A process for stabilizing soft clay soil using geopolymerization method

Abstract

A process for stabilizing soft clay soil using Geopolymerization Method Problem with existing methods for soft soil stabilization is more time is taken for gaining strength and modification of plasticity characteristics.The present invention aims to stabilize soft clay soil chemically through geopolymerization method to achieve required modification of characteristics at reduced time duration‘ The method comprises a Geopolymerization process wherein the geopolymer materials consisting of soft clay and admixtures comprising industrial wastes like cement kiln dust and ungrounded cement Clinkers. Use of industrial waste, helps in recycling and facilitates stabilization process in a cost effective way. Present process involves few stages, where an alkaline activator is prepared using a sodium hydroxide aqueous solution (102) which is mixed to sodium silicate ([04). Mixture of stable clay soil mixture is prepared by mixing clay soil with cement kiln dust and unground cement clinker (106, 108). At end, aqueous solution is mixed with stable clay soil mixture to bring final stabilization.

Description

BACKGROUND OF THE INVENTION: Field of Invention:Stabilizing the soft clay soil will be an alternate in construction field. The duration taken for stabilizing a soft clay soil will take more time with the current stabilizing methods. The present invention focuses on a process that is used for stabilizing soil chemically. The method comprises a Geopolymerization process wherein the geopolymer materials are obtained from industrial wastes.Prior Art of State: US9447555 B2Geopolymerization method for soil stabilization ApplicationThe invention proposed a methodology for soft soil stabilization using friendly raw materials such as stabilizers including fly ash, kaolin Meta kaolin, palm oil fly ash, volcanic fly ash and other combinations in the range of 0.5:1 to 1:3 by weight of alkaline activator. Where alkaline activator comprises of sodium silicate and sodium hydroxide from 1:2 to 1:3. Approximately the compressive strength was 14 MPa.CN201810456674A kind of artificial prepared stone based on carbonation compound excitation and its preparation methodThe aforementioned procedure involves mixing and molding carbonizable raw materials, industrial wastes, and activators before adding them to a carbonization kettle set at 20 °C room E temperature. Although this technology requires carbonation treatment in a separate, specializedcarbonization kettle and is labor-intensive, the 90-day compressive strength of the producedit product can reach 20-40 MPa and its anti-freezing, erosion, and weathering resistance propertiesare unknown.US10221097B1Date palm ash based cement CompositionsThey proposed a methodology for concrete or mortar composition with Portland cement whichhas I to 50% of date palm ash, where the date palm ash comprised the following chemicalcomposition by wt% 30-40% of SiC3, 10-15% of CaO, 0.1-1% of Fe2O3, 5-10% of MgO, 0.1-1%of Al2O3. The maximum particle size of the date palm ash is less than 0.2mm. Followingcompressive strength has reported after 3 days 35-50 MPa, 28 days 56-60 MPa and 360 days 83-90 MPa.CN110668772BGeopolymer-based artificial prepared stone prepared from full wastes and preparation method thereofAbove proposed method is completely made from wastes. Waste silicon aluminium material in the range of 288-412 parts; waste sulphate minerals in the range of 29-75 parts; recycled aggregate in the range of 1501-1860 parts; reclaimed water in the range of 216-241 parts; waste fibres in the range of 0-2 parts; and crop wastes in the range of 0-5 parts; The following source ingredients make up the waste silicon aluminium material in the following proportions by weight: 20 to 90 percent of granulated blast furnace slag powder, 0 to 40 percent of fly ash, 0 to 50 percent of waste concrete powder, 0 to 50 percent of waste red brick powder, 0 to 10 percent of silica fume, 0 to 10 percent of calcined gangue powder, 0 to 20 percent of tailing powder and 0 to 10 percent of crop waste ash. The artificial backup stone reported an excellent substitute because it is large in volume density, high in strength (more than 34 MPa), good in weather resistance, frost resistance, and abrasion resistance and the like, convenient to throw, good in integrity, strong in stability, resistant to freezing and thawing, weather resistance, and high-speed sand-containing water flow abrasion resistance in the using process.WO 2014 / 055558 A1Production of Bricks form Mine Tailings through GeopolymerizationIn the above methodology copper mine waste tailings of particle size of 120nm is mixed "with sodium hydroxide solution between 10M to 15M until a semi paste is formed with a watercontent of 8% to 18%. The above methodology is performed in the temperature range of 60°C toKR102060844B1Gcopolymer resin materials, geopolymer materials, and materials produced therebyIn above said method, first material is in contact with a fluid and at least some of the fluid isremoved to produce a product, the first material may be a geopolymer resin material, ageopolymer resin, or a combination of the two. Before the first material is in contact with thefluid, the first material may be created by heating and / or ageing an initial geopolymer resinmaterial. In some instances, breaking up or disintegrating the initial material upon contact withthe fluid results in the formation of particles with an exterior diameter in the range of 1 nm to 2cm.Geopolymer-based concrete for block energy storage tower and preparation methodthereofThe aforementioned procedure involves mixing of heavy aggregate, 2500-3000 parts, 0-240parts of a liquid activator, 0-138 parts of a solid activator, 2-12 parts of a water reducing agent, 2-10 parts of a retarder, 140-170 parts of water, and 40-120 parts of steel fibres and finally 400-parts of an ultrafine powder cementing material.CN110255996BFly ash geopolymer concrete and preparation method thereofThe disclosed invention is a fly ash geopolymer concrete that is made by using fly ash and metakaolin as base materials, one or more than two of sodium hydroxide, potassium hydroxide, sodium silicate, and potassium silicate, and water glass as an alkali activator, and then adding modified ceramic microsphere particles, polymer fibres, coarse aggregates, fine aggregates, and water. The fly ash geopolymer concrete has strong mechanical characteristics, is long-lasting, and resists corrosion.CN112573868BGranite micro-powder geopolymer composite base and preparation method and application thereofAbove proposed method uses granite micro powder similar to fly ash. The primary ingredients of granite micro powder are Ah O3 and SiO:- The performance of the created slurry is comparable to that of the typical geopolymer slurry because the granite micro powder is doped into the geopolymer matrix to fill and optimize the pore structure of the slurry. The granite micro-powder geopolymer composite matrix may lower the cost of raw materials; effectively address the issue of pollution brought on by the previous waste granite powder, and be employed in a variety of construction engineering applications.CN113060956AGeopolymer microspheres and preparation method thereofThe above method describes a geopolymer microsphere and a method of making one, which are primarily made of the elements listed below: 1-15 parts of pour point regulator, 850 parts of alkali activator, 1000 parts of high-titanium slag powder, 0-200 parts of fly ash, 0-200 parts of metakaolin, and 0-200 parts of common slag powder. In addition to reducing environmental pressure and efficiently expanding the use of high-titanium slag, the technology also produces E high-value-added goods and high-performance geopolymer microsphere materials.OBJECT OF THE INVENTION: primary object of the present invention is to introduce a method of soil stabilizationthat employs geopolymer as soil stabilizer for soft clay soils to achieve significant shearstrength in a shorter time.Another object of the present invention is to introduce a method for stabilizing soil whichwill be suitable for all types of soft clay soil at lower cost by using industrial wastes,The further object of the invention is the mixing of geopolymer material used in thestabilization process with alkali activators using eco-friendly material like cement kilndust and unground cement clinkers.SUMMARY OF THE INVENTION:The present invention focuses on a process which uses geopolymerization method wherein the said process is meant for improving the strength and stability of soft clay soil in a short period of time. The admixture material used in the process are cement kiln dust and unground cement clinkers that are mixed with soft clay at a desirable range which helps in recycling the industrial waste in an effective way. The proposed soil stabilization method is suitable for all kind of soft clay soil including black cotton soil having montmorillonite clay mineral. As the industrial wastes are used as admixtures during geopolymerization, the cost for stabilization process is comparatively low with the existing methods. The proposed method comprises the steps for stabilization where the stabilization material is prepared by mixing admixtures such as cement kiln dust and unground cement clinkers passing 4.75 mm sieve size with alkaline activator in a desired ratio and adding it by 5 to 30% by weight of the mixture to the soil.BRIEF DESCRIPTION OF THE DRAWING:Figure 1 is a flow diagram of an example method of stabilizing a soft clay soil using geopolymerization.DETAILED DESCRIPTION OF THE DRAWING:The present invention is a method of soil stabilization consisting of different steps ofmixing geopolymer material using industrial waste by product with alkaline activator in a desiredratio and adding 15 to 30 % by weight of the mixture to the soil. The geopolymer materialemployed can be any pozzolanic material containing siliceous or siliceous and aluminousmaterial that can react with alkali activator to form Si-O-AI bond structure. In the preferredembodiment, the geopolymer material is obtained from industrial waste which possesses naturalor artificial thermal history. The industrial waste employed in the present invention is cementkiln dust (CKD). In the preferred embodiment, the industrial waste employed is having 17.1%weight of silica, 4.24 weight % of Aluminum Oxide along with 49.3 wt.% Calcium Oxide.Another industrial waste employed is unground cement clinker (UgCC) passing 4.75mm sievesize, having 21.5 % weight of silica, 5.2 weight % of Aluminum Oxide along with 64.3 wt.%Calcium Oxide. The total percentage of theses mixture shall in no case exceed 50% by weight ofCN clay soil taken. In one of the preferred embodiments, fly ash, kaolin, metakaolin, palm ash,volcanic ash or any combination thereof is the preferred admixture geopolymer material thatessentially reacts with an alkaline activator to form a geopolymer-based soil stabilizer.Preferably, 10-12% of geopolymer material such as CKD and UgCC shall be added to claycysoil to form a stabilizing geopolymer mixture of soil, henceforth called geopolymer material,with reduced plasticity and shrinkage properties .The geopolymer material can be employed in powder form. The alkaline activator is prepared as a liquid which is a mixture comprising sodium silicate and sodium hydroxide. Nevertheless, potassium hydroxide can also be employed in order to provide an alkali environment for geopolymerization reaction. Molarity of sodiumhydroxide is an important factor in the alkaline activator in geopolymerization. It is alsoimportant that the ratio of sodium silicate to sodium hydroxide is essential to form a workable soil stabilizer. An increase in ratio of sodium silicate to sodium hydroxide enables an increase in SiO2 species, leading to an increase in the ratio of SiO2 / Al2O3. Hence, more Si-O-Si bonds are formed, where the Si-O-Si bonds are stronger in comparison with Si-O-Al bonds. Furthermore, the increase in ratio of sodium silicate to sodium hydroxide significantly increases the geopolymerization rate, as sodium silicate can fill the micro voids of clay soil as a grouting material, providing a rapid increase in strength in a shorter curing period, preferably within 30 days of a resulting geopolymer-based soil stabilizer. The sodium hydroxide / potassium hydroxide or calcium hydroxide can be prepared in a concentration range from 8 molar to 12 molar, and, the sodium silicate to sodium hydroxide can be prepared in a ratio of 2:1.Thus, in an implementation, a method for stabilizing a soil includes making an alkaline activator including making an aqueous solution of a metal-hydroxide at a concentration within a range from approximately minimum of 8 molar to approximately maximum of 12 molar, and mixing sodium silicate with the solution of metal-hydroxide in a ratio within a range from approximately 2:1 by weight. Then a geopolymer material consisting of soft clayey soil admixed with 10-12% CKD and 10-12% UgCC is mixed with the alkaline activator in the range of 5-30 percent by weight of the stabilization mixture is added to the soil.Figure 1 shows an example method of stabilizing a soil. Operations are shown in individual blocks.At block 102, an alkaline activator is created, including making an aqueous solution of sodium hydroxide at a concentration in the range of 8 to 12 molar.At block 104, sodium silicate is mixed with the aqueous solution of sodium hydroxide in a ratio within the range of 0.5:1 to 2:1 by weight.At block 106 & 108, a geopolymer stabilizing material is prepared by mixing cement kiln dust in the range of 10-12% and unground cement clinker in the range of 10-12% by dry weight of clay soil. The geopolymer material thus formed is to be mixed with the alkaline activator solution obtained in block 104.At block 110, 5-30% by weight of alkaline activator prepared in 102 to 104 is added to stabilization mixture. Pursuant to the preferred embodiment, the geopolymer-based soil stabilizer is added to a soft clay soil and preferably mixed for the stabilization process. Mixing can be performed in a stirrer or mixer, and if large quantity is desired to be mixed as in actual field applications, a mixer similar to concrete mixer using batch method to obtain a homogeneous mixture can be preferred. However, it can also be mixed manually by hand on a small scale. Soft soil or weak soil is preferably stabilized to enhance its durability such as water absorption, compressive strength and linear shrinkage.As per the preferred embodiment, soft soils such as clay soil, black cotton soil, peat soil, organic soil or any combination, thereof can be modified for construction applications, despite its original undesired properties. In one of the preferred embodiments, the strength of a soft soil canbe increased by at least 500kPa in a span of 28 days by using the geopolymer soil stabilizer in the present invention. A soft clay soil consisting montmorillonite clay mineral having unconfined compressive strength of 155kPa is being stabilized by mixing with a geopolymer soil stabilizer described in the present invention. The strength of the stabilized soil after stabilization is 385kPa in 7 days, 470kPa in 14 days and 513kPa in 28 days with 12M sodium hydroxide concentration and at 2:1 ratio alkali activator. One of the advantages of the present invention is that the stabilized soil is chemically stable due to the presence of Si-O-Si bonds and Si-O-A I bonds. Thus the stabilized soil will remain unchanged throughout its service life, because the properties of the geopolymer itself are good having better chemical resistance.

Claims

1. A process for stabilizing soft clay soil using Geopolymerization Method comprises the steps of: mixing a geopolymer material, such as, clay soil with 10-12% CKD and 10-12% UgCC by weight of clay soil with an alkaline activator consisting of sodium silicate and 12 molar sodium hydroxide in a desired ratio of 2: 1; and adding 5 to 30 weight % of the mixture to the soil.

2. A method for stabilizing soft clay soil as claimed in claim 1, wherein the said geopolymer material soft clay admixed with fly ash, kaolin, metakaolin, palm ash, volcanic ash, or any combination thereof.

3. A method for stabilizing soft soil as claimed in claim 1, wherein the said ratio of geopolymer material to alkaline activator can be in range from 0.521 to 2:1 by weight.

4. A method for stabilizing soft soil as claimed in claim 1, wherein the said alkaline activator is a mixture comprising sodium silicate and / or sodium hydroxide and either potassium hydroxide or calcium hydroxide.

5. A method for stabilizing soft soil as claimed in claim 1, wherein the said soft soil is clay soil, black cotton soil, peat soil, organic soil or any combination thereof.

6. The alkaline activator as claimed in claim 4, wherein the sodium silicate and sodium hydroxide at a ratio of 0.5:l to 2:1 by weight.

7. The concentration of sodium hydroxide as claimed in claim 6, ranges between 8 molar to 12 molar.

8. A method for stabilizing soft clay soil comprises of making an alkaline activator includes: i. making an aqueous solution of a metal hydroxide at a concentration within a range from approximately 8 molar to approximately ]2 molar; ii. mixing sodium silicate with the solution of the metal hydroxide in a ratio, the ratio within a range from approximately 0.5: l to approximately 2: 1; iii' mixing a geopolymer material with the alkaline activator in a ratio within a range from approximately 0.5:1 to approximately 2.1 by weight to make a stabilization mixture; and adding 5-30 percent by weight of the stabilization mixture to the soil.

9. The method as claimed in claim 8, wherein the geopolymer material is fly an ash, a kaolin, a metakaolin, a palm ash, a volcanic ash or a combination thereof.

10. The method as claimed in claim 8, wherein the metal hydroxide is selected from the group consisting of sodium hydroxide, potassium hydroxide,and calcium hydroxide.