RU2504523C1 - Dense vibro cast asphalt-concrete mixture - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to road construction materials and can be used in road surfaces, pavements, bridge surfaces and man-made structures. The dense vibro cast asphalt concrete mixture contains mineral material - rock chips and rock chip screenings, mineral powder, bitumen binder containing bitumen BND 60/90 with an adhesive additive KADEM-VT. The mixture further contains rubber crumbs and thermoplastic rubber RTEP, with the following ratio of components, wt %: crushed rubber crumbs - 1.00-1.20, thermoplastic rubber RTEP - 0.25-0.35, cationic reagent - adhesive KADEM-VT - 0.35-0.50, bitumen BND 60/90 - 7.80-8.20, mineral powder - 16.00-18.00, mineral material (rock chips and rock chip screenings) - the balance.

EFFECT: improved properties of the cast asphalt concrete mixture owing to its high resistance to the oxidative ageing process of the binder by preparing a mixture with a lower preparation and application temperature, high resistance to rutting owing to improved pressing-in of the indenter and other operational properties of the mixture, including thermal stability.

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Description

The invention relates to the field of road-building materials and can be used for paving roads, sidewalks, bridges, artificial structures.

Known asphalt mix for poured asphalt, intended for the repair of pavements, including patching, for sealing damages at manholes and for paving along tram tracks (patent RU No. 2062762, IPC C04B 26/26, C04B 111/20, publ. . June 27, 1996). However, this mixture is selected for work in small areas and is unsuitable for pavements of great length. The use of viscous bitumen 40/60 in this work does not provide the required crack resistance of the coating in winter.

The known composition of the cast asphalt mixture for coating the roadway of the bridge (patent RU 2341479 C1, C04B 26/26, publ. 12/20/2008). However, the resulting composition includes significant amounts of 10-16% polymer-bitumen binder using styrene-butadiene-styrene block copolymer "Kraton D-1101CM, which requires prior combination in a separate installation with bitumen before delivery to the asphalt mixer, delivery and storage of the obtained polymer bituminous binder in special conditions.

Closest to the claimed invention is a mixture for cast asphalt GOST R 54401-2011 "Hot asphalt concrete road. Technical requirements". The mixture contains bitumen, mineral filler and mineral powder in the ratio, see table. 1. The recommended bitumen content for cast mixtures of type II according to the requirements of GOST R 54401-2011 is 8.5-9.5%. It is used for paving roads, bridges, tunnels, airfields, city streets and open and closed parking lots, as well as for patching. The specified mixture is intended for new construction, capital construction and patching, has a maximum grain size of mineral material of 20, 15 and 10 mm and is divided into types I, II and III. In the production and laying of the mixture have an elevated temperature of 215-230 ° C, which contributes to the occurrence of undesirable oxidative aging processes of bitumen binder, reducing the overhaul life of the road surface and its durability.

The objective of the present invention is to improve the properties of the cast asphalt mixture by increasing its resistance to the oxidative process of aging of the binder by developing a mixture with a lower temperature of preparation and laying, increasing the resistance to rutting by improving the stamp indentation rate and other performance characteristics of the mixture, including increasing the heat resistance of the mixture.

The technical problem solved by the invention is: creating a coating that maintains high performance over a long period, including increased heat resistance of asphalt concrete, preventing the formation of defects such as rutting, as well as lowering the temperature of the mixture during production and laying while maintaining its mobility.

The essence of the invention lies in the fact that the dense vibrocast asphalt mixture comprising mineral material - crushed stone and crushed stone crushing screening, mineral powder, bitumen binder containing BND 60/90 bitumen with KADEM-VT adhesive additive additionally contains rubber crumb and rubber thermoplastic elastomer RTE the following ratio of components, wt.%:

crushed rubber crumb 1.00-1.20 rubber thermoplastic elastomer RTEP 0.25-0.35 cationic reagent - adhesive KADEM-VT 0.35-0.50 bitumen BND 60/90 7.80-8.20 mineral powder 16.00-18.00 mineral material (crushed stone and screening crushing crushed stone)  rest

Mineral material is represented by: crushed stone fraction 5-10 mm, screening crushing fraction 0-5 mm and mineral powder. Using these materials, the composition of the asphalt concrete road cast hot mix (type II in accordance with the technical requirements of GOST R 54401-2011), designed for new construction and overhaul, patching and sidewalks, was selected and tested. The selected composition of the mixture is presented in table 1.

Mineral powder is one of the most important structural components of asphalt mixtures. Its main purpose as a filler of bitumen is to translate bulk bitumen into a film state, thereby increasing its strength and viscosity. Together with bitumen, mineral powder forms a structured dispersed system, which also acts as a binder in asphalt concrete.

When selecting the composition of the mixture in the developed composition, the mineral powder content was reduced by 5-8%, which was made up for by the introduced dispersed rubber crumb. The introduced rubber-containing additives RTEP and rubber crumb create a developed system of "centers of elasticity" in the cast asphalt mixture, which contributes to a significant improvement in its structural and mechanical properties.

The combination of limestone mineral powder with crushed rubber crumb and thermoplastic elastomer RTEP has an even more pronounced structural effect on bitumen. The swollen particles of crumb rubber in bituminous oils form dispersed elastic centers connected by a polymer-bitumen binder. The use of such a composition allows, due to RTEP, to significantly increase the heat resistance of the cast mixture at elevated temperatures, and crumb rubber to improve its deformability at low temperatures.

To increase the adhesion properties of the developed cast asphalt concrete mixture, a surface-active additive, the cationic reagent KADEM-VT, was used.

The use of the developed composition of the rubber-polymer asphalt mix in combination with rubber crumb, RTEP rubber thermoplastic elastomer and the KADEM-VT surface-active additive (adhesive) provides the mixture with the properties that it exhibits in the claimed solution, namely, the mixture acquires a lower temperature for preparation and placement. The aging time (ripening) in the storage hopper is reduced to 1 hour, which reduces aging, improving the operational properties of the mixture. When using other modifying additives, for example, a complex modifier of asphalt concrete KMA, the mixture matures 1.5-2 hours.

The resulting composition of the mixture allows you to make it more dense, with higher properties, using vibration compaction, with the formation of the so-called cast asphalt mixture.

An increase in the resistance of the asphalt concrete layer to the oxidative aging of the mixture contributes to the formation of thicker binder films due to the presence of crumb rubber and RTEC. Thick films of rubber-bitumen binder with swollen rubber particles are freely placed in the interfacial voids of the mixtures when they are compacted. The use of RTEP rubber-containing thermoplastic elastomer, containing a polyolefin additive, stabilizes the rubber particles in the mixture. The mixture acquires reduced water saturation, strength index increases at 50 ° C, shear resistance and shear adhesion at a temperature of 50 ° C. Asphalt pavement becomes more wear-resistant and the formation of reflected cracks is reduced.

The developed vibro-cast rubber-polymer asphalt mix allows its use in road and airfield construction for the construction of road surfaces, sidewalks, bridges, artificial structures.

The prepared vibrocast mixture has a reduced water saturation of 0.20-0.34%, increased compressive strength of 50 ° C is 1.30-1.45 MPa, and it also ages much slower. The depth of the indentation of the stamp corresponds to the values of 2.0-2.9 mm (according to the requirements of GOST R 54401-2012 for cast mixtures of type II it should be in the range of 1.0 to 3.5 mm) see table 1. The mixture has a reduced cooking and styling temperature in the range of 190-200 ° C, and is aged (matures) in the storage hopper for no more than 1 hour, which reduces its aging, improves fire and environmental safety. In addition, the consumption of scarce mineral powder is reduced in the mixture, and the range of road cast asphalt mixes is also expanding. At the same time, the obtained values of the properties indicators of the developed cast asphalt concrete mixture exceed the requirements of GOST R 54401-2011 for type II cast mixtures.

An analysis of known technological solutions has shown that the use of vibrocast asphalt mixtures is known. However, such mixtures have a rather high cooking and styling temperature, respectively 215 and 230 ° C, require longer aging (ripening) in the storage hopper - 1.5-2.0 hours [1], which contributes to its faster aging and loss of performance , a large consumption of scarce mineral powder is required.

The use of modifying components of the developed cast mixture: rubber crumb, rubber thermoplastic elastomer, adhesive additive KADEM-VT in combination with mineral materials in the composition of asphalt concrete is also known. However, they are used in asphalt mixtures in other compositions excluding each other, in combination with other additives and in other types of mixtures. It should also be noted a very narrow range of cast asphalt mixes, known for use in road construction. The developed composition of cast asphalt concrete allows to obtain denser mixtures using pavers with vibration-absorbing effect or using a 10-ton compactor (1-2 passes on one track).

The introduction of crumb rubber (crushed rubber from worn tires) into the composition of the heated mineral mixture allows significant savings in expensive polymer materials and significantly reduce the cost of binder modification.

Characterization of raw materials

1. Oil bitumen BND 60/90. Physico-mechanical indicators used in the work of bitumen are given in table. 2.

2. Rubber crumb is crushed rubber from worn tires and tires, as well as waste products from other rubber products. This is a recycled polymer that has accumulated in large amounts of waste. The particle diameter of the crumbs used in the work is generally not more than 0.63 mm.

3. Rubber thermoplastic elastomer RTEP - granular additive of a spherical shape with a particle diameter of 3-4 mm, developed at DorTransNII RGSU. The additive contains a polyolefin component, crumb rubber with grain sizes up to 0.63 mm, bitumen and antioxidants. Such a composition is characterized by the presence of a significant amount of unsaturated bonds inherent in rubber-polymer compounds. Due to the potential of these bonds, the RTEP modifier actively interacts with bitumen particles, mainly asphaltenes of aromatic compounds, which change the colloidal structure of the binder. Physical and mechanical parameters of RTEP are given in table. four.

4. Cationic reagent - adhesive KADEM-VT is made in accordance with the technical specifications TU 2482-009-04706205-03. The reagent is a mixture of alkylamidopolyamines and alkylimidazolinepolyamines derived from C ₁₆ -C ₂₀ acids of plant or animal origin. It is a homogeneous mass from light to dark brown in color with a characteristic smell of ammonia, insoluble in water, soluble in aromatic hydrocarbons, diesel fuel, oil products. Physico-mechanical properties of the additives are presented in table. 3 in comparison with the requirements for the manufactured product.

5. Mineral powder was used in the work of non-activated carbonate. In the table. 5 presents its physical and mechanical properties. Mineral powder meets the requirements of GOST R 52129-2003.

6. The mineral material is represented by fractions of crushed granite obtained in the process of crushing crushed stone of Pavlovskgranit OJSC. Crushed stone fractions were used: 5-10 mm and screening crushing of crushed stone fractions of 0-5 mm. Used crushed stone has a brand of strength 1200, abrasion, I-1, the true density of 2.72 g / cm ³ . In the table. 1 shows the grain compositions of fractions of crushed stone and screening crushing, as well as the grain composition of the selected cast mixture.

Example. For experimental verification of the claimed composition were prepared 5 variants of the compositions of mixtures of ingredients. In the preparation of the mixtures, the above materials were used.

Samples were prepared as follows: mineral material with rubber crumb and rubber thermoplastic elastomer was mixed at a temperature of 190-200 ° C for 15-20 seconds. Then, BND 60/90 petroleum bitumen heated to 150-160 ° C was introduced into the mixture, preliminarily modified with the adhesive additive KADEM-VT. The final mixing of the material was carried out at a temperature of 185-195 ° C for 30-35 sec, after which the prepared mixture was left to ripen for 1 hour at a temperature of 180-190 ° C and vibro-compacted on a vibrating table for 5 sec with an oscillation frequency of 35 Hz.

Samples of hot asphalt concrete were prepared from the resulting mixture in accordance with the requirements of the standard GOST R 5 4400-2011 “Hot Cast Asphalt Concrete Road Test Methods”. The maximum degree of compaction of the mixture was achieved due to the effect of its vibration for 3-5 seconds.

To determine the physical and mechanical properties, cubes were made by filling molds with layer-by-layer bayonet mixing (in three steps) at a temperature not exceeding 190-200 ° C, after which it was vibrated for 3-5 seconds. The prepared cube sample was kept in shape until it reached room temperature. The test of the sample was started no earlier than 3 hours after it reached room temperature.

Determination of the porosity of the mineral core, residual porosity, water saturation, tensile strength during splitting at a temperature of 0 ° C was carried out according to GOST 12801 on samples of a cylindrical shape. The stamp indentation depth was determined in accordance with EN 12697-20-2003.

The compositions of the prepared mixtures are presented in table. 6. The table also summarizes the results of their physical and mechanical properties of comparative tests. From the data of the table it follows that the proposed complex modifier made of rubber thermoplastic elastomer RTEP, crumb rubber and the adhesive component KADEM-VT made it possible to obtain cast asphalt mixes with higher compressive strengths at a temperature of 50 ° C, reaching 1.30-1.45 MPa that provides increased heat resistance of the mixture. Water saturation decreased by 20-40%. The production and laying temperature of the polymer blends of the mixture was reduced to 185-195 ° C (10-16% less than the permissible GOST 54401-2011), which slows down the aging process and provides energy saving. The depth of the indentation of the stamp is 2.0-2.9 mm Adhesion of a binder to mineral materials according to a five-point system reached 4-5 points compared to the original bitumen, in which this indicator is 2 points. Hanging of the noted properties of the obtained asphalt mix using the developed complex modifier allows us to judge the increase in the life of coatings by 1.3-1.5 times or more.

Claims (1)

Dense vibrocast asphalt mix containing mineral material, mineral powder, bitumen binder, including BND 60/90 bitumen with KADEM-VT adhesive additive, characterized in that it additionally contains rubber crumb and RTEP rubber thermoplastic in the mixture in the following ratio of components, wt. %:
crushed rubber crumb 1.00-1.20 rubber thermoplastic elastomer RTEP 0.25-0.35 cationic reagent - adhesive KADEM-VT 0.35-0.50 bitumen BND 60/90 7.80-8.20 mineral powder 16.00-18.00 mineral material (crushed stone and screening crushing crushed stone) rest