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

点击翻译按钮获取中文摘要

Abstract This research initiative is to investigate the potential for usingsynchrotron X-ray and neutron diffraction and Raman spectroscopy to measure micro- and meso-scale strains in concrete materials. This is a collaboration leadby Tennessee Technological University (TTU). Oak Ridge National Laboratory (ORNL) and theNational 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 neutrondiffraction and laser Raman spectroscopy to make measurements of micro-scale strains understresses generated mechanically in Portland cement-based materials. Stressors will be applied byin situ loading and diffraction measurements made to establish the stress states of variouscrystalline phases including calcium hydroxide (CH), unreacted cement phases and aggregatephases. An attempt will be made to make similar measurements on hydration product phases thatare suitably crystalline including monosulfate and those of the hydrogrossular series (C3AH6 toC3AS3). Observations of the effect of stressors on the less crystalline hydration productsincluding 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 ofmechanically induced deformations will also be made using environmental scanning electronmicroscopy (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 inconcrete has broad reaching application-based implications. The results will be useful to study the impact that chemical modification of the cementhas on alkali-silica interaction induced stresses, prediction of cracking, durabilityand performance as they relate to interactions such as sulfate, alkali-silica, freeze-thaw and otherenvironmental stressors.