WO1995010663A1

WO1995010663A1 - A method and a material for making luminescent roads

Info

Publication number: WO1995010663A1
Application number: PCT/DK1994/000384
Authority: WO
Inventors: Torben Hove Jensen
Original assignee: VEJTEK INTERNATIONAL AS
Current assignee: VEJTEK INTERNATIONAL AS
Priority date: 1993-10-13
Filing date: 1994-10-13
Publication date: 1995-04-20
Anticipated expiration: 1996-04-13
Also published as: DK114793D0; FI961609A0; NO961431D0; FI961609A7; SE9601417L; SE9601417D0; NO961431L; AU7808094A; FI961609L

Abstract

For the production of fluorescent bituminous roads it has previously been suggested either to effect a mineral melt-down of a considerable portion of the stone material or to use a fluorescent oil in the material mixture. This is expensive and little efficient, respectively, and in connection with the invention there is instead made use of a dyestuff which, in a small proportion, is mixed into a matrix forming material, preferably based on cement, sand and water on a hardenable plastics compound, this mixture being used either directly, as a surface paint, or in being brought to hardening and granulation, whereby the granulate may then be admixed into the road material. Even concrete roads may be made fluorescent, and furthermore it will be possible to use phosphorescent agents.

Description

A method and a material for making luminiscent roads.

The present invention relates to a method for making a road surface of luminiscent type, primarily a surface being fluorescent by irradiation with ultravio¬ let light. According to for instance SE-B 462,109, there has previously been experimented with the principle of making the road itself luminiscent by the use of vehicle lights or auxiliary lights with a high content of UV- light, as a significant improvement of the road sight is hereby achieved. However, the previous attempts have hardly ever left the laboratory phase, as it is crucial for the applicability of the concept that the desired character of the surface is achievable in an efficient and yet non-expensive way. The hitherto suggested solu¬ tions are either too weak or too expensive for practical applicability, and it is the purpose of the invention to suggest a technique which is suitable for use in prac¬ tice in an economic and efficient way.

In the suggestion according to said SE-publication is used an admixing of a mineral prepared by a melt-down and a dotering with an actuator making the material fluorescent, whereafter the hardened material is granu¬ lated by grinding into suitable acroparticels, which are mixed into the roadsurface material. The preferred mixture is of 10-20, optionally up to 25 weight percent, but this, then, will imply a mineral melt-down of a correspondingly large part of the volume of the road layer, which is a very expensive process. At best a fluorescent marking layer of for instance lane stretches is implementable, but hardly a total road layer.

According to WO 92/18573 a significant cheaper solution can be aimed at when using a binding agent in the form of a special fluorescent oil in the road sur¬ face material. It is quite essential that it is hereby possible to avoid the said mineral melt-down, but in return it must be accepted that the fluorescent effect becomes relatively weak, as the usable oils are rather faint fluorescent, even further weakening in time.

It is at the basis realized by the present inven¬ tion that it will be possible to make use of both non- -expensive, durable and highly efficient fluorescent or even phosphorescent agents, if these are compounded into a matrix forming material being suitable to compound with the road material in an appropriate way, by admix¬ ing therein or coating thereon. There need not be direct reconciliability between the active agent and the road material, as, for instance, it will be possible to add a aqueous dyestuff to a bitumen material by first admixing the dyestuff into a cement based casting material, which, after hardening, is granulated and then mixed in¬ to the road material just like any other filling agents. The granulate in question, which can also contain for instance sand, will be coated by the binder in the road material, but after a slight wearing-off of the road surface, the granulate in the surface layer will be ex¬ posed and thus present the luminiscent effect.

Correspondingly, an aqueous solution of a lumini¬ scent agent will be applicable as a thin surface layer when it is compounded into an aqueous cement grout, which is applied as paint, preferably with a further content of sand or other wear resistant material. The paint will after setting make excellent adhesion to the base course, inter alia by being absorbed by depressions into the road surface.

Furthermore, the invention is based on the consi¬ deration that generally - no matter whether the applied active agent is liquid or solid - it will be advantage¬ ous to incorporate the agent in an independent structu¬ ral matrix, inter alia because in the same matrix there may be other agents specially suited as concomitant agents, for instance a white dyestuff that may promote the reflection from an fluorescent agent without the said concomitant agent having to be present all over the road material. In other words, the effect of the active agent can be optimized in exactly the subareas where it occurs, just as the same subareas or macroparticles, for instance by said application of sand, may be adapted to appear as mechanically acceptable parts of a road layer. The remaining part of the road material, which will normally constitute the major part of all the material, can then be prepared completely without considerations as to the desired special effects of the road surface.

According to the invention it will then also be relevant to make use of solid active substances, which can be aquired at a very low price level. In connection with the invention this price level can be extra low because it is in this connection acceptable to operate . with a luminiscense in a "muddy" colour scale, while normally bright signal colours are used, requiring ex¬ pensive active substances. It is estimated not to be relevant in the present case to delve deeply as to further comments on various applicable dyestuffs, as these in principle will be known beforehand, but it can be mentioned that a suitable dyestuff is produceable by a rather inexpensive processing of plaster, so that the price hardly gets higher than the one for cement. Cer¬ tain ones of the very inexpensive active substances, including zinc oxide, may show disadvantages as to sta¬ bility or environmental effects, viz. by a noticeable content of heavy metals, but partly there may very well be found other and more acceptable active substances, and partly there may in some incidents be compensated for the disadvantageous capabilities by admixing compen¬ sating agents into the limited matrix, in which the active substance occurs. The special structural matrix carrying the luminiscent agent need not necessarily be based on a hydraulic material, as for instance also a plastic matrix of polyester, polyurethane, acryl plas¬ tics or another corresponding material with an admixed hardener and optionally an accociated hardening accele¬ rating agent.

It may be attained for the same matrix to consist of a more or less transparent material in order to en¬ hance the effects of the active stuff. For instance, paraffin or transparent plastics may be used. By using suitable heat resistant dyestuffs even glass may be used, and generally ceramic matrixes such as for in¬ stance tile will be applicable.

However, already for cost reasons it is preferred to use cold setting or low-melting matrix materials, whereby there will be at disposal a large selection of applicable active substances. It should be mentioned, however, that the used UV-lamps should be adapted for defiltration of UV-rays in the short-waved area of the spectrum, as these rays are dangerous, and therefore active agents must be elected, which are active in the remaining, long-waved area of the UV-spectru .

By the building of concrete roads, the road materi¬ al itself may in principle be considered as a potential matrix for the luminiscent agent, almost no matter the kind or condition of this agent, when only the agent is resistant in the alkaline environments, but for good reasons it is preferred that the agent is only mixed into the top layer. This, however, will still be most suitable also for mixing into concrete or for instance by depression into the concrete surface.

The matrix granulate may be produced by a direct moulding into pellet or macro particle shape, but also by crushing of a manufactured voluminous solid material. After or in connection with the crushing a sieving may take place, whereby the actual granulate is isolated from the more fine-grained material, and the latter fraction may, optionally, be used for scattering on a not yet set road surface.

In the following the invention is illustrated by three examples.

Example 1 serves to illustrate the embodiment con¬ sisting of a fluorescent, cement based granulate being mixed into an ordinary stone material, whereby the road material or the like thus produced becomes fluorescent.

Example 1

White cement 15 parts by weight

Concrete sand 26

Fluorescent dyestuff Fiesta HMP5 1

Water 8

The applied powdered dyestuff is produced commer¬ cially by Swada Ltd., London. The dry components are mixed separately whereafter the water is added. The components are thereafter thoroughly mixed and grouted in slabs or the like, which, after setting, are crushed and sieved. The 8-12-fraction of a material produced by this recipe has been used for the making of a test road in full scale, whereby a surface treatment on an already existing road surface was effected, based on conventio¬ nal road building technique. The fluorescent granulate hereby constituted 40% of the total stone material, which consisted of bright granite. The layer showed a surprisingly powerful luminous effect, proved by test driving with a vehicle equipped with UV-lamps.

Example 2 is a recipe of a plastic based granulate, which can be applied in the same way as the cement based granulate according to example 1. Example 2

Unsaturated polyester containing:

Accelerator 25 parts by weight

Sand 110

Fluorescent dyestuff Fiesta

HMP5 2

50% solution of methyl ethylketone peroxides (MEKP) 0,5

Sand and dyestuff are mixed dry, whereafter these constituents are mixed into the polyester. When harden¬ ing is desired, the MEKP-solution is added, and the mass is moulded out. A mixture according to this recipe will harden by ambient air temperature, but the hardening may be expedited and the strength of the finished material be improved by a weak heating, for instance to 45°C. After hardening the material is crushed and sieved.

Reaction compounds according to the recipes in examples 1 and 2 will also be qualified for grouting in minor parts, these being used in a corresponding way as a given fraction of crushed material. Thus energy con¬ sumption and waste at the crushing is saved.

Example 3 illustrates the possible compound of a cement based paint for treatment of an existing road surface, whereby this is made fluorescent.

Example 3

White cement 36 parts by weight

Fine sand 64

Fluorescent dyestuff Fiesta

HMP5 2,5

Water 20

The dry compounds are mixed thoroughly, whereafter water is added. Thereby a thin paste is produced, applicable as a paint. The noticeable content of sand makes the paint wear resistant, just as it will counter¬ act moulding shrinkage and crack formations in the paint layer.

In connection with the invention it is hardly pos¬ sible to indicate specific limits for the admixture of the light substance into the matrix, but for the various applicable substances it is easy to determine a desir¬ able percentage by experiments. For the dyestuff men¬ tioned in the examples, usable results have been achiev¬ ed by an admixture of 0,05%, but of course a better effect will be obtained by a somewhat higher percentage. It has been found that with an increased admixture an area of a kind of saturation will occur, such that the effect will not be noticeably increased by any further addition. Normally, this area will be found by an admix¬ ture of less than 25%. Correspondingly, the degree of addition of dyestuff or matrix granulate in the road material may be adapted according to the desired effect, balanced with other relevant circumstances. It is even a theoretical possibility that a road can be made based solely on the matrix granulate with the use of a suit¬ able binder.

Vehicles moving in one traffic lane of a two-way carriageway may be provided with a UV-light equipment which will also activate the opposite lane for general lightening thereof. Hereby a driver driving in the oppo¬ site direction, when meeting a more or less blinding counterlight, may orient him- or herself better of the driving conditions further ahead. This effect may be further improved by the use of a phosphescent light sub¬ stance, or by the use of stationary means for an irradi¬ ation or any other actuation of the light substance. Ideally, a phosphorescence would be active during the dark hours, solely by the influence of the daylight irradiation.

It is to be mentioned that the term "road" as ap- plied will include all kinds of armoured traffic areas, including squares and airport ways.

Claims

C L A I M S :

1. A method of making luminiscent roads by incor¬ porating a luminiscent substance in a material to be laid out and then laying out the material, characterized in the luminiscent substance is mixed with a matrix forming material and preferably a mineral filler such as sand, this mixture being laid out either directly as a surface layer, e.g. as a paint, or in being laid out, in hardened and granulated condition, as or together with a separate road building material.

2. A method according to claim 1, characterized in that an aqueous cement based moulding material is used as the matrix forming material.

3. A method according to claim 1, characterized in that a hardenable plastics is used as the matrix forming material.

4. A method according to claim 1, characterized in that the crushed, hardened or solidified matrix material is sieved for separation of a regular granulate, and that the complementary fine grain fraction is used for sprinkling onto a still unset road surface.

5. A method according to claim 1, characterized in that for the building of a concrete road a top layer mixture is used, in which there is admixed a luminiscent substance, preferably the said granulate.

6. A luminiscent aggregate for road building mate¬ rials, characterized in that it is a granulate of a hardened moulding material containing a luminiscent material and preferably also a mineral filler such as sand.