Submicroscopic Deformation in Cement Paste and Mortar at High Load Rates

摘要

Submicroscopic cracking and strain-rate response of cement paste and mortar under uniaxial compression were measured and correlated with applied strain. Cement paste specimens with water-cement ratios of 0.3, 0.4, 0,5, and 0,7 and mortar specimens with water-cement ratios of 0.3, 0.4, and 0.5 were subjected to monotonic load at strain rates ranging from 0.3 to 300,000 microstrain per second. Specimens were tested at ages ranging from 27 to 29 days. After loading, slices of material were removed from selected speciment for study at magnifications of 125x and 2500 x in a scanning electron microscope. Image analysis instrumentation was used in later stages of the study. Cracks on transverse and longitudinal surfaces were measured, and three-dimensional crack distributions were obtained from the crack data. The portion of the nonlinear material response caused by the cracks was estimated using a self-consistent material model. Cement pastes; Compression; Concretes; Cracking (fracturing), Electron microscopes; Image analysis; Isotropy; measurement; Microcracking; Microscopic; Microstructures; Mortars (material) strains; Strain rate; Stress; Stress-strain diagram. (jes)