No description available.

No description available.

This thesis reports the findings of laboratory based investigations into the settlement behaviour of granular columns with respect to time, in particular the progression through initial, consolidation and creep settlements. The aim of the research is to investigate and segregate the three settlement stages of a raft and an isolated foundation, supported by soft clay improved by granular columns. For convenience, the programme of work is divided into two parts, in which : Part 1 examines the long term settlement performance of a smooth, rigid raft underlain by soft clay without granular columns, and with granular columns, under single and multiple configurations, at an area replacement ratio, As of 15%; and Part 2 examines the long term settlement performance of an isolated footing underlain by soft clay without granular column and with a single granular column at an As of 33%. The results obtained from Part 1 (raft foundation loading) of the experimental investigations challenge the effectiveness of granular columns to control foundation settlement over a prolonged period, when installed in soft clay under a range of loadings. The tests were carried out in instrumented, one dimensional testing chambers on samples (254 mm ɸ, 100 mm high) of kaolin and sleech . The results obtained from Part 2 (isolated foundation loading) of the experimental investigations suggest that granular columns are a viable option in reducing settlements (initial, consolidation and creep) in weak deposit under low bearing pressures, at which the soil is overconsolidated, and not particularly effective under moderate to high bearing pressures, at which the soil is normally consolidated. The tests were carried out in instrumented, three dimensional testing chambers on samples (300 mm ɸ, 400 mm high) of kaolin and sleech.

The effectiveness of lime as a chemical additive for the stabilisation of organic clay is considered uncertain, especially in the long term. Humic acid is believed to be the main deleterious constituent of organic matter that renders lime stabilisation inefficient. Due to this circumstance, the influence of chloride salts to mitigate the adverse effect humic acid has on lime-stabilised clay was investigated experimentally. Artificial organic clay, prepared by mixing commercial kaolin and various amounts of humic acid (0.5%, 1.5% and 3.0%) was used in this study as untreated (organic) clay. A chemical binder, hydrated lime, was used in conjunction with the chloride salts (i.e. CaC/2 & NaCI). The properties of all the organic clay mixtures including the control specimens and the salt treated limestabilised mixtures were determined by Unconfined Compressive Strength (UCS), triaxial (CU & CD) and oedometer tests. The chemical reaction known to occur during a typical stabilisation process was evaluated using microstructure analysis (Scanning Electron Microscope & X-Ray Diffractometer). Curing periods of 7, 28 and 90 days were chosen as key pOints to monitor the evolution and the effect of the stabilisation process on lime-treated specimens and specimens to which the salts had been added. A testing programme, comprising three stages, was scheduled to achieve the overall objectives of this study. The influence of humic acid on untreated clay was investigated. Masking effects which occur due to the humic acid coating the clay minerals were first detected during Energy Dispersive X-ray (EDX) analysis of a representative specimen. In addition, the SEM analysis revealed cracks on the surface of an untreated specimen containing 1.5% humic acid. Furthermore a significant shear strength reduction was noticed for untreated clay specimens containing at least 1.5% humic acid. Although successful stabilisation of organic clay specimens with 5% lime (OlC) was achieved following a cure period of 7 days, the specimen's properties (i.e. shear strength and compressibility) progressively deteriorated as cure duration was prolonged. The abovementioned observation casts doubt over the long term stabilisation potential of lime and its practicability to solve engineering problems. It was observed that the development of lime-treated organic clay properties was most affected when it contained 1.5% humic acid. However by adding relatively small quantities of chloride salts (0.5% CaCI 2 & 0.5% NaCI), a significant improvement occurred as early as day 7 of curing. The enhancement of the properties of the lime-treated organic clay augmented with chloride salts continued in long term. The formation of cementitious products (CSH) was observed in SEM images and detected quantitatively through XRD analysis. Of the two types of salts considered in this study, CaCI 2 demonstrated more superior enhancing capability. The consistent and promising outcomes of this study suggest that the deleterious impact of lime as an organic clay stabiliser can be improved by the addition of chloride salts. Consequently, the findings obtained from this study could be considered in future practice standards with regards to the requirement of lime stabilisation, specifically for organic clay.

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Composites of clay minerals have been prepared with organic monomers for subsequent study upon polymerisation. Particular combinations of clays and organic species have enabled three unique systems to be studied. The first involves the intercalation of the clay minerals Kaolin and Halloysite with Phenylphosphonic Acid (PPA). The intercalation process proceeds via the use of an acetone/water entraining agent and subsequent analysis by Diffuse Reflectance Infrared Fourier transform Spectroscopy (DRIFTS), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Evolved Gas Analysis (EGA) using TG-Mass Spectrometry. This has revealed the remarkable thermal stability of these intercalates; they are stable to above 450 °C, and exhibit interlayer spacings of 15.4 A. Furthermore, the fate of the water as the entraining agent is determined and is found to be hydrogen bonded to the phosphonic acid moiety of PPA and also weakly bound to the inner surface hydroxyls in these clays. This water represents an opportunity for displacement by an organic monomer, and the lone pair of electrons on the oxygens also provide scope for coordination. Hence, the PPA intercalates were treated with the monomer N-vinylformamide (VFA) and evaluated for subsequent polymerisation. In the second system, montmorillonite was intercalated with VFA and then treated with a polar activator (Propylene Carbonate) prior to polymerisation. The polar activator interacts with the bifunctional VFA molecules causing the clay to swell further prior to polymerisation. This produces significant differences in the XRD traces with and without polymerisation of VFA in the presence of the clay. If the polar activator is absent the d[(001)] spacing is 21.0 A. If the polar activator is present then no d[(001)] is observed , in a situation reminiscent of an exfoliated nanocomposite. In the last system studied an in-situ intercalative approach was employed. Montmorillonite was treated with dialdehydes and diamines capable of reacting together to form amino resins oligomers and polymers. The molar ratio of the two reactants determines the intermediate and hence the subsequent product that is formed as characterised by DRIFTS. In a binary mixture where both reactants are simultaneously added to the clay, if the aldehyde is in excess, then dimethylol condensation products are formed. If the amine is in excess then monomethylol condensation products are formed. Sequentially adding these two reactants to clay (i.e. treating the clay first with one reactant and washing to remove any excess, then adding a second reactant) also has a bearing on the results. If the amine is added first, then the aldehyde is able to displace it from the clay interlayer. If however, the aldehyde is added first, then monomethylol reaction product is seen and this together with DRIFTS TGA and XRD analysis indicates that some of the aldehyde has been removed during the washing process.

With the current emphasis on sustainable development, recycling in the construction industry including highway planning, design, construction and maintenance has become a default option. Traditionally, recycled aggregate has been employed as filling or capping materials. However, the need to replace virgin materials in higher grade applications and reduce landfill has stimulated the need to enhance their performance. The requirements of using low energy and low environmental impact binders such as bituminous emulsion and industrial by-products as hydraulic binders whilst maintaining a long shelf life presented a further challenge. The primary aim of this research was to investigate methods by which a mixture of recycled aggregate composed of road planings, concrete demolitions and bricks with proprietary bitumen emulsion as binder could be enhanced to comply with the prevailing specifications and performance requirements for pavement materials, by using novel combinations of bituminous emulsions and latent hydraulic binders. The preliminary investigation focussed upon the establishment of an appropriate method of compaction of bitumen emulsion recycled aggregate mixtures to ensure results were consistent and representative of field performance. The main investigation evaluated the environmental conditions including freeze-thaw, low and high humidities and varying temperatures upon the behaviour and performance of loose pre-compacted and compacted recycled product using a range of novel latent hydraulic binders and bituminous emulsion combinations. Test methods included Indirect Tensile Stiffness Modulus test, Repeated Load Axial test, Indirect Tensile Fatigue test, Compressive Strength test and a novel modification of the Indirect Tensile Strength test was proposed and developed for enhance assessment of performance. The key findings were that whilst bitumen emulsion mixtures could perform adequately, the addition of a latent hydraulic binder enhanced the mixture's performance in terms of mechanical properties and withstanding extreme conditions exemplified by freeze-thaw and high humidity, whilst maintaining shelf life. However, it was deduced that the performance could be heavily influenced by the condition, consistency and composition of the recycled aggregate. It is recommended that further work should focus on rigorously investigating the influence of recycled components on mixture properties to optimise their performance for given applications, and extended to include tar bound material.

No description available.

New findings about the geology of London Clay (King, 1981) have highlighted the importance of investigating the relationship between geology and engineering behaviour for stratified soils. Recent events, such as the Heathrow tunnel collapse in 1994 and the poorly predicted ground movements at St. James Park during the construction of the Jubilee line extension have also highlighted a local need to revise the general proprieties of the material with which engineers in London deal. This research aimed at finding a framework for the London Clay relating the engineering proprieties of this material to its geological features. High quality samples from different depths in London Clay were tested in their intact and reconstituted states using oedometer and advanced triaxial apparatus. The lithological units of the London Clay at the site have been accounted for in analysing the mechanical response of the clay. The structure and the nature of the clay from different strata were investigated microscopically and correlated with its large and small strain mechanical response. Shallower units showed a more open structure and higher clay content than deeper units. Samples from the same units had the same mechanical behaviour and engineering parameters, regardless their depth within the stratum, but differences were found between the different units, which reflected the differences in the nature and structure of clay from each stratum. The behaviour in both compression and shearing seemed to be dominated by the structure of the clay as well as by its nature, so that clay from units having a more packed and orientated structure showed a stiffer response and higher strengths than the clay from units with a more open structure. The behaviour of the clay was also investigated in the elastic region and the elastic parameters confirmed the effects of lithology on sample behaviour.

The fire retardant properties of inorganic silicate based materials were characterised by Thermal, Infrared (IR), Karl Fischer (KF), Mass Spectrometry (MS) and Cone Calorimetry (CC) techniques. Scanning Electron Microscopy (SEM) was also employed to study the sample morphologies. In this study, spectral data were analysed by multivariate Target Factor Analysis (TFA) to determine the relative evolution profiles of selected fire gases. A combination of the gas evolution profiles and further numerical treatment of the thermal characterisation data provided a novel set of protocols to assess the high temperature behaviour of the fire protective silicate materials. In the context of this work, the study discusses the structure-property relationships of the silicates, identifies the degradation stages and elucidates the processes involved during thermal treatment by comparison with mechanistic findings in published literature. The following conclusions were drawn. Five transitions were detected by thermal analyses, which correspond to; i) the evolution of water and flammable species ii) the rearrangement of interstitial ions and water molecules iii) the evaporation of water of condensation from silanol groups iv) the decomposition of samples and i) structural rearrangement. Cone calorimetry studies revealed that samples with low polyol (P) and high SiO2:Na2O weight ratio (WR) exhibited very low heat release rates (HRR) and vice versa. It was observed that in general, low polyol content and high SiO2:Na2O WR enhanced fire resistivity. This provided a better understanding of the thermo-degradation patterns of samples and the underlying chemistry influencing the performances of the inorganic silicate based materials.