Silicon is not necessarily tough in the sense of <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Toughness" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Toughness</a> -- it really depends.<p>The hard problem in road surfaces is not the sitting outside for 20 years.  Glass, even cheap crappy glass, handles this last just fine; see windows in houses.  The hard problems are dealing with repeated time-varying mechanical stress and dealing with thermal expansion (windows can play fast and loose with this by leaving expansion space around the glass inside the frame).