DE2058576A1 - Process for the production of stone bodies for road surface purposes - Google Patents

Description

Albright & Wilson Limited, Oldbury near Birmingham, Warwickshire, UK

Process for the production of stone bodies for road paving purposes

The present invention relates to stone bodies for paving purposes. You already have different ones mineral aggregates used to build road surfaces or their use suggested, namely usually together with bitumen or cement. There is a disadvantage of the materials proposed so far in that they tend to rub off until they become smooth after a relatively short period of time, and they then result in a polished surface, which is little for the tires of the vehicles driving over them is easy to grip. Other materials have the disadvantage that they are extremely porous, which in turn is a minor one Has compressive strength.

There has now been a method of making stone bodies for paving purposes that have high durability against being bare-ground (which is available as

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"Polished stone value" or P.S.V. can be measured), and developed from masses in which a high P.S.V. with a high Compressive strength is combined.

The present invention relates to a process for the production of stone bodies for road paving purposes, which consists in that a "red mud" or a powdered, siliceous, refractory, industrial by-product in the absence of solid fuels to a sintering temperature of over 1000 ⁰ C, but below The melting point of at least the majority of the powder components is heated, if necessary the sinter is crushed in order to obtain a sintered product in the form of granules. The term "red mud" used in this description of the invention is intended to denote the residue which is obtained during the alkaline extraction of bauxite for the purpose of obtaining aluminum. A typical "red mud" has the following composition: Al ₂ O, 16 %, Fe ₂ O ^ 53 %, TiO ₂ 8%, SiO ₀ 6 %, Na ₀ O 3 % and CaO 3 %.

The siliceous one. " Refractory industrial by-product can be made from a ground natural stone, e.g. quarry or other rock debris, from powdered slag such as blast furnace slag, copper slag, phosphorus furnace slag or cupola slag, from fine sand or other alluvial sand, such as is obtained from dredging, or powdered pulp ash occurs as a by-product in power plants heated with hard coal. The term "containing silicic acid" used in this description of the invention is intended to refer to a by-product which contains at least 30 % SiO ₂ .

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The "red mud" or the powdered silicic acid, Refractory material should suitably have a particle size of less than 1 mm, preferably a particle size corresponding to a mesh screen fineness of less than 50 meshes, e.g. from 400 to 50 meshes, based on sieves of the British Standard sieve series. The product should preferably be viewed (after grinding, if necessary) to obtain granules of one particle size from 3.175 mm to 25.4 mm (1/8 "- 1"), e.g. from 12.7 mm (1/2 ").

The powdery material can advantageously consist of a Mixture of 2 or more silica-containing by-products exist. For example, mixtures of slag and fuel ash, "red mud" and fuel ash or sand burglar and fine sand can be used. It is also possible to use other particulate materials, such as ground bauxite, or spinels, such as "chromium residue", to be added as described in the pending British patent application No. 58319/69 the inventor of the present process is revealed.

To facilitate sintering, the mixture can be a flux m medium, such as calcium fluoride or soda included.

However, thanks to the presence of impurities, many industrial by-products are also themselves Flux, and most of them are quite easily sinterable even without the addition of a flux.

The term "sintering" is used here to mean the aggregation of Particles when heated to a temperature below

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denote their melting point, each particle purely physically connected to those particles with which it is in contact, and it loses its separate independence, at least the majority of the material remains in the solid state,

The "red mud" or the powdery, silica-containing, Refractory material is then calcined in the substantial absence of a fuel material. The expression "essentially in the absence of a fuel material" is intended here to mean the fact be that the amount of carbonaceous or other fuel material is insufficient to the Burning the mixture to sustain itself. The presence of the Fuel material in the calcined mixture develops gases, creating an undesirably porous Product of low compressive strength is created. It is therefore more advisable to rely on heating sources that are outside of the mixture to resort to properly effecting the sintering. That way will a product of higher compressive strength and good P.S.V. obtain.

The "red mud" or the powdered, silica-containing by-product can be heated directly, for example by forming a bed on a moving grate. Eu is, however, more advisable to first slurry the by-product or moisten it with water.

The amount of water to be mixed with the powder can be sufficient to form a pumpable slurry, or it may just be enough to keep the powder moist

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and make a stiff paste or plastic material. Some by-products, such as Alluvial sand can occasionally be extracted in a sufficiently moist condition, so that in this case a further addition of water is unnecessary,

The slurry can be calcined directly, e.g. in a rotary kiln. Deviating from this, the moistened powder can be extruded or compressed or wet granulation before calcining Pellets are deformed. The pellets are conveniently shaped in the presence of a binder, such as soda waterglass, and they can be in the course of a preparatory Kalziniex'-quaint be dried before sintering. Another working method for performing the sintering is in deforming the moistened powder by molding in a press mold into brick-like shaped bodies and then to bake the bricks, e.g. in a tunnel kiln.

If the mass is deformed into bricks, it is advisable to to use a shape that has a roughened inner surface. It is much more advisable to use bricks to form in shapes that impress a system of indentations or similar constrictions, creating each Brick is divided into a multitude of tablet-like shaped bodies, which are supported by relatively narrow material pegs are in communication with each other, so that the breaking of the bricks to be appropriately dimensioned Pieces is made easier during later chopping.

Each of the three sintering methods listed as preferably suitable, E.g. the heating of a sole insulation in one

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Rotary kiln, pelletizing the batch before sintering and forming into bricks has its special advantages. The slurry is a particularly cheap one and convenient way to obtain the sinter, but leaves no precise regulation of the size of the Product granules too. Pelletizing allows better adjustment of the size of the granules. The education the brick is the most complex method, but creates the best way to adjust the ' Granule size and at the same time makes it possible, by using a suitable shape, to cut the granules with a equip roughened surface.

The powdery materials, the slurry, the Pellets or bricks are calcined by the application of external heat, i.e. they become hot Gases exposed at temperatures for as long as they are sufficient to cause these materials to sinter to accomplish in directly or indirectly heated ovens.

As was further found, a technically particularly satisfactory stone body for road paving purposes can be obtained by sintering a pelletized, ground slag, in particular also by the fact that pellets of ground slag mixed with a relatively hard, particulate, refractory material sinters.

According to a further embodiment, the present invention relates to a method for producing stone bodies for paving purposes, which consists in pelletizing a powdery slag and the Pellets then sinter.

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The term "slag" used in this description of the invention is intended to mean a material containing lime or silicic acid refer to that as a molten by-product in metallurgical processes or when heating Ores accumulate. These include blast furnace slag, phosphorus furnace slag, cupola slag and copper slag. This expression also includes falling slags, albeit less so are well suited. The preferred slag is the phosphorus furnace slag.

According to this embodiment of the present invention, the slag is first ground so finely that it

Case can be pelletized. _A typical in the slag to a particle size of less than 1 mm, preferably relative to a fineness of less than 50 mesh, on the screens of the British Standard Sieve Series, comminuted. The crushed slag can then be pelletized using various known working methods. Preferably, the powder is first converted into a paste with water and the paste is granulated or extruded and dried to form pellets. It is also possible to use binders for the pellets, for example sodium silicate. In the typical case, _the% pellets have diameters of 3.175 mm to 25.4 mm (1/8 "- L"), for example from ltj, 7 mm (l / 2 ^H), on.

The pellets can optionally contain an additive Flux, such as CaFp, contain, but this is usually not necessary, since the slags in general at the same time represent fluxes themselves.

It is possible to incorporate a carbonaceous fuel into the pellets, which by burning it

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supports the sintering, but it is better to refrain from such additions and to relate to of sintering to rely on the heat of the furnace.

The pellets are calcined in a rotary kiln, for example, at a temperature sufficient to produce a hard sinter. Typical temperatures that are used are between 1000 and ^{1200 ° C., preferably between 1100 and 1300 °} C., for example 1200 ^° C.

As has been found, with some slags it is possible to produce the stone body for road paving purposes in each desired color tones by the fact that the heating conditions adjusts accordingly. For example, phosphorus furnace slag can provide a stone that is yellow to can be dark brown, with the darker shades being achieved through prolonged firing or higher temperatures.

A preferred embodiment of the present invention thus relates to a sintered, pelletized slag, in their pellets a relatively hard, particulate, refractory material is incorporated.

The particulate refractory material can be any of Substance that is harder than the sintered slag and that is not completely at sintering temperatures melts. The material chosen is preferably one that has a limited reaction with the slag during calcination enters, so that the hard particles are chemically bound in the softer basic structure of the slag. to Typical representatives of the particulate refractory material include sand, calcined bauxite, crushed refractory bricks and those used in chemical extraction

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of the chromium obtained from chromium ore. The material listed last is special Advantage usable.

The hard, refractory particles should have a particle size aif ways that are used for pelletizing together with the powdered Slag is suitable. The particles can be smaller than 1 mm; they preferably have a mesh screen fineness of the order of 400 to 50 meshes, E.g. one of 300 to 100 meshes, each covered on the sieves of the British Standard sieve series.

The hard, refractory particles are mixed with the powdery Slag preferably in a proportion of 40 to 90 percent by weight, better still of 6o up to 80 percent by weight, e.g. from 75 percent by weight, each based on the mixture.

The hard, refractory particles can be mixed with the powdery slag before pelletization. The product can be prepared in essentially the same manner as described above with reference to the slag alone , pelletized, calcined and applied.

It has been found that the structure of the preferred article of the invention, which consists of hard particles embedded in a softer matrix, works particularly well is suitable for paving purposes as it has less tendency to be sanded smooth in use as known stone bodies.

The product of each embodiment of the present invention can be crushed and sifted and then used as a topping

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material to be used for roads. Preferably, the stone body with bitumen, cement or a Resin binders mixed to form a compact pavement.

The invention is to be explained in more detail by the following examples.

example 1

A mixture of 25 $ phosphorus furnace slag, mesh screen fineness -170 mesh, and 75 % copper loop, mesh screen fineness -52 +100 mesh, was pellefcized and fired at 1040 to 1080 ° C. for 2 hours. The product had a PSV of 74.

Example 2

"Red mud" was pelletized and fired for 1 hour at 1250 ⁰ C. The product had a PSV of 62.

Example 3

Copper slag, -100 mesh sieve, was pelletized and 1 hour at 1175 dukt had a P.S.V. from 78 to.

pelletized and burned at 1175 ° C for 1 hour. The "pro

Example 4

A mixture of 25% phosphorus furnace slag, Maschensiebfeinheit -I70 mesh, and 75% copper slag, Maschensiebfeinheit -100 mesh, was fired for 2 hours at 1050 ⁰ C. The product had a PSV of 68 and an aggregate abrasion number of 3.4.

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Example 5

Phosphorus furnace slag was reduced to a degree of fineness of -100 meshes, mixed with water to form a paste and shaped into 12.7 mm (1/2 ") granules. The Pellets were calcined at 1150 ° C. The product pointed a P.S.V. from 66 to. One not sintered and too 12.7 mm (1/2 ") granules had crushed slag comparatively a P.S.V. from 45 to.

Example 6

"Chromium residue", mesh sieve fineness -200 meshes, was mixed with 1/5 of its weight phosphorus furnace slag, which had been comminuted to a fineness of 100 meshes. The mixture was formed into 12.7 mm (1/2 ") pellets and fired at 1200-1250 ° C. The product had a PSV of Qf .

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Claims (2)

Claims 1. Process for the production of stone bodies for Road surfacing purposes by heating a powdery Mineral material to a sintering temperature that is above 1000 ° C and below the melting point at least the vast majority of the powder ingredients, and if necessary Crushing the sinter to form a granulated sintered product, characterized in that that the powdery material made of "red mud" or a silicic acid, refractory industrial by-product that is essentially free of solid fuels. 2. The method according to claim 1, characterized in that the powder from rubble or natural stone dust, pulverized slag such as phosphorus furnace slag, fine sand or alluvial sand obtained by dredging or powdered fuel ash. 3- Process for the production of stone bodies for paving purposes by heating a powdery! Mineral to a temperature above 1000 ° C, but below the sintering temperature of at least the vast majority of the powder components for the purpose of forming a granulated sintered product, characterized, that the powdery material consists of a slag, such as Phosphor furnace slag, which is slurried with water and shaped into pellets before sintering. 109824/1746 A method according to contain any of the preceding claims, characterized gekennzeichne t that the powder also particles of harder, refractory mineral substance, such as Chrornrückstand, calcined bauxite, crushed refractory bricks or quartz sand. 109824/1746