The project investor is the State Roads and Bridges Administration of Libya's Transport Ministry.
The project will start on December 21 and should be finished within two years, the company said in a statement.
Viadukt is in talks to carry out other road upgrades in Libya, the company said without elaborating.
Its shares were traded at 710 kuna by 1345 GMT on Monday, up from Friday’s close of 650 kuna. Viadukt is one of the 28 components of the benchmark Crobex share index of the Zagreb bourse.
($=0.7447 euro)