Innovative methods for Portland cement mortar and concrete fabrication with CDG and CDV soils

Abstract

Completely decomposed granite (CDG) soil and completely decomposed volcanic (CDV) are typical and abundant in-situ weathered soils on the ground which are worldwide distributed. This thesis investigates the possibility of using CDG and CDV soils as sources of aggregates and additives for the fabrication of concrete. A novel washing and sieving method for separating the CDG and CDV soils into their constitutional particles including gravel, sand, silt, and clay. The geometrical, physical, and chemical properties of CDG and CDV sands used as fine aggregates CDG gravel used as coarse aggregates, and CDG silts used as concrete filler are thoroughly examined in accordance with relevant standards. The mechanical characteristics including density, compressive strength, and elastic modulus of concrete incorporating these materials as aggregates or fillers are also investigated. Results illustrate that the properties of gravel, sand, and silt extracted from the CDG and CDV soils can all basically meet the requirements of standards. The mechanical properties of concrete using these materials show that the utilization of them can significantly enhance the performance of concrete. These findings demonstrate that the gravel, sand, and silt from CDG and CDV soils can be considered as alternative aggregates and concrete fillers in the concrete manufacturing industries. Another aspect of this thesis focuses on the effectiveness of high compression pressure applied to the initial fluid mixture of concrete materials. The initial pressure application can remove the excess void and air within the fresh mortar and concrete, thereby enhancing the mechanical properties of them. Two self-designed experimental apparatuses are used for the pressure application. CDG soil without further treatment is used as an alternative aggregate for concrete in this research. The mechanical properties including density, compressive strength, and water absorption of high-pressurized concrete with different fine aggregates are studied. Results show that the initial pressurization can substantially enhance the properties of concrete materials using CDG soil or sand as fine aggregate, providing a reference for using initial compaction pressure to the fresh mixture to manufacture high-performance mortar and concrete.