WO2024095055A1

WO2024095055A1 - Bituminous conglomerates containing an additive based on hemp canapulo fibers

Info

Publication number: WO2024095055A1
Application number: PCT/IB2023/000622
Authority: WO
Inventors: Giorgio Edoardo CALONE; Giuseppe SCAFFIDI DOMIANELLO
Original assignee: Greennovations Srl
Current assignee: Greennovations Srl
Priority date: 2022-10-31
Filing date: 2023-10-26
Publication date: 2024-05-10
Anticipated expiration: 2025-04-30
Also published as: EP4612108A1

Abstract

The present invention refers to a bituminous conglomerate comprising: a) a solid part consisting of aggregates, b) a bitumen-based binder, and c) at least one additive, characterized in that said additive comprises fibers of a portion of the woody inner core of the hemp plant stem, also called "canapulo". In this way, it is possible to obtain a bituminous conglomerate which, in terms of performance, effectiveness, efficiency and field of use, is equivalent to the bituminous conglomerates known in the art and currently on the market containing additives consisting of cellulose fibres. Furthermore, the additive based on hemp canapulo fibers was found to have better workability compared to known additives consisting of cellulose fibres. The present invention also refers to the use of at least one additive based on hemp canapulo fibers in a bituminous conglomerate, wherein said canapulo fibers are in loose form, such as sawdust or similar, or in aggregate form, such as pellets or similar. Finally, the present invention refers to canapulo fibers in aggregate form, such as pellets, added with agents capable of promoting their aggregation and subsequent breakage during the production process of a bituminous conglomerate.

Description

Bituminous conglomerates containing an additive based on hemp canapulo fibers

DESCRIPTION

Field of the invention

The present invention refers to bituminous conglomerates containing an additive consisting in “canapulo”, i.e. the woody inner core of the hemp plant stem.

The present invention also refers to the use of canapulo fibers within bituminous conglomerates.

Background

Bituminous conglomerates are typically made up mainly of three components: aggregates, bitumen and air.

Some types of bituminous conglomerates, due to their compositions, require the need to introduce additives capable of improving their qualities; in particular, the purpose of adding the additives is to ensure that the added bitumen stabilizes inside it, preventing it from leaking during storage, transport and the coating phase, when it is still hot, thus creating discrepancies in the bituminous mixture in place.

Nowadays, mineral or synthetic cellulose fibres are known as additives typically used within bituminous conglomerates; they have the function of thickening and strengthening the bitumen, as described in the following documents.

The Czech Republic patent application no. CZ307414 B6 describes an asphalt mixture for structural road subbases reinforced with plant fibres, comprises 65.9 to 95.89 % by weight of aggregate having a size of up to 32 mm, consisting of a mixture of coarse and fine crushed aggregate and a filler, up to 30 % by weight of an asphalt R-material, 4-7 % by weight of an asphalt binder, and 0.1 to 0.5 % by weight of plant fibres in the length of 3 to 60 mm in the form of yarn composed of 1 to 10 fibres with a fineness of 50 to 500 tex selected from a group of flax fibres and hemp fibres. Flax fibers and hemp fibers are therefore used for their reinforcing capabilities in mixtures within asphalt conglomerates, without describing in detail which parts of the hemp plant are used.

International patent application no. WOO 1/053417 describes a bituminous mixture for road materials including biological raw materials, such as paper, jute, hemp, sisal, linen, weaving and/or wood fibres, used as a carrier in the paraffin diffusion and distribution process within the bituminous conglomerate. However, no details are reported in this patent application relating to the dimensions of the fibers used, the specific type of plant parts used, or the fiber percentage of each plant used.

French patent application no. FR3085677 describes a method for road material manufacturing comprising hydrocarbon components and linen, hemp or coconut vegetable fibers, the latter aimed at increasing the bituminous conglomerate resistance characteristics. However, it does not disclose in detail which are the parts of the hemp plant used.

European patent application no. EP 1520932 describes a stabilizing additive for asphalts, intended in particular for road construction, consisting of an organic fibrous material in the form of hemp and linen and linseed, alone or proportionally mixed with other fibrous materials (cellulose fiber from waste paper) under a mixture form. The fibrous material is therefore made up of a mixture of hemp, linen and linseed; furthermore, it does not disclose in detail which are the parts of the hemp plant used.

The Romanian patent application no. RO 118080 describes a fibre-reinforced bituminous composition used in road paving including natural aggregates, fillers, binders and yarns made from natural fibers selected from cotton, linen, hemp and synthetic fibres. Neither the stabilizing properties of the hemp plant are examined, nor which specific parts in the bituminous composition therein described are used.

The German patent application no. DE 102007027306 describes the use of an adhesion promoter inserted inside cellulosic fibres, raw organic fibres, paper fibres, jute, hemp, sisal, linen, textiles and/or wood. Neither the stabilizing properties of the hemp fibers, nor which specific parts of the hemp plant used as the adhesion promoter are described therein.

The Applicants have found that the entire stem of the hemp plant, composed of an external surface containing long and very resistant fibers and a portion of the woody inner core of the stem, also called "canapulo", has relatively low absorbent capacities.

Similarly, even the external surface of the hemp plant stem itself was found to have low absorbent capacity.

Consequently, the entire hemp plant stem, as well as only the external surface of the stem itself, cannot be used in bituminous conglomerates with satisfactory results, as could instead be desirable from the teachings provided by the prior art documents.

The Applicants of the present patent application have therefore found the need to create a bituminous conglomerate containing an additive having good workability and constituting, at the same time, a valid alternative to the classic additives based on cellulose fibers used for the bituminous binder stabilization inside the bituminous conglomerates themselves.

Summary of the invention

According to a first aspect, the present invention refers to a bituminous conglomerate such as that one indicated in claim 1. The Applicant of the present application has in fact surprisingly found that the technical problem encountered above can be effectively and reliably solved by means of a bituminous conglomerate including: a) a solid part made up of aggregates, b) a bitumen-based binder, and c) at least one additive, characterized in that said additive is a portion of the woody inner core of the hemp plant stem, also called "canapulo".

In this way, it is possible to obtain a bituminous conglomerate which, in terms of performance, effectiveness, efficiency and field of use, is equivalent to the bituminous conglomerates known in the art and currently on the market containing additives consisting of cellulose fibres.

Furthermore, the additive based on hemp canapulo fibers was found to have better workability compared to known additives consisting of cellulose fibres.

In fact, hemp canapulo fibers essentially have a stabilizing function within the bituminous conglomerate, i.e. they prevent the bitumen leakage and reflux phenomena occurrence. A high thickness of the binder film covering the aggregate is thus guaranteed, increasing its mechanical characteristics and decreasing its shelling phenomena.

Consequently, the canapulo contained in the inner part of the hemp plant stem was found to be the only element of the hemp plant capable of satisfying the absorption requirements required by the fibers present in the bituminous conglomerates.

According to a preferred embodiment of the present invention, the canapulo is used as the sole additive in bituminous conglomerates.

According to a preferred embodiment of the present invention, said canapule has dimensions varying in the range from 0.1 mm to 20 mm, preferably from 1 mm to 10 mm. According to a preferred embodiment of the present invention, said canapulo fibers are in pure form.

According to a preferred alternative embodiment of the present invention, said hemp canapulo fibers are mixed type fibres, such as for example hemp/pet fibers or hemp/glass fibres.

In this way, both the stabilizing and thickening functions are obtained, preventing the bitumen from flowing, and also the bitumen structural reinforcement function, preventing cold and fatigue cracking in the presence of cyclic loads.

According to a preferred alternative embodiment of the present invention, said mixed type hemp canapulo fibers are added with agents capable of promoting their aggregation and subsequent breaking during the bituminous conglomerate production process.

According to a preferred embodiment of the present invention, the bituminous conglomerate of the present invention is of the non-slipping hot-packed type, according to the UNI EN 13108-5 standard.

According to a preferred embodiment of the present invention, the bituminous conglomerate of the present invention is of the high void content type, according to the UNI EN 13108-7 standard.

According to a preferred embodiment of the present invention, the bituminous conglomerate of the present invention comprises: a) inert aggregates, such as for example crushed stone, small stones, gravel, sand; b) a bitumen-based binder in the percentage from 3% to 9%, preferably from 4.5% to 7.5% by weight with respect to the aggregates, and c) said additive based on hemp canapulo fibers in the percentage from 0.05% to 5%, preferably from 0.1% to 1% by weight with respect to aggregates, where "inert aggregates" means raw granular mineral materials used in construction, natural, artificial or recycled from materials previously used in construction buildings themselves.

In a second aspect, the present invention refers to the use of at least one additive in a bituminous conglomerate such as that one indicated in claim 5.

The Applicant of the present application has in fact surprisingly found that the technical problem encountered above can be effectively and reliably solved through the use of an additive which is a portion of the woody inner core of the stem of said hemp plants (also called "canapulo”).

According to a preferred embodiment of the second aspect of the present invention, said canapulo fibers are in loose form, such as sawdust or similar, or in aggregate form, such as pellets or similar.

In a third aspect, the present invention relates to hemp fibers in aggregate form as indicated in claim 6.

The Applicant of the present application has in fact surprisingly found that the technical problem encountered above can be effectively and reliably solved by hemp canapulo fibers in aggregate form, such as pellets, added with agents capable of promoting their aggregation and subsequent breakage during the bituminous conglomerate production process.

In this way, hemp canapulo fibers in aggregate form, for example in the form of pellets, can be incorporated as additives into a bituminous conglomerate, making their workability easier than known additives consisting of cellulose fibres.

Further characteristics and advantages of the present invention will be better highlighted by examining the following detailed description of a preferred, but not exclusive, embodiment, illustrated for indicative and non-limiting purposes.

DETAILED DESCRIPTION. The following detailed description refers to particular embodiments of the present invention, without limiting its content.

The invention was characterized by referring to various laboratory tests carried out using hemp canapulo fiber (invention) and the two types of fibers still most commonly used nowadays for the addition of bituminous conglomerates, i.e. natural cellulose (comparison 1) and the mixed cellulose/glass type (comparison 2).

The fiber absorbent capacity test was carried out through an empirical test during which the fiber mass necessary to absorb a known quantity of diesel fuel, usually used as fuel for diesel engines, was determined.

The test procedure consisted of weighing 3,000 mg of diesel fuel into a watch glass with a diameter of 120 mm. The crushed fiber was added directly into the oil, gradually, until there was no longer any unabsorbed diesel fuel present.

First, the absorbent capacity of both the entire stem of the hemp plant (composed of an external surface, containing long and very resistant fibers, and the canapulo), as well as just the external surface of the stem itself, was tested.

The tests performed using the entire stem, or only the external part of the stem, provided non-significant results. Accordingly, it has been determined that such parts of the hemp plant are not useful for the purposes of the present invention.

In fact, preliminary tests have shown that the entire stem of the hemp plant provides an absorbent capacity of approximately 1,500 mg, that is an unacceptable value for the purposes of the present invention.

Similarly, preliminary tests have verified that the external surface of the stem of the hemp plant also provides an absorbent capacity equal to approximately 2,000 mg, that is an unacceptable value for the purposes of the purpose of the present invention, too.

Subsequently, the absorbent capacity of a specific part of the hemp plant, i.e. the woody inner core of the stem, called "canapulo", was verified.

The crushed canapulo-based fiber was compared with two types of classic fibers usually used for the addition of bituminous conglomerates. The results are reported in Table 1.

Table 1 : Fiber absorption

The smaller the mass of fiber necessary to absorb the quantity of diesel fuel, the greater its absorbent capacity. Consequently, the hemp canapulo fiber (invention) was found to be the type of fiber that showed the best characteristics relating to absorbent capacity, not only compared to the types of classic fibers known in the art usually used for the additives of conglomerates bituminous, but also in relation to the entire stem and to only the external part of the stem of the hemp plant itself, with much better absorption parameter empirical values.

Example 2: binder drainage measurement

The extent of bitumen drainage/segregation was verified using the beaker method (Schellenberg test). A 1,000 g sample of bituminous conglomerate, was placed in a beaker at a temperature of 170°C (338°F) for 60 minutes.

After that time, the mixture was discharged from the beaker in a single solution. The bituminous material was weighed before and after the test. The weight retained in the beaker (binder that drained from the aggregate) was divided by the original weight of the sample and this was reported as the drainage.

Losses lower than 0.2% indicate that no segregation should occur; however, values up to 0.3% are considered acceptable. Higher values are not considered to be of good quality and could indicate a tendency of the mixture to segregate from the moment of packaging until coating, making the coating uneven.

The three samples of bituminous conglomerate tested to verify the resistance to drainage of the binder were packaged in the laboratory (according to the UNI EN 12697-35 standard "Bituminous mixtures - Test methods - Part 35: Mixing in the laboratory"), using a formulation of a non-slip bituminous conglomerate (Splitt Mastix Asphalt, for brevity referred to as SMA) with modified bitumen (Pmb 45/80- 70) and adding the three different fibers seen above (Invention, Comparison 1, Comparison 2) with the same dosage equal to 0 .30% by weight with respect to the aggregate mixture.

Table 2: Drained material

As can be seen from the data reported in Table 2, hemp canapulo fiber (invention) turned out to be the type of fiber that showed the best characteristics relating to the drained material.

Example 3 : Performance checks on bituminous conglomerate samples

Two different types of bituminous conglomerates were analysed; in the present

Example 3, a closed anti-slip bituminous conglomerate type SMA was analyzed (according to the UNI EN 13108-5 standard “Bituminous mixtures - Material specifications - Part 5: Closed anti-slip bituminous conglomerate”). In the subsequent Example 4, a bituminous conglomerate with a high void content was examined (according to the UNI EN 13108-7 standard “Bituminous mixtures - Material specifications - Part 7: Bituminous conglomerate with a high void content”).

At a discontinuous bituminous conglomerate production plant, SMA-type bituminous mixtures were packaged with the same formulation, but adding two different types of fibres, respectively with crushed hemp canapulo fibers (Invention) and cellulose fiber (comparison 1), dosed at 0.30% by weight with respect to the aggregate mixture.

The following tests were performed on the collected samples:

- soluble binder extraction (according to the UNI EN 12697-1 standard “Bituminous mixtures - Test methods - Part 1 : Soluble binder content”);

- Volumetric analysis by compaction with a rotary press (according to the UNI EN 12697-31 standard “Bituminous mixtures - Test methods - Part 31 : Preparation of the specimen with a rotary press”);

- Determination of indirect tensile strength at 25°C (according to the UNI EN 12697- 23 standard “Bituminous mixtures - Test methods - Part 23 : Determination of indirect tensile strength of bituminous specimens”).

Table 3 shows the results relating to the soluble binder extraction.

Table 3 : soluble binder extraction

Table 4 shows the results relating to the volumetric analysis using compaction with a rotary press.

Table 4: Volumetric analysis

Table 5 shows the results relating to the indirect tensile strength tests, at 25°C, of the specimens packaged with the rotary press.

Table 5: Tensile strength

As can be seen from the results reported above, the bituminous conglomerates of the SMA type added with hemp canapulo fiber (invention) obtained performance values very similar to those obtained from the mixtures packaged with the classic cellulose fiber (comparison 1), especially for what concerns the tests relating to the soluble binder extraction (Table 3), and to the tensile strength (Table 5). The indirect tensile strength and indirect tensile coefficient values were found to be satisfactory for both the blends with cellulose fiber (comparison 1) and hemp canapulo fiber (invention).

Furthermore, the mixtures with the addition of hemp canapulo (invention) obtained better values, compared to the mixture with cellulose (comparison 1), during the volumetric analysis (Table 4), resulting to have a better workability and a lower void content at all the three compaction levels. Example 4: Performance checks on bituminous conglomerate samples

Similarly to Example 3, at a discontinuous bituminous conglomerate production plant, standard bituminous mixtures were packaged, this time of the wear mat type with a high void content (draining) according to the UNI EN 13108 standard -7 (instead of the SMA type as it was in Example 3), having the same formulation, but adding two different types of fibres, respectively with crushed hemp canapulo fibers (invention) and mixed cellulose/glass fiber (comparison 2), dosed at 0.30% by weight with respect to the aggregate mixture.

The following tests were performed on the collected samples:

- indirect tensile strength determination at 25°C (according to the UNI EN 12697-23 standard “Bituminous mixtures - Test methods - Part 23 : Determination of indirect tensile strength of bituminous specimens”).

Table 6 shows the values relating to the content of soluble binder extracted from the two bituminous conglomerates analyzed.

Table 6: Soluble binder content

Table 7 shows the data of the volumetric analysis of the two bituminous mixtures compacted with a rotary press.

Table 7: volumetric analysis of bituminous mixtures

Table 8 shows the results relating to the indirect tensile strength tests, at 25°C, of the specimens packaged with the rotary press.

Table 8: Tensile strength

As can be seen from the results obtained through laboratory tests (Tables 6-8), the use of hemp canapulo fiber (invention) also made it possible to obtain draining bituminous conglomerates with performances very similar to those obtained with the additive classic cellulose/glass (comparison 2).

As a result, the fiber obtained from hemp canapulo (invention) can be considered a valid alternative to the classic additives used for the stabilization of the bituminous binder inside the bituminous conglomerates with discontinuous and semi- discontinuous compositions, such as draining agents or also as Split Mastix Asphalt (SMA). Furthermore, it was found that canapulo is the only element of the hemp plant that satisfies the absorption requirements required by the fibers present in bituminous conglomerates.

Different sizes of canapulo were used in order to establish which size of the fibers could guarantee optimal performance for the bituminous conglomerate of which it was a component. The best results were obtained by using canapulo fibers having a few mm sizes within the bituminous conglomerate mixtures.

Of course, many modifications and variations of the described preferred embodiments will be apparent to those skilled in the art, while still remaining within the scope of the invention.

For example, in all the examples described above the hemp canapulo fiber used was always intended to be added to the bituminous conglomerate in loose or crushed form (even if always expressed explicitly). However, in other embodiments, the hemp canapulo fiber may be in aggregate form, such as aggregated to form a pellet. Therefore, the present invention is not limited to the preferred embodiments described, illustrated for illustrative and non-limiting purposes only, but is defined by the following claims.

Claims

Claims.

1. Bituminous conglomerate comprising: a) a solid part consisting of aggregates, b) a bitumen-based binder, and c) at least one additive, characterized in that said additive comprises fibers of a portion of the woody inner core of the hemp plant stem, also called “canapulo”.

2. Bituminous conglomerate according to claim 1, wherein said canapulo has dimensions varying in the range from 0.1 mm to 20 mm.

3. Bituminous conglomerate according to any of the previous claims wherein said hemp canapulo fibers are in pure or mixed form, such as for example hemp/pet fibers or hemp/glass fibres.

4. Bituminous conglomerate according to any of the previous claims including: a) inert aggregates, such as crushed stone, small stones, gravel, sand; b) a bitumen-based binder in the percentage from 3% to 9%, preferably from 4.5% to 7.5% by weight with respect to the aggregates, and c) said additive based on hemp canapulo fibers in the percentage from 0.05% to 5%, preferably from 0.1% to 1% by weight with respect to the aggregates, wherein "inert aggregates" means raw granular mineral materials used in construction, natural, artificial or recycled from materials previously used in construction buildings themselves.

5. Use of at least one additive based on hemp canapulo fibers in a bituminous conglomerate, wherein said hemp canapulo fibers are in loose form, such as sawdust or similar, or in aggregate form, such as pellets or similar.

6. Hemp canapulo fibers in aggregate form, such as pellets, added with agents capable of promoting aggregation and subsequent breakage during the production process of a bituminous conglomerate.