This weekend, Boston’s Logan International Airport expects to nearly finish the first runway in the nation repaved with an environmentally friendly material called warm-mix asphalt. The asphalt is heated to a lower temperature than normal, burning less fuel and emitting less carbon. Airport operator Massport says on this project that means a cut of 4,000 tons of carbon dioxide and 400,000 gallons of diesel fuel. The last batch of the asphalt will be laid on Runway 9/27 this weekend, though the runway won’t reopen until later this year. The $12.5 million project began in July. Some European airports have used warm-mix asphalt, but it had to pass Federal Aviation Administration testing before Logan could use it.