A review on effect of soil stabilization using alkali activated geopolymer

Abstract

In order to confront the issues related to clay for construction, some adequate ground improvement technique is important. To enhance the properties of clay, alkaline solutions such as sodium hydroxide and sodium silicate are used along with Class F fly ash, Ground Granulated Blast Furnace Slag (GGBS) and metakaolin as additives. Flyash greatly modifies the strength properties of soft soils and it contain silica and aluminium materials (pozzolans) also as a particular amount of lime, which chemically binds to soft soil and forms cement compounds. Metakaolin is a highly reactive pozzolana formed by the calcinations of kaolinite (China clay).In many civil engineering constructions, soft and weak soils are often stabilized with Ordinary Portland cement (OPC) and lime. The production processes of traditional stabilizers are energy intensive and emit an outsized quantity of CO2. Geopolymer offer a better alternative to OPC, with its high strength, low cost, low energy consumption and CO2 emissions during synthesis. Due to the major environmental impacts involved in the manufacturing of OPC, the use of industrial by-products has been encouraged. The reason for the increase in compressive strength due to GGBS can be caused by the high GGBS calcium content. These polymers are economic and, compared to many chemical alternatives, are more effective and significantly less damaging to the environment. The combined impact of fly ash, GGBS and metakaolin will boost the soil s engineering efficiency.The alkali activation of waste materials has become an important area of research in many laboratories because it is possible to use these materials to synthesize Sustainability, Agri, Food and Environmental Research, (ISSN: 0719-3726), 10(X), 2022: http://dx.doi.org/ 2 inexpensive and ecologically sound cement like construction materials.The activator solution is also very influential in the polymerization process and it s also one of the factors that determine the compressive strength. Keywords—Alkali activation, Geopolymer, fly ash, GGBS, clay, stabilization. RESUMEN Para afrontar los problemas relacionados con la arcilla para la construcción, es importante contar con una técnica adecuada de mejora del suelo. Para mejorar las propiedades de la arcilla, se utilizan soluciones alcalinas como hidróxido de sodio y silicato de sodio junto con cenizas volantes de Clase F, escoria de alto horno granulada molida (GGBS) y metacaolín como aditivos. Flyash modifica en gran medida las propiedades de resistencia de los suelos blandos y contiene materiales de sílice y aluminio (puzolanas) también como una cantidad particular de cal, que se une químicamente al suelo blando y forma compuestos de cemento. El metacaolín es una puzolana altamente reactiva formada por las calcinaciones de caolinita (arcilla de China). En muchas construcciones de ingeniería civil, los suelos blandos y débiles a menudo se estabilizan con cemento Portland ordinario (OPC) y cal. Los procesos de producción de estabilizadores tradicionales consumen mucha energía y emiten una cantidad descomunal de CO2. Los geopolímeros ofrecen una mejor alternativa al OPC, con su alta resistencia, bajo costo, bajo consumo de energía y emisiones de CO2 durante la síntesis. Debido a los importantes impactos ambientales que conlleva la fabricación de OPC, se ha fomentado el uso de subproductos industriales. La razón del aumento en la resistencia a la compresión debido a GGBS puede ser causada por el alto contenido de calcio de GGBS. Estos polímeros son económicos y, en comparación con muchas alternativas químicas, son más efectivos y significativamente menos dañinos para el medio ambiente. El impacto combinado de cenizas volantes, GGBS y metacaolín aumentará la eficiencia de la ingeniería del suelo.La activación alcalina de materiales de desecho se ha convertido en un área importante de investigación en muchos laboratorios porque es posible utilizar estos materiales para sintetizar cemento económico y ecológicamente sólido como la construcción. La solución de activador también es muy influyente en el proceso de polimerización y también es uno de los factores que determinan la resistencia a la compresión. Palabras clave: activación de álcalis, geopolímero, cenizas volantes, GGBS, arcilla, estabilización. Sustainability, Agri, Food and Environmental Research, (ISSN: 0719-3726), 10(X), 2022: http://dx.doi.org/ 3 INTRODUCTION Soft soil possesses low strength and undergoes excessive volume changes, making its use within the construction activities very difficult. The properties of the soft soils may also be altered by mechanical, thermal, chemical and other means in certain aspects.Expansive soil is one of the most devastation types of soil damagingroads, building, and pipe line each year. Various efforts are being done to stabilize the soil and mitigate the damage due to it. Utilization of industrial waste as low CO2 cement is one of the sustainable method for industrial growth (P S Parhi, L Garanayak, Mahasakti, &Sarat Kumar Das, 2018). Modification of soft soil by chemical admixtures is a common stabilization method for such soils. Fly ash contains siliceous and aluminous materials (pozzolans) and also specific amount of lime. It reacts chemically when mixed with soft soil and forms cement compounds.The presence of free lime and inert particles in fly ash suggests that it are often utilized in expansive soil stabilisation.Metakaolin is an amorphous alumino silicate, a highly reactive natural pozzolan formed at temperatures between 500 ° C and 900 ° C by the calcination and dehydroxylation of kaolinitic clay.Clay needs to be improved before it can be used in embankments, canal, roadway, dams, waste landfills etc.Clay soils feel very adhesive and when wet, they roll like plasticine.They can retain more total water than most other forms of soil, and crops seldom suffer from drought, but only about half of this is available to plants.Ground-granulated blast-furnace slag (GGBS or GGBFS) is obtained from a blast furnace in water or steam by quenching molten iron slag (a byproduct of iron and steel making) to obtain a glassy, granularproduct which is then dried and ground into a fine powder.Ground-granulated blast furnace slag is strongly cemented and high in CSH (calcium silicate hydrate), which is a compound that improves strength. In recent years, the novel green cementing agent Geopolymer, an industrial by-product, has been investigated as an alternative soil stabiliser to ordinary Portland cement, which during its processing emitsgreenhouse gases. There are a lot of significant advantages to the Polymer method of stabilisation over physical and chemical methods. Compared to many chemical alternatives, these polymers are cost effective, better efficient and much less harmful to the environment. In recent years, stabilisation methods have been introduced using several stabilising agents based on polymers. Potassium Hydroxide Geopolymer (PHG) and Sodium Hydroxide Geopolymer (SHG) are added to increase the strength of the UCS and young s modulus.There is very little to no problem as long as this soil is confined and dry, but when exposed to cutting or when it comes into contact with water, it significantly loses its strength. Sustainability, Agri, Food and Environmental Research, (ISSN: 0719-3726), 10(X), 2022: http://dx.doi.org/ 4 GEOPOLYMER Nearly scientists have currently been drawn and focused on the development of ecofriendly products such as geopolymer.Geopolymers, first named and developed by Davidovits in the late 1970s, are amorphous three-dimensional alumina silicate binder materials. They are a chain structure formed of aluminium (Al) and silicon (Si) ions on the back bone and are a component of the inorganic polymer family. Basically, all materials are specific sources of geopolymer production if they contain more amorphous silica (SiO2) and alumina (Al2O3). Alumina-silicate based materials rich in silicon (Si) and aluminium (Al) were needed for the production of the geopolymer, where alkaline solutions were enabled.Geopolymer is an inorganic substance of alumina-silicate formed by polycondensation of tetrahedral silica (SiO) and alumina (AlO), which are alternately connected by sharing all the oxygen atoms. Geopolymerization is a reaction between a high alkaline solution of silica-rich and alumina-rich solids to form amorphous to semi-crystalline alumina-silicate polymers exhibiting excellent physical and chemical properties. Geopolymerization can be simplified as two main steps that interact with each other along the reaction. For the first step, amorphous alumina-silicate materials are first dissolved to form reactive silica and alumina by alkali hydroxide solution and/or alkaline silicate solution, and the second step is the dissolved species then polycondensed into amorphous or semicrystalline oligomers. GGBS BASED GEOPOLYMER Alkali activation of fly ash and ground-granulated blast-furnace slag (GGBS) is a sustainable technology that promotes recycling of industrial by-products in the form of geopolymer composites.The effect of partial lime substitution with GGBFS on the strength and mechanical properties of lime stabilised clay was investigatedby conducting unconfined compressive strength (UCS).The different percentage of GGBFS to a certain percentage of lime (2%) significantly improved the compressive strength. The application of GGBFS led to a decrease in the cracks created by shrinkage by increasing the soil s tensile strength.The role of GGBFS in accelerating the production of cemented crystalline products in lime stabilised clay samples such as Calcium Silicate Hydrate (CSH) and Calcium Aluminate Hydrate (CAH) could be attributed to this trend. For soil stabilization, the most commonly used GGBS activator is, however, lime [CaO or Ca(OH)2] (Keramatikerman, M., Chegenizadeh, A., & Nikraz, H, 2016). Sustainability, Agri, Food and Environmental Research, (ISSN: 0719-3726), 1