Project Details
Projekt
Development of low-CO2 binders based on material from burned coal mining dumps
Subject Area
Construction Material Sciences, Chemistry, Building Physics
Term
since 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 541767338
The aim of the project is to develop resource-saving, low-CO2 binders based on autogenously burned tailings from coal mining as an alternative resource in low-clinker and alkali-activated systems within the Priority Program Module 1 "Alternative and Climate-Neutral Binders". Hard coal was formed over millions of years from dead plant remains by the deposition of sedimentary layers and the associated increase in pressure and temperature. As a result, the tailings arose during coal processing consist mainly of shales, clay, sandstones, limestone, gypsum, coal and sulfur compounds. The BMU estimates the mass of tailings in the area of today's Germany that were stockpiled between 1792-2003 to be about 3.6 billion tons. For a potential use of the tailings as secondary raw material in the construction industry, this thus represents a considerable resource. Many of the tailings have been exposed to increased temperatures due to spontaneous combustion of the coal residues in the humps, resulting in the so-called "red earth", which is basically clay calcined at uncontrolled and unknown temperatures. Two approaches are being pursued with the use of material from burned tailings dumps in this project: First, the clinker factor in cement-based systems is to be reduced as much as possible, including the use of multicomponent systems. The mixtures will be preselected by thermodynamic modeling of the phase evolution and the model is to be validated and optimized. On the other hand, formulations based on clinker-free, alkali-activated systems will be developed. Here, mixtures will be preselected based on a model from an empirical approach from a preliminary work, which is to be validated and adjusted for the burned tailings and other alternative precursors used. The influence of different phase compositions on the reactions and the extent to which phases usually considered inert participate in the reactions will be investigated. As a basis for this, the influence of temperature on mineral phase formation will be investigated, since the burned tailings have a diverse and complex phase composition. In parallel, a suitable processing method for the enrichment of reactive components will be developed. The mineralogy will be linked to the processing-relevant properties as well as the pozzolanic reactivity and thus to the potential of the material for the use in the cement / concrete industry. In addition to understanding the reaction mechanisms, the findings from the research project should enable an estimation of the potential of the burned tailings and an efficient use as clinker / cement substitute or as precursor for alkali-activated binders.
DFG Programme
Priority Programmes
Subproject of
SPP 2436:
Net-Zero Concrete
