Patented Mar. 9, 1943 1 OFFICE ROAD SURFACE, ROAD FOUNDATION, AND SIMILAR LAYERS Geldolph A. Heyning, Velsen,
Netherlands; vested in the Alien Property Custodian No Drawing. Application June 28, 1939, Serial No. 281,603. In the Netherlands June 3, 1937 2 Claims.
Blast furnace slag has already been employed in the construction of roads and paths, for instance in the form of blocks for footways, or of irregular lumps for road foundations, or of granules for cycling-tracks. Owing to its strength and its valuable wearing properties, said material is very suitable for the purpose stated. However, when employed on road. surfaces exposed to the direct action of sun rays, its coherence dimin ishes in the long run, so that it is liable to crumble and to drift. It has already been proposed to avoid this inconvenience by the addition to the surfacing material of cement or milk of lime as a binder, but this appreciably increases the cost of construction.
The present invention has for its object to attain the desired result in a more economical manner, namely by the addition, to the blast furnace slag, of a material that has always been considered as a mere waste product of the blast furnace process. This material is the so-called blast furnace sludge, i. e. the exceedingly fine dust washed from blast furnace gas that has already been treated in dry dust separators.
It has been found in practice that a mixture of suitable proportions of slag and sludge, for instance four parts by volume of slag to onepart by volume of sludge, is a very valuable road surfacing material. The sludge not only prevents the granulated slag from dehydration so as to ensure permanent coherency of the surface, but also has the effect of progressively increasing its strength.
It has already been suggested for dust from the throat of a blast furnace to be briquetted by the addition thereto of a binder such as blast furnace slag, for the purpose of rendering said dust suitable for smelting, but the present invention is not concerned therewith.
Another advantageous feature of the invention is that it does not offer any difiiculty to mix slag and sludge to form a homogenous mass, and that the mixing operation need not be performed in situ, but can be carried out where said ingredients are produced, since the mixture only hardens or sets under the influence of pressure exerted, for instance, by rollers.
Although it is preferred for the slag to be used in granulated form, the invention is not restricted thereto, since also relatively big lumps are suitable for the purpose under review, for
instance, for the making of road foundations.
Alternatively, the mixture of slag and sludge may be pressed into blocks, the latter to be used in the construction of road foundations, or as roadsurfacing material.
Suitable fillers such as stone-chipping, ravel, sand and the like may be incorporated in the mixture of slag and sludge for the purposes of