RU2350709C1 - Ash- and mineral composition used for roadbeds - Google Patents

Abstract

FIELD: construction industry.

SUBSTANCE: invention refers to construction industry, and namely to ash- and mineral compositions used for roadbeds, and can be used in road construction industry. Ash- and mineral mixture consists of sand with particle size of up to 3 mm and crushed stone screenings with particle size of up to 10 mm, which are used as filler; ash obtained from burnt sewage sludge with specific surface area of 200-300 m²/kg, with bulk density of 0.7-0.8 g/m³, SiO₂ - 50-60%, and pH 12-13.5, is used as ash, and bitumen and cement are used as bonding agents. Component ratio is as follows, wt %: sand with particle size of up to 3 mm - 10-18; crushed stone screenings with particle size of up 10 mm - 10-15; ash obtained from burnt sewage sludge - 35-55; oil road bitumen - 5-10; portland cement not less than 400 - 6-12; and water - 15-20% of mixture mass.

EFFECT: enlarging raw-material base of road construction industry owing to utilising burnt sewage sludge ash in ash- and mineral mixture.

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Description

The invention relates to the field of construction, specifically to ash compositions for foundations of pavements, and can be used in road construction.

During the construction of roads, it is necessary to have in large quantities raw materials, which are the basis of compositions that provide the specified requirements for pavement.

In particular, ash, which is produced in large volumes as a result of burning sewage sludge, can be used as mineral raw materials.

The relevance of the use of ash in road construction is enhanced by the fact that this ash is currently useless disposed of by storage at landfills. The maintenance of such landfills requires high material and technical costs. Ash contains salts of heavy metals, which, in an unbound state, are leached into the environment and violate environmental safety requirements.

In a bound state, these salts are released into the environment in volumes not exceeding permissible norms.

A known composition for the device of the bases of the pavement (RF patent No. 2246571), including mineral binders as a binder. This composition includes slag crushed stone and slag decay products, while it additionally contains stabilized slag as a mineral binder from the production of refined ferrochrome (RFX) with the following component ratios, wt.%: Slag crushed stone 10-70 mm - 30-40; decay products of RFX slag 0-70 mm - 20-30; stabilized slag RFX 0-10 mm - 25-35; water is the rest.

The use of this composition in road construction provides an increase in the initial strength of the composition for the device of the foundations of pavements, limiting leaching and aeration from the composition of finely dispersed slag decomposition products.

The disadvantage of this composition is that as a mineral binder, various modifications of slag are used, which is a waste of small-tonnage production, the placement of which is not always adequate for road construction sites. Such slag must be possessed and delivered to the construction of the road in large volumes, which is associated with high material and technical costs.

A known composition for the manufacture of autoclaved ash foam (RF patent No. 2256632), which can be used for the manufacture of products in industrial and civil engineering.

This composition includes cement, lime, water and a foam-forming additive, and as a filler it contains sand and ash from burning sewage sludge in the following ratio of components, wt.%: Cement 28.7-33.5, lime 4.6-7, 6, sand 17.5-18.1, ash 17.5-18.1, foaming additive 0.32-0.33, water 26.57-27.81.

The disadvantage of this composition is that for the manufacture of building products, it is necessary to form and process products in autoclaves. This process requires expensive equipment and high logistical costs for use in the manufacture of pavement.

In addition, this composition provides for the use of a relatively low percentage of ash, which reduces the amount of ash to be disposed of and the economic efficiency of ash utilization.

The closest technical solution adopted for the prototype is the ash-mineral mixture for the bases of pavements and the method of its preparation (RF patent No. 2135681). This mixture as a filler contains crushed stone of a building fraction of 5-60 mm and waste of crushed stone production of a fraction of 0-5 mm, as ash - fly ash from burning coal, and as lime waste of lime production - lime-fluff in the following ratio of components , wt.%:

- crushed stone building fr. 5-60 mm - 18-27;

- Wastes from crushed stone production fr. 0-5 mm - 23-33;

- fly ash from burning coal - 33-45;

- lime production waste - fluff lime - 4-12;

- soap lye - 8-13.

The disadvantages of the above mineral composition are:

- a relatively small amount of ash from the position of its disposal, included in the ash;

- insufficient number of binders that prevent the leaching of salts of heavy metals from pavement into the environment in the initial period of construction.

The objective of the present invention is to provide an ash-mineral mixture for building material used in road construction, provided that the ash obtained from the burning of sewage sludge is recycled and the raw material base for road construction is expanded.

The problem is solved in that the mixture as a filler contains sand FR. up to 3 mm, wastes of macadam production fr. up to 10 mm, as ash - ash from burning sewage sludge with a specific surface of 200-300 m ² / kg, bulk density of 0.7-0.8 g / m ³ , SiO ₂ content of 50-60% and pH 12 -13.5, and as binders - bitumen and cement in the following ratio of components, wt.%:

- sand fr. up to 3 mm - 10-18;

- screening of crushed stone production fr. up to 10 mm - 10-15;

- ash from the combustion of sewage sludge - 35-55;

- oil road bitumen - 5-10;

- Portland cement not lower than 400 - 6-12;

- water 15-20% by weight of the mixture.

During transportation, the moisture content of the ash should be no more than 20%.

New distinctive features of the claimed invention are:

- An increase in ash content from burning sewage sludge to 35-55%, which allows to increase the volume of recycling of ash produced in excess quantities.

- Use as fillers of sand fr. up to 3 mm 10-18% and wastes of crushed stone production fr. up to 10 mm - 12-15%, providing the necessary strength of the pavement base.

- The inclusion of bitumen by weight from 5 to 10% in the composition of the ash-mineral material allows filling micropores of the material, increasing its water resistance and, as a result, its resistance to changes in ambient temperature: resistance to freezing and thawing.

- Use as a binder in the proposed mixture from 6 to 12% cement. Cement provides an increase in the strength of the material, and also promotes the adsorption and binding of heavy metal ions, preventing their leaching into the environment and violating environmental safety.

In addition, the proposed amount of cement in the composition of the ash-mineral mixture contributes to the activation of the binding properties of the ash-cement mixture, the formation of the structure of the ash-mineral material and to obtain a monolithic mass, which leads to an increase in the durability of the pavement base.

- The composition of the proposed material lacks lime and alkali. Cementing properties provide cement and bitumen provides water resistance.

The technical result of the invention is the utilization of ash obtained by burning sewage sludge in the manufacture of road building materials, and the expansion of the raw material base for road construction.

As a result, the consumption of resources associated with the storage of ash at landfills is reduced: allocation of land and maintenance of landfills (ash delivery, environmental measurements, maintenance of landfills in working condition, etc.).

The technical result is achieved by introducing into the composition of the ash mixture 35-55% ash from the combustion of sewage sludge, fillers in the form of sand, gravel and bitumen to increase the strength of the material and its stability when the temperature and humidity of the environment are changed, as well as cement to make the ash material durable , binding of heavy metal ions and preventing their leaching into the environment.

According to the information available to the authors, the above distinguishing features are new and are not presented in the technical literature. Their combined use in the claimed utility model allows to obtain the required positive technical result.

The manufacture of the mixture is as follows.

All 5 components are mixed in three stages.

The first stage of mixing involves the dosed supply of four sand bins to a horizontal conveyor, respectively sand, gravel waste, ash from the combustion of sewage sludge and cement.

At the second stage of production, pouring and mixing the mass of four mineral components in the mixer, adding a metered volume of bitumen, continuously mixing the whole mass to obtain the desired consistency of the ash-mineral mixture.

At the third stage, the required volume of water is added to the working mixer, after which the mixture is ready for installation.

Work is carried out at a positive ambient temperature.

From the mixer, the finished mass of the ash-mineral mixture is loaded into the dump truck and delivered to the prepared place of laying. Then, the ash-mineral mixture is laid, compacted, aged and, if necessary, the subsequent laying of the asphalt mixture as a pavement coating. Within 20-30 days, the ash-mineral mass gains the strength specified by the recipe and turns into a monolith. The thickness of the base of the pavement is 18-25 cm and fits in one step.

In accordance with the utility model, three different compositions of the ash-mineral mixture were made - SZM-1, SZM-2, SZM-3.

For the preparation of the proposed ash-mineral mixtures were used components that meet the requirements of GOST and SNiP:

- sand fr. up to 3 mm according to GOST 8736-93;

- waste of crushed stone production of the 2nd class of increased fineness in accordance with GOST 8736-93;

- oil road bitumen;

- Portland cement not lower than 400 in accordance with GOST 10178-85;

- water according to GOST 23732-79.

To compose the ash-mineral mixture, ash from burning sewage sludge with a specific surface of 250 m ² / kg, bulk density of 0.7-0.8 g / m ³ and a pH of 12-13.5 was used as ash, and as binders - bitumen and cement.

Determination of the physico-mechanical properties of the samples of ash-mineral mixtures (SZM-1, SZM-2, SZM-3) was carried out after 30-day storage in wet conditions.

The characteristics of the ash-mineral mixtures SZM-1, SZM-2 and SZM-3 are presented in Tables 1 and 2.

From an analysis of the data in Tables 1 and 2, it follows that the proposed compositions SZM-1, SZM-2 and SZM-3 in terms of their physicomechanical parameters meet the requirements for materials for foundations of pavements.

In this regard, the proposed materials can be used for the manufacture of pavement foundations, in particular timber roads, providing the necessary modulus of elasticity in the range of 100-120 MPa, compressive strength in the range of 1-7 MPa, tensile in the range of 0.5-1 , 2 MPa and a coefficient of frost resistance in the range of 0.65-0.8.

In its composition, the material in comparison with the prototype is characterized by an increased ash content and, as a result, has an increased recycling capacity.

Table 1 Composition No. Material grade Modulus of elasticity, MPa The composition of the mixture in% by weight Water (% by weight of the mixture) Sand Crushed stone screening. production Ash Oil bitumen Portland cement SZM-1 K-45 E 200-450 16-18 10-12 35-40 8-10 6-7 15-20 SZM-2 K-55 E 450-550 12-16 12-13 40-50 6-8 7-10 15-20 SZM-3 K-65 E 550-650 10-12 13-15 50-55 5-6 10-12 15-20 table 2 The name of indicators SZM-1 SZM-2 SZM-3 The compressive strength of samples at the age of 30 days MPa 2-1 4-2 7-4 Tensile strength at bending of water-saturated samples at the age of 30 days MPa, not less 0.5 0.7 1,2 Coefficient of frost resistance, not less 0.55 0.65 0.8

The use of the proposed material allows for the disposal of ash obtained by burning sewage sludge, and the expansion of the raw material base for road construction.

In addition, the use of the proposed material based on ash from wastewater combustion can reduce the consumption of resources associated with the storage of ash at the landfill, which is currently underway.

The claimed technical solution can be implemented in the construction of road bases using available materials, standard equipment and assemblies.

Claims (1)

Zolomineralnaya mixture for the bases of pavements, including filler, ash and binders, characterized in that the mixture as a filler contains sand fr. up to 3 mm, screening of crushed stone production fr. up to 10 mm, as ash - ash from burning sewage sludge with a specific surface of 200-300 m ² / kg, bulk density of 0.7-0.8 g / m ³ , SiO ₂ content of 50-60% and pH 12 -13.5, and as binders - bitumen and cement in the following ratio of components, wt.%:
sand fr. up to 3 mm 10-18 screening of crushed stone production fr. up to 10 mm 10-15 ash from burning sewage sludge 35-55 oil road bitumen 5-10 Portland cement not lower than 400 6-12 water,% by weight of the mixture 15-20