Valorization of marble powder wastes using rice husk ash to yield enhanced-performance inorganic polymer cements: Phase evolution, microstructure, and micromechanics analyses
Valorization of marble powder wastes using rice husk ash to yield enhanced-performance inorganic polymer cements: Phase evolution, microstructure, and micromechanics analyses
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DOI：
10.1016/j.clet.2022.100461
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发表时间：
2022-03
影响因子：
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通讯作者：
E. Kamseu;A. Akono;R. Rosa;A. Mariani;C. Leonelli
中科院分区：
文献类型：
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作者：
E. Kamseu;A. Akono;R. Rosa;A. Mariani;C. Leonelli
可持续发展面临的挑战目前正在限制科学家和决策者考虑需要低能耗和低排放的替代材料和工艺，同时优先考虑当地材料和工业废物回收。本研究探讨如何利用大理石废弃粉末来设计一种新型的无机聚合物水泥。这些粉末是全球最重要的固体废物之一，在意大利撒丁岛，它们造成了处理问题。当这些富含硅酸钙水合物（C-S-H）相的粉末被掺入地质聚合物合成中时，这产生C-S-H和碱金属铝硅酸盐水合物（M-A-S-H）系统之间的混合物，这是本研究的焦点。详细地说，C-S-H系统是用各种Ca/Si比制备的，包括CS、C2 S和C3 S。采用X射线衍射、傅里叶变换红外光谱、扫描电子显微镜、沿着密度法（压汞法）、宏观力学测试法（弯曲强度测试）和纳米级力学测试法（压痕测试和划痕测试）对材料的微观结构和力学性能进行了研究。所得的无机聚合物水泥表现出含有钠-钙-铝-硅酸盐水合物N-C-A-S-H的无定形相和结晶相。当二氧化硅含量从CS到C3 S降低时，以及当C-S-H分数增加时，结晶相的分数增加。反过来，结晶相决定了孔结构和机械性能。具体而言，观察到具有低孔隙率的均匀且致密的微观结构。弯曲强度范围为5.8至8.7 MPa，弹性模量范围为10至17 GPa，断裂韧性范围为0.23至0.48 MPa m1/2。通常，硅酸钙水合物的二氧化硅百分比越低，硅酸钙水合物的分数越高，抗弯强度、弹性模量和断裂韧性越高。观察到的硬化、强化和韧化的潜在机制是铝在C-S-H缺陷位点中的插入以产生C-A-S-H，沿着由过量的胶体二氧化硅形成硅酸钠凝胶，这有助于减少凝胶孔和基质致密化。孔隙率，密度和机械性能的值表明，来自大理石废料的无机聚合物水泥是创新的低温和低密度粘合剂的有前途的候选人，具有低碳足迹，满足可持续发展和当地材料概念的要求。
The challenge for sustainable development is now constraining scientists, and policymakers to consider alternative materials and processes requiring low energy consumption and low emissions while prioritizing local materials and industrial waste recycling. This study investigates ways to valorize marble waste powders to design a new class of inorganic polymer cement. These powders are among the most important solid wastes globally, and in the Italian island of Sardinia they create a disposal problem. When these powders, which are rich in calcium silicate hydrate (C–S–H) phases, are incorporated into the geopolymer synthesis, this gives rise to a mix between C–S–H and alkali metal aluminosilicate hydrate (M-A-S-H) systems that are the focus of this study. In detail, C–S–H systems are prepared with various Ca/Si ratios, including CS, C2S, and C3S. The microstructure and mechanical properties are investigated using X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy, along with density methods (mercury intrusion porosimetry), macroscopy mechanical testing methods (flexural strength tests) and nanoscale mechanical testing methods (indentation testing and scratch testing). The resulting inorganic polymer cements exhibit both an amorphous and a crystalline phase containing sodium-calcium-aluminum-silicate hydrate N–C-A-S-H. The fraction of the crystalline phase increases when the silica content decreases, from CS to C3S, and when the C–S–H fraction increases. In turn, the crystalline phase dictates the pore structure and mechanical properties. Specifically, a homogeneous and compact microstructure with low porosity is observed. The flexural strength ranges from 5.8 to 8.7 MPa, the elastic modulus ranges from 10 to 17 GPa, and the fracture toughness ranges from 0.23 to 0.48 MPa m1/2. In general, the lower the silica percentage of the calcium-silicate hydrates and the higher the fraction of calcium silicate hydrate are, the higher the flexural strength, elastic modulus, and fracture toughness. The underlying mechanism for the observed stiffening, strengthening, and toughening is the insertion of aluminum in the C–S–H defect sites to yield C-A-S-H, along with the formation of sodium silicate gel from excess colloidal silica, which contributes to the reduction in gel pores and matrix densification. The values of porosity, density, and mechanical properties suggest that inorganic polymer cements derived from marble wastes are promising candidates for innovative low-temperature and low-density binders with low carbon footprint satisfying both the requirements of sustainability and the local material concept.