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Show MRU Building Modern Roads In spite of the reaction againBt macadam load construction, yet probably pro-bably moro money Is stilt being put Into this typo of construction than Into any other. But unless done In tho most thorough way, with tho closest attention to detail, It Is good only for light traffic. Heavy trucking truck-ing and fast running automobiles will broak It down In a season. The under earth must be thoroughly thorough-ly rolled when wet until soft spots are packed down. If any weak spot Is left, the crushed stono will soon drop Into It and causo holes. Side ditches and drains must be arranged arrang-ed to carry oft moisture. A firm form of rock must be chosen. cho-sen. Granite Is too coarse, limestone tco soft, though a small quantity of limestone is ofton mixed with harder hard-er rock and Is useful In giving a cementing ce-menting quality. Trap rock, dlabeie, basalt, and porphyry rocks aro the most favored. The crushed rock should bo laid In a clean condition, so that the interstices will not bo filled up, by dirt that will wash down later. Tho rock should pack togother Into the smallest possible spaco. The standard construction of macadam ma-cadam road requires four to eight Inches of coarse rock for the base, and two to four Inches smaller su"-faclng su"-faclng rock The rolling must be very thoroughs There Is a tendency for the rolling to push the surface up Into the form of waves, and some authorities urge rolling ''diagonally to overcome this.. The road will hold only If the rock pieces, which should be sharp, are pressed down so as to Interlock mechanically with each other, thus constituting a solid fabric. The standard binders outside of the bituminous materials, are fine stone screenings and water, sand and water, limestone screenings and water, wa-ter, and clay and water. |