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Southland Times, Issue 18847, 12 June 1920, Page 8

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GOOD FOR HEAVY TRAFFIC. AN INTERESTING SKETCH. At the annual meeting of the Dunedin Manufacturers’ Association last week an interesting paper on "Concrete Roads” was read by Mr J. S. Fletcher, and as the subject is one that interests Southlanders, the following generous summary is published:— After 'a brief resume of the progress of road construction through the ages, and instances of the use of cement in the anteChristian era, Mr Fletcher said: MACADAM AND CONCRETE. Macadamised roads were in use in various parts of the world, and for a long time remained the standardised road. While this is true, it must not be forgotten that in cities where heavy traffic was being carried in a circumscribed area various sorts of paving were resorted to. The old cobblestone pave place to dressed granite sets, to wood blocks, and other types of paving; but a new factor arose which has necessitated a new type of construction. This was, in many cases, met by the use of what we now know as "tar-macadam,” and it is so well known that it needs no further description. This new factor, the fastmoving and heavy traffic, was introduced by the invention of the motor car, and as the cars have developed in speed and in ability to take heavy loads there has been a consequent demand for much better roads. Bitumen and tar surfacing for various types of foundations have been tried with more or less success, but it was found that nothing in the way of foundations ultimately stood up to the severe test of carrying heavy traffic till concrete was introduced. Now, there are various types of concrete roads. There is the concrete road with wood paving; there is the concrete road with brick paving; there is the concrete road with bituminous or asphalt surfacing; and there is the concrete road where nothing but concrete is used. The reasons lor the introduction of concrete are evident. It is a material which offers the greatest resistance to wear and tear. It is consequently much more permanent, and, as a result, much more economical as a foundation base. In the United States of America and Canada, where tremendous stretches of road have got to be laid, the oppot (.unities for experiments are consequently very much greater than in any other country. In addition, the engineers in these two countries are like the men, of Athens —constantly looking for some new thing. The results of these experiments have demonstrated the tremendous advantage concrete offers over any type of road material. All sorts of arguments arise as to the relative advantages of a purely concrete highway, the concrete highway with tar or asphalt surfacing, or the road with concrete and brick or wood paving; but the consensus of opinion to-day in U.S.A. and Canada is largely in favour of the concrete road purely and simply, or with just a thin surfacing of asphalt. That they contemplate in the years 1920-25 laying down concrete roads of the value of seven or eight million pounds sterling is evidence of their belief in the utility of this material. CLIMATIC CONDITIONS. Now, I know that, an objection raised to introducing concrete roads in New Zealand is that this material is not suited to our climatic conditions. It is true that the finest stretches of concrete road in the world are found in the ideal conditions of California; but it is no less true that this material stands up to the severity and rigor of the climate in the Eastern states of America and Canada, where the frost is sometimes as much as IGdeg. below zero. Such a range of climate clearly demonstrates the fallacy of the road not being suited to our climatic conditions. We arc told, too, that concrete roads are subject. to cracking. In badly laid roads this is sty but where modern methods and modern experience arc behind the construction of the highway this no longer create? any difficulties. Certain causes of cracking that can easily be avoided are the expansion of materials owing to climatic conditions and the overloading of the highway with a consequent failure in the foundations. The first is easily remedied by the u.-e of expansion joints, where various substances of a bituminous nature can be used, anti the second, with regard to overloading the foundations, can be avoided by using reinforcing. .Against climatic conditions modern waterproofing materials incorporated in the concrete have the effect of strengthening and also waterproofing the concrete matrix. Such materials a? truscon, toxement medusa, nr a new Bri ti.-h chemical discovery known as metal lie Is mid have the desired effect. The la.-f material has a wonderful influence in hardening anti strengthening concrete product.-. Much discussion is taking place these day.- as to whether concrete roads should have reinforcing or not. There tire two big advantages from using this type of

‘.a.n-t ruction ; these are that, should the fouimaiion. through some reason or other, he detective, the defect is largely mil i g: ted, Lee:.use rein forcing in the concrete makes a slab strong enough to carry a load. Lor different purposes, or where different loads are going to be carried, variations lake place in the thickness of the concrete slab; leu speaking general ly. the range of thickness varies from tun to It in, this Din being through a point of intersection on the crown of the road. .METHODS OF CONSTRUCTION. The method of construction of concrete roads may prove of interest. When in Lon< mi last year (he waiter saw operations under way for laying wood blocks. To make a satisfactory job of this type of eons'rud ion, it is essential that a good d utv■ ’ ■;■ l:> iw first made. The foundation here \vti-- concrete; but what, strut k the writer wa- this: that to mix tins concrete the machinery u'Ct! was the human element. On a similar stretch of road in Chicago alter? prepartition was being made for similar type of paving, a big Bal'd) mover was used, which turned out a yard of eon-uete a minute, and a whole block was hud 'in the working day aim; one side of tin- main lines; whereas m 1 on. -on the. n iua s- Oxford and Bond ere is had, I believe, been up for months, a. el they were taking weeks to lay a block id loiierere. Undoubtedly these archiac methods do mil impress one so far a,, construction of economical roads is concerned : lull the manner adopted in Chicago, as r i uteri, would readily convince oue as to how these roads can be quickly and economically laid by using- concrete. If a mitably large scheme were gone in hir, largo Batch mixers, with what, is known as a paving equipment attached, would be used. To bring the aggregate to the mixer and lake it from the mixer a I ght industrial railway would be laid along the stretch of road under construction, This obviates double handling of ■the materia.!, ami consequently reduces the cost. After the concrete is mixed and put in position a machine spreads the concrete, tnmps it, and finishes it off in one series of operations, again minimising the amount of labour on the work. When the road is laid steps are taken to cure the concrete. By curing is meant steps a.ro taken to got the concrete hardened off without, allowing drying to take place too cmickly, and various devices are adopted to prevent this. Some common methods arc: First, ponding the road; and, second, covering the road with calico or canvas, to prevent moisture from coming out of the concrete too quickly. Earth kept constantly moist is also used. It may be of interest to know that great stretches of concrete roads are being laid in Honolulu, and the second method mentioned here is the one adopted to prevent the concrete drying too quickly in this tropical climate. ENGLISH ENGINEER’S REPORT. Referring to the use of concrete roads in Britain. Mr Fletcher quoted from a report on the subject by Mr Jones, engineer for (lie city of Chester. Mr Jones said: “Some nine or ten years ago a road-widen-ing in Chester had to be done, and it occurred to me that, this would be an opportune time to try a concrete road surface. Accordingly, with the permission of my Highways Committee, an area of about 400 square yards of concrete was laid. This was not reinforced, and was opened out a

blit owing, in my opinion, to its having been Opened to traffic too soon, and to the lack of reinforcement, it became wavy and bumpy, although it did not actually break up. The whole area was laid Sin in thickness, and w.as on a clay subsoil. Two months after being opened for traffic I was afraid (owing to waviness) of breaking up, and therefore overed the surface with tarred chippings. This, in my opinion obviated the breaking up, although the tarred chippings also became wavy, but not quite to the same extent as the concrete underneath. However, in the circumstances this first experiment stood well, and to-day the surface is not in bad condition. White Friars was the next carriage way treated; and here again the work was successful, although for light traffic only. The cost of this work came to Gs 3d per square yard. My Highways Committee have been so satisfied with these works that they are now allowing a reinforced concrete carriage way to be laid right through the main thoroughfare of the city—viz., Foregatc street and Eastgate street. This street takes all the through traffic from Manchester, Warrington, and Liverpool to North Wales, and, speaking roughly, there is not less than 1,500 tons of traffic passing over this roadway each day. Along the centre of these streets is a double line of tramway track, and this is being concreted in at the same time. A portion of the work has been completed and opened for traffic, and up to now the results have been all that was anticipated. Of course, three and a half months’ wear is really little to go by, but very careful observations are being made of the work, and in the event of its proving a failure it will be possible, from the statistics obtained, to find the cause and so remedy it in the future. The sanction of the Local Government Board was received to do this work, and the Road Board have shown their interest in the experiment by granting the full estimated amount for carrying it out —viz., £5,000. This work was estimated for last January at a cost of 11s 3d per square yard, but up to now the cost has been 12s 9d per square yard; this is owing to the price of cement going up 8s per ton, granite Is per ton, and slight increase in the cost of labour, and also to a strike of the men engaged or the work. From these figures it will Inseen that a reinforced concrete carriage way shows such a saving if wc can only construct these roads on rightlincs. No other method will, in my opinion, stand a chance.” GRADING AND COSTS. On the question of the grading of roads Mr Fletcher said; "It has been suggested that concrete is not a suitable medium for roads with a very steep gradient, but this is not so as it is proved by the authorities in Los Angeles who have constructed a road there with a 29 per cent, gradient. This, you will agree, is a very steep one, and I think this is sufficient answer to those who make the statement that concrete is not suitable for steep roads, when it is stated (hat (hi.-: steep gradient has been found quite all right. I have suggested in a paragraph that I would demonstrate the value to a hardheaded community from the point of view of costs. I assert, with no fear of contradiction, that concrete roads would save, time, would save tyres, would save benzine, would save wear and tear of the motor, and that they are cheaper to build. In doing that I think I will have completed the second heading under which this paper was billed. Let us take No. 3 first, the saving of benzine; this appeals very considerably more to us than it does to the American where petrol nr gas, as they call it. costs very much less. An experiment was made by the manufacturers of the well-known "White" Trucks as to the relative mileage on roads. On earth roads, the mileage per gallon was 5.78, on a good gravel road, it was 9.39 miles per gallon, and on a bituminous macadam road it was 9.-IS. while on a concrete road it was 11.78 miles per gallon. This represents, as you sea. a saving in the cost of approximately 25 per cent, on the concrete road over the tar-macadam. If we even could reduce our petrol bill by 10 per cent., the users of motor cars would have cause to rejoice .but a- shown it was a saving of 25 per cent., and, consequently, very much better for the motor car user. 1 staler! that there would be :■ saving of tyres, I wish to illustrate in two ways, first, from (he observer’s point of view, and second, from the tests (hat have been made by the Good Roads Bureau of the Californians’ State Automobile Association. It was no uncommon sight to see a car with very dilapidated tyresetting out on long journeys. Had you asked the owners they would have void you they had no fear but that .they would get to their destination without tyre 1 roubles. Had these same tyres hern used on our New Zealand roads, they would not have gone five miles without the inevitable puncture Let me say here, 1 am not one of those who say much as to the poor road? there 1 are in New Zealand. What strikes me as ueing amazing is that the roans are so good anil how much credit is due to the pioneer? who designed and built these highways. T His however, does not apply to I'uneihn's s!reels. ’Hie second point with regard to the tyre-saving is to be demon-trated ;n 'inway. It has been proved that the :uv;".;n: of pull over a level mwurfaceil concrete is 27.Gilts per ton, and over a concrete base with asphaltic oil and percentngs is 49.21b per ton. Over a gravel road the pull is ;S.2!b. Take this in conjunct hut with the j opts made by the "'While” Truck, ami it I needs no arguing to demonstrate that lucre I must he a tremendously greater resistance {offered to the tyres, and, consequent’;. - , a great deal more friction with it-- con.-e ;..rnt wear. If you reduce your tyre bills by 25 per cen ! ., then you are cert-tidy achieving

:i very bis saving. One has only to travel iivpr a bumpy road and to ra.'ih.-c ('in uirring of the whole merlin? to know that f this were obviated by havum a smooth ntrface, then the eot for wear and Puir would consequently he reduced. Traveling over concrete roads rnaides one easily to appreciate wimt a tremendous savins in ttitle is going to remit if we have cnncrelc hath' ways in piece of the present type of arterial roads. Reference w;w made to the road being the feeder of the railway, and i! is clear to me that if we na expedite the transport of poods from the place of origin to the railway and from the railway to the point of side we are going to cut down our transportation costs, and consequently make a cut in the Cost of Li vine. You are point: to make it easy for the farmer to brim: Ids products more quickly to the marxet. and by doin'; so produce a hit; savin;; in the cost of our foodstuffs. A paragraph here on (.he railway cost.s of upkeep of various types of roads would be interesting. This report, was made by the Stale Commissioner of Highways in the Slate of New York over a period of three years. For each year the relative upkeep was: On macadam, OTGcIoI per mile; on gravel, 524d0l per mile; on first-class concrete, 2-tdo! per mile. Need one say more as to their economy? As this included the upkeep of ditches, etc., it is quite clear that concrete is very much the best proposition. To get the money for making there roads the various States hat! popular polls as to whether or not road bond issues should be made. Unanimously almost in every' part of Cut c °untry t!le people agreed to have these, as all of them have realised the value of good roads. If must not be assumed that only one type of good road can be constructed, but for general purposes it is the opinion of the writer that for sound construction and real economy the only road that meets all these requirements is one constructed m concrete.