CHAPTER Ii, SECTION 4 In order to prevent surface disturbance by truck tires while spreading the base course, sandy organic top soil, which acted as a sealer, was placed over the sub-base to an average depth of 0.2 feet. This material, which was also used under the 4-inch surface course of the airstrip shoulders, compacted well and had a CBR value of 30 per cent at optimum moisture. The average gradation of material was as folows: Sieve Size % Passing 36 + 4 + 8 + 16 100 80 77 69 # 50 16 #. 30 38 #+ 100 # 200 10 7 Rock for the base and surface courses was obtained from the southern tip of the island. Crushing operations were started on 30 December 1954. The material was produced in a plant consisting of a primary and secondary crusher, in order to obtain the required 4-inch maximum size aggregate. Base and surface course aggregates were hard, durable mixtures of coral rock and sand, with a high bearing capacity either wet or dry. Placement of the 4-inch base course started on 1 February 1955; compaction was obtained by using sheep’s foot, grid, wobblywheel rollers and a Jobsite-built 45-ton pneumatic roller. The runway strip was completed on 13 March 1955. Average gradations of the base and surface course aggregate were as ollows: A. Base course aggregate Sieve Size % Passing 4 Inch 2 Inch 1 Inch % Inch # 4 # 10 + 40 100 64 49 39 29 25 17 # 200 0-5 # 80 The parking apron, helicopter mat, and the end of the runway from Station 0 to Station 3 received a top coat of approximately 0.2 gallons of bitumuls per square yard. A seal coat, consisting of 0.6 gallons per square yard mixed into beach sand, was then applied to a thickness of % inch. This seal coat was rolled and sanded as necessary. A total of 38,346 gallons of bitumuls was used. On 15 March 1955, an airplane landed on the airstrip for the first time. By 10 April 1955 the buildings were occupied, and on 28 May 1955 all work was completed. The job as completed required 500,000 square yards of site clearing and 53,414 cubic yards of borrow materials. The air operations building, of wood frame construction finished with plywood siding and aluminum roof, was 30’ x 60’ with a 9-2” x 12’-6” lean-to for a latrine, and with a 10’-6” x 10°-6” control tower. The fire-crash station of similar construction was 24’ x 36’, with a vertical clearance of 15 feet. The hangar building, 50’ x 75’ with vertical: clearance of 20 feet, was fini- shed with corrugated aluminum siding and roofing. The California Bearing Ratio Method was used on the airstrip to determine shear strength and bearing capacity. The test locations were uniformly spread throughout the area. A total of 36 tests was made for the base course with Maximum readings of 100 obtained at three locations and with a minimum reading of 38 and the average of all tests being 69. A total of 49 tests was made for the surface course with maximum readings of 100 being obtained at many of the test locations, with a minimum reading of 75 and with the average of all tests being 93. The results of these tests indicated that uniformly high bearing values were obtained. 4 B. Surface course aggregate Sieve Size % Passing 1-% Inch 1 Inch % Inch + 4 + 10 # 40 + 80 # 200 Page 2-158 100 93 63 4} 33 11 4 1 Loose dry unit weight 90.5 ibs./cu. ft. Rodded dry unit weight 101.5 Ibs./cu. ft. Rial edt PR eo ~& ot ie Figure 2-138. Operations BuildingNan Airport