Stephen Stepanian Inventor of truck-mounted concrete mixer Stephen Stepanian’s invention of the truck-mounted concrete mixer revolutionized the construction industry across the globe. As noted by Robert Garbini, president of the National Ready Mixed Concrete Association, Stepanian’s 1916 vision of a truck-mounted, revolving drum mixer “was the single greatest innovation for concrete construction during the 20th century. His genius and foresight have led to what is now the most recognizable piece of specialty equipment in construction.