RU2436888C2 - Cement and asphalt-concrete mixture preparation method and its composition - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: in preparation method of cement and asphalt-concrete mixture as mineral material there used is crushed stone and sand, and mixing is performed in two stages: at the first stage there separately prepared is "black" crushed stone and cement-sand solution; at that, "black" crushed stone is prepared by mixing the crushed stone with bitumen emulsion, and cement-sand solution is prepared by mixing the sand, portland cement and water; and at the second stage there mixed is prepared "black" crushed stone with cement-sand solution, and mixture is obtained at the following component ratio, wt %: crushed stone 40-72, sand 26-58, Portland cement 2-14, bitumen emulsion (more than 100%) 1-5, water-cement ratio (excluding water present in bitumen emulsion) 0.2-0.5. Composition of cement and asphalt-concrete mixture is described.

EFFECT: reducing the quantity of complex binding agent at improving physical and mechanical properties of the obtained material; improving water resistance and long-term water resistance, resistance to alternate freezing and melting; increasing modulus of deformation and strength.

3 cl, 1 dwg, 4 tbl

Description

Technical field

The invention relates to a technology for the preparation of cement-asphalt mixture and its composition and can be used for road construction.

State of the art

A known method of preparing a cement-asphalt mixture (the closest analogue is copyright certificate No. 193562, class E01C 7/18, publ. 03/13/1967. Bull. 7) and its composition, including mineral material, bitumen emulsion, water and Portland cement. During the preparation of the cement-asphalt mixture, bitumen emulsion is introduced into the aggregates in an amount of 7-11% over 100% of the total weight of the dry components of the cement-asphalt concrete mixture, and then Portland cement is introduced into the resulting mixture in the amount of 7-15% of the weight of the dry components of the cement-asphalt concrete mixtures.

The disadvantages of the known method of preparation and composition of the cement-asphalt mixture are: a large number of complex binders - bitumen emulsions and Portland cement, which increases the cost of production; low physical and mechanical properties, expressed in insufficient strength of the coating of cement-asphalt mixture.

Disclosure of invention

The objective of the invention is aimed at providing an effective process for the production of cement-asphalt concrete mixtures with enhanced physical and mechanical properties.

The technical result obtained by the implementation of the developed method and composition is to reduce the number of complex binder; in improving the physical and mechanical properties of the cement-asphalt mixture, in particular in increasing the water resistance and long-term water resistance; in increasing the resistance of the material to alternate freezing and thawing; in increasing the deformation modulus and strength.

The technical result is achieved by the fact that in the method of preparing a cement-asphalt-concrete mixture, comprising mixing a mineral material with a bitumen emulsion, Portland cement and water, the mixing is carried out in two stages: in the first stage, black gravel is separately prepared using bitumen emulsion in an amount of 1-5% above 100% of the total weight of dry components, and cement-sand mortar using Portland cement in an amount of 2-14% of the weight of dry components and water with a water-cement ratio of 0.2-0.5, and in the second hundred uu mixed with prepared gravel black cement-sandy solution.

Also, the technical result is achieved by the fact that in the composition of the cement-asphalt mixture, including mineral material, bitumen emulsion, water and Portland cement, crushed stone and sand are used as the mineral material in the following ratio of components, wt.%:

Crushed stone 40-72 Sand 26-58 Portland cement 2-14 Bitumen emulsion (over 100%) 1-5 Water-cement ratio (excluding water, present in bitumen emulsion) 0.2-0.5

As part of the cement-asphalt-concrete mixture, asphalt granulate can be used as a mineral material in the following ratio of components, wt.%:

Asphalt granulate 30-100 Crushed stone and sand 0-70

As part of the cement-asphalt-concrete mixture, crushed stone of a fraction of 5-20 mm and sand can be used.

The essence of the technical solution, namely, the method of preparation of cement-asphalt mixture is illustrated by the technological scheme.

The material obtained from the cement-asphalt mixture is a skeleton of small particles of mineral material (sand) connected by a cement binder, and a continuous cluster of bitumen binder on the surface of the particles of large mineral aggregate (crushed stone). Structuring in it proceeds in three directions:

a) the formation of bonds during compaction between coarse aggregate particles due to the bitumen layers adsorbed on them (after emulsion decay);

b) the formation of structural bonds in a cement-sand mortar, which fills the space between the large aggregate and creates a volume skeleton, which increases the strength of the material, which is less (compared with the closest analogue) dependent on temperature;

c) the formation of structural bonds on the surface of a large aggregate having a bitumen film (after the decay of the emulsion) with a cement-sand mortar.

The technological scheme presents the proposed method for the preparation of cement-asphalt mix.

Crushed stone and sand are used as a mineral material. From the technological scheme it is seen that in the first stage, black gravel and cement-sand mortar are prepared separately from each other. Black gravel is prepared as follows: gravel is dispensed from the feed hopper and fed to the first mixing plant, where bitumen emulsion is supplied in an amount of 1-5% over 100% of the total weight of all dry components - these components are mixed. A cement-sand mortar is prepared as follows: sand is dispensed from the feed hopper and fed to a second mixing plant, where Portland cement is fed in an amount of 2-14% of the weight of dry components and water at a water-cement ratio of 0.2-0.5 without taking into account the water present in a bitumen emulsion, - these components are mixed. At the second stage of the proposed method, the prepared black gravel is introduced into the second mixing unit and mixed to a homogeneous mass with the prepared cement-sand mortar. It is necessary to provide that the productivity of the second mixing plant is approximately 2 times higher than the productivity of the first mixing plant, since more material is mixed in it (both black gravel and cement-sand mortar). After this, the prepared cement-asphalt mixture should be delivered to the construction site, distributed and compacted. Moreover, all these operations must be performed before the start of the setting of Portland cement in accordance with GOST 31108-2003.

The composition of the cement-asphalt mix prepared by the above method includes mineral material, bitumen emulsion, water and Portland cement, while crushed stone and sand are used as the mineral material in the following ratio of components, wt.%:

Crushed stone 40-72 Sand 26-58 Portland cement 2-14 Bitumen emulsion (over 100%) 1-5 Water-cement ratio (excluding water present in bitumen emulsion) 0.2-0.5

In order to utilize the previously used pavement, asphalt granulate, crushed stone and sand can be used as a mineral material in the following ratio, wt.%:

Asphalt granulate 30-100 Crushed stone and sand 0-70

Asphalt granulate is a secondary raw material obtained in the processing of previously used pavement.

To obtain a cement-asphalt mixture used as the upper layers of the road surface, it is desirable to use crushed stone fractions of 5-20 mm and sand.

For experimental verification of the method of preparation of the cement-asphalt-concrete mixture and its composition, five compositions of the cement-asphalt-concrete mixture were prepared (see table No. 1); the comparison was carried out with the previously indicated closest analogue (see copyright certificate No. 193562), the composition of which was taken within the limits indicated in its description, while a mixture of crushed stone and sand was taken as a filler or mineral granular material indicated in the closest analogue.

Table 1 Component Name Amount,% by weight The closest analogue Composition 1 Composition 2 Composition 3 Composition 4 Composition 5 one 2 3 four 5 6 7 Crushed stone fractions 5-20 mm 67 40 48 48 48 72 Sand 58 41.5 38 38 26 Mineral powder eighteen 0 0 0 0 0 Portland cement fifteen 2 10.5 fourteen fourteen 2 Bitumen emulsion, in excess of 100% eleven one 2.5 one 5 5 Water-cement ratio (excluding water present in bitumen emulsion) 0,0 0.5 0.35 0.5 0.2 0.2

Physico-mechanical properties were determined on cylindrical samples with a diameter of 71 mm, obtained by compaction of the mixture in steel form under a pressure of 40 MPa, and on samples-beams with a size of 100 × 100 × 400 mm. Forms and methods of manufacturing samples correspond to GOST 12801-98. The prepared samples were kept for 26 days in an air-wet storage chamber, and then 2 days in water — with the samples immersed in water 1/3 of the height on the first day and completely immersed on the second day. After that, the samples were tested for compression at various temperatures and tensile under bending according to the methods of GOST 12801-98. The coefficient of water resistance and long-term water resistance of cement-asphalt concrete was determined on samples after hardening for 28 days under normal conditions for cement concrete according to the method of GOST 12801-98.

Comparative physical and mechanical properties of the materials obtained as a result of the tests are presented in table 2.

table 2 Indicators The closest analogue Composition 1 Composition 2 Composition 3 Composition 4 Composition 5 one 2 3 four 5 6 7 The compressive strength, t = 0 ° C, t = 20 ° C, t = 50 ° C, MPa: R ⁰ _cr 12.31 3,7 13.62 14.5 12.7 9.8 R ²⁰ _compress 5.65 3.15 10.94 12.9 9.1 3,5 R ⁵⁰ _Comp 1,52 2.91 8.23 9.72 7.6 2.63 Tensile strength in bending R ₂₀ , MPa 1.24 2,35 3.81 3.84 2.95 2.29 The average density, kg / m ³ 2430 2340 2390 2410 2420 2390 Deformation modulus, MPa 290 340 960 1150 790 320 Water resistance coefficient 0.91 0.92 0.97 0.98 0.95 0.94 Long-term water resistance 0.78 1.01 1,03 1,04 1.01 0.95 The decrease in strength during alternate freezing and thawing for 50 cycles,% 14.51 12.23 8.34 7.85 9.15 12.1

In order to utilize the previously used pavement, asphalt granulate can be added to the composition of the cement-asphalt-concrete mixture as a mineral material. The resulting compositions of the mixtures are shown in table 3, and the physico-mechanical properties obtained as a result of testing these materials are presented in table 4.

Table 3 Component Name Amount,% by weight Composition 1 Composition 2 Composition 3 Composition 4 Composition 5 Composition 6 one 2 3 four 5 6 7 Crushed stone fractions 5-20 mm 39.2 0,0 35.0 0,0 36,2 0,0 Sand 29.4 0,0 25 0,0 26.5 0,0 Asphalt granulate fractions 0-20 mm 29.4 98.0 26 86 26.8 89.5 Portland cement 2.0 2.0 fourteen fourteen 10.5 10.5 Bitumen emulsion, in excess of 100% 1,0 5,0 1,0 5,0 2.5 2.5 Water-cement ratio (excluding water present in bitumen emulsion) 0.5 0.2 0.5 0.2 0.35 0.35

Table 4 Indicators Composition 1 Composition 2 Composition 3 Composition 4 Composition 5 Composition 6 one 2 3 four 5 6 7 The compressive strength, t = 0 ° C, t = 20 ° C, t = 50 ° C, MPa: R ⁰ _cr 3,5 3.4 12.22 11.85 12,4 12,2 R ²⁰ _compress 3,1 3.0 9.84 7.19 8.71 8.4 R ⁵⁰ _Comp 2.72 2.61 7.13 4.72 7.26 6.86 Tensile strength in bending R ₂₀ , MPa 2,31 2.25 3.65 3.21 2.73 2,52 The average density, kg / m ³ 2320 2330 2370 2380 2410 2400 Deformation modulus, MPa 320 330 930 1150 760 750 Water resistance coefficient 0.91 0.92 0.95 0.98 0.94 0.93 Long-term water resistance 1.01 0.97 1,03 1.01 1.01 1.01 The decrease in strength during alternate freezing and thawing for 50 cycles,% 13.15 13.23 8.74 8.85 9.76 10.05

Using the proposed composition and method for preparing a cement-asphalt-concrete mixture provides, in comparison with existing methods and compositions, in particular with the closest analogue, the following advantages: the amount of complex binder is reduced; increased water resistance and long-term water resistance, the resistance of the material to alternate freezing and thawing; the deformation modulus, tensile strength in bending, and the strength of the material at high operating temperatures, in particular at a temperature of 50 ° C, increased the strength of cement-asphalt concrete samples compared to the closest analogue increased to 2.61-9.72 MPa. The deformation modulus of the resulting pavement is intermediate between asphalt concrete and cement concrete. Its deformability is higher than the deformability of cement concrete by more than 10 times, so the thickness of the layers of the claimed pavement can significantly decrease, which will reduce material consumption and financial costs.

The proposed method for the preparation of cement-asphalt-concrete mixture and its composition are simple in execution, technologically advanced, they can utilize the previously used pavement and obtain a pavement of increased strength and durability with significant economic effect.

Claims (3)

1. A method of preparing a cement-asphalt-concrete mixture, comprising mixing a mineral material with a bitumen emulsion, Portland cement and water, characterized in that crushed stone and sand are used as the mineral material, and the mixing is carried out in two stages: in the first stage, black is prepared separately from each other. crushed stone and cement-sand mortar, while black crushed stone is prepared by mixing crushed stone with a bitumen emulsion, and cement-sand mortar is prepared by mixing sand, Portland ementa and water, and in the second step is mixed with cooked black crushed stone cement-sand mortar to obtain a mixture with the following ratio of components, wt.%:
crushed stone 40-72 sand 26-58 Portland cement 2-14 bitumen emulsion (over 100%) 1-5 water-cement ratio (excluding 0.2-0.5 water present in the bitumen emulsion) 2. The composition of the cement-asphalt mixture prepared by the two-stage method and including crushed stone, sand, bitumen emulsion, water and Portland cement, in the following ratio, wt.%:
crushed stone 40-72 sand 26-58 Portland cement 2-14 bitumen emulsion (over 100%) 1-5 water-cement ratio (excluding 0.2-0.5 water present in the bitumen emulsion) 3. The composition of the cement-asphalt mixture according to claim 2, characterized in that they use crushed stone fractions of 5-20 mm and sand.

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