The Secret to Finishing Concrete is the Mix

In this video, concrete expert and professor Tyler Ley—a self-described concrete freak—explains the float test, a practical method for measuring how easy concrete is to finish. He compares cement types, fiber reinforcements, and mix adjustments to help avoid over-finishing, prevent surface defects, and produce durable, high-quality concrete. 

What's the secret to finishing concrete

It’s a lot about having a great concrete mix, and I’m going to give you ways to verify that—and also something you can implement today when you’re trial-batching your concrete mixtures.

You can get projects like this—ones that you’re super excited about—and avoid things like this, and like this, and issues like this, and over-finishing.

My name is Tyler Laay. I’m a structural engineer, a materials engineer, and a professor. What you need to know most about me is—baby—I’m a concrete freak.

I know you’re asking, “How can I design a mix to make sure it’s easy to finish?” Well, if you stick around, I’ll show you how different cements impact your finishing—yeah, like Type 1L versus Type 1/2.

I’ll also compare different fibers. But it’s all about testing.

Why slump test isn’t enough: introducing the float test

You said, “What, like the slump test?” Well, the slump test is cool. If you don’t know what it is, it’s where you take a cone, fill it full of concrete, pull that cone up, and measure how far the concrete falls. How far it falls is an indication of how workable it is.

Slump test is cool, but slump does not equal finishing. The more effort it takes to finish, the more water has to be added to your concrete—and that’s not good.

Adding water lowers your concrete strength, decreases the life of your concrete, and causes spalling.

I’m going to tell you about the float test, which measures the effort to finish concrete. It works on any concrete.

It’s pretty simple: you take some forms that are 3 feet long, 2 feet wide, and about 3 inches deep. There’s a yoke in the back to help hold your float at a constant angle. You fill the forms with concrete, smooth it out, and leave it about half an inch high.

Then you strike it off—not saw it, strike it. Come back, fill in low spots, and check the height.

Creating holes to measure effort

Next, use a template and a dowel to create three 1-inch diameter, 1-inch deep holes in the concrete. Why holes? Because when you strike concrete, aggregates sometimes get plucked out, and it’s the finisher’s job to fill them in.

We measure that effort. The float rides only on the surface of the concrete. We measure how many passes it takes to smooth the surface and fill the holes. The lower the number of passes, the better.

Running the float test

While running the float back and forth, we change the strike angle so only part of the float rides the surface—just like in the field.

During inspection, we only look in the center, not near the edges. We track how many passes it takes to fill holes.

For example:

• Zero passes—holes still visible

• Two passes—partially filled

• Four passes—better

We also track how many passes it takes to make a smooth surface, using a visual ranking scale. You decide what’s right for your project: a “3” for DOT work, a “1” for commercial jobs. Less passes = easier to finish = less water added on site.

Testing different cements

Does this really work? Yes. A third party tested different cements, keeping everything else—slump included—the same. The Type 1L cements consistently took more passes to finish than the Type 1/2 cements.

But not all 1Ls are the same—some finish just as easily as 1/2. If you know a cement will require more effort, you can adjust your mix.

Can you finish fiber-reinforced concrete? I compared eight different plastic fibers and three steel fibers at three dosage levels.

At 0.5% by volume, zero passes showed lots of fibers at the surface. Four passes looked better, and ten passes looked pretty good.

In general, higher fiber dosage decreased finishability—but not all fibers performed the same. Some did great; others had issues. The float test lets you compare them directly.

The float test was instrumental in developing the Tarantula Curve, another powerful tool. It works for testing cements, admixtures, fibers, sand content, or blended sands—anything that affects surface finish.

Implementing the float test

Run the float test during trial batching. It can be done by ready-mix suppliers, testing companies, or by yourself. Compare a new mix to one you know and trust.

Tweak your mix to make it easier to finish. The test method is linked in the video description—it’s free.

The secret to finishing concrete really is in the mix design. The float test will save labor and prevent over-finishing, so you avoid costly surface issues.

Thank you for watching. Please check out my other videos, like, subscribe, and share. Join me at concretefreaks.com to see what I’m up to.

Massive thanks to Dan Cook, who helped develop this test during his PhD, and to everyone who helped make this video.