One option for sand in construction is ore sand, recycled waste from mining. When metals are recovered from rock most of the crushed rock is left on site, up to 99%. Studies have been done on the economics of using this material. If there was a good market for it then we could use the money to make mining sustainable, use renewable energy and invest in new technology that uses less water. It seems to kick start such good requires stimulus and we may see that, then a economic boom in green metal. Maybe another article for you, I can supply a report from the University of Queensland or you can google.