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

摘要：本研究旨在探讨利用同步加速器x射线和中子衍射以及拉曼光谱测量混凝土材料微、中尺度应变的潜力。这是由田纳西理工大学（TTU）牵头的一项合作。橡树岭国家实验室（ORNL）和美国国家标准与技术研究所（NIST）是合作伙伴。将进行一系列实验，探索使用同步加速器x射线和中子衍射以及激光拉曼光谱来测量波特兰水泥基材料中机械产生的微尺度应变。应力源将通过原位加载和衍射测量来施加，以建立各种晶相的应力状态，包括氢氧化钙（CH），未反应的水泥相和聚集相。将尝试对水化产物相进行类似的测量，这些相具有适当的结晶性，包括单硫酸盐和氢盐系列（C3AH6至c3as3）。利用拉曼光谱观察应力源对钙矾石和水合硅酸钙（C-S-H）等低结晶水化产物的影响。将探讨范围广泛的机械载荷直至接近失效。机械诱导变形的直接观察也将使用环境扫描电子显微镜（ESEM）和原位荷载框架进行。提出的基于同步加速器和中子的技术的发展和示范，以量化混凝土中观和微观尺度的应力和应变行为，具有广泛的应用意义。研究结果将有助于研究水泥的化学改性对碱-硅相互作用诱导应力的影响，预测其开裂、耐久性和性能，因为它们与硫酸盐、碱-硅、冻融和其他环境胁迫有关。

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.