New Concrete on Old
Question #1: Tim, I desperately need your help. The concrete sidewalk and driveway at my house are falling apart. The top surface is crumbling yet just below the surface the concrete is as solid as rock. It’s only a few years old. What’s causing this? Contractors have told me I need to tear it all out and start over. I can’t afford this. Is there a DIY solution or a far less-expensive alternative that a handyman can do? I’m looking for a repair that will stand the test of time. Mona G., Lexington, KY
Crumbling concrete like Mona’s is very common. You may have it at your home on your driveway, patio, outdoor steps, or even a retaining wall. The great news is you can often repair this yourself with minimal expense and tools.
There are lots of reasons why concrete spalls. Spalling is where the top surface of concrete flakes off or crumbles. In many instances, it’s traceable to workmanship errors where the concrete finisher added extra water to the concrete while putting the final finish on or he started finishing the concrete while bleed water was still up on the surface.
Mixing extra water with the concrete dilutes the amount of Portland cement in the upper surface. It’s important to realize that the cement is the only component holding the sand and gravel together. If you have too little cement, the concrete can’t withstand freezing and thawing cycles and heavy use. More Portland cement in concrete is always better. This is why the concrete abutments on railroad bridges last for over one hundred years. The railroad owners only wanted to build the bridges one time so they made sure the concrete mix had extra Portland cement added.
You can repair your concrete by installing a thin overlay on top of the old concrete. There are several important steps, but they’re all easy. The first thing is to remove all of the crumbling surface concrete. A pressure washer wand held at a low angle is perfect for this job. Remove all the old failing concrete until you get to solid material.
A concrete overlay can be as thin as 1/16th of an inch or as thick as several inches. Another key point is the size of the stone or aggregate in the overlay mixture. The size of the largest stones in the mix can never exceed 1/3 the total thickness of the overlay. For example, if you’re going to add a 1/2-inch overlay, be sure the size of the largest stones in the mix is not much larger than 1/8th inch! You need a blend of stones and sand in the mix with some of the sand being extremely small. Silica sand is the strongest sand you can use and I’d suggest you buy a bag of it to include in your overlay mixture.
The secret step of the process is cement paint. This nearly forgotten trick ensures the new overlay bonds permanently to the old concrete Cement paint is made blending cold water with pure Portland cement until it resembles latex paint. You brush this onto the damp old concrete one minute before you apply the concrete overlay.
I’ve got all sorts of extra concrete overlay installation tips, mixture ratios, videos at my website waiting for you. Just go to: Concrete Overlay
Change Tile Grout Color
Question #2: Tim surely you can help me. I want to change the color of the grout in my floor and wall tile. I’ve seen ads for miracle roll-on products and wonder if they can be trusted. Can you change the color of grout so it looks fantastic? What do you use? Is it hard to do? Don’t sugar coat the answer as I can handle tough love. Margaret R., Boxboro, MA
You may be in the same situation as Margaret. There are many reasons why you might want to change the color of the tile grout. Fortunately you can do this, however, you need to realize there are scam products out there.
I’ve changed the color of grout before and it’s not easy. The color of the grout between the pieces of real slate in the entrance hall of my last home was supposed to be black. However, it came out a mottled dark gray because I foolishly added a grout additive to the mix. My wife hated the ugly appearance. I discovered there are liquid grout stains that are just like penetrating wood stains.
Using an expensive small square-tipped artist’s brush, I slowly applied the rich black stain to the grout lines. It took weeks of time doing this at night after I had come back from building homes all day.
Avoid using products claiming to be grout stains but are really just paint. Do NOT paint your grout. Keep in mind that you can really only go from light to dark when changing color. It’s virtually impossible to find a penetrating stain that will transform dark grout to a light color. If you put a form-filming paint on your grout, I guarantee you it will peel. Be sure the grout is perfectly clean BEFORE you start the process.
I’ve got great videos and extra tips for changing grout color at my website. Go to: Change Tile Grout Color