The development of fibrous concrete, first used about 12 years ago, demonstrated marked promise for this application because of its many advantages. Yet there have been enough problems with mixing and placement of fibrous concrete that it has not come into wide use. The main problem has been how to separate the fibers one from the other so they are not batched into the mixer in clumps and then keep them separate during mixing to prevent balling of the fibers in the concrete. Even when fibers have been carefully separated before batching, clumps of fibers completely or partially uncoated with cement paste have often been found in the concrete. A full scale paving overlay test project was finally undertaken in 1973 under the sponsorship of Greene County in Iowa in cooperation with a large number of materials and equipment manufacturers. Most mixes ranged from a cement content of 600 pounds and fiber content of 100 pounds to 750 pounds of cement and 160 pounds of fiber. Mixes contained either a retarding or normal setting formulation of a polymer type water-reducing admixture. Aggregates were three-eighths of an inch maximum size pea gravel and sand. Despite the effectiveness of the vibrating screen in separating the individual fibers, there were some occurrences of fiber balls, most numerous in the mixes containing two and one-half inch long fibers. These balls had to be hand picked out of the concrete. When they were not discovered until after the slipform paver had passed over the concrete the holes in the surface had to be filled. Since the fibers had been separated before going into the drum the balls in the concrete discharged from the drum into the concrete trucks must have developed during the charging or mixing operations. When the time used to charge the fibers was extended, however, to prevent introducing large concentrations at any one time the results were very encouraging. This was accomplished by a revised procedure. The practice of depositing the entire amount of fibers onto the aggregates was terminated. Instead, the practice was begun of introducing the fibers slowly into the drum throughout the entire charging cycle, even continuing the addition beyond the time when all the other concrete ingredients were in the drum.