WO2009072159A1

WO2009072159A1 - Bituminous conglomerate layer obtained by using the spent powders of extinguishers

Info

Publication number: WO2009072159A1
Application number: PCT/IT2008/000735
Authority: WO
Inventors: Pietro Milasi; Filippo Gianmaria Pratico; Maurizio Rocco Gangemi
Original assignee: Cadi Dei F.Lii Milasi & C. Snc Di Milasi Vincenzo E Pietro
Priority date: 2007-12-03
Filing date: 2008-12-01
Publication date: 2009-06-11
Also published as: WO2009072159A8; EP2235110A1; ITRM20070625A1

Abstract

A new use is described of spent extinguishing powder as filler in the production of a bituminous conglomerate mixture. Such bituminous conglomerate mixture is used for laying a surface course, or a binder layer, i.e. connection layer between the surface course layer and the base layer. It is proven that the technical-functional characteristics of the spent powder of the extinguishers are the same as or are even superior to those of the traditional fillers in the conventional bituminous mixtures.

Description

Bituminous conglomerate layer obtained by using the spent powders of extinguishers

Field of the art

The present invention regards civil engineering, in particular road construction, and specifically the making of the so-called "binder" connection layer between the base layer and the surface course (wearing course) with which the tires of the motor vehicles are in direct contact, transmitting the relative static and dynamic loads.

In particular, the present invention also regards a new use of waste material for the production of said binder layer.

In addition, the invention also regards the bituminous layer which forms the road surface or surface course, as well as a new use of waste material for the production of said surface course.

Prior art

The connection layer or "binder" normally has the function of connection between the base layer and the surface course, transmitting the vertical action of the loads, with mitigation of the permanent deformations. Such layer is situated between the layer defined as surface course and the base layer; its average thickness can vary from 5-8 cm. The conventional production method of such "binder" layer in bituminous conglomerate consists of mixing lithoid material coming from natural quarries or resulting from the crushing of calcareous rock (grit and crushed stone, i.e. inert substances, belonging to a category not greater than the 2^nd of the C.N.R. (Consiglio Nazionale delle Ricerche) regulations, sand and the so-called "filler"), made into a paste under heat with bitumen of prescribed characteristics and possible additives (for example activating the bitumen- inert substance adhesion). The paste is set in position by means of suitable vibro-finishing machines and subsequently compacted with pneumatic and/or metal wheel rollers. The men skilled in the art know that the conventional production recipe of the bituminous conglomerate which forms the binder layer, or connection layer, provides for the use of the so-called "filler", i.e. of inerts whose grains substantially have thicknesses of less than 0.075 mm.

The correct filler percentage (moreover set by the ANAS regulations on CNR indications) in the mixture forming the bituminous conglomerate also allows improving the stiffness and shear strength performances (i.e. less localized yielding (ruts) and less cracks of the pavement); therefore, it is essential that the correct filler quantities are present inside the surface course and binder.

The production regulations of the bituminous conglomerates often set, as single main constraint for the use of any material as filler, that the size of such material lies within 80% passing through the 0.075 UNI sieve and 100% through the 0.18 UNI sieve, and that the characteristics in terms of performances of the conglomerate thus produced are in accordance and/or comparable with those of a conventional mixture.

Given the increasing importance of preserving the environment from apparently useless waste, i.e. waste which appears to be non reusable or non-recyclable and whose only authorized destination is disposal at the dump, there is the technical/economical/ ecological problem of examining which type of material currently considered non- recyclable could instead be validly used in every respect as filler in the road binder layer.

Thus, one object of the present invention is that of identifying a waste material, directly obtainable at practically zero cost, or even with economical earnings, which can be reused as filler in the road binder layer, or even in the surface course, safeguarding or even improving all the technical-functional characteristics possessed by the traditional fillers in a binder layer or in a conventional surface course (wearing course). A further object of the present invention is that of identifying a waste material which can be directly used as a filler in the bituminous conglomerate mixture of the binder layer (or surface course), i.e. without being subjected to any preliminary industrial process/treatment, not even grinding.

In this manner, there would be enormous economical and ecological advantages, recycling at zero cost material which otherwise would have been deposited in a dump.

Description of the invention

Surprisingly, it was found that by using the spent powder of extinguishers as a filler of a binder layer or in a surface course, the mechanical characteristics of the relative conglomerate with spent extinguishing powder filler are actually equal to if not superior than those of a conglomerate using a traditional filler.

The UNI 9994 regulation (legally binding in Italy) from the DM 10 March 1988 provides for the following as maintenance operations of powder extinguishers: SEMIANNUAL Control TRIENNIAL Review QUINQUENNIAL Test

During the Review activity, the maintainer person is obliged to empty the extinguisher of the powder contained therein and considered expired, and to substitute it with new powder.

Such legally obligatory operation produces a waste product (the spent powder) intended for removal in dumps with the code CER 16 05 09 for non-dangerous waste.

From a research made in 2005 by the Consorzio Sicurnet (consortium which includes most of the Italian operators in the fire-prevention sector), it was estimated that there are officially present in Italy about 20,000,000 (twenty million) fire extinguishers, 85% of which are powder extinguishers and with an average capacity of 6 kg (six kilograms). Hence, every year, from the required reviews, about 34,000,000 kg (thirty-four million kilograms) of waste ("expired" powders) are produced throughout Italy, whose single authorized destination is disposal in dumps, (according to Legislative Decree No. 152 of 3 April 2006). The present inventors have confronted such problem, by means of carrying out two technological research and innovation projects.

The result obtained from such projects was the making of a bituminous conglomerate of "Binder" type that was ecological, since in place of the Filler the spent powder is contained therein.

We will illustrate in detail below, by means of particular embodiments, how such result was achieved and the performances of the "new" construction material. At this point of the description, we'll clarify with non-exhaustive examples what is intended by extinguishing powder. A non-exhaustive list of the powder types existing on the market are reported below. All the powders have the same chemical behavior and base composition. Type 1) composed of hydrolyzed calcium carbonate and potassium sulphate (white) Type 2) composed of sodium bicarbonate (white) Type 3) composed of potassium and ureic salts (white) Type 4) composed of monoammonium phosphate and ammonium sulphate (blue) Type 5) composed of monoammonium phosphate (pink) Type 6) composed of sodium chloride and ammonium chloride (gray) All of the above substances are used as fertilizers, and thus they are non-toxic, non- corrosive and not harmful. For the experimentation which led to the present invention, all of the above-described powder types were used.

Hence, in the following specified particular and non-binding embodiments of the invention, any of the abovementioned extinguishing powders can be used. A man skilled in the art will thus be capable of actually carrying out the invention.

Preferred embodiments

In July 2004, the present inventors started testing the bituminous conglomerate containing spent extinguishing powder in place of the conventional filler. The research project was carried out through the following steps: • Step 1) Granulometric analysis

• Step 2) Preparation of the mixture for the "Binder" layer

• Step 3) Preparation of the specimens to be subjected to testing

• Step 4) Execution of the Marshall test • Step 5) Washing tests in neutral and acidic solutions

STEP 1

The Granulometric analysis consists of making the material to be analyzed pass through a series of screens (whose hole diameter is in accordance with UNI regulations) and verifying the percentage by weight of substance retained by each screen. Through the execution of the test, it was verified that the spent extinguishing powder consists of 99.5% inerts, whose diameter is less than 0.075 mm, and therefore it can be classified as Filler. (See related paragraph in the "Prior Art" section). STEPS 2 and 3 The specimens to be subjected to the Marshall test were prepared with respect to ANAS regulations, which require respecting lower and upper limits (grain size distribution) of the % passing through by weight of each size composing the bituminous conglomerate mixture of "binder" type. The final specimen had the following material percentages:

For the mix, a Bitumen 50/70 was used on some specimens, and on others B 80/100 type was used.

In addition to mixtures for binders, mixtures for surface courses were also considered, with the following granulometric characteristics:

For each of these, tests were carried out with the following binder types:

STEP 4 Methodology: CNR No. 30-15/03/1973. The test is carried out on cylindrical specimens which are crushed in the direction orthogonal to the generatrices of the cylinders, between two metal jaws which partially enclose its lateral surface. The specimens are made in the laboratory or on site, within suitable moulds with standardized pestle delivering 50 or 75 blows on each face of the specimen. The samples are tested at 60°C in order to recreate the conditions which can be verified on the roads in the summer in normal climates. At the same time as the tensile strength (stability), the deformation which the specimen underwent during the test (creep) was also determined. Marshall Stiffness This is the ratio between the stability expressed in kg and the creep expressed in mm. Test Execution:

In confirmation of that stated above, a bituminous conglomerate "binder" paste was made, respecting the percentages of inerts and fillers mentioned above (see steps 2 and 3). The test results showed Marshall stability values equal on average to 1233 Kgf, Marshall creep values equal to 3.10 mm and Marshall stiffness values equal to 398 Kgf/mm. Such values are comparable to or superior than the values obtained when using a conventional filler. Therefore, it can be confirmed that the mechanical characteristics of the conglomerate with expired extinguishing powder filler are equal to if not superior than those of a conglomerate using traditional filler. STEP 5

In order to simulate the effect of atmospheric precipitations or similar flow mechanisms on the pavement, the specimen containing the spent extinguishing powder filler was immersed for 48 h in neutral solutions (pH = 7) and acidic solutions (diluted sulphuric acid, pH = 3).

Since the pH of the solution measured before and after the immersion of the specimen did not undergo significant variations, it can be confirmed that the effect of the precipitations on the chemistry of the conglomerate is null. In the case of bath in acidic solution, a transfer of organic substance to the solution was detected (presence of ammonia coming from the bitumen and from the powder); such result is perfectly consistent with the prevalent organic nature of the bitumen and the fertilizers contained in the powder.

The present invention was illustrated in detail only as a non-limiting and non-binding example, so that a man skilled in the art can actually carry it out. Of course, a man skilled in the art can make modifications while always remaining within the scope of the same inventive concept, as is expressed in the attached claims and in the previous description.

Industrial applicability

As anticipated in the introduction, the annular production of spent extinguishing powder in Italy is approximately 34,000,000 kg. Such "waste" must be disposed as is, by means of storing in pits and/or dumps (they cannot be thermally treated).

As is clear, the use of the extinguishing powder filler, in the mixture, leads to enormous ecological advantages, since a "waste" product is totally recovered, using it (directly, without preliminary/further treatments) as raw material in another production process; in addition, it is possible to reduce the volumes of material destined for dumping, in line with the principle of Italian Legislative Decree No. 152 of 3 April 2006, according to which it is required to reuse everything that can be recycled and/or reused. And all of this can be accomplished without minimally harming the environment. As is clear from the description, the spent powder filler is usable in a bituminous conglomerate, first of all in that which constitutes the binder layer, but secondly also in that which forms the road surface course.

Claims

1. A bituminous conglomerate layer, for example the surface course, or the so-called "binder" layer arranged between the base layer and the surface course, characterized in that it comprises inert materials with various grain sizes in its bituminous mixture, and as filler a spent extinguishing powder of fire extinguishers.

2. A bituminous conglomerate layer according to claim 1, wherein said spent extinguishing powders of fire extinguishers are composed, for example, of at least one of the following substances: hydrolyzed calcium carbonate and potassium sulphate; sodium bicarbonate; potassium and ureic salts; monoammonium phosphate and ammonium sulphate; monoammonium phosphate; sodium chloride and ammonium chloride.

3. A bituminous conglomerate layer according to claim 1 or 2, wherein its bituminous mixture comprises additives activating the bitumen-inert adhesion.

4. A bituminous conglomerate layer according to any one of the preceding claims, constituting a "binder" layer, wherein the percentage of the bitumen related to the inerts, i.e. the aggregates, varies between about 4.5 and 5.5 by weight.

5. A bituminous conglomerate layer according to claim 4, constituting a "binder" layer, wherein the bitumen is of Bitumen 50/70 or Bitumen 80/100 type.

6. A bituminous conglomerate layer according to claim 4 or 5, constituting a "binder" layer, wherein the grain size of the inerts is selected in the following manner:

7. A bituminous conglomerate layer according to any one of the claims 1-3, constituting a surface course, characterized in that the percentage by weight of the bitumen related to the inerts, i.e. to the aggregates, varies in the range indicated in the following table, which refers to three different types of surface course:

8. Use of a spent extinguishing powder of fire extinguishers in a production process of a bituminous mixture for a road binder layer, or for a road surface course.

9. Mixture of bituminous conglomerate, for forming a road binder layer or a road surface course according to any one of the claims 1-7.