NEW ROAD SEALING

Dominion, Volume 27, Issue 59, 2 December 1933, Page 24

NEW ROAD SEALING

Product Developed in Wellington TRIALS ALREADY MADE What has been found, to be a very effective road seal has been developed from tar manufactured in Wellington iu the process of gas manufacture. For some time past Mr. Rands, a chemist employed, in Wellington, has been experimenting with certain oil residues from the tar and has produced a substance called bitural. From this material conies the MCI fluid, which is now being used as the first sealing coat in many streets in Wellington as a dust-layer. This sealing coat does not pretend to be a leveller of road surface irregularities. Its mission is to sink into and bind the surface of macadam roads, so as to make it as nearly dustless as possible. This purpose appears to be amply fulfilled by MCI, which has already been applied to Rintoul Street south, Blythe Street. Dawson Street, Leraud Street, and Herald Street in South Wellington. When asked if the material that is being sprayed on these streets was. tar, an engineer replied that it was no more tar than soap was mutton fat — it was a mixture of tar oils with a modicum of whale oil. When applied through sprays fed with MCI (at 120 degrees q£ heat), with a pressure of 301 b to the square inch behind it, the light, oils at once commence to soak into the surface of the road, leaving the heavy oils, which are slower in action, to finish the job on top. It was shown, where a road has’been done for some days, that the MCI had penetrated to depth of an inch, and pieces of stone an inch or more in diameter, which were prised out of the surface were found to be completely covered. Cheapness and Simplicity. The chief virtues of the new road surfacing material are that it is 00 per cent, local manufacture, that it can be produced at half the cost of a bituminous product to do the same work, and that be applied by the one machine —the boiler and 6ft. spray, towed by a tractor —at the rate of 6000 square yards a day, which is roughly about a mile and a half of half-road in Wellington. The cost works out to less than 4d per square yard, so that it is nearly half the cost of other mixtures that perform the same office. The price of the preparation from the manufacturing company is 7}d per gallon, and, applied to the road, it works out at 9}d per gallon, which is considerably below the cost of the bituminous product. For the time being the plant consists of the boiler (with rear spray), tractor, and a lorry tender, which holds 400 gallons of the MCI mixture. When the going is fairly flat the boiler may be replenished from the tender while the work proceeds, and as soon as the lender empties its tank it goes off for another 400 gallons. On extra steep grades, such as that of one in seven presented by Dawson Street, the lorry helps the tractor to pull the boiler up the grade. It is estimated that, with a second coat and a sprinkling of metal chips, a really good surface may be established at a cost far less than that at which such work has been done before. Sticky in Early Stages. in connection with this work the public is warned that MCI passes through several stages before it solidifies.' For the first few hours after being sprayed -on to a road it is in a liquid for,tn; then it becomes “tacky 1 or stic’>:', and finally it dries out into a dull leathery finish. It, is while the new coating seal is in a tacky condition that pedestrians and drivers of motor-cars have to be, careful. Here and there where there have been depressions in the rdad, and the fluid has taken a little longer,than usual to soak in, it has been found necessary to dust such sections, but this really defeats the purpose of the road engineers, who want the whole of the material to “dig its claws” into the road, and pot merely soak up surface dust and chips. They want to give each road so treated a fair deal. The tacky state disappears after two days, at the outside, but during that time it is desired that motorists and the public generally should avoid using the roads so long as the warning boards are in position. While tbe-sur-face Is tacky car tires will pick up the material, as will the boots or shoes of pedestrians. This . must be avoided. Still, the discovery is of such value — it is hoped of permanent value —that the engineers want to give MCI every chance without interfering with the convenience'of the public or damaging their cars. The city engineer’s department has a programme of road sealing in hand, and wants to do as much as possible (luring the summer months.