City roads and pavements suited to cities of moderate size. . will remain firm and smoothwhen the broken stone is spread and rolled upon it, sothat the fragments shall not work down into the sub-grade, nor the material of the subgrade w^ork up amongthe fragments, under the action of the roller. Thestone thus saved is worth more than the cost of thisspecial work. Remove Stones.—Stones or rocks lying within halfa foot of the top of the subgrade, and which are largerthan six inches, should be removed, lest they serve asanvils on which traffic will crush the road-metal. QUALITY OF ROCK TO BE BROKE
City roads and pavements suited to cities of moderate size. . will remain firm and smoothwhen the broken stone is spread and rolled upon it, sothat the fragments shall not work down into the sub-grade, nor the material of the subgrade w^ork up amongthe fragments, under the action of the roller. Thestone thus saved is worth more than the cost of thisspecial work. Remove Stones.—Stones or rocks lying within halfa foot of the top of the subgrade, and which are largerthan six inches, should be removed, lest they serve asanvils on which traffic will crush the road-metal. QUALITY OF ROCK TO BE BROKEN. The rock should be hard, tough, durable and uni-form in character, fracturing with a toothed surface andshowing a tendency to break into cubes rather thaninto flakes. This latter pecularity occurs with somerocks which would otherwise be good, and in one casewas found to be the direct result of excessive use ofdynamite in the quarry. 170 CRUSllINC. The rock should ]ia\c a compositioii wliicli cementswlieii wet and rolled, and should come clean from the. Tailings larger than ^ inrheto return to cruslirr. Wagon loading c rushedsloiie from Inn. Screens and bins for screeningsand three sizes of stones. Cart dumping rork from r|narr>onto iilallorni over crusher, Crnslier prndncina 135 euliicj(ls. crushed stone per day. CRUSHIXCi AND SCREEXIXG ROCK. quarry to the crusher. A softer rock may be crushedfor the base course, and its screenings will usually forma good filler for it. (See page i6i.) CRUSHING. The crusher should be placed where the rock willpass down from the ledge through the crusher andthrough the bins into the wagons, and then down-hillto the work. The crusher should be set to producethe largest size specified, and the whole j^roduct shouldthen be screened through a series of three revolving 171 CITY ROADS AND PAVEMENTS. screens or cylinders pierced with circular holes, set ona slope so that the material passes slowly as the screensrevolve into separate bins for ea
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectstreets, bookyear1902
