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首页> 外文期刊>Cement and Concrete Research >Percolation due to overlapping ITZs in laboratory mortars? A microstructural evaluation
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Percolation due to overlapping ITZs in laboratory mortars? A microstructural evaluation

机译：实验室灰浆中的ITZ重叠导致渗流？微观结构评估

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In a commonly cited paper [Cem. Concr. Res. 22 (1994) 25], it was found that 28-day-old mortars of sand contents in excess of approx 48 percent by volume showed extra intruded pore space when examined by mercury intrusion porosimetry (MIP). The effect was attributed to 'percolation' of overlapping porous interfacial transition zones (ITZs), as modeled by a hard core/soft shell model. To examine the likelihood of this explanation, duplicate 28-day-old mortars were prepared with the same aggregate and cement using the same unusual mixing procedure and identical curing. The results of examination by backscatter mode SEM were not consistent with the ITZ interpretation. The hardened cement paste (hcp) in all mortars was found to consist of patches of brighter, dense, almost nonporous regions and dark, highly porous patches; the patches indifferently occupying both classical 'ITZ' and classical 'bulk' locations. Many sand grains were surrounded or partly surrounded by dense, almost nonporous hcp. The porous regions appeared to be visibly capable of supporting ready fluid transmission. In the lower sand content mortar, the porous regions were limited in extent and isolated from each other. In the higher sand content mortars, originally considered to percolate by virtue of overlapping ITZs, the proportion of porous hcp was greater and the porous hcp patches were visibly interconnected across the bulk of the mortar. Examination of recovered specimens of the original mortars, now 8 years old, showed the same microstructural features as these duplicate 28-day-old mortars. If percolation does in fact occur in the higher sand content mortars studied, it likely results from the interconnection or overlap of the coarsely porous hcp patches and not from overlap of ITZs.
机译：在通常引用的论文中[Cem。确认Res。 22（1994）25]，发现用汞压入孔隙率法（MIP）检查时，28天龄砂浆的砂含量超过48％（按体积计）显示出额外的压入孔隙空间。如硬核/软壳模型所模拟的，该效应归因于重叠的多孔界面过渡区（ITZ）的“渗滤”。为了检验这种解释的可能性，使用相同的集料和水泥，使用相同的不同寻常的混合步骤和相同的固化方法，制备了重复28天的砂浆。反向散射SEM的检查结果与ITZ解释不一致。发现所有砂浆中的硬化水泥浆（hcp）均由较亮，密集，几乎无孔的区域和深色，高孔隙率的块组成。这些补丁无异地占据了经典的“ ITZ”和经典的“大宗”位置。许多沙粒被致密的，几乎无孔的hcp包围或部分包围。多孔区域似乎明显能够支持流体的即时传输。在含沙量较低的砂浆中，多孔区域的程度受到限制并且彼此隔离。在含砂量较高的砂浆中，最初被认为是通过重叠的ITZ渗滤的，多孔hcp的比例更大，并且多孔hcp补片在整个砂浆中可见地相互连接。现在已经使用了8年的原始灰浆的回收标本进行了检查，显示出与这些重复使用28天的灰浆相同的微观结构特征。如果实际上在研究的含砂量更高的砂浆中确实发生了渗滤，则可能是由于粗孔hcp补片的互连或重叠而不是ITZ的重叠造成的。

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