One of the main challenges in modern building materials research is achieving sustainable development and ecological optimization of building materials through the targeted use of renewable raw materials. Therefore, an essential part of the scientific investigations within the framework of this research project consisted of advancing classic reinforced concrete construction by researching hemp bast as a starting material for producing alternative reinforcement elements and developing resource-saving concretes. The objective in concrete production was to deliberately use low-emission binders to reduce the clinker content by up to 73 wt.-%. This approach aimed to develop sustainable concretes with various densities and porosities while minimizing their carbon footprint. As the embedded classic steel reinforcement is no longer sufficiently protected against corrosion due to the reduced use of clinker, using non-corrosive hemp bast fibers in combination with epoxy resins as starting materials for a new type of reinforcement presented a potential solution to this problem within the project. The first challenge in the project was determining all material parameters for hemp fibers as well as the reinforcing bars. The natural growth of the hemp plant results in single fibers with different morphologies that influence their material characteristics. These could be effectively determined using an approach to establish equivalent cross-sectional areas. Furthermore, through this evaluation method, the tensile strength and elastic modulus of the hemp fibers could be assessed which were derived from the stem of the industrial hemp plant, Cannabis Sativa L.. A further crucial focus of the research project was investigating the durability of the hemp fibers and the epoxy resins needed for reinforcing bars in alkaline environments. To this end, tests were conducted to analyze the tensile strengths and modulus of elasticity of samples exposed to varying alkaline conditions with different pH values. The results on the alkalinity of the three tested concretes indicated that high alkali resistance of the hemp fibers and the resin bound hemp fiber rods must be ensured, particularly immediately after installation and during the initial phase of use. Hemp fibers used as such for shrinkage reinforcement are particularly effective in preventing plastic shrinkage in highly porous concretes, like the highly insulating lightweight concrete (ÖkoLB) employed. The hemp reinforcement bars manufactured in a pultrusion process originally had a smooth surface. They were subsequently manually profiled to guarantee an effective bond between the bar and the embedding concrete. Four different profiling variations were validated through pull-out tests. Sand coating proved particularly effective as profiling in achieving sufficiently high bond stresses. The integration and implementation of profiling in the continuous pultrusion process is the subject of further interdisciplinary research. The successful use of the new construction material BasEcoCrete was demonstrated by the production of bending beams as demonstrators. The demonstrators achieved sufficient tensile load capacity with the hemp bast reinforcement bars. While the use of hemp in the construction industry still requires extensive research, such as fibers pretreatment and identification of disruptive factors in the pultrusion process, the current results indicate considerable potential for the future. The portfolio of climate-friendly and sustainable construction materials will grow with hemp reinforcement bars by one prospective promising candidate besides the established building materials, which will accelerate the conservation of resources. Introducing hemp bast fibers as an alternative, ecological fiber in concrete or as a replacement for steel bars is going to create a new value chain alongside the existing one in timber constructions. Compared to conventional concretes, the eco-concretes developed in this project have up to 64 % lower CO2 emissions. In addition, they improve the outstanding construction material of the 20th century by contributing to appealing and convenient applications in the future. Costs for CO2 emissions fees can be significantly reduced by the eco-concretes' improved environmental impacts and furthermore they ensure an attractive economically reliable material in future construction practice. By utilizing BasEcoCrete, the targeted promotion of renewable raw materials can occur, sustainably and significantly reducing climate-damaging carbon dioxide emissions.     «

One of the main challenges in modern building materials research is achieving sustainable development and ecological optimization of building materials through the targeted use of renewable raw materials. Therefore, an essential part of the scientific investigations within the framework of this research project consisted of advancing classic reinforced concrete construction by researching hemp bast as a starting material for producing alternative reinforcement elements and developing resource-sa...     »