The layout of the new Miami circuit, which is 5.3 kilometers long and will circulate in a counterclockwise direction, has been designed by the British company Apex Circuit Design . The circuit winds around the Hard Rock Stadium in Miami Gardens and the lap time is expected to be around 1:35, while the average speed is expected to exceed 210 km/h.
The paving of the track has required a total of 24,000 tons of asphalt, which was distributed over the length and width of 78,000 meters on three lanes, to achieve a track with an average width of 15.24 meters. The programming of the works had to be coordinated with other events held at the stadium, such as the end of the NFL football season, a jazz music festival and the Miami Open tennis tournament.
“Of course, the asphalt has been the subject of a lot of engineering and analysis,” said Apex project manager Sam Worthy . “The FIA requires that the tarmac be ready at least 60 days before the race weekend. We have met that so it will be well cured before the race.”
“We start to see the limestone layer because the top layer of binder is peeling off. You can see white flecks in it.”
Limestone is not normally a good material for F1 tracks: firstly, it is friable, meaning it crumbles easily and can chip, and secondly, it is polished. So good tire degradation is often not achieved and grip is reduced. But, in South Florida, the predominant compound is a more abrasive limestone.
“Our asphalt specialists, R3, investigated the local limestone and said they had not seen anything like it anywhere in the world, as it is much harder than expected and will result, together with the 60% mined granite mix of the United States, coming from the state of Georgia, an adequate abrasion in our asphalt mix”.
R3 has participated in one way or another in most of the F1 circuits recently incorporated into the competition, so his knowledge of data from other places gives us a good reference.
“What R3 discovered in South Florida is that ‘our’ limestone is unique in that it has a very high silica content. Its texture is like little shards of glass, so as the limestone breaks and degrades, more of this silica is exposed and so you get an effect where you maintain much higher tire degradation than you would normally get with limestone from other parts of the world.”
“The granite was brought by train from Georgia, so our mix is an innovative blend of locally sourced granite and limestone. We are very pleased with the results.”
Extra flat track surface
Worthy also explained how the super-flat track surface was achieved, despite a lack of experience in the area when it came to the quality of finish that Apex demanded.
“The whole team is very proud of what we have achieved in terms of track flatness,” he said. “A lot of work went into it, because even though the local workers were very good at what they did with their methodology, their technology was poor, we were concerned about that.”
“When we mentioned the FIA specifications for the asphalt layout, they told us that it was impossible to make it so smooth. That scared the hell out of them.”
“That’s when we had to find workers who had the technology that we know in Europe and in other parts of the world and who had the confidence to supply us with what we needed.”
“We used specialized companies to lay the asphalt itself, although the base rock layer and subgrade and the first two structural elevations of the asphalt, the second of which was ‘overbuilt,’ were done by local workers.”
“Once those first base coats were done, we LIDAR (a kind of laser) scan the entire track, to generate a full 3D mesh of that surface before final milling and paving.”
Key to completing the process was enlisting the expertise of the construction companies, who ensured the track’s base layers were as smooth as possible.
“We work with Rifenburg Construction, upstate New York, which is a well-known user and specialist in the use of Topcon’s electronic milling and paving control,” added Worthy.
“They used GPS-controlled micro-milling to fit the ‘overbuilt’ second layer of asphalt to our design standards, bringing our design data into their machinery. These micro-milling machines use much smaller teeth in their milling process than would normally be the case.” seen to ensure pinpoint accuracy.
“We milled a very precise surface that was very close to race-ready, so when they started laying the last layer [of asphalt], which is two centimeters thick, Rifenburg was able to focus solely on making it smooth and flat while They put it in. So they didn’t have to worry about anything else, like the cross slope or the drainage of the trench, because these criteria were already at the perfect height required.”
“We spread the final wearing course in ‘echelon’ [a method that uses three pavers running simultaneously to ensure hot seams between lanes to ensure long asphalt life], and the number of quality control and assurance personnel who was participating, going behind every paver, was really impressive.
“The machine was going by, with a truck that poured the asphalt into a transfer vehicle, which had a driver with two people watching, and the pavers themselves had a team of six to eight people. Then, behind the machines, there would be a team considerable number of quality control personnel with tools that checked that everything was going well while asphalting”.
“The number of people and the effort that went into this final layout process was immense. It was important to make sure there were no potholes between the paver lanes or in the seams. They did such a good job that all the people who has seen it since has made very positive comments.
The last step of the process
Worthy explained that there is one final stage of preparation needed to get the entire track ready for the F1 weekend’s race: “We have a task to do regarding the tarmac surface ahead of the race, working with UK Roadgrip ; we are going to texture the surface with their proprietary TrackJet equipment to evenly peel the bitumen from the surface and to bring the surface to the required F1 macro-texture.”
“This work will be an annual exercise; for the first year it is more aggressive as we are preparing the asphalt for its first race. In the coming years it will be necessary to clean the track as much as in the case of the F1 headquarters in Singapore, since that the venue is used for multiple other events between races and there is likely to be dirt and contamination to remove each year.”
