Circular dry cement inclusions

: a novel approach to stabilising clay soil

  • Kristofer Martin Stuart

    Student thesis: Master's ThesisMaster of Science

    Abstract

    Limited adoption of research and development has led to Britain lagging behind many European and far-east countries in terms of geotechnical on-site innovations. This, coupled with the fact that construction costs are considered to be 30% higher than they should be for what is delivered (Egan, 1998), has led to a general change in the countries attitude and approach towards future construction. This project undertook an initiative approach to soil stabilisation, with a key aim of establishing whether or not a deliberate inclusion of dry Portland cement would induce consolidation in a clay soil, by transferring and fixating pore water into the cement and changing the structure of the surrounding soil. Laboratory prepared kaolin clay was the soil material adopted for testing purposes, with soil moisture contents of 40% and 60% and a range of curing times up to and including 28 days under investigation. Two cement materials: i) Portland cement (BS EN 197: CEM 1) and ii) Calcium Sulfoaluminate Cement (CSA) were investigated in order to determine the influence of cement material. Moisture content samples and hand shear vane tests were undertaken to determine the strength and moisture changes in the surrounding soil as a result of the cement inclusion utilising the soils pore water. The penetration of water through the cement inclusion was monitored by the cements degree of hydration using Thermogravimetric testing (TGA). The porosity of the cement was determined using Mercury Intrusion Porosimetry (MIP) and Nitrogen Adsorption. To further investigate the ability of cement inclusions to absorb pore water, capillary sorption tests were performed over a range of curing times up to 28 days. All tests were performed to laboratory scale, with an empirical approach to the consolidation effect being undertaken.Very early on in the work it was found that cement, contrary to the literature and the general debate around the approach, did absorb pore water and hydrate in such a manner as to enhance the characteristics of the surrounding clay soil. Increased curing time was seen to benefit the system; with the clay shown to continually absorb water up to 28 days. All cement within the inclusions was seen to have access to water and fully participated in the improvement process.Work was then progressed onto investigating the effects of the inclusion diameter, which suggests that larger inclusions require longer curing times to hydrate due to sorption and diffusion leading to an ‘onion skin’ effect. An investigation into grouped inclusions organised in a number of arrangements was also performed, focusing on the spacing between inclusions and the area replacement ratio. It is speculated that a simple 1-dimensional rig could be designed in order to investigate the dewatering effects experienced in both normal and overconsolidated clay soil, in relation to a layer of dry cement. Work concludes with some practical suggestions for future research; intended to further understand the advantages and limitations to this proposed system.
    Date of Award2011
    Original languageEnglish
    Awarding Institution
    • University of Dundee
    SupervisorRod Jones (Supervisor) & Michael Brown (Supervisor)

    Keywords

    • Cement
    • Dry
    • Inclusions
    • Clay
    • Soil
    • Soil Dewatering
    • Stabilising

    Cite this

    Circular dry cement inclusions: a novel approach to stabilising clay soil
    Stuart, K. M. (Author). 2011

    Student thesis: Master's ThesisMaster of Science