Micro- and meso-scale strain measurements in cement-based materials

Tennessee Technological University, Cookeville TN

Investigators

Abstract

Abstract This research initiative is to investigate the potential for using synchrotron X-ray and neutron diffraction and Raman spectroscopy to measure micro- and meso- scale strains in concrete materials. This is a collaboration lead by Tennessee Technological University (TTU). Oak Ridge National Laboratory (ORNL) and the National Institute of Standards and Technology (NIST) are partners in the collaboration. A series of experiments will be conducted to explore the use of synchrotron X-ray and neutron diffraction and laser Raman spectroscopy to make measurements of micro-scale strains under stresses generated mechanically in Portland cement-based materials. Stressors will be applied by in situ loading and diffraction measurements made to establish the stress states of various crystalline phases including calcium hydroxide (CH), unreacted cement phases and aggregate phases. An attempt will be made to make similar measurements on hydration product phases that are suitably crystalline including monosulfate and those of the hydrogrossular series (C3AH6 to C3AS3). Observations of the effect of stressors on the less crystalline hydration products including ettringite and calcium silicate hydrate (C-S-H) will be made using Raman spectroscopy. A broad range of mechanical loads up to near failure will be explored. Direct observation of mechanically induced deformations will also be made using environmental scanning electron microscopy (ESEM) and an in situ load frame. The proposed development and demonstration of synchrotron- and neutron-based techniques to quantify meso- and micro-scale stress and strain behavior in concrete has broad reaching application-based implications. The results will be useful to study the impact that chemical modification of the cement has on alkali-silica interaction induced stresses, prediction of cracking, durability and performance as they relate to interactions such as sulfate, alkali-silica, freeze-thaw and other environmental stressors.