How did China's bitumen supply shift from shortage to self-sufficiency?

How did China's bitumen supply shift from shortage to self-sufficiency?
In the early 1990s China produced only about 2 million tons of road bitumen annually, roughly equal to a single month's output today. When prices jumped from around 680 to over 1,120 yuan per ton in 1994, the government promoted cement concrete instead, subsidizing it at 60,000 yuan per kilometer. The Chengdu-Chongqing expressway was built with cement in that period. As refining capacity expanded, bitumen output surged, reaching over 50 million tons by 2019 and exceeding 62 million tons in 2020. Domestic brands like Sinopec's Donghai grade now supply demanding projects including F1 circuits, displacing imported product.