Ask the Builder: Avoid social media shortcuts

I perform media scanning on a routine basis. I’m constantly on the lookout in publications and the Internet for new products, techniques and hokum. I do this, in part, to keep my ear to the ground, but I also do it to help you save time and money.

I’ve been noticing a disturbing trend with some home improvement websites and social media. The websites appear to be hiring people with little, or no, hands-on experience in the topic they write about. Anyone who’s done the particular job can see right through the puff pieces these authors churn out. The articles have an over-arching unicorns-and-rainbows theme about how good and easy something is.

The most recent trend talks about using recycled asphalt as an affordable substitute for a concrete or hot-asphalt driveway. But before I go into this, allow me to share a similar DIY trend about creating concrete walkways, slabs or patios. When I saw this one several years ago, I knew the poor-quality concrete would fail.

Several years ago it was all the rage to watch a video on YouTube showing someone dumping bags of dry concrete mix inside of wood forms. The person on camera would use a straightedge to smooth off the powdery mix so it was flush with the top of the forms.

The next step was to mist the concrete mix with water. The entire point of this process was to avoid the hard work of mixing the concrete in a wheelbarrow, dumping it into the forms, spreading it out with a concrete rake, and then taking the time to screed, bull float and finish the concrete.

I watched these videos (some have hundreds of thousands of views) knowing the concrete would crumble in the very near future. This is especially true if the concrete was exposed to repeated freeze/thaw cycles.

Here’s why that concrete shortcut was foolhardy. The biggest reason failure was guaranteed is that the water from the hose was removing much of the Portland cement from the top layer of the concrete. The water was pulling that cement down deeper into the dry mix. The cement is needed at the surface to bond the sand and gravel together. High cement content at the surface prevents spalling and scaling. Remember, the cement is the glue that holds together the sand and gravel in your concrete. You need the cement paste to coat each piece of sand and gravel so the cement crystals interlock much like Velcro™.

The second reason the concrete would fall apart is the person misting the concrete has no idea if they’re adding the right amount of water. Concrete scientists will tell you that strong concrete requires a very important ratio of cement powder to the amount of water added to the mix. Ready-mix concrete plants have computers that ensure the right amount of water is added so the concrete achieves the correct strength.

Let’s talk about recycled asphalt now. Thousands of miles of primary roadways in the USA are made using hot-mix asphalt. It’s similar to concrete. Hot-mix asphalt has three primary ingredients: stones, sand, and liquid asphalt cement. These are mixed in a huge drum so the asphalt cement coats the stones and sand. When the hot-mixture cools down and the lightweight oils evaporate from the mix, the resulting surface is very hard and durable. The sticky asphalt cement bonds the sand and gravel together.

You know this if you have an asphalt driveway. You can pressure wash it and not cause any visible damage. Concrete is even stronger. Neither of these pavements create dust when you drive on them, and they don’t rut in wet weather.

Recycled asphalt is created when it’s time to repave a roadway. A giant grinding machine equipped with hundreds of carbide tips grinds and planes the roadway surface. Think of a massive belt sander on steroids. The milling process grinds up the old asphalt paving breaking the bonds created by the asphalt cement years before when the paving was put down.

The grinding process can also happen at a remote site. Some repaving contractors will dig out old asphalt paving in huge pieces and drop them into a dump truck. This material is taken to a remote dumping ground where the chunks of asphalt paving are dumped into a machine that pulverizes it. Think of a massive food processor you might use in your kitchen to mince onions or other vegetables.

This crushed asphalt can be bought. Here in New Hampshire, the cost of the recycled asphalt is about the same per ton as regular crushed gravel. Both materials can be used for a driveway. I’ve used both on a 1/2-mile driveway I use to access a 90-acre tract of undeveloped land I own.

The proponents of recycled asphalt say the material will establish some bonds once it’s compacted and the summer sun heats it up. This may happen on a small scale, but I’ve not seen it happen on my driveway.

Heavy rain can wash the recycled asphalt away. You can’t hose it off or use a pressure washer on it. Driving on this material in dry weather can create clouds of dust. In the absence of a thick base material under the recycled asphalt, rutting is guaranteed in wet weather.

The bottom line is this. If you’re tempted to buy into some shortcut method you see online, go seek out places where the material has been in place for two or four years. Don’t hope for great results when you take a shortcut!

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