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

Unconfined compressive strength (UCS) of synthetic biochar mixed clays (BMC) treated with lime-GGBS has been investigated. Biochar utilized in this study was produced from the slow pyrolysis of green waste residue. Treated biochar mixed clays have also been tested for microstructural and mineralogical developments. Results of this study showed that a lime content of 2 wt%, which is much lower than the conventionally used 10 wt% lime for synthetic clay, can be effectively incorporated to improve BMCs. X-ray Diffraction analysis carried out on treated BMCs showed the development of cementitious minerals (C─S─H, ettringite). Scanning Electron Microscopy with Energy Dispersive Spectrum (EDS) enabled identification of three separate types of microstructural interactions between biochar and soil particles, namely interface cementation, surface deposition and pore space filling by cementitious minerals, all of which are responsible for the enhancement of UCS with curing.

Biochar Sequestration in Lime-Slag Treated Synthetic Soils: A Green Approach to Ground Improvement

The stabilization of soils with additives is a chemical method that can be used to improve soils with weak engineering properties. Although the effects of non-traditional additives on the geotechnical properties of tropical soils have been subject of investigation in recent years, the effects of magnesium chloride (MgCl2) on the macro- and micro-structural characteristics of peat soil have not been fully studied. This study investigates the effect of MgCl2 on the physico-chemical characteristics of tropical peat. Unconfined compression strength tests were performed as an index of soil improvement in treated samples. In addition, the micro-structural characteristics of untreated and treated peat were investigated using various spectroscopic and microscopic techniques such as X-ray diffractometry, energy-dispersive X-ray spectrometry, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and Brunauer, Emmett, and Teller surface area analysis. From an engineering point of view, the results indicated that the strength of MgCl2-stabilized peat improved significantly. The degree of improvement was approximately six times stronger than untreated peat, after a 7-day curing period. Additionally, the micro-structural study revealed that the stabilization process led to a few changes in the mineralogical, morphological, and molecular characteristics of the selected peat. The pores of the peat were filled by newly formed crystalline compounds known as magnesium aluminate hydrate (M–A–H).

Effect of magnesium chloride solution on the physico-chemical characteristics of tropical peat

This paper presents the results of treatment of an expansive soil by mechanical and chemical techniques against swelling. Mechanical treatment was done by reinforcing the soil with randomly distributed fibres and chemical treatment by using cement or lime as a chemical agent. All the experiments on untreated and treated samples were conducted in an oedometer. The experimental programme consisted of two groups of tests. The first group involved the tests on expansive soil reinforced with randomly distributed fibres (mechanical improvement) with different percentages (0.5, 1 and 1.5%), and different lengths (10, 20 and 30 mm), in bar shape with diameter of 0.30 mm or tape shape with two different widths (3.0 and 5.0 mm). The second group of tests consisted of samples that were mixed with different percentages (5, 8 and 10%) of cement or lime (chemical improvement) for different curing times. The results showed that, compared with the natural soil, the swelling behaviour (swelling potential and swe...

Treatment of an expansive soil by mechanical and chemical techniques

This paper studies the effect of lime and discrete plastic fibre on the strength and stiffness behaviour of clayey soil. A series of unconfined compressive strength (UCS), split-tensile strength (S...

The strength behaviour of lime-stabilised plastic fibre-reinforced clayey soil

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.

John Adamson

Papers

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

Stabilisation of reactive subgrades by cementitious slurry injection - a review