Amélioration des propriétés géotechniques des matériaux de fondations routières par un procédé de calcification

«ABSTRACT: The accelerated development of large cities has produced a series of new challenges, affecting the planning, construction and maintenance of infrastructure. The deterioration of Quebec's roads is one of the topics that has been widely discussed in recent years due to the increase in damage, population pressure and, above all, the high cost of maintenance. Many of the techniques for improving road performance involve the development of new road surfaces or repair procedures. Despite their good technical results, the application of most of these methods is quite complex and requires large budgetary sums to be implemented. In order to present an alternative to traditional solutions, this project introduces chemical calcification as a tool to control and reduce road damage. This technique offers simple compressive strength greater than that of conventional concrete and additional self-healing potential, which makes it possible to consider applications in a freeze-thaw context. Chemical calcification is a technique of induced precipitation of calcium carbonates from the addition of one or more chemicals to the soil. The precipitates form extremely strong bonds between soil particles providing improved strength and mechanical behavior. In order to provide the most effective result for the technique, the basic chemical reaction has been traced and several optimizations have been made, especially with regard to cure time and temperature. The activities of this project began with the selection of basic reagents, examining the role of each of them in the potential for soil calcification. In search of an optimal soil treatment protocol, an experimental plan based on curing time, reagent type and concentration, the preparation method and soil mineralogy was put into practice. For each variation made in the properties of the protocol, series of simple compression tests were carried out in order to define the most efficient paths. These optimizations generated very resistant and homogeneous soil samples with a texture close to concrete. From the optimal protocol, new series of samples were prepared in order to show the potential of chemical calcification in situations close to reality. Stresses such as freeze-thaw cycles, immersions and simulated precipitation were applied to the improved samples. The results of the tests confirmed the technical feasibility of the treatment: optimum compressive strength after 30 days of curing at 37 MPa, retention of rigidity after 30 freeze-thaw cycles, preserved solidity after 72 hours of immersion and resistance to rain erosion three times greater than untreated soil. Compressive strength results are approximately 10 times better than cement improvement. In addition, after 30 freeze-thaw cycles, they are 9 times greater than the soil-cement mixture subjected to 12 cycles.»