It's going to be torn up; it's just a test. But the test itself a very important step. The composition of the tarmac is a very exact science. Subtle changes to the mixture can influence grip levels, durability, settling rates and a whole host of other factors. Take, for example, Montreal - the surface there has very low grip. This is because the tarmac is not porous. Because Montreal is so far north, the city often experiences snow and freezing conditions in the winter, and this is problem because water can seep into the porous tarmac and then freeze. As any sixth-grader can tell you, when water freezes, it expands. And when it expands in the porous tarmac, it damages the surface. So in order to coutnermand this process, the tarmac in Montreal is much less porous. The water cannot filter down to the base, so the surface cannot be damaged as much as it might normally. Inversely, there is less for the tyres to grip onto because there is very little space between the stones that make up the tarmac.
In Texas, the opposite holds. Because of the roasting summer temperatures, the integrity of the surface can buckle and break. We can see this in Elroy Road, one of the roads leading into the circuit - over time, the traffic has steadily pushed the road out of shape. Where it was once straight, it now curves slightly. This is obviously something everyone involved in the CotA project will be eager to avoid (the 1984 Dallas Grand Prix experienced a similar phenomenon), and although Tilke employs a group of chemical engineers specifically for the purposes of making the perfect tarmac mix, they're obviously going to want to test the tarmac first to make sure they get it right. Once they do, they'll tear it up, rebuild the section of road base at that corner, and start sealing the surface. At a guess, I'd say the first layer (of three) will go down at the end of the month.