RU2331728C1 - Method of cold recovery for pavement clothing layer - Google Patents

Abstract

FIELD: construction, road works.

SUBSTANCE: invention is attributed to road repair works and can be used for asphalt concrete recovery during repairing of pavement clothing for highways, municipal roads, pavements, areas, etc. Method of cold recovery for road clothing layers includes loosening of road clothing layers while adding necessary quantities of broken stone, sand, bonding substance and water and compaction of road clothing. As bonding substance, unhydrated lime carbonate is used. It is distributed onto old layer before recovery of road clothing layer while adding necessary quantities of broken stone and sand depending on grain size of road clothing layer being recovered, and water is added during recovery depending on humidity of road clothing layer being recovered and amount of bonding substance. Amount of substance and water and compaction of road clothing constitutes 2.5-3.0% of recovered road clothing layer mass.

EFFECT: increase in bearing capability, enhancement of mechanical and physical properties of road clothing structural layers and lowered energy and labour consumption for road repair works carried out by cold recovery method.

4 cl, 3 tbl, 2 dwg

Description

The invention relates to road repair work and can be used for the regeneration of asphalt concrete in the repair of road clothes of automobile and city roads, sidewalks, sites, etc.

A known method for the regeneration of asphalt by mixing it for 30 s at 20 ° C with 0.1 ÷ 1.0% of used engine oil, into which tetraethoxysilane is additionally introduced in an amount of 5.2 ÷ 42.8% by weight of the oil (see A .S. USSR No. 1599340).

The disadvantage of this method is the need to grind the regenerated asphalt concrete into small fractions, which leads to the destruction of crushed stone, deterioration of the grain composition of the finished asphalt-granular concrete mixture and is associated with high energy costs.

A known method of preparing a regenerated asphalt mixture, including mixing heated crushed stone and sand with cold crushed asphalt and heated bitumen, cold mineral powder is added to the mixture, crushed stone and sand are heated to a temperature of 210-280 ° C, and the bitumen is heated to operating temperature, mixing is carried out for 3-7 s, the resulting mixture is kept in a thermos hopper for at least 2 minutes and finally mixed until completely homogeneous (see US Pat. RF No. 2164900 C2, IPC ⁷ С04В 26/26, ЕСС 19/10 04/10/2001).

The disadvantages of this method are low technology and high energy costs associated with additional heating of mineral materials, bitumen, with the need to withstand and additional mixing of the regenerated asphalt in special mixing plants, which significantly reduces the performance of the above technology and increases the cost of finished products.

Closest to the proposed invention is a method of cold regeneration of pavement layers, which consists in loosening them by milling, introducing a binder and water into the crushed material, mixing the components, distributing the mixture and compacting it, while the viscous bitumen heated to the working temperature is used as a binder (with penetration from 70 to 200), which is introduced with stirring into a cold mixture of crushed material, powdered filler and water, with a ratio of bitumen: filler (by weight) from 1: 1 d about 1: 3, and the amount of bitumen and filler is from 4 to 10% by weight of the crushed material of the pavement (see US Pat. RF No. 2232841 C1, IPC ⁷ Е01С 7/18 2004.07.20).

The disadvantages of this method are the need for transportation and additional mixing of the milled material at the mixing plants, and heating the bitumen to operating temperature causes additional energy and labor costs, which together increases the cost of the structural layer of pavement.

The invention is aimed at increasing the bearing capacity, physico-mechanical properties of the structural layers of pavement and reducing energy and labor costs of road repair work by cold regeneration.

The result is achieved by the fact that in the method of cold regeneration of layers of pavement, which consists in loosening layers of pavement with the addition of the necessary amount of crushed stone, sand, binder and water, compacting it, according to the invention, non-hydrated lime is used as a binder, which is distributed over the old layer before regeneration layer of pavement with the addition of the necessary amount of crushed stone and sand, depending on the grain composition of the regenerated layer of pavement, and water is added during the regeneration process depending on the humidity of the regenerated layer of pavement and the amount of binder, while the amount of non-hydrated lime is 2.5 ÷ 3.0% by weight of the regenerated layer of pavement.

The result is also achieved by the fact that they make preliminary loosening of the layers of pavement and its compaction.

The result is also achieved by the fact that non-hydrated lime is subjected to mechanical activation.

The result is also achieved by the fact that water for lime hydration is taken in an amount of 25-35% by weight of unhydrated lime.

Quicklime is used as a binder in accordance with GOST 9179-77. During hydration of lime and water, a large amount of heat is released - 1160 kJ (277 kcal) per kg of calcium oxide (I.A. Khint. Fundamentals of the production of silicate products. - Leningrad, Moscow: Gosstroyizdat, 1962. - 601 p.; M.P. Vakhnin, A.A. Anishchenko. Production of silicate brick. - M .: Higher school, 1977. - 159 p.), Which provides heating of the cold components of the regenerated layer of pavement and weakening of bitumen bonds in grains, which allows to improve the processes of structure formation and get the maximum density of the regenerated layer.

Figures 1 and 2 show the schemes of work, where 1 is a distributor of technological materials, 2 is a recycler, 3 is a water tank truck, 4 is a roller, 5 is a grader.

The method of cold regeneration of layers of pavement is as follows.

Determine the grain composition of the regenerated layer of pavement. The required amount of mineral aggregate: crushed stone and (or) sand, is preliminarily distributed on the old pavement coating layer to be regenerated, depending on the grain composition of the regenerated pavement layer. Further, using the distributor of technological materials 1 immediately before the regenerating unit (recycler) 2 distribute unhydrated lime in the amount of 2.5-3.0% by weight of the regenerated layer of pavement. By recycler 2, the old coating layer is crushed with mineral aggregates and non-hydrated lime distributed over it. The required amount of water is supplied from the tanker with water 3 through nozzles in the mixing drum of the recycler 2. The required amount of water is calculated from the condition that for hydration of lime it needs 25-35% by weight of non-hydrated lime and additionally water is necessary to achieve the optimum humidity of the regenerated coating layer , which is determined according to [1] (G.S.Bakhrakh, V.A. Kretov, G.S. Gorlina. Guidelines for the restoration of asphalt concrete pavements and the foundations of roads ami cold regeneration. - M.: Rosdornia, - 2002). Next, rolling is performed by the roller 4, alignment by the grader 5 and the final compaction of the regenerated layer of pavement by the roller 4.

The method of cold regeneration of layers of pavement can be carried out in 2 stages (figure 2).

At the first stage of work, preliminary regeneration of the “old” coating layer is carried out using recycler 2, followed by rolling of the regenerated layer of pavement with roller 4. Next, the method is carried out as in FIG. 1: the required amount of mineral aggregate is distributed: crushed stone and (or) sand. Then, using the distributor of technological materials 1 immediately before the regenerating unit (recycler) 2 enter unhydrated lime. Then, recycler 2 re-regenerates the coating layer with mineral aggregates and non-hydrated lime, and the required amount of water is supplied from the water tank 3 through nozzles in the mixing drum of recycler 2. Next, they are rolled by roller 4, leveled by grader 5 and final compaction of the regenerated layer of pavement skating rink 4.

In the method of cold regeneration of the pavement layer, non-hydrated lime mechanically activated (dispersed) for 6 s in a disintegrator unit can be used.

To study the effectiveness and experimental verification of the proposed method in laboratory conditions, the moisture and grain composition of the regenerated layer of pavement were previously determined, then the amount of sand, gravel and water was calculated to obtain the optimal grain compositions and humidity of the regenerated layer of pavement. The grain composition of the regenerated layer of pavement, taken for testing and which is an asphalt-granular-concrete mixture according to GOST 9128-97, corresponded to a fine-grained asphalt mixture of type B, with a grain content of more than 5 mm 41.6% (Table 1).

Table 1 Grain composition of asphalt-granulobetonny mix Sieve size 40 twenty fifteen 10 5 2,5 1.25 0.63 0.315 0.16 0,071 According to the results of the study of the selected asphalt-granular-concrete mixture Passed through a sieve,% - 92.5 88.2 76.8 58.4 50.7 43.3 36.9 21.9 10,2 6.8 According to the requirements of GOST 9128-97 (for a dense, fine-grained mixture of type B, intermittent grain composition) Passed through a sieve,% - 90-100 80-100 70-100 50-60 38-60 28-60 28-60 14-34 10-20 6-12

Samples from asphalt-granular concrete mixture were molded in accordance with the requirements of [1] and GOST 12801-98. To determine the optimum moisture content of the asphalt-granular-concrete mixture, comparative tests of molded samples without adding unhydrated lime with a moisture content of 1.0 to 4.0% by weight were carried out in terms of compressive strength at a temperature of 20 ° C and compressive strength at a temperature of 20 ° C after prolonged saturation with water (within 15 days). The optimal humidity of the mixture was 2.5% (table 2).

table 2 Determination of the optimum moisture content of the asphalt-granular concrete mixture Sample No. d mm h mm P, H R ₂₀ , MPa R ₂₀ ^lasts , MPa To _water ^lasts Humidity,% one 101 101 10762 1.3433 0.6010 0.45 1.00 2 101 101 11163 1.3933 0.6311 0.45 1,50 3 101 101 11216 1,3999 0.7007 0.50 2.00 four 101 101 10740 1,3405 0.7874 0.59 2.25 5 101 101 11516 1,4374 0.8633 0.60 2,50 6 101 101 10561 1,3182 0.8319 0.63 2.75 7 101 101 10489 1.3092 0.7159 0.55 3.00 8 101 101 10047 1.2540 0.7832 0.62 3,50 9 101 101 10820 1,2505 0.6521 0.52 4.00

To compare the effectiveness of using a mineral filler from non-hydrated lime according to [1], cylinder samples were formed from asphalt-granular-concrete mixture with a moisture content of 2.5% by weight and a diameter of 101 mm, without a mineral binder, with an addition of 1.0 to 3.0% by the mass of non-activated lime and mechanically activated (dispersed) for 6 s in a disintegrator installation of finely ground non-hydrated lime. After 3 days after pre-drying, samples were tested for compressive strength at 20 ° C (R _20), at 50 ° C (R _50), a compressive strength at 20 ° C after prolonged exposure in water (R ₂₀ ^long) ( within 15 days) and an indicator of long-term water resistance (within 15 days) (K _water ^lasts ).

Physico-mechanical properties of the molded mixtures are given in table 3 and meet the requirements [1].

Table 3 Physico-mechanical properties of asphalt granular concrete samples with optimal mixture moisture Indicators According to [1], not less Without unhydrated lime The amount of mineral binder,% 1,0 1,5 2.0 2,5 3.0 NO ^* AI ^** No AI No AI No AI No AI P ₂₀ , MPa 1.40 1.44 1,57 1,67 1,66 1.78 1.78 1.89 1.78 2,32 1.72 2.16 R ₂₀ ^lasts , MPa 0.84 0.86 1,03 1.38 1.28 1,56 1.30 1.70 1.39 1.98 1.15 1.49 R ₅₀ , MPa 0.50 0.51 0.52 0.53 0.55 0.63 0.62 0.74 0.61 0.79 0.60 0.71 To _water ^lasts 0.60 0.60 0.66 0.83 0.77 0.88 0.73 0.90 0.78 0.85 0.67 0.69 Note: NOR - non-activated lime;
AI - mechanically activated lime.

Optimal is the use of mechanically activated non-hydrated lime in an amount of 2.5% by weight of asphalt granular concrete (Table 3).

The results allow us to conclude that the use of non-hydrated mechanically activated lime in an amount of 2.5% by weight of the asphalt-granular concrete mixture increases the physical and mechanical properties, including (compared with the mixture without the use of non-hydrated lime) compressive strength at 20 ° C - 23.6%, and the introduction of a mechanically activated lime - 61.1%, ^long indicators R ₂₀ - 61.6 and 130.2% respectively.

It should be noted that the structural layer of pavement obtained by the method of cold regeneration of the pavement layer with preliminary loosening is characterized by a more homogeneous and high-quality asphalt-granular concrete mixture, which allows to improve the processes of structure formation and to achieve maximum density and physico-mechanical properties with minimal expenses for leveling and compaction regenerated layer of pavement, and the use of mechanically activated lime contributes to a significant reduction in the process of and exothermic reactions release more heat, minimizing the cost of the seal asfaltogranulobetonnoy mixture and increase the physico-mechanical properties.

Thus, the physicomechanical properties of asphalt-granular concrete samples obtained using mechanically activated mineral filler exceed the known analogues, which helps to increase the bearing capacity of the structural regenerated pavement layer. In addition, the proposed method is more technological and can reduce heat and energy consumption.

Claims (4)

1. The method of cold regeneration of layers of pavement, including loosening layers of pavement with the addition of the necessary amount of crushed stone, sand, binder and water, compacting it, characterized in that as a binder use non-hydrated lime, which is distributed over the old layer before the regeneration of the layer of pavement with the addition of the necessary amount of crushed stone and sand, depending on the grain composition of the regenerated layer of pavement, and water is added during the regeneration process depending on the humidity of the regenerated the pavement layer and the amount of binder, while the amount of non-hydrated lime is 2.5-3.0% of the mass of the regenerated pavement layer. 2. The method according to claim 1, characterized in that they produce preliminary loosening of the layers of pavement and its rolling. 3. The method according to any one of claims 1 and 2, characterized in that the non-hydrated lime is preliminarily subjected to mechanical activation. 4. The method according to any one of claims 1 and 2, characterized in that the amount of water for lime hydration is 25-35% by weight of unhydrated lime.

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