Archer de Carvalho Tomás, Gaspar Florindo, Marques Ana C, Mateus Artur
Centre for Rapid and Sustainable Product Development, Polytechnic of Leiria, 2430-028 Marinha Grande, Portugal.
Centre for Rapid and Sustainable Product Development, School of Technology and Management, Polytechnic of Leiria, 2430-028 Marinha Grande, Portugal.
Materials (Basel). 2023 Mar 29;16(7):2741. doi: 10.3390/ma16072741.
The widespread use of geopolymer cement (GPC) has been hindered by a lack of scientific knowledge that still exists regarding its synthesis process. Key points, such as the release of aluminosilicate species from the raw materials and its link to the properties of GPC, have still not been completely studied. As a result, most of the GPC formulations covered in the literature are based on precursors' elemental analysis using XRF (X-ray Fluorescence), or other equivalent analysis methods, and consider that the total aluminosilicate content of the precursors is available for participating in the geopolymerization process, which seems very unlikely. In this study, the amounts of aluminate and silicate species released from metakaolin (MK), electric arc furnace slag (EAFS), and biomass fly ash (BFA) in alkaline dissolution tests were determined by simple spectrophotometric methods. It was found that MK yields the highest aluminosilicate dissolution amount, about 2.1 mmol of silicate + aluminate per gram of MK, while EAFS and BFA yield about 0.53 and 0.32 mmol/g precursor, respectively. These results were used to estimate the total amounts of dissolved aluminosilicates in a series of GPC mortars prepared from these raw materials, which were thereafter subjected to mechanical tests. It was shown that the mortars' compressive strength (which ranged from 1 to 63 MPa) is linearly correlated with their estimated total amount of dissolved aluminosilicates, with the best linear fit yielding a coefficient of determination above 0.99. It was concluded that by using the results of the dissolution tests, the estimation of compressive strength is greatly improved when compared to using the elemental analysis obtained by XRF, which yields a coefficient of determination of 0.88 and a larger dispersion of data points. The results reveal the usefulness of this simple method for evaluating the potential of inorganic industrial waste streams as precursors for GPC.
地质聚合物水泥（GPC）的广泛应用受到阻碍，因为目前对于其合成过程仍缺乏科学认识。一些关键问题，如原料中硅铝酸盐物质的释放及其与GPC性能的联系，仍未得到充分研究。因此，文献中报道的大多数GPC配方是基于使用X射线荧光光谱仪（XRF）或其他等效分析方法对前驱体进行元素分析，并认为前驱体中的总硅铝酸盐含量可用于参与地质聚合过程，但这似乎不太可能。在本研究中，通过简单的分光光度法测定了偏高岭土（MK）、电弧炉渣（EAFS）和生物质飞灰（BFA）在碱性溶解试验中释放的铝酸盐和硅酸盐物质的量。结果发现，MK产生的硅铝酸盐溶解量最高，每克MK约为2.1 mmol的硅酸盐 + 铝酸盐，而EAFS和BFA分别产生约0.53和0.32 mmol/g的前驱体。这些结果用于估算由这些原料制备的一系列GPC砂浆中溶解的硅铝酸盐总量，随后对这些砂浆进行力学测试。结果表明，砂浆的抗压强度（范围为1至63 MPa）与其估算的溶解硅铝酸盐总量呈线性相关，最佳线性拟合的决定系数高于0.99。研究得出结论，与使用XRF获得的元素分析结果相比，使用溶解试验结果可以大大提高抗压强度的估算精度，XRF分析的决定系数为0.88，数据点的离散度更大。结果揭示了这种简单方法在评估无机工业废物流作为GPC前驱体潜力方面的实用性。
