An experimental road of no-fines concrete was constructed in England after the use of this material for parking areas in Europe and minor roads in Switzerland had proven successful. The English road has performed satisfactorily for the past few years. Some 700 square yards of paving were placed in the 600 foot long section, which lies on an embankment 8 feet above ground level. One of the advantages offered by no-fines concrete is its excellent drainage properties. The open texture enables water to immediately percolate away form the surface of the slab. Spray thrown up by moving vehicles in wet weather is negligible. The surface dries quickly and skidding is decreased. Frost damage is low because of the number of voids present, usually 40 percent of the total volume. A no-fines concrete surfacing is placed monolithically with a structural base slab of normal dense concrete. For the British road, the base slab was 8 inches thick, reinforced with a single layer of mesh. Surfacing was 2 inches thick. The sub-base was an 8-inch layer of 2-inch graded dry limestone covered with a water-proof underlay of polyethylene sheet. The mix can be expected to have a 28 day strength of 2000 psi. Only sufficient water should be added to ensure that each piece of aggregate is coated with a thin layer of grout. A moisture content of between 6 and 7 percent meets this requirement. Compaction and surface finishing are best executed semi-manually by rolling a steel pipe over the spread mix. A 12 inch diameter pipe with a weight of at least 30 pounds per foot is recommended. Six passes of the pipe are sufficient to compact the no-fines concrete to level. After finishing, the surface of the road is cured by covering it with a polyethylene sheet for at least 7 days.
