PL235765B1 - Reinforced asphalt-aggregate mixture - Google Patents

Description

The subject of the invention is a reinforced asphalt mix, intended in particular for carrying out repair treatments on road surfaces in poor condition, in particular cracked surfaces, including thermal and fatigue origin.

Usually, the addition of fibers, both natural and artificial, improves the properties of binding the aggregate with the bituminous mixture, and also improves the physicochemical properties, especially reducing the sensitivity of the pavement to changes in volume depending on weather conditions, and improves adhesion of the pavement.

GB447416 discloses a mixture of asphalt and rubber fibers obtained from used car tires or rubber or latex, which mixture can be heated and supplemented with oils, rosin, can serve as a primer for the surface.

Chinese Patent No. CN1908069 discloses a mixture consisting of modified tar and polymer fibers of irregular shapes, aggregates and asphalt, the fibers may be polyester, polyacrylnitrile, polyamide or their compositions, which improves the adhesion properties and strength parameters of the pavement.

US 9,469,944 describes a method of preparing aramid fibers by coating them with FT-wax. In this way, the fibers are glued together and dosed into asphalt concrete (ACC), where the wax dissolves under the influence of temperature, releases the fibers and, at the same time, affects the asphalt binder. This type of wax reduces the viscosity of the asphalt, makes it easier to cover the aggregate with asphalt and can be used to lower the process temperatures in the production process.

From the US patent application US 2014 0303288, Asphalt Cement Concrete (ACC) with the addition of various fibers, including aramid fibers, is known.

The use of hot thin wear layers as a maintenance treatment that restores the road surface properties ensuring the comfort and safety of users is a known and used technology, including in the Catalog of Reinforcements and Renovations of Flexible and Semi-Rigid Surfaces. For this purpose, discontinuous grain size mixtures are most often used. Such a solution is based on mineral aggregate and polymer modified bitumen. Additives in the form of adhesives, mostly amine, and cellulose fibers. Cellulose fibers are introduced in order to reduce the effect of asphalt flowing off the mineral mix, due to their strength properties they do not constitute reinforcement.

The aim of the invention is to develop such a reinforced asphalt mix that will enable the performance of repair treatments on road surfaces in poor condition, in particular cracked surfaces, including thermal and fatigue origin.

The difference between the asphalt concrete of US 9,469,944 and US 2014 0303288 and the discontinuous grain mix according to the present invention is substantial and results from the proportion of the components used. Particularly important is the grain size of the mineral (aggregate) mixture which is the basic component. In the asphalt concrete for the wearing course, the graining is continuous, the weight fraction of the filler fraction (<0.063 mm) is about 5-10%, the sand fraction (0.063 to 2 mm) 30-40% and the grit fraction 50-65%, the asphalt content is about 5-6%. In contrast, mixes with discontinuous graining are characterized by discontinuous graining, the weight fraction of the filler fraction (<0.063 mm) is about 4-6%, the sand fraction (0.063 to 2 mm) 20-30% and the grit fraction 75-85%, the asphalt content is about 6-8%. As a result, a different structure of the asphalt mixture is obtained. In asphalt concrete, the space between the largest grains is filled with smaller grains and asphalt mastic. In the mixture of discontinuous graining, there are no grains of intermediate size, hence the largest grains of aggregate are in contact with each other, wedging each other, and the space between them is filled with fine aggregate and asphalt mastic. In this way, both different properties related to the greater angle of internal friction in the discontinuous grain mix as well as a different texture of the paved layer are obtained. The asphalt concrete layer has a closed texture, while the mixture with discontinuous graining has an open texture, which translates into better anti-noise properties and a better roughness coefficient. Asphalt pavement technology clearly distinguishes between asphalt concrete and discontinuous graded mixes, which, depending on the country, may be called gap-graded, S-shaped, BBTM, MNU and others.

PL 235 765 Β1

The asphalt-aramid mix according to the invention is particularly suitable for carrying out renovation works on road surfaces in poor condition, in particular cracked surfaces, including those of thermal and fatigue origin. The appropriate composition of the mixture according to the invention provides a layer with high strength parameters, in particular resistance to water, low-temperature cracking, crack propagation resistance and rutting resistance. These are the key features to obtain a wearing course (top coat) with high operational durability, resistant to climatic and environmental factors. It is significant to increase the resistance to crack propagation from the lower, old construction layers.

The introduction of aramid fibers to the mixture allows to obtain the effect of spatial dispersed reinforcement. The spatial structure obtained in this way consists of a mixture of mineral aggregate with a specific grain size, surrounded by asphalt, and aramid fibers embedded in asphalt mastic filling the space between the grits.

Aramid fibers have a much higher tensile strength than other polyamides. This is the effect of the internal structure of aromatic groups and amide bonds creating a structure with high rigidity and ordered microtexture.

The effect of the use of aramid fibers is visible in conditions where the asphalt-aramid mixture according to the invention is subjected to tensile stress, in particular due to thermal shrinkage, bending and stress concentration from cracks in the lower structural layers (notch phenomenon). In such a load condition, the aramid fibers absorb some of the stresses, increasing the tensile strength of the composite and delaying the damage process.

The use of asphalt highly modified with polymer 45 / 80-80 ensures good functional properties of the mixture at high and low temperatures.

The effect of the appropriate composition of the asphalt-aramid mixture according to the invention is to obtain high mechanical and strength properties, which significantly exceed the results of mixtures with discontinuous graining.

In particular, the following parameters were found in the Thermal Stress Restrained Specimen Test (TSRST) for the asphalt-aramid mix according to the invention:

- rupture point below -35 ° C;

- fatigue life expressed by the parameter εβ above 280 mm / m;

- resistance to rutting in a large apparatus up to 10% of the rut depth.

These parameters were included in the requirements for the mixture given in the tables below.

Table 1

Requirements (minimum values) for the asphalt-aramid mix

Property Compaction conditions according to PNEN 13108-20 Method and conditions research Requirements Minimum and maximum void content C.1.5, gyrator, 25 turns PN-EN 12697-31 VgI2-19 Resistance to permanent deformation: proportional rut depth,% C.1.20, rolling, Pys-PitM) PN-EN 12697-22, large apparatus, PNEN 13108-20, D.l.6, 60 ° C, 10,000 cycles Pio

PL 235 765 Β1

Low-temperature cracking resistance, ° C C.1.20, rolling, P98-P100 PN-EN 12697-46, p. 8.2, TSRST method <-35 Fatigue durability C.1.20, rolling, P98-P100 PN-EN 1269724,4PB-PR, 10 ° C, 10Hz E6-280 Water sensitivity C.l.l, tamping, 2χ35 thighs PN-EN 12697-12, conditioning at 40 ° C with one cycle of freezing ^b1 , test at 25 ° C ITSRgo Maximum runoff of the binder - PN-EN 12697-18, p. 5 To. 3

Table 2

Requirement for graining of the mineral mixture

Property Screening, [% (m / m)] Sieve size #, mm: from down 11.2 100 100 8 90 100 5.6 40 75 2 25 35 0.063 6 10

Comprehensive application of the proposed solutions significantly affects the durability of the maintenance procedures performed. It is estimated that, depending on the condition of the pavement and the traffic load, maintenance measures allow the wearing course to be kept in an appropriate condition for 5-8 years, and the proposed solution will extend this period by at least another 3 to 8 years. Increasing the efficiency can be achieved by laying an additional tie layer.

The subject of the invention is therefore a reinforced asphalt mix containing:

- mineral aggregate mixture, meeting the technical requirements as for road aggregates for asphalt mixtures for the wearing course, which forms a mineral mixture with an acceptable graining curve (according to Table 2), in an amount from 92 to 94% by weight;

- asphalt highly modified with SBS polymer (Styrene Butadiene Styrene rubber), type 45 / 80-80, defined in accordance with PN-EN 14023: 2011, in an amount from 6 to 8% by weight;

an adhesive to improve the adhesion of the asphalt to the aggregate, in an amount of 0.1 to 0.5% by weight in relation to the weight of the asphalt;

PL 235 765 Β1

aramid fibers 15 to 25 mm long, preferably 19 mm long, with a cross-sectional area of 0.0014 to 0.02 mm ² , for example circular or rectangular (for example 0.5 mm wide and 0.03 mm high) ), in an amount of from 0.025 to 0.06%, preferably 0.03% by weight.

Mineral aggregates should meet the requirements for mineral aggregates for mixtures with discontinuous graining, for example in accordance with the document WT-1 Technical Requirements "Aggregates for mineral-asphalt mixtures and surface treatments on national roads", issued by the General Directorate of National Roads and Motorways (25/09/2014 r.).

Highly-modified asphalt should meet the requirements of PN-EN 14023: 2011 or its update.

Known adhesives for improving the adhesion of the bitumen to aggregate, such as hydrated lime, imidazoline, fatty amines, can be used as the adhesive.

Execution example

A mixture of mineral aggregate with the following parameters was prepared:

Sieve size #, mm: Screening, [% (m / m)] 11.2 100 8 98 5.6 65 2 thirty 0.063 7

Mixed:

- the above mixture of mineral aggregate in an amount of 93% by weight;

- polymer modified bitumen 45 / 80-80 in an amount of 7% by weight;

- adhesive: Teramin-14 in an amount of 0.3% by weight with respect to the weight of the polymer modified bitumen;

- aramid fibers with an average length of 19 mm and an average cross-sectional area of 0.02 mm ² in an amount of 0.03% by weight.

A mixture with the following properties was obtained:

Property Compaction conditions according to PNEN 13108-20 Method and conditions research Score Minimum and maximum void content C.1.5, gyrator, 25 turns PN-EN 12697-31 12% Resistance to permanent deformation: proportional rut depth,% C. 1.20, rolling, Pse-Pioo PN-EN 12697-22, large apparatus, PNEN 13108-20, D. 1.6, 60 ° C, 10,000 cycles 7.5%

PL 235 765 Β1

Low-temperature cracking resistance, ° C C.1.20, rolling, P98-P100 PN-EN 12697-46, p. 8.2, TSRST method -36.5 ° C Fatigue durability C.1.20, rolling, P98-P100 PN-EN 1269724,4PB-PR, 10 ° C, 10Hz £ 6 = 291 pm / m Water sensitivity c. 1.1, whipping, 2 x 35 thighs. PN-EN 12697-12, conditioning at 40 ° C with one freezing cycle, test at 25 ° C 98% Maximum runoff of the binder - PN-EN 12697-18, p. 5 0.25

Patent claim

Claims (1)

1. Reinforced mineral-asphalt mixture intended for renovation treatments on road surfaces, containing: - a mixture of mineral aggregate with sieving parameters: 8 mm - from 90 to 100% by weight, 5.6 mm - from 40 to 75% by weight, 2 mm - from 25 to 35% by weight, 0.063 mm - from 6 % to 10 wt.%, in a total amount of from 92 to 94 wt.%. mixtures; - asphalt highly modified with SBS polymer, type 45 / 80-80, in the amount of 6 to 8% by weight. mixtures; an adhesive for improving the adhesion of asphalt to aggregate, in an amount of 0.1 to 0.5 wt.%. asphalt masses; - reinforcement; characterized in that as reinforcement it contains: - aramid fibers with a length of 15 to 25 mm, the cross sectional area of 0.0014 to 0.02 mm ^2, in an amount of from 0.025 to 0.06% by weight.