* Diluted headline EPS at 67.5 cents vs 98.2 cents
* Order book at 46 bln rand vs 37 bln rand (Adds details)
JOHANNESBURG, March 14 (Reuters) - South Africa's biggest construction group Aveng reported a 31 decline in first-half profit, hit by contract execution problems in Australia and an industry-wide slump at home.
Aveng, which also operates in the Middle East, said diluted headline earnings per share totalled 67.5 cents in the six months to end-December compared with 98.2 a year earlier.
Headline EPS, the main profit measure in South Africa, strips out certain one-time items.
South African construction firms avoided the 2008 global building slump thanks to the construction boom in the run-up to the 2010 soccer World Cup.
But they are now struggling to replenish their order books as the South Africa government delays rolling out its nearly 1 trillion rand ($132.24 billion) infrastructure investment package.
Aveng said its two-year order book rose by 24 percent to 46 billion rand in the past six months, underpinned by strong demand from mining and energy sectors in Australia.
Shares in the company have gained about 11 percent so far this year, outpacing a 5 percent gain the JSE All-share index . ($1 = 7.5619 South African rand) (Reporting by Tiisetso Motsoeneng; editing by David Dolan)