CO2-neutral biomass-based particle interactions for NET-ZERO concretes (BIOMAC) - experiments and modeling

The aim of the BIOMAC project is to develop_CO2-neutral concretes with environmentally friendly aggregates in combination with reactive binders, both based on carbonized biomass. The use of these_CO2-negative residues in cementitious systems makes it possible to significantly reduce the_{CO2 footprint} of future concrete systems in order to use them in an environmentally oriented construction industry.

In order to meet the necessary requirements in the construction industry, a comprehensive characterization of the residual materials to be used and dedicated research into their interactions in the material composite will be carried out in the first funding period. In order to achieve this goal with such low-strength starting materials, a packing density-optimized system, known from ultra-high performance concretes, will be used as a basis. The loads that are transferred via the SC in normal concrete must be transferred via the concrete matrix of strength-forming material bands (ribbons). These are made up of the strength-forming phases of the binder matrix and the contact zone (ITZ) binder-biochar aggregate. In order to develop these_CO2-neutral concretes up to their application in the second funding period, the Portland cement will first be partially substituted by reactive biomass ash at the TU Darmstadt (TUDa) and the GK by_CO2-negative biomass coals at the University of Kassel (UK), e.g. from the reducing combustion of residues from biogas production. In a subsequent joint step, these two approaches will be combined.

The research focus of TUDa is on the integration of biomass ashes as cement substitutes (SCM) at binder level and that of the UK on the integration of biomass aggregates in the cement-bound system. The joint research focuses on the interactions in the ITZ. A model approach is being developed to predict the interactions and mechanical behavior of the ITZ between the matrix and biomass aggregates. Experimental investigations are carried out to simulate the interaction between biomass chars (UK) and binder matrix (TUDa) in order to define the boundary conditions of the model. The model approach is based on a two-particle system, which culminates in a scalable BIOMAC-model-element. This will be extended experimentally and simulatively to a multi-particle system in cooperation with both project partners.

The results of the first funding period form the basis for a concrete technology upscaling to a future and environmentally oriented BIOMAC system in the second funding period. Furthermore, the BIOMAC results are to be interlinked with the three modules of the SPP2436 in the second funding period in order to identify possible paths for a new type of NET-ZERO concrete.