Search

Lightweight alkali-activated ground granulated blast furnace slag (LAS) is an energy-efficient and environment-friendly cementitious material that can be used as a binder for the fill soil stabilization in subgrade construction. Although physical, hydraulic and mechanical properties of LAS stabilized clayey soils have been previously characterized, their long-term durability under deteriorating environments has not yet been well assessed. This paper reports an experimental study on the sulfate attack resistance of a LAS stabilized clayey soil, which is composed of GGBS, sodium silicate, calcium carbide residue (CCR), air foam, and clayey soil. Stabilized soil specimens are submerged in a sodium sulfate solution for varying periods (3, 7, 14, 28, 60, 90 and 120 days). The mass change percentage, unconfined compressive strength and thermogravimetric characteristics are evaluated at the end of each varying soaking periods. The same virgin soil stabilized by the lightweight Portland cement (LPC) is also tested as a benchmark. The results suggest that the LAS stabilized soil has superior sulfate attack resistance in terms of greater water absorption and higher strength, which is attributed to the presence of larger amount of cementitious hydration products in the LAS stabilized soil, as confirmed via thermogravimetric measurement. [ABSTRACT FROM AUTHOR]

Marl was treated with Mg-rich lime to evaluate the effectiveness of lime stabilization for this expansive, clay- and carbonate-rich material. XRD and TEM analyses revealed very limited dissolution of expandable clay minerals and neoformation of Mg-enriched smectites. C-(A)-S-H phases formed and initially cemented clay particles. However, they experienced decalcification and decomposition over time, leading to disaggregation of clay particles and deterioration of some of the marl's geotechnical properties. Results question the effectiveness of lime stabilization for marls, especially using Mg-rich lime. Modifications to commonly used treatment protocols in order to overcome these shortcomings are discussed. [ABSTRACT FROM AUTHOR]

The achievement of Optimum Compaction Moisture Content (OCMC) of clay soil plays an important role in compaction as well as the durability and strength of compacted soil. This is due to its effect on the structure and orientation of the clay soil particles. Most researchers on stabilised systems involving soils and/or industrial waste by-product additives for applications in roads and buildings are faced with the problem of how to approach the establishment of OCMC, when the complex mixtures involved. This paper reports on the laboratory investigation of theoretical methods of two different approaches to establish the OCMC in the stabilisation of clay soil involving multi-binary binder in cementitious binder system. Furthermore, this research also explores the use of an industrial by-product, Pulverized Fuel Ash (PFA) as partial target material and ground granulated blastfurnace slag (GGBS), with a view to reducing the reliance on the traditional cementitious binders, such as lime and/or Portland Cement (PC), in stabilising Lower Oxford Clay (LOC) soil combining with PFA at 50:50 ratio. LOC + PFA was stabilised both in conventional manner using Lime and PC as control and using sustainable binders incorporating GGBS. The results show that there was no one particular approach to the establishment of the optimal compaction moisture content for best strength development and durability. The best approach being dependent on the period of curing, stabiliser content and whether GGBS was blended with Lime or with PC. Of the various stabilisers studied, the highest strength magnitudes were however recorded with LOC-PFA stabilised using the blended binders incorporating GGBS. For all 7, 28 and 56 days of curing periods, the PC-based stabilisers were observed to be less sensitive to the different approaches to compaction moisture content, relative to the lime-based systems. [ABSTRACT FROM AUTHOR]

Clay soils, especially soft clay soils covered considerable parts of the earth. Cement and lime are used as traditional additives for clay soils stabilization but unable to increase the strength properties of clay soils significantly. So, it seems necessary to use new additives to increase the strength parameters of soft clay soils. Therefore, cement and epoxy resin are used for stabilization of soft clay soils in this study. The main objects of this study are the determination of the effect of epoxy resin on the mechanical parameters and microstructure properties of clay soils, the phenomenon of clay concrete and effect of clay minerals on its properties and also, using knowledge of the elastic modulus, toughness and elastic and plastic strain of the stabilized soft clay as a practical criterion for determination of the optimum additive percentage in soft clays stabilization in addition to UCS. In this study, two samples of clay soils with different clay minerals were investigated. Clay soil samples that tested experimentally were bentonite and kaolinite. A series of microstructure and macrostructure experiments were conducted on the samples. The results show that using epoxy resin increases strength parameters about 100 to 1000 times while UCS reaches to more than 50 MPa in some samples based on the clay mineral types in the soils. Unlike the cement concrete, as the strength increases the failure strain and material toughness will increase simultaneously as well. In addition, the important and prominent result of stabilization by epoxy resin is the best efficiency in the weakest and the most sensitive soils. [ABSTRACT FROM AUTHOR]

Dispersive clays may pose considerable distress if not adequately taken care of. On the other hand, the treatment of problematic soils with waste materials has been recently proved to be a useful option from economic and environmental view point. Hence, in this research, the potential use and effectiveness of dispersive soil stabilization using two types of industrial by-product, including granulated blast furnace slag (GBFS) and basic oxygen furnace slag (BOFS) were investigated. The slags were separately added (ranging from 2.5 to 30%) to a laboratory dispersed sample and a set of experiments were performed to study the physicochemical, mechanical and microstructural changes of the stabilized soil. The results indicate that the soil dispersion can be eliminated upon adding 10% BOFS. This is attributed to the exchange of interlayer sodium ions on the clay surfaces by multivalent cations from the agent. Besides, an increase in the ion concentration of soil-additive mixtures induces a more depression of the diffuse double layer that decreases the soil dispersivity potential. With increasing the curing time, an improvement in the strength of composite samples is observed. The formation of cementitious compounds due to the pozzolanic reactions is responsible for such a treatment, as confirmed by the XRD analyses and SEM micrographs. It appears that the GBFS has a lower activity as compared to BOFS, therefore causes less influence on the soil engineering parameters and a higher percentage (20–25%) of GBFS is required to govern soil dispersion. Overall, utilization of the studied slags particularly of BOFS is very effective to overcome the problems associated with dispersive soils. [ABSTRACT FROM AUTHOR]

This paper investigates the microstructure and mineralogical compositions of soft clay soil stabilized with bassanite that is produced from gypsum waste materials. Bassanite was mixed in different ratios with cement and lime, as a solidification agent, to prevent the solubility of bassanite. Different amounts of these admixtures were mixed with the tested soil. Scan electron microscopic (SEM) and X-ray diffraction (XRD) were used to identify the microstructure and mineralogical compositions of stabilized soil specimens, respectively while unconfined compression test was used to examine the compressive strength. Test results showed that the addition of recycled bassanite improves the strength of the tested soil. The improvement in the soil strength, based on compressive strength, is in agreement with the SEM and XRD results. The XRD results revealed the presence of various cementation compounds in the soil matrix when recycled bassanite was added. Both the content and ratio of the admixture had a significant effect on the formation of the cementation compounds and the improvement of compressive strength. The formation of ettringite increased with the increase of admixture content in soil mixture for both admixtures used. The ratio of admixture had a clear effect on the reduction of the formation of ettringite in the case of bassanite–cement admixture while it had no significant effect in the case of bassanite–lime admixture. Curing time had a significant effect on the formation of ettringite and the improvement of compressive strength. These results support the suitability of using recycled bassanite produced from gypsum wastes as a low cost and efficient stabilizer material in ground improvement projects. [ABSTRACT FROM AUTHOR]

Abstract: Expansive clay soils are extensively distributed worldwide, and are a source of great damage to infrastructure and buildings. These soils can cause heavy economic losses, as well as being a source of risk to the population. This article presents an experimental study in the stabilization of an expansive soil, consisting of the reduction of its swelling capacity and the improvement of its mechanical capacities by the addition of by-products and waste materials of industrial origin. This achieves the double objective of reducing the problems of this type of soil, and also of providing a use for the additives, thus eliminating the economic and environmental cost involved in managing them. From the point of view of expansivity, it was possible to reduce it to levels well below what Spanish legislation contemplates for expansive soils. As to the improved mechanical capacities of the soil, all treatments tested offered improvements of between two and four times the compressive strength of the untreated soil. Of the waste materials, the most notable is the behavior of Rice Husk Fly Ash, highly effective in stabilizing soil from the two aspects considered in this experiment. [Copyright &y& Elsevier]

Abstract: This paper reports some results of an experimental investigation on the strength anisotropy of a compacted clayey soil typical of those used as impermeable cores of earth dams. Large cubic samples of the selected soil were first prepared using various compaction levels. Cylindrical specimens were then taken from the block samples both along and perpendicular to the compacting direction. The strength anisotropy was evaluated by carrying out unconfined compression tests. The influence of compaction moisture content and dry density on the strength anisotropy was also investigated. The strength anisotropy was observed in all specimens i.e. the unconfined strength in the compacting direction was larger than that in lateral direction. The strength anisotropy ratio varied from about 1.04 to 1.23 depending on the soil state parameters. [ABSTRACT FROM AUTHOR]

Abstract: Low rise buildings are particularly vulnerable to ground movements sourced from swelling and shrinking of the expansive clay soils. Geotechnical engineers have long recognized that swelling of expansive clays caused by moisture variation may result in considerable damage to the overlying structures, and engineers should take them into the consideration. The literature contains a vast number of stabilizing techniques such as lime, cement, and fly-ash for treatment of expansive clay soils. However the use of gypsum as a stabilizing agent is currently not clear. This paper deals with the performance of the gypsum as an additive for treatment of the expansive clay soils by means of swell potential and strength. Optimum water content for the best compaction of the bentonite was first determined by standard compaction tests. Different quantities of gypsum such as 2.5%, 5%, 7.5%, and 10% by mass were added to bentonite and compacted in optimum water content obtained. Atterberg limits, free swell and unconfined compressive strength tests were performed on treated and untreated samples, after a curing period of 7 days. Obtained changes in the plasticity, swell percent and strength parameters of treated and untreated samples indicated that gypsum can be used as a stabilizing agent for expansive clay soils, effectively. [Copyright &y& Elsevier]

Abstract: Clayey soils containing smectites are widely used for construction of liner and cover systems to reduce the hydraulic conductivity in geotechnical applications because of their low permeability and high cation exchange capacity. However, the compacted clayey soils crack on drying because of their high swelling potential, and their hydraulic conductivities increase. To solve this problem, it is essential to stabilize the clayey soils using additive materials. The aim of this study is to examine the suitability of silica fume as a stabilization material to reduce the development of desiccation cracks in compacted clayey liner and cover systems. Natural clayey soil and clayey soil–silica fume mixtures were compacted at the optimum moisture content and subjected to laboratory tests. The results show that silica fume decreases the development of desiccation cracks on the surface of compacted samples. We concluded that silica fume waste material can be successfully used to reduce the development of desiccation cracks in compacted clayey liner and cover systems. [Copyright &y& Elsevier]

Abstract: Failures in soil stabilization have been reported previously as being due to the formation of ettringite, an expansive mineral which develops in the presence of sulfate, calcium, and aluminum compounds of clay fraction in high pH levels between 10.36 and 14. By comparing the pattern of formation of ettringite, formed from different possible sources and specifically in stabilized soil, it is expected that a clearer picture of the kinetics of ettringite formation from different sources will be obtained. In this paper, a set of physico-chemical experiments and XRD tests were performed to investigate the process of ettringite formation and to explore its possible performance in clayey soils. The growth of the ettringite XRD peaks was used as a measure of the rate and its formation pattern. It is shown that the rate of ettringite formation in soil stabilization is much slower than that of artificial ettringite. Furthermore, it is shown that ettringite swells to the order of 50% and its fluid retention is significantly higher (by as much as 400%) than that of the soil sample studied in this research. [Copyright &y& Elsevier]