I’ve struggled for years trying everything to permanently fill aggravating cracks in blacktop. The magic caulks sold at the big boxes have provided me with dismal results. The worst part is that no matter what I try, sometimes the repair looks worse than the actual crack. The repair material stands out like a sore thumb. Have you had any luck fixing blacktop cracks so you can’t see them? Do the repairs last? — Kathy Z., Mills River, N.C.
I used to struggle with blacktop crack repairs, too. When I was in college, I started a house painting business with a good friend. While we were painting a house, the homeowner asked if we could seal her blacktop driveway. Never having done it before, we said yes and figured it couldn’t be that hard.
The drive had some cracks so we just mixed up some sand with the liquid blacktop sealer and poured that into the cracks. While the sealer job came out great, the crack-filling experiment ended in a dismal failure. So, yes, I know what you mean about the repair looking worse than the crack.
When a new blacktop drive is installed, it’s jet black. This is because each piece of stone and sand in the mix has been coated with the black asphalt cement that’s the glue holding the stones and sand together. Over time, Mother Nature washes away the black asphalt from the surface and you see the different colored pieces of stone and sand. When you then fill the crack in your blacktop with a monotone-colored product such as deep-black caulk, that black line stands out like a sore thumb.
My second-to-last blacktop crack filler was a special caulk that had small pieces of silica sand in it and was extremely sticky. I installed some on my drive five years ago and it looked pretty good for about three years, but then it started to succumb to the stresses of harsh New Hampshire winters and the punishing ultraviolet rays of the sun.
When I installed it, I did push some small stones into the gooey caulk to help disguise the repair, but you could still see it if you looked closely.
Over the years, I’ve tried many products looking for the Holy Grail of crack fillers. I believe I may have found it.
The material is a semi-liquid epoxy that’s in a regular caulking tube. It’s battleship gray in color and it contains very fine silica sand in it. The caulk-tube design is unique because it comes with a long nozzle that blends the two epoxy components as you squeeze the caulk gun handle.
Most epoxies have extremely high tensile strength and can resist strong pulling or bending forces. This makes them ideal for blacktop crack fillers because asphalt is a flexible pavement that does move.
Using this material is caveman simple. You simply cut off the tip of the caulk tube above the threads, screw on the long nozzle and start to squeeze the gun handle. You can see the two-part epoxy start its journey down the nozzle, and it mixes as it travels to the tip.
The secrets to success are simple. I made sure my driveway was dry and I brushed out the cracks, removing all debris to a depth of 1 inch. I allowed the sides of the crack to dry. While doing this I spent time along the edges of my driveway gathering loose, clean stones.
I made sure I got stones of all different sizes and colors to match what I saw in my blacktop. The size of the stones ranged from lima bean down to the size of a peppercorn. I also swept up a generous amount of clean sand from my driveway.
These components are what you use to disguise the epoxy. I’ve used epoxy for years to repair all sorts of things and I know it works well to bond things to concrete. Blacktop is nearly identical to concrete because the stones and sand in blacktop are the same used to make concrete.
I applied the epoxy carefully into the crack, making sure I left it about 1/8 inch below the surface. I found it best to caulk about 1 foot of crack at a time. While the epoxy was fresh, I carefully embedded the stones into it, pushing them into the product and making them flush with the adjacent stones. I made sure to mix the sizes so everything looked like it was original.
Once most of the epoxy was covered with stones, I then broadcast the sand over the crack. The sand completely hid the gray epoxy, making it invisible. I’m very confident I won’t be repairing any blacktop cracks for a very long time! Try it yourself and see.
Tim Carter is a columnist for Tribune Media Services. Contact him through his Web site: www.askthebuilder.com.