EP0091603B1 - Building material of mine waste and binding agents for the lower supporting layers in road construction, and process for its production - Google Patents

Description

The invention relates to a building material for the lower base layers in road construction from mining material and binders and a method for producing this building material.

In road construction, it is common to first solidify the grown subsoil and then to apply multilayer lower base layers and multilayer upper base layers. The lower base layers primarily serve to protect against frost and usually consist of a first layer of sand or gravel and a second layer of blast furnace slag, hard limestone or similar materials, the total thickness of the lower base layer being around 30 cm. Bituminous, hard materials with low moisture absorption are used in the upper base layers to prevent the upper base layer from flaking off in the event of frost.

In the past, attempts have been made to improve the frost resistance of the lower base layers by using mineral mixtures or frost-resistant sands with a grain size of 0/56 in this area. This procedure required careful previous leveling and compaction of the grown soil and subsequent thorough compaction of the base layer with vibrating rollers in order to obtain the most homogeneous lower base layer possible with high density.

Attempts have also already been made to use cement-bound recovery material in the lower base layers (DE-A-2522851). Such so-called "hydraulically bound" base courses require, depending on the moisture content, different, longer setting times during which they cannot be used. In addition, with such a material for base layers, there is a risk of cracking and bulging.

The invention is therefore based on the object to provide a building material of the type mentioned, which does not have the aforementioned disadvantages and is easy to process; in particular, this building material should be insensitive to frost and ensure good strength of the lower base layers. The solution to this problem is based on the basic idea of mixing mining material with a bituminous material and processing it in the usual way into one or more lower base layers; such mixtures preferably have the compositions mentioned in claims 2 and 3.

Such a building material has excellent frost resistance and is at the same time very homogeneous and protected against cracking and bulging. Such a building material is comparatively light and can be applied in any width with a normal paver on the grown and possibly compacted surface for a street. In comparison to the use of mineral mixtures for the lower base layer, only a very few machine hours are required for this. The building material has the further advantage that it can be driven on with heavy equipment at any time immediately after being rolled off and has permanent flexibility. Lower base layers made of the building material according to the invention can be about a third thinner than when using the previously known material.

It should be surprising that the well-known high tendency of mining material to decay in air and especially in connection with moisture could be prevented by the use of bituminous binders and that extremely small amounts of binders are necessary for this. It was also surprising that the strengths of the lower base layer produced from such a building material are extremely high at a relatively low weight, although the mining material itself has considerably lower strengths than the previously customary building materials for the purpose in question. Compared to the hydraulically setting materials, in which salvage material is used, it was particularly surprising that the use of bituminous binders, despite the poorer wetting properties known to be worse than the hydraulic binders, permanently protects the salvage material against decomposition by air and moisture.

Untreated mountains can be used as starting material, which accumulate as a secondary rock in the extraction and processing of coal. Possible bituminous binders are those based on petrochemicals or tar, but also corresponding products of coal extraction. The softening points of the bituminous binder are largely in the free choice of the user, who selects this criterion on the basis of empirical values that are well known in road construction. - The latter also applies to the grain band of the recovery material. A mineral fine-grained filler (claim 3) can be of basically any origin, its grain size must be such that this filler fills the particle gaps in the recovery material. For this purpose, grain size ranges between 0 and approximately 1.5 mm can be considered. The use of mining material itself as a filler has proven to be particularly advantageous for achieving the homogeneous lower base layers; it is advantageous because of the grain spectrum to remove this filler from recovery material from the so-called abrasion, which inevitably arises and is separated when the recovery material dries (according to patent claim 3).

It has been shown that the building material according to the invention can preferably be used in two different modifications:

In the case of multi-layer lower base layers, the overall thickness of the lower base layers, while otherwise being insensitive to frost and strength, can be reduced by (according to claim 2) untreated, i.e. unclassified and moist washing mountains as recovery material and 1 -5% by weight of a cold to be processed as bituminous binder bituminous binder can be used. To process such cold Tending bituminous binders are generally known, but have so far only been used in connection with specially selected minerals for road construction. These so-called cold bitumens consist of the known bitumens, which are still sufficiently liquid with a so-called flux oil up to temperatures of around 5 ° C to be mixed and processed with a filler. The flux oils escape from the cold bitumen under the pressure when the lower base layer is compacted; only then can the bitumen produce its known binding effect; such cold bitumens are understood to mean bitumen emulsions, bitumens dissolved with solvent and correspondingly soft tar products. This processing can - also with the washing mountains according to the invention - be processed in the so-called “mixedand plain method”, in which the bottom support layer is applied to the substrate in the desired thickness exclusively from washing mountains and then with the appropriate amount of preferably 1.5- 3% of the cold bitumen can be sprayed. This layer is then mixed with a milling machine and then compacted with a static roller or a vibration compactor. Of course, this building material can also be processed using the mixed and place method, ie mixed first and then applied and compacted as a base course. - Surprisingly, such a building material is very insensitive to frost and wetting agents (examples ...) which are known per se are only required in exceptional cases in order to ensure thorough washing of the washing mountains with the cold bitumen. This is surprising insofar as the wash mountains, which are very sensitive to frost, with their high proportion of inner surface, slate cleavage surfaces and so-called cohesive fine grain, allow a good covering with cold bitumen, thereby eliminating the sensitivity to frost.

The other modification (according to claim 3) is that both single-layer and multi-layer lower base layers, but in particular the upper layers of multi-layer lower base layers, are produced from mixtures according to features a) to c). The bituminous binder used can only be processed warm. Although this building material requires more energy due to the drying of the mining material and the subsequent hot processing, it has the advantage that it can also be used for the upper layers of a multilayer lower base layer. Of course, all lower base layers can consist of this building material, but there is a particular advantage if additional lower base layers made of a building material (according to claim 3) are applied to a bottom lower base layer (according to claim 3), because then the total thickness of the lower base layer is added same quality properties can be reduced.

The object is achieved with regard to a method according to the characterizing features of patent claim 5. It is advisable to sieve oversize and / or so-called fishy material that may still be present after classifying the recovery material and before the drying process in order to increase the homogeneity of the building material; since such oversize usually only occurs to an extremely small extent, the weight loss resulting from the screening can be neglected. Drying is preferred at 140 to 220 ° in a rotary kiln with simultaneous elimination of the abrasion, which is temporarily stored in a special silo for further use as a filler. It is particularly advantageous to use all of the dried recovery material, including the abrasion, and to add 2.5 to 5% by weight of its total weight of bitumen to this dry substance. 2.5 to 5% by weight of the dry substance consist of the fine-grained filler.

During mixing, temperatures must be maintained at which the bituminous binder is free-flowing. The processing for lower base layers in road construction takes place at temperatures between approximately 100 and 140 ° C. Lower base layers obtained in this way meet the regulations of ZTVE-St B 76 (additional technical regulations and guidelines for earthworks in road construction, edition 1976).

Examples:

For a heavily loaded road for the transport of salvage material on heaps, which is loaded with an hourly load of about 1000 t payload plus the weight of the transport vehicles, the following overall road construction had been implemented: First the terrain was rolled out of piled-up material and then with a 20 cm thick layer provided from the building material according to the invention, to which, after rolling, an upper base layer of conventional bitumen-bound minerals was applied. A mining material was used as the starting material for the building material, which was obtained in a processing plant of a shaft system in the eastern Ruhr area in the laundry with a grain size of 0 to 120 mm. This starting material was classified on a grain belt between 0 and 80 mm. The oversize was then screened again. This material was then dried in a gas-operated rotary kiln in an open flame at temperatures of around 180 ° C. in the drum. The drying time took about 5 minutes and the original moisture of the starting material was reduced from about 5% by weight to an insignificant residual moisture of less than 0.5% by weight. During this drying process, a dust-like abrasion of the starting material in the furnace air occurred, which was sucked off together with the furnace air and then separated from the furnace air and collected by filters. The raw material treated in this way became there after in a compulsory mixer at about 170 ° C with about 2.6% (based on the total material discharge from the dryer) of a petroleum bitumen B 80 according to the regulations of road construction ZTVE-ST B 76. In addition, 4.6% by weight (related to the total discharge from the rotary kiln) of the abrasion, which had been separated from the furnace air as described above. The building material thus obtained was transported directly to the construction site and applied to the prepared substrate at about 120 ° C. by means of a paver and then compacted with a rubber wheel roller and static roller.

. The lower base layer produced in this way was therefore easy to process and did not require a large amount of machinery and, despite its low specific weight, withstood the aforementioned high loads without damage, and in particular no frost broke out.

Claims (5)

1. Building material for the lower base course in road construction made from mine waste and binding agents, characterised by a mixture of mine waste with 1 to 6 wt.-% - in relation to the total mixture - of a bituminous binding agent.

2. Building material according to claim 1, characterised by untreated tailings as mine waste and 1 -5 wt.-% of a bituminous binding agent which is to be used in a cold state, for the lowest layer of a multi-layer lower base course.

3. Building material according to claim 1, characterised by a mixture of

a) approximately 88 to 98 wt.-% of dried mine waste with a grain size range from 0 to a maximum of 120 mm;

b) approximately 2 to 6 wt.-% of a bituminous binding agent and

c) 2 to 6 wt.-% of a substantially mineral fine- grained filler for filling the gaps between the particles of the mine waste.

4. Building material according to claim 3, characterised in that the filler consists of the fines from the drying of the mine waste.

5. Process for the production of a building material according to claim 3, characterised in that the mine waste

a) is classified according to a predetermined grain size range,

b) is then dried at approximately 140 to 220° C and has the fines which are produced removed from it, and

c) is then homogeneously mixed in a mixer together with 2 to 6 wt.-% of the filler- in relation to the total weight.