Date of Award
Master of Science
Civil, Construction, and Environmental Engineering
Jeramy C. Ashlock
This study evaluated the shear strength behavior of bio-stabilized soils over a range of amended bio-monomer and biopolymer soil addition rates using Western Iowa loess and Ottawa 20/30 sand. The unconfined compressive strength and ductility of loess was characterized after adding 2% to 4% monomer. For Ottawa sand, the shear strength and volume-change behavior of specimens stabilized by three different biopolymers at concentrations of 1%, 2% and 4% was tested. All specimens were prepared at moisture contents of optimum or 2% dry of optimum. To determine the optimum moisture content of the loess material, a modified 2"Ã?4" compaction test was conducted to satisfy the specimen aspect ratio requirement.
The unconfined compressive strength of monomer-amended loess was decreased significantly within the first 7 days of curing, but increased compared to untreated soil over 28 days of curing time. Based on these results, the monomer shows some potential for providing strength and ductility benefits for loess after curing times of 28 days or more.
For the Ottawa 20/30 sand, the peak strength of polymer-amended specimens for a given normal stress was increased by 1.5 to 2 times that of untreated sand. The G54 polymer gave the best results with a peak shear strength 1.4 to 1.5 times that of the 8% cement-amended sand, but this was lower than the strength using 12% cement. However, the values of cohesion imparted by all three polymers were comparable to those resulting from 8% and 12% cement. The failure behavior of the sand was made more ductile by the polymer, and beneficial effects of polymer aging and healing abilities were discovered.
The strength of the cohesionless sand improved significantly in all polymer-amended specimens. The improved results from the G54 biopolymer compared to those from cement demonstrate the potential of biopolymer as a substitute for traditional stabilizers.
Guo, Liuhui, "Investigation of soil stabilization using biopolymers" (2014). Graduate Theses and Dissertations. 13909.