KARACHI: Wicketkeeper Alex Carey hoped cracks on the pitch would help spinners take 20 wickets after Australia piled up 505-8 on the second day of the second Test against Pakistan in Karachi on Sunday.

The left-hander became Pakistan skipper Babar Azam's only second Test wicket as he missed the part-timer's straight delivery and was bowled for 93 with just two overs left before close.

When stumps were drawn, Mitchell Starc was batting on 28 with touring skipper Pat Cummins yet to get off the mark after Usman Khawaja hit a memorable 160 in the country of his birth.

"There are some cracks opening," said Carey. "I still think there's opportunities for us to pick 20 wickets going into tomorrow and day four and five."

On missing a hundred, Carey admitted the opportunity was lost.

"I am always disappointed when I get out. It was so close. Unfortunately, it's the way it goes."

When the wily Pakistan spinner Sajid Khan produced a sharp turning delivery that beat Khawaja's defensive push on the back foot to clip the top of the off stump, Pakistan had thought they would wrap up the Australian innings soon.

But Carey and Starc frustrated the home team during their eighth-wicket stand of 98 as the National Stadium pitch offered slow turn and low bounce.

Carey batted for 187 minutes, hitting seven boundaries and two sixes in his highest Test score, improving upon his previous best of 51 against England at Adelaide in December last year.

Sajid's spin partner Nauman Ali bowled Cameron Green for 28 in the last over before tea but Pakistan's plans to bat today were spoiled by Carey and Starc.

Pakistan took the third new ball after 163 overs with Australia's total at 453-7 but none of the pace bowlers could get the breakthrough.

Ashraf (2-55) and Sajid (2-151) were the main wicket takers in Pakistan's 180 overs of hard work.

This is the first time Australia have batted 180 overs in Asia since their 179.3 overs, scoring 577 against India in the Delhi Test of 2008.

Sajid had given Pakistan a double break in the post-lunch session with the wickets of a stubborn Khawaja and Travis Head for eight.

Until then, Khawaja had defied Pakistan's attack for nine hours and 12 minutes in an anchoring role since Australia won the toss and opted to bat on Saturday.

The left-hander from Queensland smashed 15 boundaries and a six in his third 150-plus masterly knock.

Sajid had earlier dismissed Head, leg-before wicket off a sharp delivery, while nightwatchman Nathan Lyon was bowled by Ashraf in the first session for 38.

It was a dull morning session as Australia added 81 after resuming on 251-3 as the pitch held its flat nature.

Khawaja added 54 for the fourth wicket with Lyon to frustrate the Pakistan bowlers who were looking for early wickets to halt Australia's progress.

Ashraf could have dismissed Lyon on 31 but failed to hold on to a return catch to his left.

Lyon capitalised on the reprieve with a sweetly-timed boundary but Ashraf had the last laugh three overs later, with a delivery that clattered into the stumps after brushing the Australian's pads.

Lyon, dropped on nought by Imam-ul-Haq off pace bowler Shaheen Shah Afridi on Saturday, hit five boundaries during his stubborn knock of 38.

Khawaja was unflustered and pushed Hasan Ali for a single to complete his 150.

Australia, touring Pakistan for the first time in 24 years, will play three Tests, three one-day internationals and a single Twenty20 international on the tour.