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AR .19:.1975 <br />to lose its adhesiveness as a result of being <br />covered with dust or other foreign material. <br />The tack coat shall be kept free from traffic <br />until the wearing surface is laid. <br />The constituents of the mixture shall • be combined <br />in such proportions as to produce a mixture having <br />at least 1600 lbs. stability at 140° F. as deter- <br />mined by the Hubbard field stability test. The <br />asphaltic concrete mixture shall be dumped into <br />an approved mechanical spreader and immediately <br />spread and struck off to the full width required <br />and to such an appropriate loose depth for each <br />successive course that, when thework is completed, <br />the weight or the mixture required or specific <br />thickness per square yard wi11 be secured. An <br />excess amount of mixture shall be carried ahead <br />of the machine at all times. <br />Hand raking shall be done behind the machine as <br />required. In no case shall the mixture be laid <br />while rain is falling or when there is water on <br />the surface to be covered. The temperature of the <br />mixture at the time of spreading shall be done <br />between 250 and 340 degrees F. No skin patching <br />shall be done. Irregularities shall be cut to <br />the full depth of the layer and replaced with <br />fresh mixture. <br />After spreading the mixture, it shall be rolled <br />immediately. Rolling shall begin at the sides <br />and progress toward the center parallel to the <br />center line of the roadway. The roller shall be <br />of the 5 to 10 ton tandem type. The motion of <br />the roller shall be at all times slow enough to <br />avoid displacement of the mixture. To prevent <br />adhesion of the mixture to the roller, the wheels <br />shall be kept properly moistened, but an excess <br />of water shall not be used. The mixture, after <br />compaction, shall be of the thickness required <br />as specified heretofore. All places damaged by <br />deposit of gasoline or oil shall be removed and <br />replaced as directed by the engineer. Longitudinal <br />joints along the center line of the pavement are <br />permissible. An asphaltic concrete surface shall <br />not be placed on a soil cement base within one <br />month of its completion in order to allow for the <br />formation of hydration cracks, unless otherwise <br />designated by the engineer. <br />10 - <br />BOOK a PAGE153 <br />