Field stabilization of Ponca City shale /

Abstract

The microstructure of stabilized shale was studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM) in conjunction with energy dispersive spectroscopy (EDS). The non basal (hkl) reflections in stabilized oriented specimens suggest that the clay particles in the stabilized shale acquired high resistance to dispersive forces. SEM observations in conjunction with EDS, depicted the presence of some newly formed hydration products and a rather dense degree of packing. These characteristics are significant in improving strength and deformation characteristics of stabilized shale.

Analyses of the samples prepared during construction and those cored from under the pavement after construction showed significant amelioration of the engineering properties of stabilized shale as manifested in their plasticity and strength compared to raw (non-stabilized) shale. The improvement in strength was measured in terms of unconfined compressive strength, cohesion, angle of internal friction, and beam action. In addition Benkelman beam measurements obtained from the test sections also reflected higher deformation resistance (improved stability) of the stabilized section.

This study is an attempt to investigate the field implementation of shale stabilization on an experimental project. A number of test sections were set on the south bound lane of U.S. Highway 77, north of Ponca City, Kay County, Oklahoma. To compare the effectiveness of various stabilizing agents, the base courses of these test sections were stabilized with cement (14%), quicklime (4.5%), fly ash (25%), and an optimum mixture of 8% cement + 3% quicklime + 18% fly ash used conjunctively. Also a control (non-stabilized) section was set as a reference section.