CEMENT OR BITUMEN?

Dominion, Volume 21, Issue 17, 14 October 1927, Page 8

CEMENT OR BITUMEN?

ADVANTAGES AND COSTS WELLINGTON & AUCKLAND FIGURES When Wellington abandoned the original idea of putting the Hutt Road down in cement concrete and went in for bituminous concrete instead it was represented that as good a pavement would be obtained at a greatly reduced cost. Since then much bituminous concrete has been extensively laid in the city, and it appears that the cost has been higher than estimated. When bituminous concrete costs begin to approach cement concrete costs it becomes a question of which type represents the best value for money. Unde r the city paving loan of 1925 approximately 20 miles of streets, having a total area of 279,293 square yards, were listed to be paved, at an estimated cost of £lBO,OOO, the remaining £20,000 of the £200,000 loan being listed for the Evans Bay sea wall and filling. This worked out at an average cost of 12s. per square yard, inclusive of over 33,000 square yards on steepish grades to be paved in brick on a concrete base, at an estimated cost of £1 per square yard. The position to-day is that no brick paving has been laid, as proposed, and that of the twenty miles of streets listed, apparently somewhere between twelve and fifteen miles, have been paved. Although the City Council has sought unsuccessfully to secure the ratepayers’ sanction for a further and still bigger paving loan, it has vouchsafed no statement of the position on the last loan. , As no paving has yet been started this season, it would appear that it is because funds are virtually exhausted. Until a detailed statement is made, the position necessarily remains obscure. The indications are, however, that the paving has probably cost 25 per cent, above the estimate. If this should prove to be the case, it means that bituminous concrete is costing round about 15s. per square yard in the city. In Auckland cement concrete roads are being laid at from 16s. to 18s. 'per square vard, according to figures published in that centre. The indications thus are, the first cost of bituminous concrete is not proving greatly below that of cement concrete. .

There is, of course, considerable diversity of opinion as to the relative merits of cement and bitumen for paving purposes. ' Figures issued recently by the United States Bureau of Roads show clearly that the •(reference in that country, with the heaviest motor traffic in the world, is emphatically for cement concrete as against bitum-

inous coucretc for roads i -quiriug hightype pavements, Ou the various State highways systems of the United States the total mileage of the different high-type pavements at the end of 1926 was as follows:— Miles. Street asphalt 890 Bituminous concrete 4,815 Cement concrete 31,935 Brick 3,215 The advantages of cement roads are that when properly built they can carry heavier loads than bituminous concrete. They are not subject to waving, and being light in colour they are safer for travel at night. The advantages of bituminous concrete is that it can be laid with less interruption to traffic as no period of three weeks or so for curing before use is required: that an occasional overload can be borne without material damage to the pavement, whereas cracking results in cement; that it is quieter for traffic; and that in bright sunshine there is no glare from it as from cement. The idea that either type offers a “permanent” surface is, of course, entirely fallacious. The permanent pavement has yet to be discovered, and maintenance has to be expected with any type of pavement laid. The position roughly is that there is almost universal prefe’rence for cement concrete for roads carrying the heaviest traffic, and that where bituminous concrete is approaching the cost of cement concrete most authorities would be inclined to view it as a dubious investment. There is a further question as to how far either expensive type of pavement is called for by the volume of traffic, and how far traffic requirements can be economically met by preserving the surfaces of existing macadam roadways from disintegration by bituminous sealing. This latter work really conies under the heading of maintenance, and is much more properly .done out of revenue than out of loan money. If loan money is used it should be on the: basis of paying it off in a season or two. To raise long-dated loans for maintaining roads by painting their surfaces with bitumen is about as sound finance as it would be to borrow money to pay the dustman’s wages. It seems to be Wellington City finance, however. It is about time that the city took sleek of where it is getting to in paving fiitancc.