DISCRETE ELEMENT SIMULATIONS OF TRIAXIAL COMPRESSION TESTS OF CSA CEMENT-TREATED SAND

Abstract

The CSA cement is an eco-friendly material with fast-strength development. The general application of the CSA cement in the construction industry as a concrete part is well studied and used in situations where early strength is required such as tunneling. One of the relatively new scopes of research related to CSA cement is using it as binding material in soil stabilization. This thesis work studied the improvement of properties due to CSA cementation for geotechnical application. The experimental UU triaxial compression test was conducted to identify the mechanical properties of CSA cemented sand. The samples contain 3%, 5%, and 7% of the dry mass of sand cement content and tested at 1 day, 3 days, and 7 days dry curing. The output results of testing give an approximate relationship of material properties to cement content and curing time. To understand the underlying microscale physics of the cementation effect, a discrete element model (DEM) was used. The model was created and analyzed by PFC3D software and the cementation effect was reproduced by a build-in parallel bond contact model. The contact model properties were calibrated by matching the simulation results with experimental results represented as deviatoric stress vs axial strain curve. Suitable bonding properties were identified by collecting the simulation results with a large girth of possible combinations of properties and analyzing them. The calibration stage is extended by using python scripts which are used in data collection and analyzing stages. Finally, the corresponding properties of the parallel bond model were identified for different cement content and curing times. According to the result, it can be concluded that the radius multiplier could effectively represent CSA cement content and elastic modulus and strength properties of bonding material in the PFC3D model comparable with realistic concrete past properties. The results of the research could be used in the future to optimize and design problems of sandy soil cement stabilization.