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Show BRICK OR BLOCK AND FLEXIBLE FILLER MAKES BEST PAVEMENT V By PREVOSI Ml BIJARP. Former Chh'f. Division of Tests, I". 8 Bureau of Public Roads. It is an almost Ineomprehenslh'e fact thru in building our state and counts highway systems more weigh' has been attached to paving practice in our cities where many of the problems prob-lems of meeilng heavy and varied traffic conditions were successfullv poir,i before such conditions made their appearance o ncountry and suburban su-burban highways In our cities the original water-bound water-bound macadam nnd gr.ivei roaijil have for the most part given way to higher types of construction until today to-day they constitute an avernge of onlv about 26 per cent of the total yard-age. yard-age. The three most widely used city types are asphalt, brick and stone block. If we eliminate the water-bound water-bound pavements we find that of the higher city types asphalt constitutes about 55 per cent, brick about 19 pet-cent pet-cent and stone block about 14 per cent, giving a total of 88 per cent for those three types. in connection with the preponderance preponder-ance of asphalt pavements the present pres-ent trend of paring practice in the construction of modern brick and stone block pavements is of consid-erable consid-erable significance as It recognize a principle which Just now is attracting a great deal of attention on the part of our highway engineers I refer to the use of a ilexlble Joint filler for brick and block pavements as against the rigid grout fillers formerly to !'"'"'"'""'""""""" popular Such cities as Xw York and Philadelphia arn now uslnK asphalt as-phalt fillers for heavy traffic streers paved with stone block and the Paving Pav-ing Brick Manufacturers association is preferentially recommending asphalt as a filler for If type of pavemen' The reason for this lies in the fact that absolute rigidity in a pavemehl structure is not a desirable charac-i terlstic. . Service results and comprehensive field tests conducted by the United St itcs bureau of public roads have demonstrated that th'- brick or blpcK pavement with a flexible filler is I more resistant to traffic than with a ri;ld filler. A certain degree of Flexibility Flexi-bility Is highly advantageous in mep- inp the heavy Impact of modern traffic. traf-fic. FLEXIBILITY NEEDED. B.UOb flexibility is an Inherent characteristic char-acteristic of bituminous pavomcnls and is Imparted to brick and block pavements when asphalt is used as a Joint filler. While in certain section'; of the country the experience of our pities appears to have been overlooked. It is a fact that the flexible or semi-flexible types of construction predominate In our country roads and If we consider con-sider the total mileage of state, coun- ty and municipal highways higher than jrravel and macadam consider-1 ably more than 50 per ent may be so classed. By reducinK all yardage to a basis of sixteen feet width, we estimate that at least 4ft per cent of! the mileage of the ir.Khr tvpes oi . . . .i.. -. . .. . i'.i.i.i i - ni t ui i hit iiui-iiiiAra US" l halt types. The latest available information in-formation indicates ihat last year the total area of asphalt pavements constructed con-structed approximated 88,000,000 Square yards, which was greater than for any other tpo Mi.st of the stone block pavements constructed that year were filled with bituminous mi-tcrlal mi-tcrlal ard about GO per cent of th" brick pavements were similarly tilled. There are, it Is true, many advocates advo-cates of the all rigid monolithic types of construction and in certain se -Hons such pavements predominated In last year's work This is not true, however, of the country, as a who?'' Those who favor rigid construction hai. constantly been obliged to in-crsase in-crsase the masslvenesa of design of sulIi pavements and also the amount of reinforcement in an endeavor successfully suc-cessfully to meet the destructive action ac-tion of heavy traffic, while those who have favored the semi-f lexlblo c-flexible c-flexible types have. In general, found that the old standards or flexible ,tpes have proven eatisfactoty. The all flexible types, surh as the hlaik buse pavements so extensively adopted in our far western states appear to be the most highly resistant per inch of lotal thilkncss. and may therefore be sunsidered the leaft massive and in this respert tho most efficient of the heavy traffic pavements. TRAFFIC IMPACT. It is probable that such pavemen's will be given considerable attention in the 1922 program of some of our eastern states owing to the remark-ably remark-ably satisfactory results obtained over a long period of years in the west. Many r.f these pavements are six in hs or less in total thickness. What we have learned In the last few years about the destructive effect ef-fect of traffic Impact and the resistance resist-ance to Impact offered by seml-flex-lble and flexible highway structures has a peculiar significance in connection connec-tion with a great economic problem, hat of connervlng our investment in old roads, particularly gravel and macadam, when it becomes necessary to adopt a higher type of wearing shrface. Prior to the carofhl Investigation Inves-tigation of this Important subject there existed a marked and growing tendency to discredit the use of old gravel and macadam roads for foundations foun-dations for the higher types and this in spite of many remarkahle service records of macadam foundations For example, in the city of New York a number of the most heavily traveled streets were constructed years ago on macadam foundations and some are still glvlnc satisfactory service In 1890 Broadway, between Fifty-ninth Fifty-ninth anil Seventy-ninth streets, was paved with asphalt over an old macadam ma-cadam base and for 2 2 years paw good service, lis replacement at the end of this period was largely due to subway excavations. Seventy-second street paved in a similar manner, il-o il-o pave 22 years of service under Increasingly severe traffic conditions and the same is true for a 19-year period for Fifth avenue between 110th and 120th streets. Lenox avenue ave-nue between 110th and 124th streets was surfaced with asphalt over old macadam in ino4 and is still giving good service. Tho cost of maintaining maintain-ing this section in 1919 fourteen years after construction was only 1 per cent, certainly a remarkable record rec-ord Many similar cases might be cited from various localities, ROLLED STONE BASES. A recent Investigation of rolled stone bases for brick pavements was conducted by the U. S. bureau of public pub-lic roads, and A. T. Goldbeck of that bureau his published a very favorable report on this type of brick construction construc-tion All in all It appears that 'he old waterbound base is again coming into its own. ne reason for much of the former dlssatisfai tion for such bases was undoubtedly un-doubtedly due to a fault which has been all too prevalent In the rapid development of our country highwiy systems. I refer to inadequate preparation" prep-aration" and dralnace nf our sub-l sub-l grades, fostered by the false Idea that the cost for such work w.juld make the total cost prohibitive, rolitlcal pressure nnd popular demand for the rapid construction and the greatest possible mileage of lmproed roads for a given amount of money has been to a great extent, responsible for this state of affairs. However, this subject is receding an increasing increas-ing amount of attention and is be-, ing most carefully investigated by the; government and a number of public service bodies and technical societies, the work of the various organizations bMnj? correlated by the advisory board on highway research of the natlonjl research council. |