Nelson Evening Mail MONDAY, JUNE 14, 1920. CONCRETE ROADS

Nelson Evening Mail, Volume LIV, Issue LIV, 14 June 1920, Page 4

Nelson Evening Mail MONDAY, JUNE 14, 1920. CONCRETE ROADS

SOONER or later this district will have to face some really comprehensive scheme of road improvement, and it is well to keep in touch with what is being said and done in regard to roadmaking- The other day Mr J. S. Fletcher read an interesting paper on concrete roads at the. annual meeting of the > Dunedin Manufacturers’ Association Dealing with the various types of concrete he said, there is the concrete road with wood paving ; there is the concrete road with brick paving; til ere is the concrete road with bituminous or asphalted surfacing ; and there is the concrete road where nothing but concrete is used. Tire reasons ' for the introduction of concrete are evident. It is a material which offers the greatest resistance to wear and tear. It is consequently much more permanent, and, as a result, much more economical as a foundation base. In' the United States of America and Canada, where tremendous stretches of road have got to be laid, the opportunities for experiments are consequently very much greater than _in any other country. In addition, the engineers in these two countries are like the men of Athens—-con-stantly looking for some new thing. The results of these experiments have demonstrated the tremendous advantage concrete offers over any type of road material. All sorts of arguments arise as to the relative advantage of a purely concrete highway, the concrete highway with tar or _ asphalt surfacing, or the road Avith concrete and brick or wood paving ; but consenus of opinion to-day in E.S.A. and Canada is largely in favour of the concrete road purely and simply, or with just a thin surfacing of asphalt. That Ihey contemplate- in the . years 1920-25 laying down concrete roads of the value of seven or eight million pounds sterling is evidence of their belief in the utility of this material.

Referring to an objection raised in New Zealand to the _ effect that concrete is not suited for road-making under our climatic conditions, he says it is true that the finest stretches of concrete road in the world arc in the ideal conditions of California; but it is no less true that this material stands up to the severity and rigor of the climate in the Eastern states of America and Canada, where the frost is sometimes as ranch as I.6deg. below zero. Such a range of climate clearly demonstrates the fallacy of the road noticing suited to our climatic conditions. Wc are told too, that concrete roads are subject to cracking. In badly laid roads this is so, but where modern methods and modern experience are behind the construction of the highway this no longer creates any difficulties. Certain causes of cracking that can easily he avoided are the expansion oi materials owing to climatic conditions and the overloading of the highway with a consequent failure in the foundations. The first is easily remedied by the use of expansion joints, where various substances of a bituminous nature can be used, and the second, with regard to overloading the foundation.s, can be avoided by using reinforcing. Against climatic conditions modern waterproofing materials incorporated in the concrete have the 'effect of strengthening and also waterproofing the concrete matrix. Such materials as truscon. toxemeut medusa, or a new British, chemical discovery known as metallic liquid have the desired effect. The last material has a wonderful influence in hardening and strengthening concrete products. Much discusdon is taking place, he goes on to remark, as. to whether concrete ■•..■ ids. '-lion Id have' reinforcing or i’ll. There are two big ad van- ■ from using this -type of

construction ; these are that, should the foundation, through some reason or other, ho defective, the defect is largely mitigated, because reinforcing in the concrete makes a slab strong enough to carry a load. For different purposes, or where different loads are going to be carried, variations take place in the thickness of the concrete slab ; but, speaking generally, the range of_ thickness varies .from Gin. to TOin. this loin being- through a point of intersection on the crown of the road.