EVALUATION OF CEMENT-TREATED SOILS SUBJECTED TO CYCLES OF FREEZING AND THAWING

Abstract

An extensive experimental study was performed to provide an insight on design and evaluation of cement-treated materials subjected to freeze/thaw (f/t) cycles. Poorly designed stabilized materials showed increases of up to three orders of magnitude in hydraulic conductivity and decreases of up to 95 percent in unconfined compressive strength values. Decrease in water to cement ratio was shown to partially improve f/t resistance for some of the scenarios investigated. A factorial experiment was designed to investigate the influence of curing time (immature vs. mature), freezing temperature (-2C vs -10C), and number of f/t cycles (4 vs. 12) during laboratory evaluation of a cement-treated silty sand. Results showed all the factors were significant in the observed changes in mechanical and hydraulic performance of the specimens. Observations emphasized the need for developing site-specific exposure scenarios in assessment of soil-cement under f/t exposure. An investigation on the influence of freezing dimensionality also showed a more practical three-dimensional f/t exposure can adequately represent a realistic one-dimensional f/t exposure scenario in terms of mechanical and hydraulic performance degradation. Monitoring percent mass loss (an indicator commonly used in industry) and compressive strength after f/t exposure under various scenarios showed they are not reliable indicators for predicting changes in hydraulic conductivity values under exposure to cycles of f/t. Resonant frequency measurements performed using the impact resonance method was suggested as a non-destructive technique in evaluation of hydraulic performance of cement-treated materials after f/t exposure. Microstructural evaluation of specimens using transmitted light microscopy showed matrix disruption and aggregate-paste interface cracking to be the main damage mechanisms for highly affected specimens. However, this technique was found unsuitable in detecting early stages of damage.