SPECIAL INTERVIEWS,

New Zealand Herald, Volume XXXIX, Issue 12001, 25 June 1902, Page 3

SPECIAL INTERVIEWS,

FACTS ABOUT ASPHALT. CHAT WITH MR. A. B. WOOLF. During the whole time in which the laying of the asphalt in Queen-street has been in progress very general interest has been displayed by the public as to the process, and many have been the conjectures as to what the ingredients of the asphalt are. With the view of allaying this natural curiosity a Herald reporter yesterday waited upon Mr. A. B. Woolf, manager of the Neuchatel Asphalte Company, and obtained from that gentleman an interview. Asked to describe the ingredients of the asphalt his company are now paving the main street with, Mr. "Woolf said: Many people imagine that the asphalt is a manufactured article, but it is not. It is a natural mineral obtained in Switzerland from the Val de Traver mine in the Canton of Neuchatel. It is mined there, coming out in great boulders of rock of a soft nature. These boulders are crushed to powder, and there you have the material for the asphalt ready for use. In this state it is shipped here, arid treated by being heated in furnaces, and applied on the road as you have seen. There are different grades of the powder, which have to be studied according to climate, became the rock being a natural limestone impregnated by nature with bitumen, it depends on the quality and quantity of the latter in the rock as to which grade will stand a hot or a oold climate."

How do you differentiate?" " Well, for a hot climate the rock must not contain too much bitumen or the asphalt would soften in summer, whilst for a oold climate there must not be too little bitumen present or the material would crack in win tea-. In India we should use a still harder rock than here, but in Wellington or Dunedin, where there are. frosts, we should use the same w» use in London."

" Does the rolling process we see compress the asphalt to its limit?" "No; it if* only partially compressed when laid on the road, sufficient space being left in the thickness to allow of it being compressed further by traffic. The idea is, that the more traffic it bears the greater will be the compression, and in consequence the more hard and durable the asphalt becomes. It is only in the first stage, before the traffic has had time to compress it that damage is done by metal, etc., being ground into it. This damage cannot, take place after a time, as the material will be too hard to penetrate. The nature of the stuff is so elastio that it is not only .easy for horses to run upon, but it gives a considerable saving in the wear and tear of vehicles. The trouble with your roadway here' is that of the spreading of metal over the asphalt, due to us only doing half the street at a time, but we could not help ourselves in this. If. however, we were paving another street we should ask to have the whole width of it."

''You have used' a different- kind of material in paving the floor of the new fire brigade station, have you not?" It is the same powder, but it is' mixed with a. small percentage of extra bitumen. This is heated up to such a degree as will cause it to liquify. The reason is that there being no heavy traffic upon it, compression would not follow, and it therefore becomes necessary to lay down something harder in the first place. It is this liquid asphalt, or ' mastic,' as it is called, we are to lay a section of footpath in. It costs about half the other kind of path, being only necessary to lay to a thickness of one inch. Our reason for using this for the footpath is, that when once put down you have a permanent footpath, inxepensive to take up, if necessary, and which would not wf£jr soft in the summer. Another advantage is that it requires no top-dressing generally so disliked by shopkeepers, as it is dragged into their shops by pedestrians." "I notice you have laid this liquid asphalt along all the tram lines. What is the reason for this?"

"You may have noticed that much of the traffic keeps along the lines. Well, this lias a tendency to form ruts. The mastic has two objects, one to obviate the likelihood of these ruts being created, the other to prevent any play of "the rails from disturbing the bulk of compressed asphalt forming the roadway. We have laid this material on all the boulevards of Paris and in Vienna, and most of the Continental cities, also in London. No, it is not slippery in wet weather." " When do you anticipate completing the asphalting of Queen-street?" "... "In six weeks, or perhaps less. That entirely depends upon the weather." " Is it the intention of your company to retain their local office after finishing Queenstreet?"

"Yes, we shall make our office here a permanent one. My company, which, by-the-bye, is, despite its name, an English one, with English capital, invested, to the amount of three-quarters of a million, will be prepared to undertake all sorts of work. I have just returned from Wellington, where I secured contracts for flooring a new woolshed for the Harbour Board, also for flooring part of the new town hall. I also secured the prospect of a good deal of Government work, and am in negotiation for street-paving work in Southern cities."