Abstract
The building sector accounts for approx. 40% of total energy consumption and approx. 36% of all greenhouse gas emissions in Europe. As the EU climate targets for 2030 call for a reduction of greenhouse gas emissions by more than half compared to the emissions of 1990 and also aim for climate neutrality by 2050, there is an urgent need to achieve a significant decrease in the energy use in buildings towards Nearly Zero-Energy Buildings (nZEBs). As the energy footprint of buildings includes the energy and greenhouse gas consumption both in the construction phase and during service life, nZEB solutions have to provide energy-efficient and less carbon-intensive building materials, specific thermal insulation solutions, and a corresponding design of the nZEB. Carbon reinforced concrete (CRC) materials have proven to be excellent candidate materials for concrete-based nZEBs since they are characterized by a significantly lower CO2 consumption during component production and much a longer lifecycle. The corresponding CRC technology has been successively implemented in the last two decades and first pure CRC-based buildings are currently being built. This article presents a novel material system that combines CRC technology and suitable multifunctional insulation materials as a sandwich system in order to meet future nZEB requirements. Because of its importance for the life cycle stage of production, cost-efficient carbon fibers (CF) from renewable resources like lignin are used as reinforcing material, and reinforcement systems based on such CF are developed. Cutting edge approaches to produce ultra-thin lightweight CF reinforced concrete panels are discussed with regard to their nZEB relevance. For the life cycle stage of the utilization phase, the thermal insulation properties of core materials are optimized. In this context, novel sandwich composites with thin CRC layers and a cellular lightweight concrete core are proposed as a promising solution for façade elements as the sandwich core can additionally be combined with an aerogel-based insulation. The concepts to realize such sandwich façade elements will be described here along with a fully automated manufacturing process to produce such structures. The findings of this study provide clear evidence on the promising capabilities of the CRC technology for nZEBs on the one hand and on the necessity for further research on optimizing the energy footprint of CRC-based structural elements on the other hand.
Highlights
The European Green Deal defines the goal of the European Union being the first climate-neutral continent by 2050
While the energy consumption of buildings strongly depends on the climate and local weather conditions, other aspects result from the selection of appropriate materials and technical components for a successful implementation of Nearly Zero-Energy Buildings (nZEBs) envelopes
The carbon reinforced concrete (CRC) technology is very promising in this context since it drastically reduces the energy and greenhouse gas consumption in the construction phase
Summary
The European Green Deal defines the goal of the European Union being the first climate-neutral continent by 2050. The thickness of a steel reinforced concrete façade of 8–10 cm can be reduced to 3 cm thickness [10] This makes CRC a promising technology to decrease greenhouse gas emissions during the building phase. The production of “green” fibres based on renewable raw materials such as lignin is a new way to open up the market for the construction industry This will provide a sustainable and at the same time cost-effective fibre alternative [22,23,24]. Material reduction using material substitution (fibre level and insulation level) and structural optimization of the reinforcement geometry will be examined in detail along with the development of an associated manufacturing process for the automated and resource-efficient mass production of nZEB façade elements. The consequent use of those highperformance materials with low-cost raw materials will result in lightweight, adaptable, and material-efficient building components
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