EP0659202A1

EP0659202A1 - Method of producing synthetic gravel and/or chippings containing salt

Info

Publication number: EP0659202A1
Application number: EP93918985A
Authority: EP
Inventors: Wilhelm Kämereit; Alois Boes
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1992-09-09
Filing date: 1993-09-08
Publication date: 1995-06-28
Also published as: NO950872D0; WO1994005740A1; FI951075A0; NO950872L; CA2144150A1; FI951075A; DE4230545C1; JPH08501116A; AU4943993A

Abstract

A mortar mixture, made up with mixing water, is used in particular for bitumen-bound road surfacings and consists of salt (preferably NaCl or KCl) having a grain size not exceeding 0.5 mm, mineral fines having a grain size not exceeding 1 mm, and cement.

Description

Process for the production of a synthetic saline

Crushed sand and / or chips

The invention relates to a method for producing a

synthetic salty crushed sand and / or grit for the

Production of cover layers of traffic areas such as roads or sidewalks according to the preamble of claim 1.

A generic method is from Czechoslovak

Patent document Z5S 296 B1 known. In this procedure

40 - 70 parts by weight of NaCL with 10 - 20 parts by weight of granite chips with a maximum grain size of 4 mm and 20 - 40 parts by weight of cement, mixed with mixing water and hardened. Additional proportions of sand and limestone powder can be added to the mixture. The hardened dry mortar mixture forms a solid block and is then broken in a stone crusher so that a coarse-grained material (grit) is present. This synthetic grit can be used for the production of bitumen-bound cover layers for traffic areas. Due to their salinity, the grains of gravel lying on the surface or exposed by the wear and tear on the ceiling lower the freezing point of water. This can ensure that, for example, road surfaces, in which this material was installed, at temperatures around the

Freezing point (e.g. down to approx. - 3 ºC) remain ice-free and can easily be cleared of snow in heavy snow, since the snow does not adhere. A disadvantage here is, however, that the salty chippings from surface water over time

is inevitably leached out, i.e. the salt grains are dissolved to a considerable extent and the solution is flushed out. Only one remains of the original grit

skeletal matrix body with numerous pores. This matrix body inevitably has a considerably reduced impact strength compared to the original grit. Investigations have shown that leached chippings in the impact crushing test generally no longer have the required minimum strength values for a road surface. Use of this synthetic grit e.g. in road surface construction can therefore lead to the fact that

Traffic load after advanced leaching

The resulting porous chippings break up, i.e. in themselves

coincide, so that larger voids can arise in the top layer covering, which ultimately lead to a premature destruction of these

Lead surface layer.

From DD 271 347 AI the production of a concrete traffic area from a mortar mass is known, to which 2-5% chloride- or sulfate-containing compounds are added to lower the freezing point of water. The amount of the freezing point lowering agent is relatively small, so that there is no blooming of salt. Since the salt used is not hydrophobic, it can be washed out quickly under the influence of moisture, so that the freezing point-lowering effect wears off relatively quickly. The preparation of a salt-containing crushing sand or grit is not considered in this document.

DE-A 29 23 939 describes the production of a salt-containing filler as an additive for road surface construction, a fine-pored mineral (red filler) being used as the basis. The red filler is treated with a saline solution so that the solution penetrates into the cavities of the red filler and the added salt is deposited therein by drying. In order to prevent an undesirably rapid leaching out of the salt when this agent is used in road construction, the filler is made hydrophobic with the aid of silicon compounds. In this document, the production of a salty crushed sand or grit is also proposed. The binder is not cement, but a hardenable synthetic resin, so that there is no water-containing mortar at any time during the production process.

Furthermore, various patent documents such as

EP 0 422 753 A1, DE 34 04 271 A1 and DE 41 29 621 A1. Processes known for producing salt-containing fine grain mixtures with a grain size of less than 0.2 mm, the salt portion being provided with a hydrophobization. These fine grain mixtures also serve as fillers for the

Production of bitumen-bound surface layers of traffic areas and in turn have the task of preventing or at least greatly delaying icing of the surface layer surface.

The Feinkorngemsich according to DE 3404 271 AI is produced by dry grinding several components together. In a variant of this method, cement is added to the mixture. However, this measure only serves to bind any small amounts of moisture that may be present and to reliably maintain the flowability of the fine-grain mixture until it is used. A water-based mortar is not present either in the production or in the use of this fine grain mixture when installed in traffic areas.

Since the proportion of chippings in a bitumen-bound top layer is considerably larger than the prescribed proportion of filler material, synthetic grit can be added to the top layer mixture

correspondingly more salt than the freezing point lowering center L than through the filler. The amount of salt available in the top layer is, however, a major determinant of the frost temperatures up to which the desired effect lasts. This temperature limit should

of course as low as possible for reasons of

Traffic safety and to largely avoid the use of additional road salt as a thawing agent.

The object of the invention is therefore a manufacturing process for a synthetic salt-containing chippings according to the generic term of

To propose claim 1, through which a grit is available that shows a significantly improved stability behavior and is well suited for the production of traffic surface coverings.

This object is achieved by a generic method with the characterizing features of claim 1. Advantageous

Further developments of the invention are specified in subclaims 2 to 9. The invention is described in more detail below.

The invention provides for a mortar mixture with salt mixed with water (preferably NaCl or KCl) with a grain size of at most 0.5 mm, preferably at most 0.2 mm, and from mineral fines with a grain size of at most 1 mm, preferably at most 0.5 mm, and cement. The mineral fines can, for example, in the form of sand or rock flour (in particular

Limestone powder) can be added. This addition can also be carried out in a moist state, so that 5 grinding sludges which are produced in stone processing and which in themselves have to be disposed of at low cost are added to this Purpose are easily usable. It is particularly important that the salt granules have been made hydrophobic before the mortar mixture has been prepared. The proportion of the hydrophobicized salt can advantageously be in the form of a fine grain mixture beforehand, for example according to EP 0 422 753,

DE 34 04 271 A1 or DE 41 29 621 A1. In this respect, the "salt fraction" can also be a certain mineral fraction

Contain fillers. It is important that mixing in a lot

intensive form in a compulsory mixer over a sufficiently long time. The time required depends on the design of the mixer and its mode of operation (e.g. speed). An inadequate one

Mixing leads to a "blooming" of salt crystals from the hardening mixture, so that part of the salt is not bound by the cement into the matrix bodies of the individual grit grains, so that the salt content of the grit grains is reduced accordingly from the outset. The amount of mixing water to be added should be kept as low as possible in order to produce a particularly hard grit. The water / cement factor can range from 0.3 to 0.6. Lower values lead to even better results. To

With sufficient mixing, the mortar produced is at least cured to a certain degree before it is crushed to the desired size of the grit in a stone crusher. A grain size of at most 5.6 mm is preferred. The shredding can take place as soon as the mortar is dry and sufficient

Has reached minimum strength, ie a complete hardening is not necessary before the shredding. It is only necessary that a strength is achieved at which an undesirably high fine fraction no longer arises during the comminution. The final hardening can easily take place even in the crushed state. It is advisable to classify the shredded product, whereby the fine fraction is separated out. Grain size fractions in the range 0.09-5.6 mm are preferably sought for the synthetic grit. In a further development of the invention, a fiber material, in particular glass fiber material, is added to the mortar during mixing. It is particularly expedient to use a recycling material for this purpose, which is obtained by shredding glass-fiber-reinforced plastic waste. Only the coarse fraction with a fiber length of 2 - 8 mm should be used, especially since the fine fraction again for the

Manufacture of new glass fiber reinforced plastics can be used. The impact strength of the grit is significantly improved by the fiber material. In addition, there is the advantage that the bitumen adheres to the chippings much better when a mixture for the covering of a traffic area is subsequently produced.

The composition of the mortar mixture is expediently in the following areas:

20 - 70 parts by weight of hydrophobic salt

5 - 30 parts by weight of mineral fines

10 - 40 parts by weight of cement

6 - 25 parts by weight of water

In addition, a proportion of 2 to β parts by volume

Fiber material are added to the mortar mixture.

Finally, the usability of the synthetic chippings produced according to the invention can be improved further by the hydrophobized salt (eg NaCl, KCl) being mixed with a Corrosion protection agent is treated. This reduces the corrosion potential which increases as a result of the salinity and which, in particular on road structures (for example bridge structures), could cause disadvantages.

The formation of inadmissibly large voids in the top layer covering, which would lead to premature wear of the top layer, is caused by the following when using chippings produced according to the invention

Effects avoided: The use of a particularly fine-grained salt reduces the possible pore size in the individual grit accordingly. In addition, the leaching by the surface water is significantly reduced or greatly delayed by the hydrophobization. In addition, the strength remains from the outset thanks to the installation of fiber material, even with leached grit, at significantly higher values. Finally, the limitation of the grit size to a maximum of 5.6 mm means that the resulting cavity of the top layer can also be at most 5.6 mm even in the event of the destruction of a single grit.

Overall, this leads to a considerable extension of the service life of the top layer. It is also advantageous that a finer and more uniform distribution of the batch in the top layer is ensured as a result of the smaller grit grains. The "active" surface of the salt portion is increased compared to the conventional coarse synthetic grit, so that the thawing effect of the salt is particularly good. Of course it is possible to

Chippings produced according to the invention can also be used together with a filler, which also has a freezing point-lowering effect, in a top layer covering. This allows the effect of ice formation inhibition to be achieved at considerably lower temperatures

ensure than was previously possible. Because of the hydrophobization, the grit produced according to the invention could also be used for cover layers other than bitumen-bound,

for example, on the basis of concrete mixtures.

Execution example:

In a concrete mixer

40 parts by weight of hydrophobic salt

(produced according to DE 41 29 621 A1 with a NaCl content of 90% by weight)

15 parts by weight of mineral fines

35 parts by weight of cement PZ 55

3 parts by weight of shredder material made of glass fiber reinforced

Epoxy resin waste with a grain size of 1 to 4 mm

12 parts by weight of water mixed intensively. The mixing time was at least 4 minutes. After a hardening time of 7 days, the stone blocks produced from the mortar mixture were crushed in a stone crusher to a maximum grain size of 5.6 mm. The finest fraction below 0.09 mm was discarded and the rest of the shredded material in grain fractions of

0.09 - 0.25 mm, 0.25 - 2.0 mm and 2.0 - 5.6 mm split. The synthetic crushed sand and synthetic grit produced in this way could be processed in a bitumen mixture to form a road surface that remained ice-free up to temperatures of - 8 ° C. The examination of individual grains in impact crushing tests, which was carried out after intensive leaching of the grains with water, showed strength values which correspond to the requirements with regard to the life requirements of road surfaces.

Claims

1. Process for producing a synthetic saline

Crushed sand and / or chippings for, in particular, bitumen-bound top layers of traffic areas, whereby a granular salt is mixed with cement, mineral fines and water, the mortar obtained is largely hardened and broken into grains in the dry state,

characterized,

that a hydrophobized salt with a grain size of less than 0.5 mm is used, that the grain size of the mineral fines is less than 1 mm and that the mixing is carried out intensively in a compulsory mixer.

2. The method according to claim 1,

characterized,

that the grain size of the hydrophobicized salt used is less than 0.2 mm.

3. The method according to any one of claims 1 to 2,

characterized,

that the hardened mortar is broken down to a grain size of maximum 5.6 mm.

4. The method according to claim 3,

characterized,

that the broken hardened mortar is classified to achieve grain size fractions between 0.09 and 5.6 mm.

5. The method according to any one of claims 1 to 4,

characterized,

that a fiber material, in particular glass fiber material, is added to the mortar before curing.

6. The method according to claim 5,

characterized,

that a recycling material is used as the glass fiber material, which was obtained as a coarse fraction with a fiber length of preferably 2-8 mm from shredded glass fiber reinforced plastic waste.

7. The method according to any one of claims 1 to 6,

characterized,

that the proportions of the components of the mortar mixture are within the following limits:

20 - 70 parts by weight of hydrophobic salt

5 - 30 parts by weight of mineral fines

10 - 40 parts by weight of cement

6 - 25 parts by weight of water

8. The method according to claim 7,

characterized,

that in addition 2 to 8 parts by volume of fiber material in the

Mortar mixture can be given.

9. The method according to any one of claims 1 to 8,

characterized,

that the hydrophobicized salt used with a

Corrosion protection agent is treated.