The eco-friendly sodium silicate and promoters which are compatible with OPC to get super properties have been developed into a variety of soil stabilizers. In this paper, the development of mechanical properties of specimens stabilized with CSCN, which consists of OPC, sodium silicate and composite promoter, is investigated by unconfined compressive strength (UCS) test and scanning electron microscope (SEM). The failure strain and secant modulus are also obtained in UCS tests. The testing results indicate that the compressive strength and secant modulus of CSCN stabilized specimens increase as increasing the CSCN content at different curing ages. The strength of the CSCN stabilized specimens is much higher than that of specimens stabilized with the same content of OPC. Compared with samples stabilized with 8% OPC, the strengths of samples with 8% CSCN consisting of only 5% OPC at 7 and 60 days are 86 and 221 kPa respectively, which are almost equivalent to the strengths of samples with 12% OPC. The types and amounts of new minerals in stabilized clays are the possible mechanisms controlling the enhancement of mechanical properties.

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Cement-treated Dredged clays have been used as a construction materials, backfilling of quay wall, artificial barrier layer of waste disposal site and submerged embankment. However, strength mobilization has not been fully understood from immediately after mixing to long-term curing time. Hence, unconfined compression test and vane shear test were carried under different stages of curing time, i.e., ranging from 0.5 hours to 90 days. On the basis of results, it was found that the strength at 1 hour of curing can be estimated by initial water content and specific volume ratio by normalized liquid limit. In addition, strength mobilization can be divided two stages depending on curing time; first stage within 3 days and second stage after 3 days. The formulas to estimate strength of cementtreated marine clay were proposed based on strength at 1 hour of curing and ratio of strength inclement before and after 3 days, and combined with previously proposed formula related to volumetric solid content.

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Consolidation of cement-treated high-water content clays during their initial curing stages is a rarely considered factor in design practice, due to the assumption that cement hydration progresses much faster than consolidation in clays under typical circumstances. Certain situations, however, seem to point to importance of early-age effective stress developments in treated ground when its interim and eventual shear strengths are evaluated. This study experimentally investigated manners in which cement-treated clays develop its yield stress and shear strength through interactions between bonding and densification when subjected to effective stress changes prematurely before the hydration processes are complete. The investigation involved a suite of undrained triaxial tests on cement-treated specimens that were cured under different isotropic stresses, supplemented by K0 compression tests. The results suggested that apparently opposite consequences could be observed depending on the cement doses; reductions in undrained shear strength were observed when early-age consolidation occurred in clay treated with a larger cement dose, while the opposite was true for a smaller cement dose. These apparently complex effects seem to be only explained by kinematic development of a state bounding surface, which adjusts itself to a consolidation stress regime during curing.

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In general, a high strength soil improvement can be achieved by increasing cement amount or decreeing water-cement ratio(w/c). However, because cement milk of low water-cement ratio is viscous, when the cement milk with w/c under 60% is used in the soil improvement, the pressure feed of cement milk cannot be performed. To solve this problem, fluidizers are used with cement milk. On the other hand, in the field of concrete it is known that mobility will increase by mixing urea with concrete. In this research, the attention is paid to fluid improvement mixing urea with soil -cement water. Laboratory experiments and field experiments were conducted to clarify the effect of using urea on the improved mixed soil by discussing its strength variation and mobility.

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The use of randomly distributed fibre as a reinforcement medium for cement-treated soil has been receiving some attention in recent years. Studies have shown this to be an efficient method to control and improve the brittle behavior of cement-treated soil. However, the fibres may be non-uniformly distributed over the mixture. This issue with non-uniform fibre concentration or difficulties with fibre mixing could be significant in the field, and it may affect the overall behavior of the treated soil mass. This paper presents a laboratory study on fibre distribution effect on behavior of fibre-reinforced cement-treated Singapore marine clay. The fibre distribution analysis will be conducted with randomly selected samples while the behaviour will be investigated mainly through unconfined compression test. Polypropylene (PP) fibres with 6 to 12mm cut length and 0.25% to 2.0% fibre content (by weight) will be mixed with high cement-admixed clay. The results show that for 6mm long PP fibres reinforced mixture, fibre distribution shows higher non-uniformity when fibre content is lower(0.5%) or higher(2.0%), which results in higher variability in peak strength and ductility. This non-uniform fibre distribution has more significant effect on ductility than on peak strength. Corresponding density analysis indicates very minor fibre distribution effect. For 12mm long PP fibres reinforced mixture, the high non-uniform fibre distribution due to lower or higher fibre content seems to be more significant. However, the fibre distribution effect on strength and ductility looks quite similar to 6mm long PP fibres reinforced specimens.

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Rice hush ash (RHA) and ordinary Portland cement (OPC) were used to stabilize a lead-contaminated soil. The effects of RHA content on the permeability, diffusion and sorption of lead ions for stabilized soil are presented. Test results indicate that replacement of OPC with RHA can increase significantly the short-term permeability of stabilized soil, but its effect on the long-term permeability is negligible. Furthermore, the retardation factor of lead ions increases substantially with increasing RHA content. As a result, the apparent diffusion coefficient decreases significantly by replacing OPC with RHA. Thus, a binder system with RHA could be a better option to reduce the long-term leachability of lead than the one using OPC alone.

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