| This research investigates the use of two nontraditional stabilizers, recycled gypsum produced from sheetrock and a sodium silicate solution, to enhance the strength of two types of clay soils, bentonite and kaolinite. Three different stabilizer combinations are assessed during this study: (1) gypsum only, (2) sodium silicate only, and (3) a 50/50 combination of gypsum and sodium silicate. For both of the clay minerals that were stabilized, as well as the three stabilizer combinations that are denoted above, four levels of additive stabilization were explored, at 3%, 6%, 9% and 12%. After stabilization, prepared specimens were subjected to various curing intervals, including 0, 3, 7, 14, 28 and 56 days of curing, and unconfined compressive strength (UCS) testing was conducted to determine the strength development with curing time for each of the stabilized soil mixtures. The UCS test results demonstrate that the use of powdered recycled gypsum, a sodium silicate solution, and their combination all considerably increased the strength of both stabilized clay soils. Additional microstructural characterization tests including X-ray diffraction (XRD), field emission scanning microscopy (FESEM), energy-dispersive X-ray analysis (EDAX), Fourier transform infrared spectrometry (FTIR), and the nitrogen-based Brunauer-Emmet-Teller (N2-BET) test were used to develop an understanding of the chemical mechanisms of soil stabilization at the micro-level, and to assess changes in the soil microstructure as soil stabilization progressed with curing time. The results from the microstructural analysis testing that was performed support the gains in strength that were observed in the UCS testing. |
