Investigation of the interphase between recycled aggregates and cementitious binding materials using integrated microstructural-nanomechanical-chemical characterization
Investigation of the interphase between recycled aggregates and cementitious binding materials using integrated microstructural-nanomechanical-chemical characterization
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DOI：
10.1016/j.compositesb.2018.09.041
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发表时间：
2019-02-01
影响因子：
13.1
通讯作者：
Turner, Joseph A.
中科院分区：
文献类型：
--
作者：
Khedmati, Mandieh;Kim, Yong-Rak;Turner, Joseph A.
与传统混凝土混合物相比，包括破碎再生骨料的混合物具有多个复杂的骨料/浆体界面区域，这在理解和表征其性能方面带来了重大的技术挑战。为了更好地了解这种复杂的材料组织，本研究采用了多尺度实验方法，通过使用纳米压痕测试分析，激光扫描显微镜和能量色散光谱。多尺度的方法被施加到两个不同的复合材料中，相同的再生骨料混合两种不同的水泥粘结剂：粉煤灰基地质聚合物和传统的波特兰水泥。试验分析结果表明，在水泥混凝土混合物与再生骨料（CCRA），预先存在的不完整的界面内的再生骨料观察，虽然新的膏体是相对较好的粘结到旧的再生骨料膏体具有约20 μ m厚的界面过渡区。在地聚合物混凝土混合物与再生骨料（GCRA），旧的和新的界面出现致密。更有趣的是，再生骨料中预先存在的不完全界面被填充在GCRA中，这不是从CCRA观察到的情况。使用能量色散光谱的进一步分析表明，地质聚合物材料可以达到预先存在的不完全界面，并产生结合了联合收割机硅酸钙水合物（C-S-H）和铝硅酸钠水合物（N-A-S-H）凝胶的水合地质聚合产物。由于界面区的存在，水泥基复合材料的力学性能将得到提高。
The mixtures including crushed recycled aggregates have multiple complex aggregate/paste interphase regions compared to conventional concrete mixtures, which brings significant technical challenges in understanding and characterization of their properties. To gain a better understanding of such complex material organization, this study adopted multiscale experimental methods by using nanoindentation test-analysis, laser scanning microscopy, and energy dispersive spectroscopy. The multiscale methods were applied to two different composites in which the same recycled aggregates were mixed with two different cementitious binders: a fly ash-based geopolymer and conventional Portland cement. The test-analysis results demonstrate that, in cement concrete mixtures with recycled aggregates (CCRA), the pre-existing incomplete interphase within the recycled aggregares was observed, although new paste was relatively well-bonded to the old recycled aggregate paste by having an approximately 20-mu m thick interfacial transition zone. In geopolymer concrete mixtures with recycled aggregates (GCRA), both the old and new interphase appeared dense. More interestingly, the pre-existing incomplete interphase within the recycled aggregates was filled in the GCRA, which was not the case observed from the CCRA. Further analysis using energy dispersive spectroscopy suggests that geopolymeric materials can reach the pre-existing incomplete interphase and create hydration-geopolymerization products that combine calcium-silicate-hydrate (C-S-H) and sodium aluminosilicate hydrate (N-A-S-H) gel. The resulting cementitious composite is expected to show enhanced mechanical properties owing to a better interphase region.