Victory in race one was a relatively easy result, a flag to flag domination of the 22-strong grid in a car that suited the hot, dry conditions. It was his second win and sixth podium finish of the championship.
"I was very happy with the car, it was almost perfect for that race," he said afterward.
Starting from P4 on the second row of the grid for the second race, Armstrong shot up to second overall behind his team-mate, Juri Vips.
"In Race 2, we made great progress early on. I got a good start and overtook cleanly to slot in behind Juri. With a few more laps I could maybe have gone past hims as well, but second was good enough," he said.
In the final race Armstrong was on pre-used tyres. He started 14th and shot through the pack up to seventh overall on lap one. He held that position until three laps from home, when he was overtaken by Artem Petrov.
"That run of overtaking was pretty busy, but I managed to carve through without putting the car at risk. At the end, Artem just had more grip so there wasn't much I could do. Eighth was a good enough result in the circumstances."
The next round of the Italian F4 Championship will be held at Imola on September 8-10.