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Effect of pulp mill fly ash and calcium bentonite on the mechanical and microstructural behavior of organic soil from Alberta, Canada

University of British Columbia

The high compressibility and low shear strength characteristics of organic soil are significant challenges for the infrastructure development in Canada and across the world as well. This research investigated the use of pulp mill fly ash (PFA), alkaline activator and calcium bentonite (Ca-bentonite) to improve the engineering behaviour of the organic soil consisting of 26% organic matter, obtained from the wetlands in Wabasca region, Northern Alberta, Canada. Cementitious materials such as lime, and Portland cement have been successfully used to improve the engineering properties of problematic mineral soils having low organic content. However, limited studies have been devoted to stabilization of organic soils commonly encountered in forested regions of Canada. Series of fall cone tests and one dimensional oedometer tests were carried out to evaluate the effect of PFA, alkaline activator and Ca-bentonite on the engineering behaviour of the stabilized organic soil. In addition to fall cone and oedometer tests, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) test were conducted on regular and stabilized organic soil to analysis the change in microstructure and chemical components of the soil after stabilization. The results showed that the strength and compressibility behavior of the organic soil can be improved when treated with PFA and Ca-bentonite. Moreover, a potential large settlement of the organic soil can be reduced by adding PFA and Ca-bentonite to the organic soil. The amount of secondary compression index (Cα) was decreased significantly when compared to untreated organic soil, indicating that the PFA and Ca-bentonite stabilizer can effectively improve the creep behavior of organic soil. However, within the scope of this work, use of alkaline activator did not show any improvement in engineering behavior of the stabilized organic soil. This study implies that beneficial utilization of PFA and Ca- bentonite for stabilization of soil organic matter in forests and lowlands could be a practical step towards environmentally sound management of this waste byproduct.

Text

2020-07-16

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/75189

Civil Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/