveways so we did most everything by hand. It was always a race to get the asphalt raked and compacted while it was hot. We never tried to work if it threatened rain.