CS260577B1 - Mixture for earthes stabilization on base of quick-bonding cement - Google Patents

Abstract

The proposed soil stabilization falls into engineering and is especially useful in road, airport and construction in the area military. Conventional devices used to date to stabilize soils limit the range usable soils predominantly on wood non-cohesive or non-cohesive soil mixtures cohesive and characteristic slow increase in strength and low values of stabilization strength achieved. The essence is the design of the stabilizing compound soils, containing a lactic acid cement free of gypsum, with specific surface overSlm than 600 m2.kg_1, up to 15 « weight of stabilized dry soil a ingredients-setting control, forming in connection with soil and water solid structure mass. The proposed blend extends usability local materials for stabilization o fine-grained cohesive soils (prickly clay). Soil stabilization by the proposed mixture they reach high strength in short Sase and are water and frost resistant.

Description

The invention relates to the stabilization of cohesive soils (in particular dusty) and non-alumina soils (especially fine-grained sands) with a fast-bonding binder based on gypsum-free silicates.

Various stabilizers have been sought in the world and in our country for a long time, guaranteeing a rapid increase in the strength of the soils in which they are. admixed or significantly increasing strength in order to obtain a layer of higher load-bearing capacities and resistance than simple untreated soil. A number of substances have been tested, based on chemicals, eg various resins, water glass, hydrophobic substances - sodium and potassium methylsilanolate, calcium acrylate, etc., and on the basis of special preparations, eg foreign substances Soil Consolid RPS, Soil Conservex , XKP, etc., whose chemical composition is unknown. These means are generally expensive and their effects are not always satisfactory, therefore they are used only in exceptional cases and have not penetrated into wide construction practice. (Spůrek J., Road Construction II, Road and Motorway Construction, SNTL Prague, 1980., Žalský V., Chemical Strengthening and Modification of Soil Properties. Military Buildings Prague, 1980).

Cement and lime are commonly used to stabilize certain soil types. The CSSR applies ON 73 6181 Soil Stabilization * and ON 73 6186 Cementitious Soil Stabilization *, which lay down the conditions for the preparation, execution, acceptance and testing of cement stabilized and cemented soils. According to these standards it is necessary to use gypsum cements Portland and slag-portland, in the sense of ON 73 6186 for cohesive soils these cements class 325 and 400, in most cases in combination with lime.

According to ON 73 6181, only certain types of soils, in particular soils with a predominantly sandy fraction, with a grain content of less than 0.063 mm at most 50 t, a largest grain of 45 mm, a plasticity number I _p 17 and a sand equivalent of EP B 15 can be stabilized. The required compressive strength of the cement stabilization according to this standard should be 2.5 MPa to 3.5 MPa after seven days for grain size I and 1.5 MPa to 2.5 MPa for grain size II.

According to ON 73 6186, a wider range of soils can be reinforced with cement. However, cohesive soils are labeled as conditionally suitable (clay and clay clays, sandy and clay clays) and must first be lime-hardened and then after eight hours at the earliest. These soils have a clay content less than 40 », a maximum liquidity limit w _L » 50 8 and a maximum value of plasticity value I _p “27 t. after freezing test 1.2 MPa. In both cases the increase in strength is long-term.

The disadvantages of the existing methods of soil stabilization and consolidation described in the above-cited standards ON 73 6181 and ON 73 6186 lie mainly in

- the limited range of suitable usable soils given by the grain boundary lines,

- the need for prior application of lime on cohesive soils and, at the earliest after eight hours, the use of cement, which considerably prolongs the execution time, requires a double binder and a double mixing of the mixture,

- a slow increase in strength and its low absolute values, moreover achieved after seven days.

SUMMARY OF THE INVENTION The present invention is based on the design of a mixture which enables the stabilization of soils while avoiding the above-mentioned disadvantages of the known and established methods.

According to the invention, a mixture containing quick-bonding cement free of 2 " gypsum and having a specific surface area of more than 600 m < 3 > kg is used to stabilize soils in an amount up to 15% by weight of stabilized dry soil. cement:

- soluble lignin (lignin sulphonate) deviate or soluble sulphonated polyphenolate,

- alkali metal carbonate and / or bicarbonate and / or hydroxide,

optionally, the alkali salts of organic hydroxy acids or other substances for retarding the setting of cementitious mortars, for example sodium potassium tartrate and sulphite leach substances.

The stabilizer mixture (binder) is prepared by simply mixing the materials. The mixing of the soil with the mixture (binder) and water can be carried out either on site (in the route) or in the mixing center. The amount of water used must ensure that the optimum moisture stabilization is achieved and depends on the type of soil used and its natural moisture content.

The high fineness of the grinding of the binder allows the coating of fine grains of soil to form a concrete structure (aggregate + binder), resulting in a considerable increase in strength. Furthermore, high strengths are achieved relatively quickly. The cause of this phenomenon is the processes in the mixture of soil + + binder + additives. The additives have the function of solidification regulators and allow processing and storage of the mixture. Thereafter, the soil stabilization according to the invention can be carried out essentially by the same equipment and process as described in ON 73 6181 and ON 73 6186.

The use of the stabilizer composition according to the invention has a number of advantages over the existing established binder for soil stabilization and consolidation and brings new and higher effects.

The invention makes it possible to extend the applicability of the cohesive soils to the dusty clays for stabilization, without prior application of lime. These soils are often found in nature and on construction sites; in their natural form they are very sensitive to water, they are fluctuating, and with increasing humidity their strength (bearing capacity) drops sharply. According to ON 73 6181, Portland cement and slag-portland cement cannot be stabilized, according to ON 73 6186, lime must be used first to consolidate this type of soil and then, at the earliest, eight hours later, cement with longitudinal strength increases and low strengths. The proposed mixture according to the invention allows the stabilization of these soils, in addition to eliminating the dual type of binder (lime, cement) and the double mixing, thus reducing the time required to carry out the stabilization.

Other significant benefits of the proposed soil stabilization mixture are rapid stabilization increases, high strengths, water and frost resistance.

The proposed mixture can also stabilize other types of soils where it is desired to achieve the above properties or stabilization with conventional binders is poorly effective.

An important advantage of the present invention for practical implementation is the availability of the proposed binder (CSS) in the CSSR and conventional stabilization technology in accordance with applicable standards.

FIG. 1 shows a grain size limitation to generally determine the suitability of soils and grain size areas I and II of the most suitable soils for cement stabilization according to ON 73 6181, as well as the grit line of powdered clay stabilized by the composition of the invention and described in the following example. The position of this grain line shows a substantial expansion of the area of soils suitable for stabilization up to the cohesive soils. In terms of classification and basic physical properties, the soil used is characterized by this grain line and the limits of fluidity and plasticity.

FIG. 2 shows the increase in compressive strength of the dusty rollers stabilized according to the invention, ascertained after four hours, one, three and seven days. As can be seen from this figure, the increase in the stabilization strength according to the invention, expressed graphically by the compressive strength-time dependence, significantly exceeds the requirements of ON 73 6181 and ON 73 6186, both from the point of view of? discs of time, as well as absolute values achieved by strength.

Example

Soil stabilization with the compositions of the invention consists of the application of '2 -1'

- gypsum-free quick-bonding cement with a specific surface area of 600 m. kg in the amount of 12% by weight of stabilized dry soil and additives - sodium carbonate 1%, soluble lignin derivative (Ligrasol) 0.7 4 and sulphite leachate (Kortan) 0.5% weight of high - speed cement, up to

- loess, classified according to CSN 72 1002, the grain size of which is shown in Figure 1, with a flow limit of - 36,8%, a plasticity limit w _p = 21,3% and a plasticity number I _p ”15,5 %

- water, containing 20% by weight of dry soil.

Stabilization was prepared by simply mixing the above components.

Laboratory stabilization tests were performed according to ON 73 6181. The mixture was compacted .3 to a dry bulk density P & = 1740 kg.m. Compressive strength was tested after 4, 24, 72 and 168 hours on three rollers with the following results:

testing after 4 h h

• 72 h

168 h average compressive strength (MPa) 0.87 2.48 3.40 4.93

The results show a rapid increase in compressive strengths with time, as well as high strength values (see Fig. 2). The compressive strength required according to ON 73 6181 after seven days was achieved by stabilization according to the invention in 24 hours to 3 days and after seven days it was 1.4 to 2.7 times greater than the requirement of the cited standard. The compressive strength required according to ON 73 6186 after seven days was achieved with the mixture according to the invention in about 8 hours and after seven days it was almost 5 times greater than the strength required according to this standard without prior lime application as this standard for the type of soil used prescribes.

The resistance of the dusty clay stabilized according to the invention to the effects of alternating moisture changes was verified according to the former CSN 73 6181 standard on six rollers, and after twelve cycle cycles the samples showed no weight loss or cracks.

The frost-stabilized dusty soil of the invention was evaluated according to ON 73 6181 by the compressive strengths determined on four rollers, stored for 28 days in a humid environment and subjected to a 10-fold freezing and thawing cycle, with the following results:

Roller number diameter

Stabilization density after freezing and thawing, cycles (kg.m ^-3 )

020 2,020 2,060 2,060 2,040

Compressive strength stabilization after freezing and thawing, cycles (MPa)

8.10

10.10

5.70

6.25

7.54

In all cases, the determined compressive strengths are higher than required by ON 73 6181, namely

1.6 to 2.9 times (average 2.1 times) for stabilization I (standard requirement is 3.5 MPa, resp.

2.7 to 4.8 times (average 3.6 times) for stabilization II (standard requirement is 2.1 MPa).

The invention is particularly useful in road, airport and railway construction and in foundation engineering. It is also important in the military field, especially in terms of the time factor of the rapid increase in strength.

The invention does not endanger or disturb water and soil and is harmless from an environmental point of view.

Claims (1)

OF THE INVENTION A gypsum-free fastening cement-based soil composition comprising: - Gypsum-free high-speed cement with a specific surface area of more than 600 m / kg, - soluble lignin derivative such as lignin sulphonate and / or soluble sulphonated polyphenolate, in an amount of up to 3% by weight of the quick-binding cement, - alkali metal carbonate and / or bicarbonate and / or hydroxide, in an amount of up to 3% by weight of quick-binding cement, optionally, alkali salts of organic hydroxy acids and / or other solidification retardants of cementitious mortars, e.g., sodium potassium tartrate and sulphite liquor based paper industry wastes, up to 3% by weight of the quick bonding cement.