Epoxy is fairly strong, but it becomes even stronger and durable when you mix in glass fibres to make fibreglass. You can also mix glass fibres with concrete to make a stronger, lightweight material that is used for decorative building materials.
Why aren't we mixing glass fibres with concrete used for all other purposes? It would add a bit to the cost, but it would help prevent cracking, spalling, and other common failure modes of concrete. Glass has about the same density as the gravel and sand used for concrete aggregate, so even with bulk pours there wouldn't be a risk of it separating out. Am I missing something here, or is this an opportunity to make more durable concrete structures?