CHEAP CONCRETE ROADS.

Manawatu Herald, Volume XLI, Issue 2044, 21 October 1919, Page 1

CHEAP CONCRETE ROADS.

EXPERIMENTS AT PAIIIATUA

A REVELATION IN COST AND

RESULT,

Air Reuben Parker, late engineer to the Pahialua Borough Council, in a chat with a representative of the Eden Gazette, described some interesting experiments he had recently conducted under instruction of the Pahiatua Borough Council. ... Fur efficiency and low cost the experiments are a revelation, and will be read with great interest by local good road enthusiasts. The experiments were instituted at the suggestion of Mr Joseph Dawson, the well-known road and bridge contractor, who claimed that he had evolved an economical and practical formula and method of converting macadamised tracks into permanent and durable concrete roadways.

TREATMENT

A section of suitably-graded macadamised road was selected for the experiment, ils area being: length 100 yards, width 10 yards. This was treated in half-yard full-width courses in the following manner: — A- two-ineh layer of fine concrete was applied to the macadam surface, Upon this were paved, line to the macadam, river-bed spawls of approximately Sin. in diameter. The spawls were grouted with thin cement, and over the whole a further coat of tine concrete' was laid and brought to a finished surface, the interstices being carefully tilled, making in all a 0-ineh covering-over the macadam. TESTING AND LOW COST. Several weeks afterwards the experimental block was examined, and subjected to (be most severe le.-ts by means of both traffic and sledgehammer pounding. It bore the tests in a completely satisfactory manner. The cost worked out at 3s per superficial yard; or £2,bit) per mile for a 30ft. roadway. A !) foot country roadway could thus be constructed on these lines for £702 per mile. This, Mr Parker assured the writer, is cheaper limn good macadam can be laid in the majority of cases. As far as is known, the cost of this experiment is Ihe lowest ye I secured in Ibe Dominion, others ranging from seven shillings per vard upwards. TRAFFIC PREFERENCE.

The experimental bloek above described has now been laid a year, and shows no signs oT'wear under conlimml heavy and various vehicular and other Ira Hie, and il has been officially and publicly noted that the concrete piece of road wa- at all times preferably used by every description of (ruffle, thus causing unusually heavy- use of' the experimental block.

RIVER-WORN METAL I’SED. It should be staled that Hie metal for this job was all obtainable within 1 a. mile distant (from the Mangatainoka river) and the spawls were quickly collected from the river bed. They were, of course, just the ordinary smooth-worn river boulders, of as uniform a size as conveniently obtainable. It quarried stone bad been available il 'would have been used, as it lias a better holding surface; but this notwithstanding, the result has been in every way satisfactory. The cement mixture used was in the proportions ui tour of (dean, sharp river gravel ami sand, to one of cement.

DKY-MIXIXO EXPEUIM FATS. Further tests made by Mr Dawson and Mr Parker include the plan of dry mixing’, whieh will eventually supercede the older method tor the reason that the density oi the work when roiled dry would be much greater than when laid down' wetted in the ordinary way, as in this ease a great proportion of the water eventually inters away,-leaving certain voids whieh would not occur with dry mixing and rolling. Experiments whiefi these gentlemen have carried out have proved conclusively that cement concrete mixture laid down on this principle will set and attain its maximum strength, a fact whieh many experts may discredit.

One "rent advantage of either of the above methods, states Mr Parker, is that they may be applied with equal success to either macadamised or hard clay surfaces.