Best concrete patio sealant

Answer:  I do not know which is the best sealant, but in this post I show two products that appear to have some promise.

But first, a rant.

Actually I do always rant. 

In this previous post, I wondered aloud why Houstonians tend not to maintain their fences with pressure washing and stain.  In our land of cheap housing, we live in gorgeous McMansions, most of which are surrounding by cedar enclosures that reflect appalling neglect, or at least an incongruent plain-ness.

There's simply no comparison:  Our backyard four years ago in its very early stages of development, before and after fence staining.  For a few bucks and a few hours of time, this, too, could be your look.  Pics from this post. 

It is with a similar degree of exasperation that I wonder why most Houstonians do not clean and finish-seal their concrete.

This type of blackness and despair is the eventual result of non-action.  At left you see the edge of our concrete patio, freshly pressure-washed.  At right you see a concrete paver stone that has not yet been pressure washed.  Prior to washing, the appearance of the patio essentially matched that of the stone to the right. 

Not only is this kind of mildew and algae build-up unsightly, it's dangerous because it's very slippery when wet.  More than once I have nearly broken my neck after losing my footing in this area.

Unfortunately, the remedial choices are few, especially if you do NOT want an epoxy or "wet look" sealant, both of which I think make outdoor concrete look plastic and fake.

This chart summarizes the choices, which basically fall into four categories, only one of which (that excerpted above) maintains natural looking concrete. 

Here's the kicker, though: Perhaps because concrete sealing is not very popular in this area, few products in the silane / siloxane / silicate class were for sale locally.  (The other probable reason for the non-availability is that, here in the deep south, we don't have to worry about frost damage to our concrete, and frost damage is what these things were intended to prevent).  After doing additional research, we settled upon Drivehard Concrete and Masonry Weatherproofer for our main patio, which we had to order for delivery.

It looks like this and is described as being a "nano-silicone / silicate" based product. 

However, we have two patios, and with so little information to go on, we were not sure which formulation would work best in our climate.  Therefore, we also bought this other option which was available locally at big-box hardware stores.  We figured we'd compare the performance of the two over time, one on each patio.

Behr Premium Protector and Waterproofer.  It is described mostly as a silicone product, whatever that means.  

Especially this year with the abnormally high rainfall we have been having, it has been a struggle to keep both patios even slightly clean.

I had initially pressure washed earlier this spring and then was waiting for a dry day to apply the sealant. Well, with all the rain, a dry day did not arrive, and meanwhile, this is the amount of algae that re-grew just within a matter of weeks.  I had to pressure wash all over again as if the first washing never even happened.  

Here is a test spot of the Behr product on our smaller patio.  I had put down the tape because when the concrete is dry, it's impossible to see where the product was applied.  But you sure can see the application when the un-treated concrete gets rained on.  

This is a view of the Drivehard product application in progress on our larger patio.  It goes down like plain water.  I did not just apply one coat - I went over it, and over it, and over it, each time making a new pass to add more product to areas where the concrete soaked up the initial roll-out.  The instructions say that you can do this as long as the initial coat does not completely dry in between applications.  

Here is a finished view of the larger patio while it is partly wet and partly dry.  If you look carefully, you can see that the edges beyond the concrete seam have some standing water, but the sealant excludes a lot of it from soaking in, such that it no longer darkens when wet.  

This is a close-up view of the treated concrete.  Some water does still penetrate, but a lot of it beads on the surface. 

Both products performed as advertised in that they did not leave a visible residue or coating.  The concrete on both patios still looks "natural" and uncoated.  I will re-edit this post in the future with a verdict if one proves to be superior to the other.

And this is the first of two posts that will celebrate that fact.