Simplex Lattice Design and X-ray Diffraction for Analysis of Soil Structure: A Case of Cement-Stabilised Compacted Tills Reinforced with Steel Slag and Slaked Lime

Abstract

Evaluating the structure of soil prior to building construction is valuable in a large variety of geotechnical and civil engineering applications. To built an effective framework for assessing the strength of the stabilised soil, the presented workflow includes a complex approach of simplex lattice design and X-ray diffraction for the analysis of soil structure. Different from the traditional in situ measurements, we propose a statistical framework for effective decision-making on binder combination to stabilise soil collected in three localities of Southern Sweden—Bromölla Municipality (Skåne County), Petersborg (Östergötland County) and Örebro (Örebro County). A practical solution is presented that includes the evaluation of strength properties of various types of soil using ordinary Portland cement (OPC), slaked lime and steel slag as pure agents and blended binders. The specimens were collected in Southern Sweden and included sandy silty tills and clay till (clay content 6–18%). The preprocessing included the mineralogical analysis of mineral composition and soil structure by X-ray diffraction (XRD) and a sieve. The soil samples were fabricated, compacted, rammed, stabilised by six binder blends and assessed for uniaxial compressive strength (UCS). The moisture condition value (MCV) and water content tests were done for compacted soil and showed variation in the MCV values for different binders. The study determined the effects from binder blends on the UCS gain in three types of soil, measured on days 7, 28 and 90. Positive effects were noted from the steel slag/lime blends on the UCS gain in sandy silty tills. A steel slag/slaked lime mixed binder performed better compared to the pure binders. The effectiveness of the simplex lattice design was demonstrated in a series of ternary diagrams showing soil strength evaluated by adding the stabilising agents in different proportions.