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

摘要本研究旨在探讨利用同步辐射X射线、中子衍射和拉曼光谱测量混凝土材料微观和细观应变的可能性。这是由田纳西理工大学（TTU）领导的一项合作。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在机械应力下的微观应变。应力源将通过原位加载和衍射测量来应用，以建立各种结晶相的应力状态，包括氢氧化钙（CH）、未反应的水泥相和骨料相。将尝试对水化产物相进行类似的测量，这些水化产物相是适当的结晶，包括单硫酸盐和氢钙铝榴石系列（C3 AH 6至C3 AS 3）。利用拉曼光谱观察应力源对钙矾石和水化硅酸钙（C-S-H）等结晶度较低的水化产物的影响，并探讨了直至接近破坏的各种机械载荷。直接观察机械引起的变形也将使用环境扫描电子显微镜（ESEM）和原位负载框架。提出的发展和示范的同步和中子为基础的技术，以量化中，微观尺度的应力和应变行为inconcrete具有广泛的应用为基础的影响。研究结果将有助于研究水泥化学改性对碱-硅相互作用应力的影响，以及与硫酸盐、碱-硅、冻融等相互作用应力相关的开裂预测、耐久性和性能。

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.