RU2746327C1 - Injection bentonite composition for waterproofing and strengthening of natural soil - Google Patents

Abstract

FIELD: environmental protection.

SUBSTANCE: invention relates to the field of environmental protection, in particular, to the isolation of groundwater and natural soil, localized under buried and underground storage facilities, and disposal of various types of waste (pools, barns, storage facilities, reservoirs, containers, bunkers, buildings and structures) from ingress of pollutants. Injection bentonite composition for waterproofing and strengthening natural soil contains bentonite clay powder, fine silica. Additionally, it contains plasticizing and hydrophobizing additives, with the following ratio of components, wt%: bentonite clay powder - 40 - 90; finely dispersed silica - 0.1 - 45; plasticizing additives - 0.1 - 5; hydrophobic additives - 0.1 - 10.

EFFECT: invention is aimed at increasing the durability of the waterproofing screen due to the presence of hydrophobizing additives, increasing bearing capacity of soils, as well as reducing their porosity and capillarity.

3 cl, 1 tbl

Description

Technology area

The invention relates to the field of environmental protection, in particular, to the isolation of groundwater and natural soil, localized under buried and underground storage facilities, and disposal of waste of various classes (pools, barns, storage facilities, reservoirs, tanks, bunkers, buildings and structures) from ingress of pollutants. The invention improves the bearing capacity of soils, to reduce their porosity and capillarity.

Prior art

For strengthening and waterproofing soils, injection technology is very common, the essence of which is to inject an insulating hardening or gel-forming material into the soil. The material is fed under pressure: the rotary percussion mechanism drills the soil and delivers the solution into the depths. Injection waterproofing is a universal method of strengthening various objects. For work, they use polymer (acrylate, polyurethane) compositions, compositions based on inorganic binders (cement, gypsum), cement-sand and clay fillers, as well as compositions with silicates and siloxanes. Thanks to these materials, it is possible to perform soil cut-off, horizontal barrier, vertical reinforcement of the base of the building foundation. By strengthening the soil by injection, it is possible to restore, raise or renew the foundation.

In the patent for invention RU 2439246, published on 10.01.2012, a method of strengthening the soil is described, including drilling wells, installing injectors with a perforated part in them, pumping through injectors under a load of injection cement mortar into the soil with ensuring its hydraulic fracturing at a pressure of 5-20 atm , and the injectors after strengthening the soil are not removed from it. At the same time, either bentonite clay, or water glass, or bentonite clay and water glass, or cement dust and water glass, or cement dust, bentonite clay and water glass, or cement dust are added to the cement mortar, consisting of cement and water, fine sand and liquid glass.

In the copyright certificate SU 1778130, publ. 07/02/1990, a method for increasing the reliability and durability of the waterproofing screen, formed in two stages, is described. At the first stage, a fixing composition is sprayed, containing water, clay powder (up to 75%), backfill cement and calcium chloride. After the primary screen has cured, the second composition is sprayed, which is an aqueous suspension of clay powder (up to 10%), oil well cement (up to 45%) and polymer (polyacrylamide or polyethylene oxide) (up to 0.2%).

Bentonite clay is often used as the basis for gelling compositions for waterproofing. So, in the application for invention RU 2013128889, publ. 12/27/2014, a method for the preparation of a water-based clay paste is disclosed, which consists in processing a concentrated clay suspension containing up to 70% clay, phosphoric acid, neutralizing agents (sodium silicate, sodium hydroxide) and a deflocculating additive (sodium tripolyphosphate).

The disadvantages of the above technical solutions include the complexity of the technological process, insufficient durability of the waterproofing screen and the presence in the formulation of organic polymer components prone to biological destruction.

The analogs of the present invention are waterproofing mixtures based on bentonite clay "Bentogrout" (company "CETCO", Poland) and "Eco-Inject" (company "Isobent", Belarus).

The closest in terms of the totality of essential features to the claimed invention is an injection waterproofing composition disclosed in the patent for invention RU 2672069, publ. 11/09/2018, containing from 10 to 99% bentonite clay (containing montmorillonite); 0.1 - 90% fine-graded silicon dioxide; 0.1-50% sodium polyacrylate; 0.1-30% polyacrylamide and 0.7-70% fatty acid triglycerides.

This injection waterproofing composition has the following disadvantages:

1. The composition lacks components capable of modifying and plasticizing the structure of a concentrated suspension of bentonite, as a result of which flat dispersed particles are associated in the form of an electrostatically stable “edge-to-edge” scheme. Therefore, a concentrated aqueous suspension containing more than 70 wt.% Bentonite clay has an increased ultimate strength, which does not allow the use of high-quality bentonite containing more than 85% montmorillonite in sodium form in the waterproofing composition. According to the formula of an injection waterproofing composition, a suspension containing more than 70% clay can be obtained only from sodium bentonite-like raw materials, the concentration of montmorillonite in which does not exceed 60%, or from calcium bentonite.

2. There are no hydrophobizing additives in the composition, which leads to high wettability by the aqueous phase of the resulting bentonite dough. As a result, the waterproofing screen does not have acceptable durability and is gradually eroded by groundwater.

3. To ensure the required level of viscosity, synthetic polymer additives (sodium polyacrylate, polyacrylamide), as well as vegetable oil enriched with fatty acids, are introduced into the composition. This creates the problem of gradual softening of the waterproofing screen due to the biodegradation of organic additives, as a result of which their molecular weight decreases and, accordingly, the gel-forming properties are degraded.

Disclosure of invention

The problem to be solved by the claimed invention is to create an injection composition for waterproofing and strengthening natural soil, which allows to ensure maximum durability of the waterproofing screen in the absence of organic polymer components in the formulation, which are prone to biological destruction.

The technical result achieved by the implementation of the claimed invention is to increase the durability of the waterproofing screen due to the presence of hydrophobic additives, increase the bearing capacity of soils, as well as reduce their porosity and capillarity.

The specified technical result is achieved due to the fact that the injection bentonite composition for waterproofing and strengthening of natural soil contains bentonite clay powder, fine silica and additionally contains plasticizing and hydrophobizing additives, with the following ratio of components, wt%:

Bentonite clay powder - 40 - 90;

Finely dispersed silica - 0.1 - 45;

Plasticizing additives - 0.1 - 5;

Water repellent additives - 0.1 - 10.

This technical result is also achieved due to the fact that phosphorus-containing complexones are used as plasticizing additives: nitrilotrimethylphosphonic acid and / or oxyethylene diphosphonic acid and / or sodium trimethyl phosphate and / or sodium hexametaphosphate and / or sodium tripolyphosphate, and basic hydrophobizing additives compounds of alkali and alkaline earth metals: sodium metasilicate and / or calcium hydroxide, and / or sodium carbonate.

The preparation of the injection composition is carried out as a result of dispersing the bentonite powder in the aqueous phase at a mixer rotation speed of 10,000 rpm for 10 minutes, after which silica, a plasticizing additive (sodium tripolyphosphate) and a hydrophobizing additive (sodium carbonate) are introduced into the resulting suspension. The stirring time of the suspension after the introduction of each of the additives is 5 minutes. The concentrations of the reagents in the studied injection formulations are shown in Table 1. The finished injection composition is investigated by determining the following technological characteristics: the tensile strength of the gel is determined on a rotary viscometer of direct indication in accordance with GOST 33213-2014 (ISO 10414-1: 2008); the wetting angle of the water extract is determined in accordance with GOST 9038-90; the pH level of the suspension is determined according to GOST 33776-2016.

The declared injection bentonite composition for waterproofing and strengthening natural soil has the following advantages in comparison with the closest analogue:

1) In the new injection bentonite composition, special plasticizing additives are used based on phosphorus-containing complexones, which makes it possible to obtain an extremely concentrated bentonite suspension with a sufficiently low ultimate strength (less than 200 dPa) for insulation work. So, an aqueous suspension of a new injection composition containing 90% bentonite has a tensile strength of 120 dPa, while the tensile strength of the suspension according to the closest analogue is 800 dPa, which is many times higher than the permissible level (Table 1, example 1).

2) The new injection bentonite composition contains hydrophobic components that provide increased hydrophobicity of a concentrated aqueous suspension. This is reflected in a higher value of the wetting contact angle of the aqueous extract of the suspension on the quartz surface. So the contact angle of wetting of aqueous extracts of suspensions of the new bentonite injection composition is 30 ^o , which is 6 times more than the value of the contact angle of water extract according to the closest analogue (Table 1, examples 1, 2).

3) In the new injection bentonite composition, there are no polymer components capable of chemical or biological degradation. So the pH level and ultimate strength of an aqueous suspension of a new injection bentonite composition does not change within 30 days of exposure at room temperature, while the pH level and ultimate strength of the suspension according to the closest analogue decrease with time (Table 1, examples 1, 2) ...

Table 1

Technological parameters of aqueous suspensions of injection compositions

Injectable formulations Gel tensile strength, dPa Ultimate gel strength after 30 days, dPa Contact angle of wetting, degrees PH level PH level after 30 days Example 1:
Bentonite - 90%
Silica - 0.1%
Tripolyphosphate Na - 5%
Na carbonate - 4.9% 120 120 thirty 9.1 9.1 Example 2:
Bentonite - 40%
Silica - 45%
Tripolyphosphate Na - 5%
Na carbonate - 10% 60 60 35 9.8 9.8 Closest analogue
(RU 2672069) 860 640 five 8.3 7.8

Claims (7)

1. Injection bentonite composition for waterproofing and strengthening of natural soil, containing bentonite clay powder, fine silica, characterized in that it additionally contains plasticizing and hydrophobic additives, with the following ratio of components, wt.%: Bentonite clay powder - 40 - 90; Finely dispersed silica - 0.1 - 45; Plasticizing additives - 0.1 - 5; Water repellent additives - 0.1 - 10. 2. Composition according to claim 1, characterized in that phosphorus-containing complexones are used as plasticizing additives: nitrilotrimethylphosphonic acid and / or oxyethylene diphosphonic acid and / or sodium trimethylphosphate and / or sodium hexametaphosphate and / or sodium tripolyphosphate. 3. Composition according to claim 1, characterized in that basic compounds of alkali and alkaline earth metals are used as hydrophobizing additives: sodium metasilicate and / or calcium hydroxide and / or sodium carbonate.