NZ232117A

NZ232117A - Surface stabilisation of soils

Info

Publication number: NZ232117A
Application number: NZ232117A
Authority: NZ
Inventors: Laurent Voegeli
Original assignee: Diffusion Et Rech Tech Et Fina
Priority date: 1989-01-16
Filing date: 1990-01-16
Publication date: 1992-05-26
Also published as: DE69002417D1; FR2641806A1; JPH03503431A; DE69002417T2; AU632082B2; FR2641806B1; PH26814A; WO1990008226A1; EP0407513B1; KR910700380A; AU4805490A; CA2024706A1; MY106262A; CN1044317A; EP0407513A1

Abstract

The stabilizing method of the invention comprises the impregnation of mineral substances present on the site with at least a mixture of a binder based on sodium and/or potassium alcaline silicates, at least a plastifying additive and at least a liquid reagent. According to a preferred mode of execution, the liquid mixture includes a water-addition. The method is used to stabilize a ground surface intended to the construction of lines of communication, particularly roads, runways for aircrafts, basis for railway tracks, verges of roads and of trenches, or for building storage surfaces, rigid plates or load-carrying slabs as well as for any rigid surface in order to withstand and support moving or still loads.

Description

<div id="description" class="application article clearfix"> New Zealand Paient Spedficaiion for Paient Number £32117 r 232 1 17 <r* ;t L- ■.)' 2Tj ;.iL-....i •](:• ,.eO>.Ci3.[i:>- ;26 ..WW...®?.... ;./30(fin ;MQ 0 -. - ;liv fc^i wA k«ViUO ;Patents Form No;5 ;PATENTS ACT 19 53 ;COMPLETE SPECIFICATION ;SURFACE STABILISATION PROCESS FOR SOILS ;WE, SOCIETE DE DIFFUSION ET RECHERCHES TECHNIQUES ET FINAN-CIERES SA, a company organised and existing under the laws of Switzerland, of 21, route de Sion, CH - 3960 Sierre, Switzerland, hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: ;1 ;(Followed by 1A) ;232 1 1 7 ;SURFACE STABILISATION PROCESS FOR SOILS ;The present invention relates to a process for the stabilization of soils, for example the surface of a soil destined for the construction of communication tracks, especially roads, airport runways, railway tracks, paths, edges of roads, trenches, or for the creation oL storage areas, rigid mineral surfaces able to bear mobile or immobile loads. ;There are at present many different techniques for the construction of roads and airfields using a large quantity of various materials. Generally, airfield or road construction is realised through the addition of mineral materials such as crushed rocks with a particular granulometric size. Depending on individual cases, various binders may be used in association with these materials. These binders are either of a hydraulic nature such as cement or lime, or of an organic fossil nature such as asphalt. One or several coatings of mortar, obtained this way are generally necessary to complete the roads or airfields. ;These traditional materials always require additional material like rock in the form of gravel and/or sand to be layered on a pre-compacted and levelled soil. ;To make the foundation, these materials are compacted and vibrated so as to form a layer strong enough to bear the loads of a vehicle which will move on the track afterwards. ;This foundation base usually receives a finishing coating, usually consisting of a layer of cement mortar, or a layer of asphalt mortar or a combination of these two types of layer. ;According to the currently used techniques, these tracks ;2 ;232 1 1 7 ;are known as light traffic tracks or heavy traffic tracks, and are intended for the use of vehicles which are respectively light or heavy. ;These tracks are rigid or flexible depending on their composition. However, all these traditional processes present a certain number of drawbacks. ;The first, and not the least, is the fact that these methods involve the provision of large quantities of rocky material of a particular granulometric size. These materials sometimes have to be extracted from faraway quarries and transported to the site where they are to be used, which consequently increases the manufacturing costs. ;The second, resulting from the first, is the fact that these methods require the organisation of a large quantity of transport vehicles and storage areas close to the workyard for the storage of these materials. ;Thirdly, before these materials can be put into place, the contractor must remove a layer of existing vegetal soil, which must be sent to a special storage area. In addition, the above techniques do not possess the required impermeability characteristics. Roads and plane runways are very often damaged from the effect of rain and freezing temperatures. ;For these reasons contractors are often obliged to predict a large network of drainpipes to evacuate water. In cold winter countries, authorities have to close or reduce traffic for heavy vehicles. ;The present invention proposes the elimination of these various above-mentioned drawbacks and the provision of a simple and rapid method of construction for all types of transport tracks or other stabilised surfaces, without ;3 ;f"* the obligation of bringing traditional materials. In addition the present invention ' • 1 eliminates damage due to water penetration. The present invention provides a method of reinforcing the strength and impermeability of the surface of soils for the construction of roads, aeroplane runways, railroads, road embankments and trenches and the construction of storage areas destined to receive mobile or immobile loads, comprising the steps of preparing a mixture of at least one liquid binder made out of sodium and/or potassium alkaline silicates with at least one blending agent and with at least one liquid reactive agent capable of reacting with said alkaline silicates to create a silica gel, and impregnating mineral substances of the soil on site with said mixture. According to a first suitable composition, at least one blending mineral agent such as clay is used. According to o sccond suitable composition, at least one blending agent comprising an organic agent such as casein is used. According to a third suitable composition, at least one vegetable blending agent such as vegetable oil is used. According to a fourth suitable composition at least one synthetic blending agent such as carboxymethylcellulose, sodium salts, ethylene-glycol, glycerine, acrylic or vinyl resins, bituminous emulsions. According to a particularly suitable composition, very finely pulverised mineral filler is added to the formulation, with components which eliminate static electric charges in order to favour penetration of the liquid binder into the soil. 4 232 1 Acid reactive components may be chosen from the following list of components: chlorides such as sodium, potassium or calcium chlorides; sulphates such as aluminium sulphate; carbonates such as sodium hydrogen carbonate; sodium aluminate, sodium fluorosilicate, mineral and organic acids, esters such as diestermethyl or ethyl esters, used as a dilution or suspension in water. Preferably, the impregnation or the mixing of the said binder on site would be done at between 5° or 35°C. Preferably, the percentage of liquid components mixed with others will be fixed between 30% and 150%, relative to water-glass weight. If native earth material already on the site contains sodium chloride (briny soils), an additional percentage of reactive acid salts will be added to the existing soil materials to provide the necessary amount of reactive agent. In such a case, admixture of the binder will be used without the reactive component. Only the mixing procedure will be possible. If native earth on site contains moisture soils (vegetable earth) an addition of siliceous materials before treatment will increase the compression strength of the soils. According to a preferred method, native earth mineral substances are treated by spraying, impregnation, and/or mixing procedure. Further examples of the present invention will show further possibilities of adaptation according to the quality of native soils and climatic conditions. The technique of silica gels to reinforce compression 5 232 1 1 7 strength of soils is well known through injection under pressure. However, silica gels technique has not been used for construction of roads, tracks and surfaces because of certain problems: - rapid damage to treated surfaces, due to solubility of incorrect silica gels formula - cracking of surfaces due to wrong formulation of silica gels done without blending agents. The present invention eliminates the above problems due to the fact that blending agents are used in addition to the correct quantity of reactive agents. Different conditions must be taken into consideration when using the present invention, i.e.: - soil temperature and atmospheric temperature when the binder is applied - quality and nature of soils to be treated - chemical components of soils to be treated - Granular size of different components - hygrometric conditions on site. Under normal conditions, the present invention can be applied without difficulties or particular care under temperatures between 5° and 25° centigrade. Above 25°C the setting time will be reduced by half for every increase of 10°c. 6 232 1 1 7 Foe example, the general setting time, with a temperature of 25°C will be 60 minutes. Some difficulties may be experienced when outside temperatures exceed 35°C, particularly for temperatures in excess of 40°C. In such cases it must be taken into consideration that these soil temperatures will decrease quickly below a depth of 15 centimetres. In the meantime it must be considered that a preliminary spraying of water over the surface of the soil will decrease the temperature down to 20 or 25°C. For reasons of convenience treatment will be done, in hot desert areas, very early in the morning when the soil temperature is low. Generally the presence of water in the admixture according to the invention, will assume a regulation of temperature of the soils according to the phenomenon of cooling due to evaporation. This means that under the worst working conditions, setting time will not be less than 30 or 40 minutes which leaves time to compact and vibrate the soils after treatment. In relation to the quantity and nature of the soils to be treated, particular care will be taken with the percentage of air existing between the granular components of the soils. As an example, sandy soil may present 36% air. According to the nature of soils: clay, lime, silica, moisture, sand, the contractor will have to determine, depending on the compression strength he needs to obtain, if he needs to add mineral components such as sand, gravel, crushed rocks etc. In addition, the chemical composition of soils must be controlled, especially the pH. Under pH 7 the setting time may change and become shorter. Hygrometric conditions on site are important. Contractors must adjust the quantity of water existing in native earth soils to the quantity needed in the binding 7 232 1 1 7 mixture, and reduce the quantity of water in the formula in relation to the quantity of water existing in the soil to be treated. Normally the quantity of water in the formula of binder never exceeds 1201 of water-glass weight. Finally, it is an object of the present, invention to provide a method for the construction of any surface, layer, path, road, aeroplane runway, railroads, with any existing native soils except briny soils, which under this present invention will require a special way of application, i.e. pre-mixing of soils with reactive agents, this may be done until a percentage of 5% of soil weight is reached. When the native soil on site is clay or moisture earth, an additional amount of granulated silica or lime will be necessary to get the compression strength required. In such a case, a premix of soil without binder will be necessary. One of the advantages of the present invention is the fact that components of the binder can be stored for a long period without the usual humidity problems of damage to cement and lime. This is provided that these components are protected against freezing and light. The reactive agents will be added to the formula just before application, to give the contractor enough time to work. The preferred method is to mix the reactive agent through a dosing pump fixed on top of the mixing engine. Details of the present invention are better elucidated by the following non-limiting examples: EXAMPLE I 232 1 For sandy soil treatment - Sodium silicate (r.p. 3/3 to 4) 100 kg. - Acrylic resin (e.g. Acronal S.400 BASF 2 to 5 kg. or ARMH Rhone Poulenc) - Monoethylene glycol 2 kg. - Teepol R (Shell) 0.5 kg. - Reactive (Diester methylic Rhone Poulenc) 20 kg. - Water 80 kg. EXAMPLE II For clay or moisture soil - Sodium silicate r.p. 3/3 to 4 100 kg (7H34 or 5N40 Rhone Poulenc) - Acrylic resin (ARMH Rhone Poulenc) 15 kg. - Teepol n (Shell) 0.2 kg. - Reactive (Diester methylic) 25 kg. - Water 5 kg. EXAMPLE III Finishing treatment formula over sand - Sodium silicate 100 kg - Acrylic resin (ARMH Rhone Poulenc) 50 kg. 9 232 1 1 7 - Reactive (Diester methylic) 25 kg. - Silicones (Siliconate R 51T/RP 20 kg. Water 50 kg. When there is an extreme concentration of existing water in the soils e.g. water-logged sand, the quantity of water added to the binder mixture will be calculated minus the quantity which already exists in the soil. This is so as to stay within the limits of water mentioned above. Certain cases may occur where no water will ba added to the formula, the existing water in the water-glass will provide the base of the reaction between water-glass and reactive. As a general definition, calculation bases for quantity of water in the admixture will be defined as follows: - On very previous soil such as sand, percentage of water (in relation to water-glass weight) may vary between 30 and 120 per cent. - On less or non-previous soils, percentage of water will vary from 0 to 50 per cent. -As a final coating, percentage of water in the admixture will vary from 0 to 120 per cent depending on the method of use: - sprayed over already treated previous soil such as sand, the percentage of necessary water in the admixture will, at least, be within the range of 80 to 120 per cent. Finishing over a non previous soil will require a low percentage of water, 20 to 30 per cent will be a usual 10 232 1 1 7 quantity. In such a case, only mixing with soil can give a regular result. Generally, the proportion of water is determined on site, according to the hygrometric conditions, applying the rule of a maximum of 120 per cent, including existing water in the soil, and according to the nature of the treatment to be made: spraying, stretching or mixing. When the admixture is mixed with soil, the usual rule of percentage of water does not exceed 50 per cent, including existing water in the soil. For the finishing coating, the degree of humidity of soils does not have to be considered because of the fact that the quantity of water in the admixture determines the viscosity thereof, and the quantity of blending agent will be higher, giving the finished surface a better resistance to abrasion. As an example, a finishing coating made from an admixture in which water will represent 120 per cent (in relation to water-glass weight) sprayed over an already treated sandy soil, will give an important hardening of the superior layer and will resist efforts of tearing up by vehicle tyres. Over a sandy soil already saturated with water, i.e. approximately 35 per cent, spraying of an admixture containing 80 per cent of water will produce the same effect of hardening and fixation of superficial sand grains. As a general result, utilisation of blending agents such as synthetic resins or other components as above, decreases hardness of silica gel and increases suppleness of gel according to the invention, and its resistance to being torn up. The proportion of blending agents must not 232 1 1 7 exceed 50 per cent but may be rcduced down to 1 per cent. The correct quantity of blending agents will be determined according to the quality of the treated soils, the required results and the cost of the construction. The depth of treatment will depend on the quality of the native earth soil and the final resistance required. An aeroplane runway will require a deeper treatment than a simple path for bicycles. As an example, on sand in desert areas, an aeroplane runway with a depth of treatment of 0.50 meters plus the finishing sprayed coat may support the landing and taking off of 50 tonne weight planes. It is an advantage of the invention that the fact of using a liquid binder, either diluted with water or any other liquid base such as alcohol or organic solvent, offers more facilities than with the use of other dry binders such as cement or lime. One of the advantages of the process according to the invention, compared with a treatment made only from bituminous emulsion, is the absence of flowing phenomena against repeated thermal constraints. Another advantage of the present invention is the waterproofing of treated soils eliminating capillary phenomena and avoiding the rising up of fine mineral particles. This result eliminates sap effects of water due to underground waters and damage due to elimination of fine grain particles and frost effects. To obtain better hydrophobic properties, a percentage of silicone may be added to the admixture, such as "Siliconate 51.T R", a Rhone-Poulenc product. The proportion of such a component in the admixture will vary between 2 and 20 per cent depending on the results </div>

Claims

<div id="claims" class="application article clearfix printTableText"> 232 1 1 7 wanted. Over 20 per cent compression strength of silica gel will be reduced and cost price will be prohibitive. Bituminous anionic emulsions can also be used in the admixture as blending agent, it will give a traditional aspect to the surfaces treated, but it must also be considered as an advantage that the final aspect will have a more "ecological appearance". Bituminous emulsions used are uniquely of the anionic type. Used with silica gels they become resistant to thermal effects of the sun. The proportion of these anionic bituminous emulsions in the admixture may reach 90 per cent, according to water-glass weight, with a minimum of 15 per cent. These emulsions will usually be used in combination with water-glass for upper layers and finishing coatings. The present invention is not limited to the above examples of construction; it may receive different modifications. In particular, the proportion of components can be modified according to needs on the work site. 13 ? 3 2 1 1 7 WHAT WE CLAIM IS:-1. A Method of reinforcing the strength and impermeability of the surface of soils for the construction of roads, aeroplane runways, railroads, road embankments and trenches and the construction of storage areas destined to receive mobile or immobile loads, comprising the steps of preparing a mixture of at least one liquid binder made out of sodium and/or potassium alkaline silicates with at least one blending agent and with at least one liquid reactive agent capable of reacting with said alkaline silicates to create a silica gel, and impregnating mineral substances of the soil on site with said mixture.
2. A method according to claim 1, wherein the liquid reactive agent includes water.
3. A method according to claim 1, wherein said at least one blending agent comprises clay or other mineral substances in powder form.
4. method according to claim 1, wherein said at least one blending agent comprises casein.
5. A method according to claim 1, wherein said at least one blending agent comprises a vot^otable oil.
6. A method according to claim 1, wherein said at least one blending agent Is chosen from the group consisting of : carboxymethylcellulose, sodium salts, ethylene-glycol, glycerine, acrylic or vinyl resins, and bituminous emulsions. I •-3 APR 1992
7. A in ethod according to claim 1, wherein mineral loads in form of finely pulverised mineral particles are added in said mixture.
8. A method according to claim 1, wherein the reactive agents to create the silica gel are chosen from the group consisting of : sodium and „ calcium chlorides, aluminium sulphate, sodium carbonates, sodium ^ aluminate, sodium fluorosilicate, mineral and organic acids, methylic It and/oi ethyhc esters, said reactive ager.tr being used in dilution and/or in suspension in a liquid.
9. A method according to claim 1, wherein the impregnation of the mineral substances of the soil with said mixture is done at an ambient temperature between 5 and 35°C.
10. A method according to claim 1, wherein the percentage of the liquid reactive agent contained in the mixture is comprised between 30 and 150% of the silicates weight.
11. A method according to claim 1, wherein on briny soils an additional amount of an acid reactive agent is added and pre-mixed into the briny soil before impregnation with said mixture.
12. A method according to claim 1, wherein on moisture soils an additional amount of silica sand and/or calcium sand is added and pre-mixed into the moisture soil before impregnation with said mixture.
13. A method according to claim 1, wherein the mineral substances of the soil are impregnated by a spraying and mixing procedure.
14. A method of reinforcing the strength and impermeability of the surface of soils, as claimed in claim 1 and substantially as herebefore described wirh refin-f»ncp to any one of examples I - III. ■ 3E 2 0 MARj032 J societe de diffusion et recherches \ j techniques et financieres sa. by their authorised agents, P.r,. BERRY 6 ASSOCIATES, i </div>