Microstructure and geotechnical properties of lime-treated expansive clayey soil

Lime generally improves the performance of soils. However, some cases reported an adverse effect. To develop an understanding of the underlying mechanisms, a systematic study covering a wide range of plasticity and mineralogy of soils was carried out. Six different soil samples were reconstituted using two extreme types of soils, in other words, a montmorillonite rich expansive soil and a silica-rich non-expansive soil. The influence of lime stabilization on these soils was evaluated through determination of geotechnical properties such as liquid limit, plastic limit, swell, compressive strength, mineralogy, and microstructure. An optimum lime content beyond which the strength improvement decreased was found. This phenomenon is more prominently observed with silica-rich soils that form silica gel. As the silica gel is highly porous, when formed in large scale the strength gain from cementation is substantially countered by the strength loss from gel pores, giving rise to a visible reduction in ove...

Lime Stabilization of Soils: Reappraisal

Microstructural and mechanical properties of marine soft clay stabilized by lime-activated ground granulated blastfurnace slag

This paper investigated the stabilization efficacy of alkali-activated ground-granulated blast furnace slag (GGBS) for a marine soft clay, compared with that of portland cement (PC). The influence of activators, including NaOH, Na2CO3, carbide slag (CS), NaOH-CS, Na2CO3-CS, and Na2SO4-CS, on the stabilization efficacy was investigated. A range of tests were conducted to investigate the properties of stabilized clays, including unconfined compressive strength (UCS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP). The results indicated that Na2CO3-GGBS had no stabilization efficacy for this marine soft clay. NaOH-GGBS-stabilized clay yielded the highest UCS at 7, 28, and 90 days; however, the UCS decreased from 90 to 180 days because of the microcracking. CS-GGBS-stabilized clay had higher 90-day and 180-day UCS than that of PC-stabilized clay, but significantly lower 7-day and 28-day UCS. NaOH, Na2CO3, and Na2SO4 could enhance the strength devel...

Alkali-Activated Ground-Granulated Blast Furnace Slag for Stabilization of Marine Soft Clay

This paper addresses the use of ground granulated blast furnace slag (GGBS) and reactive magnesia (MgO) blends for soil stabilization, comparing them with GGBS-lime blends and Portland cement (PC) for enhanced technical performance. A range of tests were conducted to investigate the properties of stabilized soils, including unconfined compressive strength (UCS), permeability, and microstructural analyses by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influence of GGBS:MgO ratio, binder content, soil type, and curing period were addressed. The UCS results revealed that GGBS-MgO was more efficient than GGBS-lime as a binder for soil stabilization, with an optimum MgO content in the range of 5–20% of the blends content, varying with binder content and curing age. The 28-day UCS values of the optimum GGBS-MgO mixes were up to almost four times higher than that of corresponding PC mixes. The microstructural analyses showed the hydrotalcite was produced during the GGBS hydr...

Properties of Two Model Soils Stabilized with Different Blends and Contents of GGBS, MgO, Lime, and PC

This paper describes the strength and microstructural behaviour of lime–slag-treated clay. The microstructure was investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the strength of the treated clay was measured using the unconfined compressive strength (UCS) test. Untreated clay was prepared in the laboratory by mixing commercially available kaolin and bentonite, while hydrated lime and ground granulated blastfurnace slag (ggbs) were used as binders. XRD analyses of lime–slag-treated clay showed the existence of numerous reaction products such as calcium silicate hydrate (C–S–H), calcium aluminium silicate hydrate (C–A–S–H), and hydrotalcite (HT), which facilitated the strength increment. For a fixed proportion of lime, the relative intensity of pozzolanic reaction products was found to increase with increasing slag content. Slag was found to be very active to promote the pozzolonic reaction with lime, as evidenced from the presence of crystalline reticular (C–S–H) and ...

Behaviour of lime - Slag-treated clay

The use of industrial by-products in the stabilisation of problematic soils presents economic, environmental and social benefits. The geotechnical and physico-chemical behaviour of some Australian clayey soils of contrasting mineralogy stabilised with commonly employed industrial by-products has been investigated in the laboratory for developments in pH, plasticity, and undrained shear strength at curing periods of up to 1 year. Stabilising agents including hydrated lime, fly ash and ground granulated blastfurnace slag (‘slag') were utilised. The results of this study showed that soils mixed to moisture contents well above their respective liquid limits developed substantial undrained shear strength directly upon exposure to cementitious stabilisers and continued to gain significant strength thereafter. It is noteworthy that samples treated with slag activated with hydrated lime gained more strength at shorter periods of curing than comparable samples of activated fly ash and samples simply treated with e...

Stabilisation of clayey soils with industrial by-products: part A

Lime slurry pressure injection (LSPI) is a stabilization operation used in problematic soils by transportation industries with the aim of improving the geotechnical properties and bringing excessive maintenance costs to an acceptable standard. This paper presents detailed field and laboratory studies of a lime/fly ash stabilized site at Breeza, NSW, Australia. The mixing of slurry into the soil with depths was investigated by excavating a trench while the improvement of geotechnical properties was determined in detailed field and laboratory tests. Visual observations of the surfaces of an excavated trench showed slurry to be distributed within the shrinkage cracks in the desiccated upper soil horizon whereas slurry was conveyed through planes of hydraulic fracture in the soils at greater depths. Laboratory swell tests on the stabilized soils demonstrated a statistically significant reduction of the intrinsic swell properties in the upper horizon of highly plastic clayey soils by LSPI. A gain in soil strength was observed in cone penetrometer test soundings conducted in stabilized soils. Scanning electron microscope and x-ray diffraction studies proved the underlying physicochemical and cementitious reaction processes in stabilized soils. Aggregation of the soils was observed with the outward diffusion of calcium cations within proximity of slurry seams and resulted in a subdued shrink/swell propensity.

Improvement of problematic soils by lime slurry pressure injection: case study

Slurry Injection Stabilisation is a cost-effective method for the remediation of discrete sections of railtrack subgrade. It is generally applied to subgrade soils that experie nce fluctuations in strength and volume with varyin g seasonal moisture contents, thereby undermining the performance of the track. This technique involves the dire ct injection of cementitious slurry to the subgrade where it reacts with soil particles to enhance the strength and st iffness while decreasing permeability and plasticity. The aim of the slurry injection operation is to ex pose as much volume of subgrade soil to chemically active slurry material as possible. The mechanics of slurry inf iltration of the subgrade strata and the subsequent reaction of the cementitious additives within the soil mass are two distinct fields of study that influence the scale of subgrade improvement. These fields have been examined in order to develop a comprehensive account of the techn ical processes involved in the stabilisation technique. This shou ld help the improvement of slurry design and inject ion procedures to suit site-specific subgrade conditions.

Alexander Douglas Wilkinson

Papers

Behaviour of lime - Slag-treated clay

Stabilisation of clayey soils with industrial by-products: part A

Improvement of problematic soils by lime slurry pressure injection: case study

Stabilisation of reactive subgrades by cementitious slurry injection - a review

Factors Affecting Cementitious Stabilization in a Range of Geo-Environments