[okal]

She's a materials scientist. I'd wager that she's considered all of these factors. She's also been doing this for a while, and produced tonnes (literally) of these for, if I read correctly, a year and a half. Maybe consider that she's thought through this?

[darksaints]

Of course she has. In fact she indirectly confirms that the common misconceptions regurgitated about plastic do not apply here. She takes the plastic that cannot be recycled using typical methods. The reason why some types of plastic cannot be recycled is because they cannot be melted. This is true of all thermoset plastics, and it is practically true of some thermoplastics as well (at least after they have been repurposed a couple times). The only way they could be softened enough to bind with sand is by softening them in an environment with high enough pressure and temperature, but devoid of oxygen (otherwise they'd just burn).

And even if they were using melty thermoplastics, the properties will still change drastically the moment you introduce a substrate like sand or gravel and turn it into a composite. Just like how there is a massive difference between pure Portland cement (extremely brittle, with almost no load-bearing capability) and concrete, which is a composite. Nobody seems to regurgitate these rubbish misconceptions about plastic when talking about carbon fiber composites (which are held together by plastic!).

I don't think I'll ever understand the techie's tendency to think they know more about certain fields than specialists that work in those fields.