1925 (#1403-1607) - Laserfiche WebLink

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lotions per minute. The hot coarse aggregate and sand, and the cold stone dust shall be placed in the mixer and thoroughly mixed for not less than fifteen (15) seconds, after which the hot asphalt cement shall be added and the whole mixed for at least one (1) minute or longer if necessary to produce a homogeneous mixture, in which all particles of the mineral aggregate are uniformly coated. Time shall be allowed for charging the mixer, but in no case shall the time be less than ten (lO) seconds. An accurate time piece shall be provided at the mixer. Mixer paddles shall be replaced when worn to such length that they cannot reach all of the material in the bottom of the mixer. SRCTION 5. TRANSPORTATION OF MIXTURE. The asphaltic concrete wearing surface shall be transported from the paving plant to the work in tight vehicles, previously cleaned of all foreign material and shall be covered with canvas or other suitable material, of sul~clent s/ze to protect it from weather conditions. No loads shall he sent out so late in the day as to interefere with spreading and compacting the mixture during the daylight. Each load on reaching its destination, shall have a temperature of not less than two hundred fifty (250°) degrees Fahrenheit. SECTION 6. LAYING. (a) Prior to the arrival of the surface course mixture on the work the prepared base shall be cleaned of all loose and foreign materials. The mixture shall be placed only upon a base which is dry or at least free from standing water and only when weather conditions are suitable. Upon arrival on the work, it shall be dumped either inside or outside of the area on which it is to be spread. Every portion of the loa. d shall he turned with hot shovels. It shall be evenly raked to correct depth with hot rakes, the teeth of the rakes extending through the total depth of wearing surface mixture. Whenever the workmen step on the mixture, after spreading, the foot prints shall be loosened to their full depth with the rakes. (b) Contact surfaces of curbs, gutters, manholes, etc., shall be painted with a thin uniform coating of hot asphalt cement or asphalt cement dissolved in naphtha, just before the surface mixture is placed against them. SECTION 7. ROLLING. Immediately after the wearlog surface mixture has been spread and raked, initial compression shall be attained by the use of a power driven tandem roller weighln~ not less than eight (8) tons. While thc wearing surface is still hot and plastic, it shall -be rolled with a twelve (12) ton three wheel power roller, having a weight of not less than four hundred (400) pounds per linear inch of tire width, until the surface is unyleldlnf and true to grade and cro~-scctinn. Rolling shall start longitudinally at the sldcs and proceed tuward the center o1 the pavement, overlapping on succcsslve trips by at least one-half (~) the tire width of the roller. The pavement shall then be subjected to diagonal rolling in two directions, the second diagonal rolling crossing the lines of the lfrst. If thc width of the pavement permits, it shall, in addition, be rolled at right an~les to the center llne. ]Rolling shall be contlnucd until all roller marks arc eliminated. The motion of the roller shall at all times be slow, to avoid displacement of the hot mixture and any displacements OCCUfflng as a result of reversln~ the direction 'of the roller, or by any other cause, shall at once be corrected by the ~se of rakes and by the addition of fresh mixture when l~equlred. Rolling shall proceed at an average rate of not to exceed two hundred (200) square yards per hour per roller and shall continue until no further compression is possible. The specific gravlty of the material after rolling shall be not less than two and fifteen hundredths (ZI$). To prevent adhesion of the surface mixture to the roller, the wheels shall be kept properly moistened, but excess o{ either water or oil will not be permitted. (b) Along curbs, headers and similar structures; and at all places not accessible to