Concrete Roads.

Waikato Independent, Volume XVIII, Issue 1440, 30 April 1914, Page 6

Concrete Roads.

m (By W. G. Care.) HfyA.ll over New Zealand, and, one Blight say, * throughout the civilised Hforld, one of the gr atest problems fronting engineers, Governments, Hind local bodies todav is, how t - cope Byith' the increasing traffic in their ■roads and streets. ■ i ( Bf>fe£eriK?eh]fs’have been made with hundreds of different forms of 'con-' ■' siraction but one only ha - ti look in'o ' the cost of maintenance in s me of the v large centres to realise that the per- • feet road has not yet been evolved, j In America where many engineers have been specially educated ior this ’ wrk and where lens of too s: ads of 'V dollars have been spent in experiments all sorts they, do not appear to have much headway, for we read that (.pin IQI2 every miie of r<ad in-New York ’State cost 826 dollars to n ahi'V tain. •••; •. ' .During the last few yea s the traffic U .on t’’e roads has-not only increased but ■ ; it has to a very large extent changed

fr.-'iCharacter so much that roads v/hich K- a few years ago often d reasonable re-.fc.-.-si lance to wear and tear,' have -.gone g’l to pieces unde - the altered emotions. Under t- e old conditions a awil or macadam road re-made itself a great exteht, some of the sand be-??J-'tween t e stones would be disturbed fe?by tfie horse(,oofs and by steel-tired Ipwh'eels, but the action-of those wheels ■intended to grind more binder off the pfhton is and with : he' help of ram stuie ■fibroin the atmosphere to re-bind and jh/render the surface waterproof. With %;the advent of fast driven, .motor all this had I e'en 'altered.; . ' k is con eilded by some - peoTe ' .that m >tor traffic does very Tittle 'damage to' the roads, but it is- only to. sup ose th -t , to. get ,!=peCd.vou must,have power, and to T get power y u must l ave somethin;; Uto push ag inst, so that the. rear ’T, delving wheels of a. car weighing 35 -i. which is being driven T ioi, miles ah hour riiUft be gripping f ' The road fairly hard, it Driven'slowly a car has no more effect on a macadam road than a 1; horse and cart, perhaps not so much, - but a/-, the .speed, increa es the suc--tion set up by the wheels draws the Binding materials from between the , ..stones, kicks th m up in a cloud of - (Tost and scatters them beyond rei When th ’ ■ urfacc has been loosened I this \vay rain penetrates, gets •the foundation' and very* soon the begins to break up. *?he-e remarks apply not only to jVsan 1 and gravel roads but to the great 1; rani rifcv of the more expensive hie--U-heds. In England and America it ' ha-.bo n fount that even wood blocks aie loosened Under the strain of fast > mot r traffic. . o It is these altered conditions that *bwe have to consider in any road-r-ihakj g schema of today. The days .fThaye gone when, a sand road, would ca yvj the traffic economically. ,We must have something more lasting in the .towns .at Jeast, a- d before 'very Kjjong ,qn the .main country roads as well. Inferring to arrive at a conclusion as the b st method to adop , the first » com-ide ation*is' one of cost. In ar--riving at the cost we - m st consider, ' -not on; first coot but the probable life of Tie work and cost of rnaintenan ife. ' This latter is pa ticulavlV .-important in view or the'fact that in most cases-' ?•'. work of this'sort has to be done with borrowtM money, and we have to be k/'carcful .that we do not find ourselves ■- with toe d bt and without the ro ml ■;fo,> winh it was incurred; or that we rho not discover' that we fiave »*aie [Ty morc road than we have means to keep f, Tp.proper cider. Summed- up the position is this: We Dnust ou-ild roads that are permanent., • antj ( n v/hich die cost 1 of tpkesp will’ •" he reduce to a 'mi imum;,, In most parts < f the Vv aika‘o there is soitabie material for making fairly gded ; / but wn.it is lacking is an efficient •" bin er. v I , some parts ot New Z aland, nolab'y in .the Eltfiam county and ■ town, <ar has been largely used as the binding agent but the weak point about , tar b- mid or sprayed maca'ara is the cost of raain'enance. ft has been clearly demonstrated wherever fcar hqs been used to spray ■, or paint the surface of a 'macadam, ■ r hd, -toat a fresh coat must be applied at least annually; thus'each year Tie coating of tar becomes thicker and will event sally scale off leaving 'too macadam in a worse state than before. . v

' . One disadvantage of coating a ■’ road with tar is the effect it has on ' ' >he macaaam beneath it. The ,tar is -put on .when the road is dry and some of it penetrates the sand between the stones and destroys its binding propurties. While- the tar retains its life no damage is done but as soon . h s it loses its gloss or becomes won the macadam rapidly loosens and holes~are formed. . Summed up the main disadva tages a of ar pavements are, first of all the , annual cost of re-spraying and the fact 'hat the tarts all the time becoming dearer .and harder to procut e; and any, local; body embarking on a large scheme of tarred roads might fi d Meniscives with more roads than they could procure ta* 1 to cover. • There is also the considera'ion that in the'event of a very wet summed it (.light be impossible to get the tar on * nnd if Ipft for two years the roads > would undoubtedly cost a good many -pounds te-repair. This brings us again to the question i which is the best hi ding agent.writer’s opini n it is cement, -in advoc I ng c ncrefe road, no new has been _evolvel - M' re than two years ihe Romans' built

concrete roads, some of which are still in existence.

To cornu, to more mod rn times during the last twenty years hundreds of miles of concrete roads have been constructed in America and every year a largely increased .mileage of this form-of pavement is being laid.

’ One of the first towns in America to try concrete streets was Bejlefontainc, in Ohio. Their first concrete sleds were laid twenty-one years ago,‘and in one of the streets Hie cost of .maintenance for seventeen: years ?s given as nil. In the other streets the upkeep has cost only a few*'dollars per year, ana even this slight cost.was largely due to errors im construction which have been corrected ; /n later effort'. As a binder comet differs from all others that have been use in road making in that it provides a positive mechanical bond between the stones forming the road. This actual tigid bond enable the road to increase • its carrying capacity by spree ding the strain over a much larger surface tba i is the case with ordinary macadam cp/ls. This bridging quality ot concrete is of special value on,roads where, owing to insufficient drainage or for other reasons the foundation •is apt to become soft in spots. In other ro id making methods in which there is ho actual bond between the particles, any weak spot in the founda-* tion is at i.ncey 1 apparent on the surface'of Tie road aud of course as soon as a slight hollow is formed that portion of the pavement is subjected to increased strain owing to each load that comes along dropping into it with a bump, so that :-oon a bad hole is formed. . The bridging quality of concrete has been utilised for a long time to provide a solid and even foundation for wood blocks, Neuchatel asphalt and various other forms of street paving ’ An objection-that some people will raise is that concrete is too slippery and some of the'first t'mt was . laid in 'America was ruled off in brick squares with grooves about half ni inch deep to prevent slipping, but it was found that these grooves subjected the ,con- i ■ cretc t" a ,tration, particularly on i those running in line with the traffic. Exc pt for these early experiments .nearly the whole of the concrete roads laid in America have been constructed without grooves of any kind and they have not i roved too slippery even on grades as steep' as one n twenty. Concrete roads are less slippery than Neuchatel Asphalt,, creosote! wood' blocks and several other forms of contructi n Tiey srejiot slippery in wet weatbfer except when it is cold enough to freeze, and of course ice is slippery.. To c rrugate the surface of concrete mads with the idea of giving a -“grip for horses feet would do away with one of their chief advantages, that is the smooth running of steel-tyred wheels which would entail the minimum strain oh them. , No matter how sc;all the bump it; adds some extra strain, and so shortens the life of the road and the life.of the vehicle passing over it. A y road to last and to be sanitary . must be waterproof and one advantage ( of 'a concrete road is that it not: off t the water but will carry' it off Okh a very small fall, so that it is' not necessary to build the road with a very/high crown. A flat road is much easier to maintain brealise the traffic is spread, a bout more. In many places, where concrete roads have been laid a great deal of preliminary work is necessary to secure a foundation, but where we have a splendid base ready made, no drainage and very little.' consolidating would be required.

Most of the concrete roads which have been constructed in America have eeh laid in either on; or two c urse work. ‘A nthnber of < thvr forms of construction h - ve been ivied, such as the.Haisam plan,' wbicn consists of a six-incii laver of broken stone, which compacted by.' roiling, a grout composed t f one part of cement to two of sand, mixed wet, is then poured over the stones 'and the rolling continued till all the voids are filled with cement and sand. Probably the .best .method to adopt for focal roads ; will be found to De th > one course pavement laid about six /inches thick a d composed of three parts of broken stone,, two oar|;s of coar-e sand and one psrt of cemeu'; or if local gravel is used the two course system wiJJ h- the belter, the lower four'and one half inches -to be composed of six parts of gravel to one part of cement, the upper two inches to be two of gravel to one of cement. In laying the two course pavement it would be necessary to place the second in position within an hour of' depositing the first so that the work could he monolithic. in most of the concrete highways that Inve been built in America provision has been made for contraction and expansion but in that country they, have a v_-ry much wider range of temperature than we have here. Concrete contracts in drying and expands slightly in wet weather, but if provision is made for contraction, expansion points will be hardly nec e-sary. JSlow as -to the cost of concrete as 'a roadmaking material, the average man will at once jump to the conclustion that concrete is so costly as to be out of the question, -but when we come to consider the! los cost of upkeep it will compare favorably with any class or pavement that can be mentioned. The real cost of a road must be nv.asurea by the service which it yields in proportion to the money .invested in it. It is useless to put down a cheap road:; which requires ceaseless at'cation' tip "keep it in order, far better to make a permanent job of

one street so that when it is finished you will not have to go back over - that portion of the work again. This is the great point about concrete roads; They may cost in the first place 15 or 20 per cent more than macadam roads, but when the cost of maintenance is taken into cmsideration they are much • cheaper. The total cost of maintaining thirty mile*, of concrete road in Michigan panned out at £27, or less than £1 per' mile. The Massachusetts works report • shows that on 243 miles of bituminous macadam road in 1911 they spent an average of £258 per mile for maintenance. No community din- afford to invest its-revenue in any class of roads that are known to deteriorate rapidly, since concrete though a little higher in first cost is practically free from maintenance charges. It,is cot claimed for concrete that it is the last word in road construction nor that it is a cure for all road troubles, but it is claimed that it is a practical and economical form of construction worthy of receiving consideration not only for town streets but for country roads as well.