Stabilizing soft clay soil using nano-modified cementitious binders, basalt fiber pellets, and a novel geosynthetic composite
Loading...
Date
2023-03-22
Authors
Eissa, Abdalla
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Constructing on soft clay entails engineering challenges, such as significant volumetric changes and/or differential settlements. Hence, a prompt solution, like chemical stabilization which effectively imparts additional strength and durability, is needed for this problematic soil. While lime is the commonly preferred choice, it is prohibited in many regions, including Manitoba, Canada, due to environmental concerns about groundwater quality and vegetation. Hence, it is imperative to find innovative alternatives.
The first part of this thesis investigated the effects of nano-modified cementitious additives, comprising cement, slag, and nano-silica, on the properties of soft clay at optimum moisture content under reference (22±2°C) and cold (+5°C) temperatures representing different periods of the construction season. The second part investigated using higher binders’ proportions with a wide range of water contents simulating wet conditions in the field. Subsequently, promising stabilizing binders were reinforced with a novel type of fiber (basalt fiber pellets) to achieve a balanced mechanical and durability behavior at a lower binder content. The mechanical properties (e.g., California Bearing Ratio, compressive strength, unconsolidated-undrained triaxial behavior) and the durability performance (freezing-thawing resistance) of treated soft clay were assessed along with microstructural analyses. In the last part of the thesis, a new geosynthetic composite containing a reinforcement layer (geogrid) to provide stiffness and volumetric control, and a filtration layer (geotextile), has been investigated by conducting large-scale pullout and direct shear tests. Furthermore, a numerical study using SIGMA/W (GeoStudio software) was carried out to predict the behavior of the new composite in a full-scale pavement application.
The synoptic results of this thesis showed that stabilizing the soft clay using nano-modified ternary binders presents a viable option for field applications with the possibility of extending the construction season in cold regions during fall and spring periods due to the synergistic effects of combining variable reactivities and multiscale materials. Additionally, incorporating the basalt pellets provided further skeletal rigidity and reduced the required binders’ content. Lastly, the proposed novel geocomposite granted significant interaction improvements (adhesion and internal friction angle) and enhanced the long-term behavior by providing a higher Traffic Benefit Ratio under cyclic loading.
Description
Keywords
Soft clay, Cement, Slag, Nano-silica, Statistical Analysis, Cold weather, Pullout, Direct Shear, Geosynthetics