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结剂材料，它不依赖于使用石灰石与高温燃烧过程相结合，因此可以生产出没有二氧化碳排放的粘结剂。这种生产是基于研磨富含橄榄石的岩石，而不需要额外的工艺步骤。这种粘结剂的水化速度非常慢，但可以通过高温养护和添加Puzzolana来加速。总而言之，与传统水泥相比，粘结剂生产更简单、更环保，但混凝土生产需要与高温养护过程相关的额外努力和能量。使用橄榄石基粘结剂可以获得高达60兆帕的抗压强度，这与传统水泥相当。本研究建议的目的是为进一步开发此类粘结剂提供可靠的科学依据。这包括三个方面的研究：水化过程的详细描述，关键动力学步骤的确定，碳化作用。(1)将根据粘结剂组成和物理条件调查水化细节，如水化产品的鉴定和表征。这些结果使水化的化学方程式得以表达，并提供了取决于时间、温度和粘结剂组成的水化程度的数据。除了水化程度外，还分析了水化过程中的其他性质，如孔溶液组成、微观结构和比表面积。这些更多的唯象信息在第(2)节中用来确定关键的动力学步骤。这还需要分析作为溶液组成的函数的排泄物的溶解速率和产物的沉淀速率。在工作计划的第一部分中获得的与孔溶液成分和表面积相关的数据的综合，使得能够确定排泄物的溶解、产物的生长或运输是否是限制水化更快进展的关键动力学步骤。这些结果可用于确定水化反应的加速机理。最后，在第(3)节进行了碳化实验。橄榄石基粘结剂能否与CO2反应并将其结合在稳定的反应产物中是一个重要的信息。这将允许二氧化碳吸收行业中的二氧化碳排放行业转型，因为在粘结剂生产过程中没有显著的二氧化碳排放。在这种情况下，水泥行业可能会从生产石灰石水泥时排放的大气中去除二氧化碳。

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.