Quantitative Evaluation of Microstructure in Cement Pastes by Second-Order Stereology

二阶体视学定量评价水泥浆体的微观结构

基本信息

批准号：
18560449
负责人：
IGARASHI Shinichi
金额：
$ 2.5万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

1. The two-paint functions for unhydrated cement and coarse capillary pores were not influenced by the magnification of the SEM examination. The magnification generally used in the backscattered electron image analysis for cement pastes covers sufficient area as the representative volume element, which is necessary for unbiased evaluation of the amount of each constituent phase Continuity of a phase could be characterized by the lineal path function. Reduction in the continuity for cement particles and capillary pores was expressed as decreases in the lineal path function with time. The evolution of solid skeleton in the pastes was also represented by the increase in the path function. The distance of negative correlation in the two points cross function between cement particles and pores was greater at high water/cement ratios. The distance increased with time at high water/cement ratios whereas there was little increase in the distance at an extremely low/water cement ratio of 025. T … More hese tendencies reflect characteristics in the deposition of hydration products around unhydrated cement particles. At high water/cement ratios, the greater degree of hydration of cement resulted in the thicker layers of inner hydration products around the cores of unhydrated cement particles. This led to the greater distance of the negative correlation.2. Effects of bleeding and the addition of superplasticizer on spatial distribution of constituent phases in cement pastes were investigated by backscatter based SEM examinations. Heterogeneous distribution of the phases was observed in cement pastes with a water/cement ratio of 0.60. Such heterogeneity due to bleeding was not found in cement pastes with anti-washout admixture. Spatial features of microstructure and degrees of hydration of cement in the cement pastes with the admixture were almost the same as those in the middle part of a specimen without the admixture. Therefore, the middle part in the admixture-free specimen may be regarded as a representative area for the high water/cement ratio even when the bleeding occurs. Setting times of cement were apparently delayed by the addition of superplasticizer. However, degrees of hydration in cement pastes with the superplasticizer were greater than in a cement paste without the admixture. Furthermore, all the cement pastes with different dosages of the superplasticizer had the same lineal path function for the solid phase at the final setting times. It was confirmed by the two point function that cement pastes attained to the final set when certain continuity for solid phase was developed at microscopic scale.3. Microstructure revealed by SEM-BSE image analysis of cement pastes was compared with a simulated structure generated by the CEMEHYD3D hydration simulation model. The spatial dispersion of unhydrated cement particles was well simulated by the model. However, spatial features in capillary pore structure in the cement paste are not well represented by the simulation. This disagreement results from the differences in porosity as represented by the two methods. Only coarse pores are detected in the SEM examination while the total capillary porosity and its whole spatial structure are virtually simulated in the model. Care must therefore be taken in interpreting agreement of simulation models and their comparison with real microstructures. Less

1。未覆盖水泥和粗毛细血管孔的两杆功能不受SEM检查的放大倍数的影响。水泥糊的反向散射电子图像分析通常使用的放大倍数涵盖了足够的面积作为代表性体积元素，这对于对相位的每个组成相连续性的量无偏见是必要的，可以通过线性路径函数来表征。水泥颗粒和毛细血管孔的连续性的降低表示，随着时间的推移，线性路径函数的降低。粘贴中固体骨骼的演变也由路径函数的增加表示。在高水/水泥比下，水泥颗粒和孔之间的两个点交叉功能中负相关的距离更大。在高水/水泥比下的距离随着时间的增加而增加，而在极低/水泥比为025的距离几乎没有增加。t…更多这些趋势反映了在未溶解水泥颗粒周围水合产物沉积中的特征。在高水/水泥比下，水泥的水合更高，导致内部水合产物的较厚层围绕未氢氢水泥颗粒的核心。这导致了负相关的更大距离。2。通过基于反向散射的SEM检查研究了出血和添加超增塑剂对水泥糊中成分相的空间分布的影响。在水/水泥比为0.60的水泥糊中观察到了这些相的异质分布。在具有抗冲洗混合物的水泥糊中未发现由于出血引起的这种异质性。微观结构的空间特征和水泥水合物在带有混合物的水泥水泥水平几乎与没有混合物的试样中间部分相同。因此，即使发生出血，也可以将无掺杂标本中的中间部分视为高水/水泥比的代表性区域。显然，通过添加超级塑料剂来延迟水泥的设定时间。然而，具有超塑料剂的水泥糊中的水合程度大于没有混合物的水泥糊中。此外，所有具有不同剂量的超塑料剂量的水泥糊具有在最终设置时间的固相的线性路径函数相同的线性路径函数。两个点函数证实，当以微观量表开发固相的某些连续性时，将水泥粘贴到最后一组上。3。通过将水泥糊的SEM-BSE图像分析与Cemehyd3d水合模拟模型产生的模拟结构进行了比较，从而揭示了微观结构。该模型很好地模拟了未溶胀的水泥颗粒的空间分散。但是，水泥糊中毛细管孔结构中的空间特征并不能很好地代表模拟。这种分歧是由于两种方法表示的孔隙率差异而引起的。在SEM检查中仅检测到粗孔，而总毛细管孔隙率及其整个空间结构在模型中实际上是模拟的。因此，必须在解释模拟模型的一致性及其与实际微观结构的比较时要注意。较少的