We've all run into them at one point or another - in your yard, in your garden, in your driveway, cracks in the sidewalk - you know what I'm talking about... dreaded ant hills that seem to pop up out of nowhere. Sometimes they show up over night. How can such small ants quickly dig out so much dirt? Well, they do... and now you're trying to figure out how to get rid of ant hills that plague your very existence.
Unfortunately it's not a simple matter of kicking it down with your feet and plugging up the hole. The ants will simply rebuild it, literally over night. You have to deal with the source and that's the ants themselves. There are several articles on this site already that outline how to get rid of ants. I recommend reading them all - it is extremely important that you determine what type of ant you're dealing with before you can properly treat it. What works well on some ant species does not work so well on others.
More specifically, when you're dealing with ant hills that are generally found concrete objects outdoors: curbs, driveways, landscaping, sidewalks, brick patios, etc... what you're probably facing is the pavement ant. Check out this article on how to get rid of pavement ants, and this should help you deal with your ant hill problem.
The best product right now on the market to deal with problematic ant hills is to purchase an ant control stake. The most popular by far is Grant's Kills Ants - Ant Control Stakes. There are many very positive reviews of this product on Amazon. The trick is to place these stakes in problematic areas, near the ant hills. They are safe to use in the garden and even indoors. The bait inside the stake is irresistible to the ants, so they take it back to the ant hill and spread the poison to the colony. Once the queen eats it, your ant problems will be over as the colony will no longer be able to reproduce and grow. Some people report results within days, so it's definitely something to consider. Each package comes with 10 stakes, which is definitely enough to get you started... you might want to consider picking up a couple boxes because they do need to be replaced periodically as the bait is removed by the ants. You want to make sure you provide a continous supply of food (poison) until the ants are completely eradicated. You don't want to run out of the stakes and have to wait 5 days for the next delivery giving the ant colony a chance to recuperate and multiply.
An alternate option (that doesn't always work) is to try pouring boiling water down the ant hill. The ants will not drown quickly - some can actually survive under water for as long as 14 days! The key is to be certain the water is boiling. Dead is the result of the scalding hot water, not drowning. That being said, an 8 ounce cup of boiling water will not suffice. Ant nests are very large and complex networks - an underground labyrinth - use about 3 gallons of water to effectively deal with the problem. This may kill grass or other nearby plants, so I recommend only doing it when the ant hills are in the middle of concrete surfaces such as your driveway. If you're looking for an ant control method safe to use near vegetation, your best bet really is to deploy ant control stakes.