Show UTAH ROCK ASPHALT ON SALT LAKE STREETS by L 0 HOWARD M E most of the rock asphalt comes to salt lake in box cars and is unloaded in wheelbarrows by two men who dump it along a ion long platform men with sledges there brcak it down from pieces one foot in any ally kind of a jaw crusher the ground material is picked up by a bucket elevator discharged to a bin and drawn off into wa wagons golis by which it is hauled to the job owing to the tendency of the rock to mere ly deform instead of cracking it is necessary on warm days to chill it with water when crushing the material is distributed along the street ahead of the work and as paving proceeds is shoveled up in one ton lots into a charging hopper of a koering heater where it is subjected to an oil flame under blast As shown in the illustrations this heat er consists of a revolving cylinder in which the material is thoroughly mixed and heated the specifications of the city of salt lake call for a heat between an and d degrees fahrenheit on the day when the observation was made the temperature pera ture of the batch shortly after discharge varied from to degrees atter after eight minutes of heat only four minutes was used at first the cylinder dis dig f 77 7 7 hand breaking and crushing rock asphalt photo by L 0 howard charging the koering heater photo by L 0 howard diameter to a size which will go into a no 2 williams crusher where it is pulverized A gang of twelve men prepares the rock and feeds it to the because bebau se of the nature of the rock it will pack in charges the inspector then takes a temperature pera ture reading by inserting a thermometer in the top of the pile the question has been raised whether this temperature as read fulfills specifications of course it A ka 17 Z M owl hopper of koering heater and final rolling and charge blast pipe showing tho the koering heater discharging men spreading and rolling asphalt photo by L 0 howard photo by L 0 howard is evident that in heating by a direct dire ct flame some of the material is heated to a very much higher temperature than other portions and that the temperature as taken can only be an average dense volumes of smoke roll out of the cylinder indicating the combustion of the valuable oils at this high temperature this may have a great deal to do with killing the resiliency of the completed pavement for it is the oil which gives resilience and the natural asphalt will not well stand the high temperature of the blast A glance at the series of photographs shows the successive steps spreading the asphalt sand rolling with a hot hand roller and finally after cement has been sprinkled over the surface the rolling with a 7 ton road roller the pavement as completed has a six inch concrete base and a two inch asphalt surface the above is a description of the work now going on on seventh east street salt lake in laying the pavement a crew of about a dozen men is employed but with the intermittent operation of the heater they have many idle moments the present method of handling involves a great deal of hand labor and suggestions have been advanced whereby a heater which discharges continuously aou would d be provided with an efficient crushing plant and continuous heating the cost of laying the pavement could be cut down largely one ton of the asphalt sand lays about twelve square yards of pavement suggested process one way suggested by which the cost of laying the pavement could be cut down and the heating safeguarded embodies a compact plant for crushing and heating the crude material would be unloaded by hand and fed to rolls thus reducing hand labor the roll product going to WilliaJ Willi aims ms crushers after crushing the sand asphalt would be elevated to a long cylindrical steam jacketed heater where superheated super heated steam would provide a readily controlled angi and uniform heat which would prevent all danger of burning As the men become more familiar with the utah asphalt better results are being obtained increasing the length of time of heating has already resulted in a better pavement pavement wears well A glance at the records shows that the pavements laid with natural rock asphalt have excellent records here are a few taken from the files in the city engineers office salt lake ladd city west temple from south temple to fourth south laid with california natural rock asphalt in 1893 surface repaired during thirteen years hard use 49 4 9 square yards at a cost of after nineteen years use less than fifteen per c ent cent has been replaced state street from south temple to fourth south laid with california natural rock asphalt in 1892 after fourteen years heavy use repairs amounted to 1386 69 6 9 cost of less square yards at a than fifteen per cent had been replaced after twenty years of use second south from west temple to first west laid in 1896 with utah natural rock asphalt the first ten years cost for repairs was around city and county Buil building dint g laid with utah natural rock asphalt in 1905 only two and one half to three inches thick with dirt only for foundation has had bad no repairs in seven years and is apparently in first class condition most people are aware that asphalt pavements are ordinarily composed of several grades of sand which when mixed shall be compact and a binding of asphaltum mixed hot with the sand it is stated that the utah rock asphalt is by nature a very satisfactory mixture containing the proper of sand and the proper amount of bitumen and that it is rich in which gives it life and resli resiliency ency so resilient is it when properly laid that it ma makes keEran an ideal material for grade crossings in place of lumber and stands the jar of heavy trains without cracking off when laid next to street car tracks A it springs with the track quite different from some of the asphalt pavements in ia salt lake which were laid with oil residue for instance a glance at the pavement along main street next to the ear car tracks shows that it is badly broken it lacked resiliency the opinion is generally expressed that the utah rock asphalt makes a more resilient pavement one having more life and a longer life than that where oil as phalas are used A representative of the united states office of public roads was so str strongly ongy impressed in with the he possibilities of this utah asphalt that in to the commissioners ners of salt lake county materials for the model roads to be built the only surfacing considered was utah rock asphalt it is probable that the said commissioners ners will lay a stretch of road in four sections all faced with utah rock asphalt and having different bases such as concrete crushed gravel and slag |