A reinforcing fiber to mix with concrete is one.

One use that fascinates me is with foamed concrete (literally mixing concrete with a foaming agent) can be used to create cheap lightweight, insulating blocks, slabs or pours. While it shouldn’t be considered “structural” (low compressive strength), it can be quite durable and withstand and dissipate very energetic impacts when blended with chopped fibers (like basalt). The exact use will effect the ultimate blend and resulting density.

Not a typical material for sure, but I do see it come up in some countries when someone is having to DIY a lasting shelter. For a lot of situations it’s quite a sensible choice, and much healthier than spray foams. Depending on how open/closed the cells end up and freeze thaw cycles, protection from water saturation may be needed.

This combination of materials is also sold as prefabricated bullet stops for training, meant for retaining lead in an alkaline environment: https://www.terrancorp.com/sacon