The cash will be found from deeper savings of 2% demanded by the Chancellor across a string of Whitehall departments.
Extra infrastructure spending announcements will again be at the heart of economic stimulus measures in the Budget.
But the construction industry will be wary of former announcements dressed-up as new spending.
Contractors will also be demanding proper timetables for projects which have been conspicuously absent for many schemes since the Government launched its first National Infrastructure Plan in 2010.
One contractor told the Enquirer: “Nobody stops in our office to watch the Budget because year-after-year it is just more hot air and points scoring.
“It’s a political sideshow rather than a genuine source of work and most of the projects mentioned have been around for years or have such a vague timetable there’s little to get excited about on the day.”
The Enquirer will be bringing concise and focused coverage of the important announcements affecting construction as they happen today.