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Show Sand-Clay And Gravel Roads And Their Construction By Manen Allen AH highway types are in a stato of evolution nnd it is likely that many years will pnss before we shall bo able to design, build, and uso each so as to sccuro tho best osulte. Tho types that are In general use are, earth, sand clay, gravel, macadam, concreto and block. Tho sand clay road is made uso of whero the materials are available for this type. Like tho earth road it will not stand up under heavy traflic through cither a prolonged dry spell or a prolonged wet spell. It is a little lit-tle moro durable however; than tho earth road, but not so good as well built gravel road. The samo precautions precau-tions in the matter of drainage should bo taken as in the case of the earth road. All types are alike in this regard, re-gard, and in order to secure tho best results, thoroughly drainage must first be provided. The said clay road is ono composed of a combination in the proportions of one part of clay and three parts of sand. Tho proportions propor-tions must bo varied to fit the character char-acter of the materials. Usually the best clay to use Is that which is the stickiest, and a graded sand is usually usual-ly better than sand or uniform sized grains and sharp sand is, better than sand of round grains. Tho Band and clay are first mixed dry to secure n 'uniform mixture. It is then thoroughly thorough-ly wetted cither by sprinkling or rain, mixed again, shaped by tho road grader, rolled, nnd put Into' finished shape by tho drag. Tho mixing Is usually dono by a harrow and a disk harrow followed by a straight or a spike tooth harrow gives good results. re-sults. The crown of a complotcd sand clay road should bo about thrco quarters ot an Inch to the foot. Much better results will bo obtained If tho subgrade Is thoroughly consolidated by rolling beforo placing tho sand clay mixture. ThiB is true of any typo of road, even thnt ot earth. It is not possible by ordinary methods of rolling to consolidate a thickness of more than about Ave to six inches inch-es of material at n tlmo. Tho maintenance of tho sand clay road Is performed in the same manner man-ner as tor tho earth road, except that for somo tlmo after construction tho surface must bo carefully Inspected to determine whether the proper proportions pro-portions of sand and clay wero useu or the mixing well dono. If there n pears to bo a surpVus of sand on tho surface, It should receive a thin covering cov-ering of dry clay, and, if sticky, a llttlo coarao sand should be uniformly uniform-ly applied. The cost ot maintaining a sand clay road should not exceed that of an earth road. In many localities gravel Is abundant abun-dant nnd may bo uiscd to advantage In road construction. Par moderate traflic, tho gravel road gives excellent excel-lent results. The gravel for tho purpose pur-pose should bo hnrd and tough and contain approximately 1G per cent of binding material In tho shapo of llmo, clay, or loam, tho preference being In tho order given. Tho gravel should bo nngular rather than smoothly rounded or spherical nnd for this reason rea-son pit gravel Is usually (superior to creek or river gravel. Pit gravel will usually contain a larger proportion ot binding material than stream gravo. Satisfactory results are dllllcult to obtain without screening. The per centage of flno material is quito often of-ten execsstvo in gravel deposits and unless screened a road formed of it will bo likely to break up in spots. Tho gravel road should bo constructed construct-ed in two courses. Tho bottom course should ho about six inches in thickness thick-ness attor consolidation, and for it tho larger sizes used, from 1 1-2 to 2 1-2 Inches, This should bo ovenly spread, rolled, filled with finer material ma-terial containing about 15 jior cent of binding material, nnd rolled until solid, after which tho top courso of about four inches should bo put on. Tho top couiso should bo composed of matorlnl from 3-4 to 1 1-4 Inches. It should bo rolled lightly at first, then filled with flno material containing contain-ing amout 15 per cent of binding material, ma-terial, rolled, sprinkled, and rolled again, until solid and with nil voids filled. After tho road has been woll consolidated, It should bo coverod with a thin layer uf course sand, at-tci at-tci which it Is ready for traflic. It Is f'llly as important to J oil tho sub grado for a gravel road us for an earth or a sand clay road, Tho malntonanco of a gravel road, if not treated with bituminous material materi-al is about tho same as for en earth road. If tho gravel road Is subjected to a moderate amount ot automobile traffic, It should be given n surface application of bituminous material, about 12. gallon to tho square yard, applied hot, under pressure. Previous to this application, the road should be thoroughly swept to remove all fine material and immediately after application, a thjn coating of fine gravel or coarse sand, should bo put on. i |