Synthesis and Reactivity Testing of Artificial Supplementary Cementitious Materials

Cement is the most produced construction material and due to its high CO2 emissions, cement production is responsible for around 8 % of global CO2 emissions [1]. A simple method to minimize this environmental impact is to replace cement clinker partially with supplementary cementitious materials (SCMs). SCMs can origin from different sources and can therefore show varying chemical and mineralogical compositions. Consequently, SCMs cover a broad range of compositions in the CaO – SiO2 – Al2O3 ternary diagram. Due to additional minor components that might be present in SCMs, their composition is even more complex. Hence, various SCMs show differences in reactivity and affect the properties of cement and concrete at the fresh and hardened state differently. To investigate the reactivity of various SCMs based on their compositions, powder samples, which contain the main oxides (CaO, Al2O3 and SiO2) in ratios aligned to real SCMs, are melted and quenched in air to produce a glassy product. In future synthesis, Fe2O3, MgO, Na2O and K2O will be added during the synthesis to depict more realistic SCM compositions. Synthesizing SCMs enables comparability due to easy adjustment of the particle size distribution and investigations of the effect of the minor components in SCMs on cement hydration. After characterization of the glasses, the R3 test [2] is used to determine their potential maximum reactivity. Next to the results of the R3 test, the degree of reaction of SCMs in hydrated cement pastes is an important parameter to characterize the performance of an SCM. Scanning electron microscopy combined with energy dispersive spectroscopy (SEM-EDX) and image analysis (IA) showed promising results for the quantification of the degree of reaction of SCMs in hydrated cement pastes [3]. However, the technique is difficult to use because of the high time expenditure and user skill level required. In a next step in this project, the synthesized and characterized SCMs will be hydrated with cement under different conditions. SEM-EDX and IA will then be used to analyze the degree of reaction of the various SCMs in the hydrated samples. This data will then serve as training data for a neural network, which is to be generated within this project. With this neural network, it should be possible to determine the degree of reaction of various SCMs under different hydration conditions based on SEM-EDX maps. Literature: [1] A. Favier et al., A sustainable future for the European Cement and Concrete Industry: Technology assessment for full decarbonisation of the industry by 2050, ETH Zurich, 2018. [2] F. Avet et al., Cem. Concr. Res. 2016, 85, 1. [3] P. T. Durdziński et al., Cem. Concr. Res. 2015, 73, 111.     «

Cement is the most produced construction material and due to its high CO2 emissions, cement production is responsible for around 8 % of global CO2 emissions [1]. A simple method to minimize this environmental impact is to replace cement clinker partially with supplementary cementitious materials (SCMs). SCMs can origin from different sources and can therefore show varying chemical and mineralogical compositions. Consequently, SCMs cover a broad range of compositions in the CaO – SiO2 – Al2O3 ter...     »