It's the new breakable concrete they put at the end of runways in case of emergencies. If an airliner is in trouble and uses up the runway, when they reach this portion, the concrete breaks-up and slows down the airliner.
About half a century ago runway extensions from fine grit were tested for the same purpose. I suppose it was difficult to keep it clean and it was never operationally deployed. This seems to be the solution.
I believe its used for large aicraft both civilian and military most small military planes use a wire runway arester system.
It is concrete designed to break apart when a specific amount of pressure like what the landing gear wheels put on the ground i think its been around for many years.
Engineered Material Arresting System (EMAS). Most major Chinese airports have them installed, at least on newer runways. But they are pretty expensive and mostly imported, so maybe they are testing a domestic product.