olivine-based cements- basic research for CO2-neutral binders

众所周知，使用石灰石和热能生产水泥会导致大量二氧化碳排放。然而，在初步研究中开发了一种粘合剂材料，其不依赖于与高温燃烧过程结合使用石灰石，因此可以在没有CO2排放的情况下生产粘合剂。这种生产是基于研磨富含橄榄石的岩石而无需额外的工艺步骤。这种粘合剂的水合作用非常缓慢，但可以通过高温固化和添加puzzolana来加速。总之，与传统水泥相比，粘合剂生产更简单，更环保，但混凝土生产需要额外的努力和能源，这与高温固化过程有关。使用橄榄石基粘结剂可以获得高达60 MPa的抗压强度，这与传统水泥相当。该研究提案的目的是为进一步开发此类粘合剂提供可靠的科学依据。这包括在三个方面的调查：详细描述的水化过程中，识别的关键动力学步骤，碳酸化。(1)水化的细节，如识别和表征的水化产物取决于粘合剂的组成和物理条件将进行调查。这些结果使得水化的化学方程式的配方，并提供数据的水化程度取决于时间，温度和粘合剂的组成。除水化程度外，还分析了水化过程中孔溶液组成、微观结构和比表面积等其他性质。这些更多的现象学信息在第（2）节中用于确定关键的动力学步骤。这需要另外分析离析物的溶解速率和产物的沉淀速率作为溶液组成的函数。在工作程序的第一部分中获得的与孔溶液组成和表面积相关的数据的整合允许决定离析物的溶解、产物的生长或运输是否是限制水合的更快进展的关键动力学步骤。这些结果可用于鉴定水化反应的加速机制。最后，在第（3）部分进行了碳化实验。这是一个重要的信息，如果橄榄石基粘合剂可以与CO2反应，并结合它在稳定的反应产物。这将使二氧化碳排放行业转变为二氧化碳吸收行业，因为在粘合剂生产过程中没有显著的二氧化碳排放。在这种情况下，水泥工业可能会从大气中去除生产石灰石水泥时排放的二氧化碳。

It is well-known that production of cements using limestone and thermal energy results in massive CO2 emissions. However, a binder material was developed in preliminary research which does not rely on the use of limestone in combination with a high temperature burning process and thus the binder can be produced without CO2-emissions. This production is based on grinding olivine-rich rocks without additional process steps. The hydration of such binders is very slow but can be accelerated by elevated temperature curing and addition of puzzolana. In conclusion, the binder production is simpler and much more environmentally friendly compared to traditional cement but concrete production demands additional efforts and energy which is associated to the elevated temperature curing process. A compressive strength of up to 60 MPa can be obtained with olivine-based binders which is comparable to traditional cements. The aim of this research proposal is to provide a reliable scientific basis for a further development of such binders. This includes investigations in three areas: detailed description of the hydration process, identification of the critical kinetic step, carbonation. (1) Hydration details such as identification and characterization of hydration products depending on binder composition and physical conditions will be investigated. These results enable the formulation of a chemical equation for the hydration and provide data for the degree of hydration depending on time, temperature and binder composition. In addition to the degree of hydration, other properties such as pore solution composition, microstructure and specific surface area are analyzed during hydration. These more phenomenological information are used in section (2) for the identification of the critical kinetic step. This requires additionally the analysis of dissolution rates of the educts and precipitation rates of the products as a function of solution composition. An integration of data related to pore solution composition and surface area obtained in the first section of the working program allows the decision if dissolution of the educts, growth of the products or transport are the critical kinetic step limiting a faster progress of the hydration. These results can be used for the identification of acceleration mechanisms for the hydration reaction. Finally, carbonation experiments are conducted in section (3). It is an important information if olivine-based binders can react with CO2 and bind it in stable reaction products. This would allow the transformation of a CO2-emmitting industry in a CO2-adsorbing industry, as there are no significant carbon dioxide emissions during binder production. In this case, the cement industry might remove CO2 from the atmosphere that was emitted earlier when producing limestone-based cements.