CONCRETE ROADING.

Otaki Mail, Volume 26, 28 July 1919, Page 4

CONCRETE ROADING.

WORKS m UNITED STATES. An address on concrete roads was given by the Mayor of Auckland, Mr J. H. Gunson, at a meeting at Onehunga last week, the Mayor of Onohunga, Mr J. Park, presiding. Mr Gunson said he had dealt fully in his previous address with the concrete work in the city, and its relations to the Manukau road proposals. His object was to place before the ratepayers the latest information as to the cost and construction of concrete roads. This he had obtained from Mr IV. H. Hamer, engineer to the Auckland Harbour Board, who had recently returned from America. Mr Hamer had carried out more concrete work than anyone else in New Zealand, arid in 1904 introduced the system of concrete construction of the Auckland wharves. He was, therefore, an authority on the subject, and well qualified to speak of the most modern methods of concrete work in the United States. Mr Hamer found that in California, for concrete roads throughout the State, the following loans were authorised: —1909, £3,600,000; 1915, £3,000,000. These two loans had been practically expended, and a further loan had just been authorised of £7,000,000. There wero 4500 miles of concrete roads in the -State. The general practice had been to form a 24ft subgrade, 15ft w-ide, of concrete to a thickness of 4sin, leaving 3ft shoulders on either side of the concrete. In many parts oiled crusted rock was topped off on the concreting The cost of this in the past had been approximately £2200 a mile. Four to four and a-lialf inches was the thickness of concrete laid generally throughout the State of California. From San Francisco to Los Angeles, a distance of 441 miles, there was a concrete road of 4tin standing excellently. Tar-topping was formerly used, but the concreto was standing so well that the use of the former had been • discontinued. Californian Car Tax. In California there was a motor-car tax of £2 a car a year. Mr Gunson said local bodies in New Zealand had no power to levy such a tax, bat ho hoped the municipal conference would adopt the remit favouring one. Besides aiding local bodies in their road construction work, the tax would result in a boon to motorists.

Engineers in California advised Mr Hamer that the interest and cost of maintenance of concrete roads was less than water-bound roads. The counties spent annually £4,000,000 on maintenance of roads. Shingle concrete was found to be not successful and had been abandoned in favour of cubs chips. The cartage contracts in California over these roads had dropped from 26$ to 12 cents a ton a mile. With the 1909 loan of £3,600,000, 2950 miles of concrete were laid, 4sin thick, at a cost of £1240 a mile.

| In one day 650 ft of concrete, 15ft wide, was laid by 20 men, whose wages were £1 Is a day.. The cost of this ' was about £4OOO a mile, including fillings for the valleys, which had been considerable, but on flat sections the cost had run out at £2200 a mile. All the concrete roads in Redwood City. California, were 4sin thick. They had started with 6in. experiments had j been so successful that they were dropping into line with other centres, and now generally adopted 4sin. In 1916, in another centre, test speeds were held a,s follows: —16$ miles on concrete. 41 miles on earth, and 91 miles on gravel, while the oil consumption on concrete was only half that on gravel. Experience at Seattle. In Seattle, right in the heart of the city, 6in had been laid, with 21 in of sheet asphalt. The engineer of Seattle stated that ordinary concrete 6in thick made as nearly a perfect road as could be made, and that they were now abandoning any topping on the concrete, not even asphalt or tar, as the results with the concrete had been so good. They were very particular - about the grading of their sand. New York had just appropriated a loan of £20,000.006 for roads, and a vigorous policy was now being launched there in furtherance of the concrete roa'b agitation. In other parts of the State they were carrying out concrete work four inches thick at 5s and 4s a square yard, in many places no metal at all being used as a foundation. The cncrete was simply laid on solid earth eurface after being rolled- In Seattle there were many miles of streets laid off in concrete.