Stress–Strain Responses of Calcium Fly Ash

Abstract

The paper aimed to present the stress–strain and yielding response of dry and wet molded calcium fly ash in connection with the deformation characteristics at small strains for different stress paths and stress states. Moreover, these responses were compared with the characteristics of reference soils: quartz sand and kaolin. The physical properties of fly ash and natural soils were presented, then tests of K0 and isotropically consolidated drained triaxial extension and compression stress paths were performed on all three types of soils to investigate the elastic and yielding response of soils. The results of laboratory tests confirmed that the fly ash had higher shear and bulk modulus values than reference soils and brittle damage of fly ash occurred at lower strains, independently of the sample forming and consolidation method. In addition, there were visible differences in the shape and size of Y1−Y4, the yielding surfaces of the tested soils. The Y4 zone was not identified in all paths in each of the soil samples. The fly ash samples exhibit stiffness anisotropy. It was also proved that the method of preparation for the fly ash samples had an impact on the stiffness of this material, which was shown based on triaxial tests and scanning electron microscope (SEM) micrographs.