Bangladesh were bowled out for 159 in their follow-on innings after being dismissed for 153 in the first innings.
"The wicket was good but it had a bit of bounce and the batsmen couldn't apply themselves," said Ashraful.
The left-handed Mehrab Hossain provided the only highlight for Bangladesh Saturday as they lost seven wickets for 92 runs, with the match ending 20 minutes before lunch.
Fast bowler Dale Steyn took five for 63, his ninth five-wicket haul in 26 Tests.
Ashraful said he would look for an improved performance in the second and final Test starting in Centurion Wednesday but indicated there would be no change from the generally aggressive approach by his team's batsmen.
Responding to a suggestion that some of the batsmen may have thrown their wickets away, Ashraful said: "It might appear that way but in Test cricket you also have to score runs."
There is unlikely to be any respite for Bangladesh as South African coach Mickey Arthur said he had requested a pitch with pace and bounce at Centurion.
South African captain Graeme Smith, who was named man of the match after scoring 157 in South Africa's innings, said he was satisfied with his team's first Test outing in almost three months.
He was not concerned by the lack of form of some of his top order batsmen, with the side slumping from 327 for one to 441 for nine.
"We wanted everyone to have a good go in the middle in these two Test matches.
"It wasn't a wicket where it was easy to force the pace and when we tried to do that in the middle order we lost our way a bit, with maybe one or two careless shots.
"But 450, 500 was a total we wanted to declare on so we could have a go at their batsmen that afternoon."
Smith and Arthur indicated that fast bowler Monde Zondeki might come into the side in place of injured left-arm spinner Paul Harris for the second Test as part of an all-pace attack, despite the recall of Robin Peterson, another left-armer, for Centurion.
Overnight batsmen Ashraful and Hossain survived the first half hour without any major alarms before Makhaya Ntini switched to bowling around the wicket. His first delivery after the change reared up at Ashraful who could only fend the ball to Neil McKenzie at gully.
It was the start of a disastrous period for Bangladesh as three wickets fell for one run in 11 balls.
Shakib Al Hasan was undone by the pace of Steyn, caught behind as he tried to withdraw his bat, before first innings top scorer Mushfiqur Rahim was run out for nought after a mix-up with Mehrab Hossain.
After that Bangladesh were doomed to an early defeat, with Steyn having Naeem Islam caught behind off a classic fast bowler's away swinger. Mashrafe Mortaza was bowled before Mehrab Hossain and Shahadat Hossain put on 44 for the ninth wicket.
Shahadat, whose stand of 60 with Mushfiqur Rahim was the best of the first innings, again lived dangerously as he made 16 before he was bowled by Steyn.
Jacques Kallis completed South Africa's win when he had last man Muhbubul Alam caught at mid-on.