Macmahon announced late on Monday it had rejected the buy-out of its construction business because Sembawang had failed to provide information requested by Macmahon's board and that there was an "uncertainty and risk" associated with the takeover.
It also accused Sembawang of "inconsistent conduct, including its breach or normal commercial confidentiality".
Macmahon is looking to become a dedicated full service mining contractor, and in December struck a $20 million deal with its biggest shareholder Leighton to sell its construction projects, including equipment and staff, with the exception of some assets and its rail business.
The first offer - to buy all of Macmahon's construction businesses - lapsed over the weekend.
But the second offer - to replicate the deal with Leighton but for an additional $5 million - remained in play.
"Sembawang wishes to proceed with the transaction on the exact same terms as those entered into with Leighton, however, Sembawang is offering a further $5 million as purchase consideration," it said in a letter to Macmahon's board.