South Africa's four-pronged pace attack struggled all day trying to wrest the initiative, but an unresponsive wicket has stood between them and a breakthrough for 32 minutes over six hours. It was only the 10th time in 1,356 Tests that a wicket had not fallen in a full day's play.
Blewett has reached a career-best 153, his third Test century in 14 outings since making his debut against England in Adelaide in 1994-95. Waugh, hampered after the tea break by a muscle strain in his left leg, preferred to play second fiddle to his junior partner but in the process reached his 12th century in 87 Tests. His 136 has come from 302 balls in 400 minutes with 19 fours.
Blewett reached his century in the penultimate over before tea with his 17th boundary when he drove Jacques Kallis and in the process brought up the 200 partnership.
The stand is already an Australian record Test partnership for any wicket against South Africa, eclipsing the 45-year-old mark of 275 between Colin McDonald (154) and Lindsay Hassett (163) in Adelaide in 1952-53. The only other Australians to achieve the feat of batting throughout a full day's Test play were Bill Lawry and Bob Simpson against the West Indies in Bridgetown (1964-65) and Mark Taylor and Geoff Marsh against England at Trent Bridge (1989).
Blewett made the South Africans pay dearly for repeatedly pitching short on a surface that lacked bounce, as he cut, pulled and hooked most of the 26 boundaries with his 156 coming off 321 balls.
Waugh enjoyed the luxury of a reprieve on 44, when a sharp catch off a Lance Klusener bouncer flew past the outstretched hands of South Africa's wicketkeeper Dave Richardson with the score on 265. The only bowler to command some respect was the unorthodox left-arm spinner Paul Adams who bowled 43 well controlled overs, conceding 130 runs.
The stand is only the second above 300 for any wicket in Test cricket in South Africa, following Len Hutton and Cyril Washbrook's 359-run partnership for the first wicket, also in in Johannesburg, but at Ellis Park, in 1948- 49.
Third day; South africa won toss
SOUTH AFRICA - First innings 302 (W J Cronje 76, J Richardson 72no).
AUSTRALIA - First innings
(Overnight 191 for 4)
S R Waugh not out 137
G S Blewett not out 156
Extras (lb9, nb7, w3) 19
Total (for 4) 479
To bat: M G Bevan, I A Healy, S K Warne, J N Gillespie, G D McGrath
Bowling: Donald 29-6-113-2 (w2); Pollock 26-3-82-2 (nb7); Klusener 29- 7-91-0; Kallis 15-4-35-0 (w1); Adams 43-4-130-0; Cronje 10-3-19-0.
Umpires: C J Mitchley and S Venkataraghavan (Ind).