RU2468139C2 - Composition for arrangement of lower layer of road surface base - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: composition makes it possible to efficiently use production and heat power engineering wastes in road construction. The composition for arrangement of lower layers of road surface bases includes a mineral binder - cement, ash and slag mixture, wastes of asbestos cement production (WACP) and tall pitch at the following ratio of components, %: soil 52.0-60.0; cement 3.0-5.0; ash and slag mixture 12.0-18.0; ACP wastes 5.0-7.0; water 14.0-22.0; saponified tall pitch 0.5-1.5 of the cement weight.

EFFECT: expansion of a list of organic and mineral components for complex reinforcement of soils, increasing operating characteristics of roads and sites.

2 tbl, 3 dwg

Description

The invention relates to the construction and repair of roads and can be used for the device of the lower layers of the base of clothes and the upper layers of the subgrade in road and agricultural construction, as well as for sites of grain currents or storage of agricultural machinery.

The bottom layer of the base, perceiving operational loads from vehicles and other equipment, as well as subject to constant exposure to climatic factors, should provide high strength, water resistance, and frost resistance. An analysis of the intense destruction of the roadway indicates the relationship between the durability of soil concrete with low tensile strength of the pavement bases of bricks and high shrinkage of fortified soils, which in the initial period after the construction of the road leads to the formation of cracks and a decrease in performance. Widespread in road construction are complex methods of strengthening soils using water repellents, mineral and organic binders and various active additives for special purposes, providing water resistance and frost resistance of concrete bases. This approach is economically feasible and allows you to get material with specified operational properties (see Bezruk VM "Strengthening soils in road and airfield construction", M., Transport, 1971. - 246 p.).

The known composition of the mixture for the device of the lower layers of the base of pavements according to the patent of the Russian Federation No. 2305149, including soil - 77.89-83.91, cement - 4-6, water - 12-16 and cationic active substance DON-52KP - 0.09 -0.11. However, this composition has obvious disadvantages: increased shrinkage (more than 1.5-2.0 mm / m) and low tensile strength in bending (less than 0.6 MPa), as a result of which the durability of roads with such bases is very limited.

Known compositions of reinforced soils for the device of the lower layers of the base of pavements, consisting of (%): soil 70-75, cement 8-12, ash and slag mixture 15-18 and water-repellent additives 0.5-2.0. They have a sufficiently high compressive strength of 4.5 MPa and lower shrinkage rates of 0.8-1.3 mm / m. However, the introduction of ash and slag additives into the soil while improving the overall structure and increasing the strength of soil concrete does not contribute to increasing tensile strength in bending, which is an important operational characteristic of the lower base layer.

These disadvantages can be eliminated by introducing into the lower layer of the base of complex additives directional purpose. As structural components that reduce the coefficient of linear thermal expansion of the concrete base, it is rational to introduce ash and slag mixtures into the strengthened soil. To increase the tensile strength during bending, it is necessary, together with a mineral binder, to introduce asbestos-cement production wastes into the reinforced soil, providing dispersed reinforcement, and to impart hydrophobic properties, together with mixing water, the introduction of saponified tall tar pitch.

The composition for the device of the lower layer of the base of the pavement contains these components in the amount,%:

clay soil 52.0-60.0 cement 3.0-5.0 ash and slag mixture 12.0-18.0 ADC waste 5.0-7.0 saponified tall pitch 0.5-1.5 by weight of cement mixing water 14.0-22.0

The use of this composition contributes to a significant increase in operational performance and increases the service life of the lower layer of the base of the pavement.

Characteristics of additives that make up the bottom layer of the pavement base:

1. Clay soil

To strengthen the lower base layer, clay soils are claimed, spread over the entire territory of Western Siberia, which are loam of low strength, heavy, silty, hard, slightly downy. The granulometric composition of loams is presented in table 1.

Table 1 Loam name The content of fractions in percent by volume Clay Dusty Sand Dusty loam 13.2-19.3 61.2-67.9 8.9-18.1 Heavy loam 18.4-24.5 59.8-64.7 1.8-11.4

The analysis of particle size distribution shows that these soils are classified as coarse raw materials and consist mainly of dusty particles. The main minerals of loam are hydromica, mainly muscovite with an interplanar distance d = 0.983-0.998 nm. In addition, the presence of a large amount of quartz (d = 0.423 and 0.330 nm) and feldspar (d = 0.404; 0.384; 0.366; 0.319 nm) should be noted. The presence of calcium carbonate was noted (d = 0.3028; 0.2273 nm). In some samples, montmorillonite (d = 0.640; 0.442; 0.318; 0.247 nm) with impurities of calcite (d = 0.304 nm) is fairly well fixed. In terms of ductility, clay materials are moderately ductile with a ductility number from 7.5 to 12.5.

2. Cement (mineral binder)

As a mineral binder, Portland cement grade ПЦ400 D20 of Iskitim cement plant (GOST 10178-85 “Portland cement and slag Portland cement” is introduced into the composition

3. Ash and slag mixture

Ash-and-slag mixtures are formed from burning coal of grades D (long-flame) and G (gas) of the Tom-Usinsky coal basins at thermal power plants and boiler houses in Novosibirsk and the Novosibirsk region. Fuel ash and slag in the dumps are heterogeneous in their chemical, mineralogical and granulometric composition. Tests of ash and slag mixtures were carried out in accordance with the requirements of GOST 25592-91 “Ash and slag mixtures of thermal power plants for concrete. Technical conditions ”and showed the following results:

slag content by weight 11.3-19.7% (20%) the content of ash and slag grains passing through a sieve No. 0.315 65.8-823% (50-100%) grain content larger than 5 mm 13.1-17.9% (up to 15%) maximum grain size of slag 19-24 mm (up to 20 mm) humidity 14.3-19.5% bulk density 795-850 kg / m ignition mass loss 8.7-15.1% (up to 10%)

Due to the low calcium oxide content, the ash and slag mixtures and slag used are inactive inert aggregates according to the existing classification. According to the calculated indicators: basicity modulus (M ₀ = 0.14), silicate module (M _C = 2.23) and quality factor (K = 0.51) ash and slag mixtures are classified as acidic hidden active ash and slag materials according to the current classification. A characteristic feature of acid ash and slag is their heterogeneity in particle size, configuration, color and structure, spherical particles predominate predominantly.

4. Wastes of asbestos-cement production of the ADC

For dispersed reinforcement of the lower base layer, asbestos-cement production waste associated with the production of asbestos-cement products is used, which are large-tonnage sludge from hydrated cement on asbestos fibers with a diameter of 0.02-0.08 mm and a length of 2-6 mm. The daily volume of waste collection is more than 40-50 tons, and the annual volume exceeds 15 thousand tons. The sludge is loose and contains aggregated or dispersed particles of asbestos cement with up to 50-60% hydrated Portland cement grade 400 manufactured by Iskitimcement LLC. Chrysotile asbestos contained in the sludge is represented by fibers 1 to 6 mm long and 0.02-0.8 microns in diameter. The chemical composition of chrysotile asbestos is magnesium hydrosilicate and can be expressed by the formula 3MgO · 2SiO ₂ · H ₂ O.

5. Saponified tall oil pitch (water-repellent additive)

Tallow pitch, which is a non-volatile part of tall oil in the process of rectification, is used as a hydrophobizing agent and modifier of cement-soil mixtures. This is an intermediate product of the deep chemical processing of wood in the sulfate-cellulose production. To impart water-soluble properties, the pitch is treated with an alkali solution (saponification). Saponified tall tar pitch (OTP) is produced in accordance with TU 13-0281078-146-90 and two grades are produced for their main purpose: B - for gluing cardboard, wood-fiber boards, technical paper grades; K - for the production of agricultural krelin. In appearance, the pitch is a solid mass of brown or dark brown color that is readily soluble in water with a softening temperature of 70 ... 85 ° C. According to the chemical composition, saponified tall pitch contains: fatty acids - 31-34%; resin acids - 18-26%; oxidized substances - 13-17% and neutral substances - up to 25-31%.

The fraction of resin acids contains abietic and dehydrobietic acids most of all, i.e. in terms of the set of acids, pitch is close in composition to tall lignin and rosin. The pitch fatty acids are represented mainly by saturated acids, oleic and linoleic acids prevail, which corresponds to their content in the original tall oil.

6. Mixing water - technical

Example. For experimental verification of the proposed composition for the device of the lower layer of pavement, various versions of reinforced soil were made with a combination of all components both within the framework of the proposed compositions and outside the indicated values.

The preparation of a cement-soil mixture with the addition of mineral and organic additives for complex purposes was carried out as follows. An ash-and-slag mixture, asbestos cement waste and cement were added successively with obligatory mixing to a soil sample of 50.0-62.0 g. After obtaining a homogeneous mass, the calculated amount of water was introduced with the saponified tar pitch previously diluted in it and stirring was continued for 2-3 minutes. Beams 4 × 4 × 16 cm in size were formed from the obtained cement-cement mixture, which, after storage in a humid environment for 28 days, were tested to determine the tensile strength in bending and the ultimate compressive strength, as well as other indicators. The results of comparative tests are shown in table 2.

table 2 Physico-mechanical properties of soils reinforced with cement and complex additives The content of additives,% The limit of compressive strength, MPa Bending Strength, MPa Shrinkage, mm / m Priming ZHS OACP * Tall pitch Cement 1. 62 twenty 3 - 2.0 1.71 0.42 1,1 2. 60 eighteen 5 0.5 3.0 3.82 0.98 0.8 3. 56 fifteen 7 1,0 4.0 5.47 1,03 0.5 4. 52 12 9 1,5 5,0 5.59 0.97 0.6 5. 50 10 eleven 2.0 6.0 4.16 0.92 0.5 Analogue DON-52KP- 74.88-86.92 - - 3-7 3,5-5,0 0.4 1.8-2.1 0.08-0.12% * The consumption of tall pitch was calculated from the cement content

The introduction of tall pitch significantly reduces the water requirement of the soil-concrete mixture. Analysis of the test samples shows that rational values of the density of compacted soil-concrete mixture are values of more than 1800 kg / m ³ . In this case, even with a minimum consumption of cement, the specified parameters of the strength of the road base are ensured.

An equally important technological impact on the soil-concrete mixture is the compaction process, which determines both the density and strength of the soil concrete, as well as the water resistance and frost resistance in the road base. As a recommendation for compaction, a shock method or vibration compaction may be proposed.

The use of a mixture of ZHS and OACP leads to hardening of the structure, which was noted when studying the proposed compositions by differential thermal analysis in the form of a shift of the peaks of exo and endothermic effects towards higher temperatures compared to binary compositions (Fig. 1).

The study by the capillary impregnation express method showed that the use of tall pitch not only significantly reduces capillary suction of soil-concrete material, but also significantly increases its service life (Fig. 3).

The use of the claimed composition of the lower base of the pavement will significantly increase the service life of the pavement by increasing frost resistance, reducing cracking, as well as reducing shrinkage deformation (Fig. 2).

Claims (1)

The composition for the device of the lower layer of the base of the pavement, including clay soil, mineral binder - cement, ash and slag mixture and water, characterized in that it additionally contains waste from asbestos-cement production of the ADC and saponified tall tar in the following ratio of components,%:
clay soil 52.0-60.0 cement 3.0-5.0 ash and slag mixture 12.0-18.0 ADC waste 5.0-7.0 saponified tall pitch 0.5-1.5 by weight of cement water 14.0-22.0

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