ROAD TESTING

Evening Post, Volume CVI, Issue 81, 3 October 1923, Page 5

ROAD TESTING

AN, AMERICAN EXPERIMENT

CONCRETE GIVEN FIRST PLACE

A 400,000-TON TR¥«UT.

Probably no people believe more thoroughly in tests and testing than do-tha Americans; they test anything and everything, from Einstein's theory to boot pegs, practical tests, laboratorytests, mixtures of the two, and plainly it pays to test and afterwards to advertise, that is, of course,' i£ the test pans out rightly. Some of the means employed are remarkable indeed, for instance, during the war the Americans employed a machine to try oit service boots. "Thesa were laced on dummy feet on the outer circumference of a wheel of considerable diameter, and, as it revolved, cam* in contact with a sanded surface with approximately the pressure of the weight of an average Fit A man, but that was not enough- a man twists his foot slightly in walking, and so places another ■wearing strain upon his boot leather, and accordingly mechanism was provided to give that*twist, arid ofi the boots went; They_ route marched, for fearsome times and distances, coming" down on tha artificial road surface with a regularity that would have- inspired Kipling- to something still more weird than his route march poem, "Boots," had ha seen the machine in action, yet the left loot mate of the right boot of known 10,000 mileage perhat>s gave out during the first three weeks or so under actual service conditions. It was a spectacular test in its way for the first three on four hours, but after that became rather monotonous to -watch, and in the end was not quite true to real conditions. A road test recently carried out" neap fcpringfield, Illinois, certainly did'not era on the side of theory, for it was an. actual condition test without regard to this money required to produce those condi- v tions. The object was to determine which class of road was the cheapest in the long run, that is, the road that'cost least, first and ultimate cost both- taken into consideration. The test, moreover, was more than merely a surface try-out, for one of the objects was also to determine the value of different types and thicknesses of foundations. Three surfaces were tried out, brick, concrete, and asphalt, and three foundations wera also tested, macadara, concrete, and reinforced concrete, and the result, according to a writer in "The Roadmaker, published in England, by tha way, was a fairly complete victory for reinforced concrete.

The teat road consisted of sikty-threa sections, each 18 feet wide and from 100 to 250 feet long, laid end to end to form, a continuous straight road two miles long. Twenty-two sections, were of brick, aevnteen of asphalt, and twenty-four of concrete. Over this pavement a fleet- of lorries : made 23,200 round trips, starting off with, a bare chassis, weight threa tons, and carrying increasingly heavy loads by increments of one ton until a gross load of ten tons was reached, the greatest traffic imposed on any-"section during the test being j«et under 400,009 tons. Pretty theories and complicated natural-artificial conditions did not, therefore, enter into this test; it was straight ahead work and heavy work at that.Faults developed in the various sections as follow :— ■ first increment: One asphalt on macadam. One brick on two-inch concretp. One plain concrete four inches thick with special cement. Under second increment: Six brick macadam. Two asphalt on macadam. Five brick on concrete. Two concrete with special, cement or chemicals. . One concrete four inches thick with steel bars along edges only. Under third increment: One asphalt on macadam. Six .brick on concrete. Two plain concrete. Three concrete with special cement a chenycals. Under fourth increment: . One asphalt on macadam. Five asphalt on concrete. One brick on concrete. Two plain Under fifth increment: One asphalt on macadam. One asphalt on concrete. . Two brick on concrete. One plain concrete. 1 One concrete with edge reinforcement One reinforced concrete five. inche« ..' thick. ..-.-•■

Under sixth increment: Three asphalt on concrete. Five brick on concrete. One plain concrete. x One reinforced concrete.

No failures: Two asphalt on concrete. One brick on concrete. Four plain concrete nine to serea' ■ inches thick. > Two plain concrete seven inches thick with edges reinforced. • ■ Four ordinary reinforced concrete five to sis,, inches thick. ■■ ■ - The non-rigid foundations, i.e., the macadam foundations, failed at an early stage, and the fewest failures were in the reinforced concrete, the first i'to fail being five inches thick at the fifth increment of loading, which increment had produced .failure in plain concrete seven inches thick. i,,; 4, nofch t f: ? eil! f°rejd concrete section six niches thick failed at the sixth increment, and after that no further increments of loading were made, there beiiiothirteen sections which had seen the test out, ten of concrete, either plain or re inforced (the reinforced concrete^ bein ff generally -two inches less in thfckoes! than the p am concrete), one brick-fa special bnck, of course, in all these sections) and two asphalt on concrete, and of tnose roads which went right through the tests the least expensive were of reinforced concrete five inches in thick- ]££■ t le writer adds that'the sKand that five new salons, each 350 feet long, had been built for the finals, all of them of concrete or reinforced concrete thickness, just as was demonstrated Vv the concrete sections. Wellington has" a particular interest in all road-testin?* relrd "£ M rC|a^ S dtl roads > *™t *i& regard to the Hutt road.