Why do interlock blocks disintegrate?

From time to time Interlock Blocks disintegrate. It isn’t a thing that happens overnight. It isn’t as though you walk up to your set of interlock steps one day and fall through a mess of crumbling concrete. It happens over time.

Sometimes it happens over a long period of time. Sometimes it happens over a short period of time. And it happens.

Why does it happen?

Interlock blocks are made of concrete. Concrete includes three main ingredients: aggregate, cement, and water.

The aggregate is usually a small gravel or sand, the cement is cement (a glue that holds the aggregate together), and the water is what you add to the aggregate and cement to wet them and make them sticky. It actually is more chemical and scientific than that, put that is actually what happens. You throw those ingredients in a big mixer, and then you either let them dry naturally or put them in an oven.

If you poured and mixed and dried correctly, you have a solid piece of concrete that you can use to construct a walkway/patio/driveway or a step/wall. If you poured and mixed and dried incorrectly you have a piece of concrete that is susceptible to eroding and disintegrating over time.

Now we have the second part of the equation, the disintegrating over time part.

Water, the thing that helped the aggregate and cement get all sticky and mixed up. Water.

He comes back to town.

And when he comes back he is not friendly. He now seeks to kill and destroy.

With the help of foot and vehicular traffic, he tries to separate the bonds that he helped make one, three, five, ten, twenty years prior. He has allies.

They are :

Poor grading (when the interlock is graded poorly, water is able to puddle)

Bad base materials (if the base holds water it will rot the underside of the pavers)

Traffic aids and abets water by pounding on the pavement over and over again.

Gradually, as time goes on, if the blocks weren’t made correctly, and water has had its way, the paver’s or wall blocks start to crumble.

And you are left with a sandy mess where you used to have a walkway or step/wall system.

And you are sad.

Why did this happen?

Because your interlock blocks were made poorly. There was too much sand or cement or water or (new problem) the molds the blocks were made in were no good. Or there was too little sand or cement or water.

If I had to guess, I would say that there was too little cement. Because sand and water are EXTREMELY inexpensive.

It isn’t as though cement is super pricey, but it is the obvious choice.

And then it rained.

And now the interlock blocks are disintegrated.

All done!