Martin Marietta Materials Inc., which produces construction aggregates, made an unsolicited $5 billion offer to buy rival Vulcan Materials Co. to create the global leader in the industry, Reuters reported. In a letter to Vulcan CEO Donald James, Martin Marietta offered 0.5 share of its stock for each Vulcan share. As of Friday’s close, the bid was worth $36.69 a share, a 9 percent premium to Vulcan’s closing price of $33.55. Shares of both companies surged after the bid was announced today, with Vulcan jumping 25 percent to $41.97, well above the bid’s value. Martin Marietta shares were up 5.9 percent at $77.70. Martin Marietta said the deal would create cost savings of $200 million to $250 million per year and higher dividends for Vulcan shareholders.