quite incapable of serving the expanding commercial traffic using Skymasters and Constellations. It was finally decided that sufficient strength could be obtained by rebuilding the worst of the Japanese work with sound foundations and good concrete, then sheeting the runways with a 31″ thick flexible surface. On the grounds of economy and time the resurfacing was reduced to a 150 feet wide strip flanked on either side by a 20 feet wide feather strip tapering in thickness from 31″ to 4″. This work on the two runways, 4,600 feet and 4,800 feet respectively, was let on contract to a British firm. As far as possible mechanical methods were used and the contractors were restricted to the four months of the year prior to the rain commencing in May. After correcting the depressions the existing concrete runways were given a tack coat by a pressure sprayer. The 21″ thick base coat was of open texture bituminous macadam of 11⁄2″ max. granite aggregate mixed in a Barber-Greene central mixing plant and spread and consolidated by a paving machine of the same make. The 1″ wearing coat consisted of asphaltic concrete ″ max. size aggregate with granite flour substituted for the more usual Portland cement filler mixed and spread by the same plant.
149. Concurrently with the above work a 50 feet wide taxi track parallel to the main runway was completed. Construction was of a 41⁄2″ consolidated thickness of two coat bituminous macadam on an 18″ thick bed of hardcore and granite sets.
150. Materials testing laboratory:- The work carried out and results achieved by this comparatively new section of the department more than justified its creation. From a small beginning a year earlier, with 150-ton Avery compression machine and some B.S. sieves housed in an old wooden shed re-erected at the Port Works Depôt, the arrival of equipment ordered on indent in 1947 was the opportunity to demonstrate the necessity for its being. Equipment restricted work to the testing of cements and concrete, bituminous products and soil foundations. The staff of the laboratory-superintendent and two assistants-made some 3,400 tests during the year, On the contract for the construction of the 1,400' x 100' nullah at Kuntong, the design of concrete mixes for the invert slabs with subsequent field control pushed the quality of this vibrated 1:6 mix to the point when some of the 6″ cubes were beyond the capacity of the compression machine (9,333 lbs. per sq. in.) at 7 days. As a direct result of this, on the next sea-wall contract at North Point the mix for the precast foundation blocks was reduced from 1:6 to 1:8 with a consequent valuable saving in Portland cement. On this work with a 3″ max. aggregate the 1:8 mix gave a steady 7,000 lbs. per sq. in. at 28 days and on occasions the strength was as high as 9,000 lbs. per sq. in. With cement costing $170.00 (£10-12-6d.) per ton the saving in cement alone by using the controlled leaner mix represents a direct saving of approximately $40,800.00 (£2,550) on the 4,000 cub. yards of
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