RU2471913C2 - Method of making pavement structural layer based on ashes of effluents sediments combustion - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: method of making pavement structural layer consists in mixing 30-70 wt % of ash of effluents sediments combustion with natural sand with particle size of 0-5 mm (the rest), 6-10 wt % of mineral binder, M400-grade cement or fine burnt lime with activity of, at least, 60 wt % of CaO and MgO. Mineral mix is damped with water. Said mix is mixed with 4-8 wt % of liquid bitumen "СГ" 90/130 cutback in 1:1 ratio and compacted at 30 MPa.

EFFECT: higher strength.

6 cl, 1 ex, 2 tbl

Description

The invention relates to the field of construction, in particular to road mixtures and soil strengthening methods suitable for structural layers of pavement.

The well-known "Method of disposal of fly ash by liquid solutions of phytosan and tannin" (DE 4141889 A1, 06.24.1993).

This method is based on the binding of various heavy metals and other harmful substances with the help of phytosan and tannin (5-20%) into complex organic compounds, which solves the disposal of waste such as fly ash TPP.

However, the use of this mixture in road structures is impossible because of the low physical and mechanical properties.

The well-known "Method of fixing soils" (RU 2148689 C1, 05/10/2000).

This method is based on the use of fillers - briquettes obtained by pressing a mixture of sludge from water treatment of TPPs, treated with 10-15% cement and lime binder - 2%, mixed with soil in a ratio of 3: 1: 6.

A disadvantage of the known method of fixing soils is the complexity of the technology for producing a lime binder (drying, firing and grinding a mixture of carbonate sludge from thermal power plants with calcium chloride), as well as the formation of briquettes by pressing.

The well-known "Asphalt mixture" (patent RU 2204539 C2, 05.20.2003) in the ratio of components, wt.%:

- limestone crushed stone fraction 2-20 mm - 30-45;

- viscous petroleum bitumen - 5-6;

- fly ash from TPP electrostatic precipitator - 3-8;

- still residue - 0.5-1.75 by weight of bitumen;

- sand fractions up to 5 mm - the rest.

This mixture is the prototype of the proposed method, provides the following properties of road material (compressive strength of the samples at 20 ° CR ₂₀ C, MPa at least 4.56; water saturation - 1.97%; water resistance coefficient - 0.98 and with long-term water saturation - 0 , 75).

High performance of the lime mixture is achieved due to the introduction of polymer additives to bitumen and the presence of limestone gravel in the mixture, which provides the conditions for active structure formation processes. However, the use of fly ash in the amount of 3-8% instead of mineral powder is insufficient for the sufficient utilization of waste from the burning of sewage sludge from municipal and municipal economy from the environmental side.

Known "Binder for fixing the soil" (USSR AS 384974, E02D 3/14, 1973).

This method of fixing the soil is based on the use of a lime-bitumen binder (paste) and fly ash of thermal power plants.

The disadvantage of this method is that the resulting material has low strength and deformation characteristics.

The closest prototype of the present invention is "Raw mix for the manufacture of cellular concrete" (patent RU 2148050, C04B 38/02, 04/27/2000).

The mixture relates to the production of building materials, contains an ash component, Portland cement and aluminum powder, as an ash component contains ash from burning sewage sludge from municipal and municipal services with a specific surface of 400-600 m ² / kg, bulk density of 600-800 kg / m ³ and the content of SiO ₂ - 1.5-2.0%, with the following ratio of components, wt.%: Ash - 38.4-61.4; Portland cement - 38.4-61.4; aluminum powder - the rest.

Effect: utilization of municipal waste in the construction industry. The material from this mixture has high strength, achieved by a significant consumption of binder - Portland cement, which is economically disadvantageous for road construction. Concrete made from this raw mix has significant water absorption and has a relatively low frost resistance, which limits its use in road structures.

In our proposed method, we use a mixture of ash (a product of burning sewage sludge from municipal and municipal utilities) wt.% - 30-70 and mineral natural sand - the rest, which allows us to utilize significant amounts of municipal waste. Cementing materials use quicklime (cement grade M400) and bitumen grade SG 90/130, liquefied in a ratio of 1: 1 by weight. After adding mineral binders - quicklime (cement) to the sand-sand mixture, it is moistened, which ensures the normal course of adsorption and chemisorption reactions during the chemical interaction of lime (cement) grains with ash and sand components during the structure formation of the material.

This is achieved by thorough mixing of the components and uniform distribution of finely dispersed Ca (OH) ₂ particles of hydrolysis and hydration processes in the sand and sand mixture, which ensures the normal reaction of amorphous silica SiO ₂ , aluminum oxides and heavy metals in the ash with the formation of water-insoluble compounds on their basis type of hydroaluminosilicate calcium.

The proposed method for producing road-building material allows one to reduce the leachability of heavy ash metals by an order of magnitude and ensure its allowable MPC values.

The subsequent introduction of bitumen, evenly distributed over the sinter soil mixture, provides an increase in the water resistance of the material due to hydrophobization of the structural bonds of particles and conglomerates of the material.

The introduction of a mineral binder into the zologrun mixture, moistening and then liquid bitumen and its uniform distribution, due to mechanical stirring and physical action, allow active chemical reactions to occur between the components of bitumen (asphaltenes, asphaltic acids, resins, etc.) and the appearance of high molecular weight compounds in the structure of the material waterproof type.

Compaction of the mixture leads to the convergence of the centers of crystallization, an increase in the contacts of particles and neoplasms leads to an increase in polymerization and polycondensation reactions, physical adsorption processes and provides a new, durable and water-resistant road-building material.

An important difference of the proposed method is the use of a significant amount of ash utilization (a product of incineration of sewage sludge from municipal and municipal utilities), a small consumption of traditional binders (cement, quicklime, bitumen), obligatory humidification of the mixture to the optimum value and simplicity of technological operations for obtaining material.

Example.

For experimental verification of the claimed method were prepared variants of mixtures of the above components. A mixture of ash from the burning of sewage sludge from municipal and municipal services, natural sand of a fraction of 0-5 mm and quicklime was moistened with continuous stirring (1-2 min) until a homogeneous composition was formed. Then introduced liquid bitumen grade SG 90/130 (liquefied in a ratio of 1: 1 by weight). The mixture was again stirred, kept for 2 hours, and then samples with a diameter and a height of 50 mm were produced from the mixture under a pressure of 30 MPa.

The results of the comparative analysis are shown in tables 1 and 2.

Table 1 The composition of the mixture for road construction No. Mixture components The content of components, wt.% Mixture number Prototype one 2 3 four 5 6 7 8 one Liquid bitumen - 8 8 8 6 8 8 6 6 2 Oil Viscous Bitumen 5-6 - - - - - - - - 3 Quicklime - 6 6 6 8 - - - 10 four Cement M400 - - - - - 6 6 6 - 5 TPP fly ash 3-8 - - - - - - - - 6 Ash - a product of incineration of sewage sludge - thirty fifty 70 thirty 40 fifty fifty one hundred 7 VAT residue 0.5-1.75 - - - - - - - - 8 Limestone crushed stone fr. 5-20 mm 30-45 - - - - - - - - 9 Natural sand fraction 0-5 mm REST

table 2 Physico-mechanical properties of mixtures No. mixes Property metrics Compressive strength, R ^ext _{compression channel,} MPa Water absorption, Wvp,% The coefficient of water resistance, the share of units Coefficient of frost resistance, fractions of units The total content of heavy metals in the hood, mg / l Prototype 4,56 1.97 0.75 - - one 9.0 0.73 0.83 0.83 - 2 9.1 0.30 0.88 0.92 0,077 3 7.1 4,51 0.78 0.82 - four 10.5 0.24 0.87 0.84 - 5 7.3 1,02 0.77 0.81 - 6 8.1 4.3 0.91 0.80 - 7 8.8 3.0 0.85 0.82 - 8 9.0 16.3 0.72 0.55 - Ash - - - - 0.670

Claims (6)

1. The method of constructive layer construction of pavement, which consists in mixing (wt.%) 30-70 ash from the burning of sewage sludge from municipal and municipal services with natural sand of a fraction of 0-5 mm (the rest), 6-10 mineral binder of material - cement of a grade of at least M400 or fine ground quicklime with an activity of at least 60 wt.% in the content of CaO and MgO, moisten the mineral mixture with water, mix with subsequent processing of 4-8 liquid bitumen SG 90/130, diluted in a ratio of 1: 1 by weight and compacted with a load of 30 MPa. 2. The method according to claim 1, in which finely ground quicklime with an activity of at least 60 wt.% In the content of CaO and MgO is used as a mineral binder, the mixture is kept for at least 2 hours after compaction of all binders until compaction. 3. The method according to claim 1, in which cement of a grade of at least M400 is used as a mineral binder. 4. The method according to claim 1, in which the road mixture is mixed in a mechanical stirrer for 1-2 minutes. 5. The method according to claim 1, in which the road mixture is mixed on the road with a milling cutter until a homogeneous composition is obtained. 6. The method according to claim 1, in which as the organic binder material is used liquid bitumen in the composition of 50% bitumen and 50% diluent by weight, prepared by mixing in a heated state at a temperature of 80-100 ° C.