Why is broken glass added to concrete in the USA?

One of the readers wrote about his neighbor in the comments. He collected glass and bottles in order to add battle to concrete. Allegedly, this is done in the United States, concrete from this only becomes stronger.

At first I replied that your neighbor probably confused ordinary glass with liquid glass. With the addition of the latter, concrete actually becomes stronger and more frost-resistant (less hygroscopic). But such a mixture needs to be laid and leveled in 20 minutes, it quickly sets.

Logically, ordinary glass shards will reduce the strength of the concrete, because their smooth surfaces have poor adhesion. But still I decided to look, maybe there are some technologies and we just don't know something ...

I found a few notes that say that broken glass actually increases the strength of concrete. It turns out that glass chemically bonds with the concrete mix due to the fact that concrete is alkaline. And glass (silicon dioxide - acidic oxide) reacts with alkalis to form silicates. Because in addition to the mechanical bond, a chemical bond in the cement mortar with glass is also obtained. A more durable monolith is formed.

They say that if a bottle is half-drowned sideways into concrete and next to it is a stone of the same area and smoothness, then after a while the bottle cannot be torn off, but the stone can be knocked out.

Isn't it easier to use ordinary sand? This is also quartz, silicon dioxide. Ideally, the sand should be washed and cleaned of impurities. To a greater extent, it goes simply as a filler. And the glass is 99% clean.

This was especially well shown by a group of Australian scientists at Deakin University. They crushed glass breakage to the size of sand and made concrete based on this filler. It showed much better performance than with sand filler.

There is another way to increase the strength of concrete with broken glass and soda ash. In the factory, when they are melted, cooled and dissolved in water, liquid glass is produced. As we know, it significantly increases the strength of concrete. Perhaps some kind of reaction occurs even without high temperatures: Na2CO3 + SiO2> Na2SiO3 + CO2 ^

By the way, carbon dioxide from the reaction can also participate in the processes of increasing the strength of concrete.

Probably, in the USA there is a lot of waste from glass production, therefore, they began to look for technologies where glass can be recycled, applied.

In addition to increasing strength, glass in concrete also plays a decorative function. In the USA, the following countertops are often made with the addition of broken glass:

The view, of course, is for an amateur, but they love unusual design solutions. But to get this look, it will take a long time to grind such a tabletop with a grinder with a nozzle.