Marnus Labuschagne could scarcely believe how well Australia's day against Pakistan went as he and David Warner posted both centuries to leave them firmly on top in the second Test.

Warner and Labuschagne each recorded hundreds in the first Test, when Australia won by an innings and five runs, and the two continued their fine form with an unbeaten second-wicket stand of 294 in Adelaide on Friday.

That partnership - already the highest in day-night Tests - meant Australia reached stumps at 302-1 as Warner ended the day unbeaten on 166 while Labuschagne was not out on 126.

The latter had made a career-best 185 in the opening match of the series and was pinching himself after making his second career hundred in his very next innings.

"It's a bit surreal," he said in his on-pitch interview as he walked off with Warner.

"It's just amazing to be out here with Davey and put on a big partnership. Really happy with that.

"We were running hard, [I] almost ran myself out there at the end.

"I love the intensity at the crease and how hard we ran. It was real fun."

Warner, who reached three figures for the 23rd time in his Test career, was delighted to see Australia's number three extend his purple patch.

Labuschagne has so far scored 793 Test runs in 2019, more than any other batsman in the world.

"His knock up at Queensland was outstanding," Warner added.

"Credit to him, he started where he left off at the Gabba."