Dhawan, who slammed 107 runs off 96 deliveries, became the first Indian batsman to notch up a ton in the first session of a Test match.
The southpaw's knock contained 19 boundaries and three sixes.
Speaking after the match, Dhawan said: "Scoring a century in a single session was a great thing. Didn't know no Indian batsman had done that."
"I was in a good mindset, knew what I had to do out there, and things went my way. I was focusing on my fitness between the IPL and this game, didn't really bat that much," the 32-year-old explained.
Dhawan's opening partner Murali Vijay, who also smashed a century on the opening day of the one-off Test credited Australian legend Michael Hussey for helping him improve his batting.
"I work hard on my batting, I've worked with Hussey during the IPL and I would like to thank him for that," Murali said.
"You've got to stick to your gameplan, even though Shikhar was going really hard. He was phenomenal today," the 34-year-old added praising his partner.
Commenting on debutants Afghanistan, who became the 12th Test playing nation on Thursday, Murali said the newcomers enjoyed their game on the opening day.
"I personally thought they (Afghanistan) enjoyed their cricket, and finished the day on a high note," the opener opined.
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