Since the construction sector uses 50% of the Earth’s raw materials and produces 50% of its waste, the development of more durable and sustainable building materials is crucial. Today, Construction and Demolition Waste (CDW) is mainly used in low level applications, namely as unbound material for foundations, e.g., in road construction. Mineral demolition waste can be recycled as crushed aggregates for concrete, but these reduce the compressive strength and affect the workability due to higher values of water absorption. To advance the use of concrete rubble, Completely Recyclable Concrete (CRC) is designed for reincarnation within the cement production, following the Cradle-to-Cradle (C2C) principle. By the design, CRC becomes a resource for cement production because the chemical composition of CRC will be similar to that of cement raw materials. If CRC is used on a regular basis, a closed concrete-cement-concrete material cycle will arise, which is completely different from the current life cycle of traditional concrete. Within the research towards this CRC it is important to quantify the benefit for the environment and Life Cycle Assessment (LCA) needs to be performed, of which the results are presented in a this paper. It was observed that CRC could significantly reduce the global warming potential of concrete.

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Thermal transformations occurring during firing of recyclable concrete and hydrated Portland cement paste were monitored quantitatively by in situ and ex situ X‐ray diffraction, thermal analysis, and clinker microscopy. Reactions below 1150°C were dominated by either the decarbonation of calcium carbonates of the limestone aggregate fraction in the recyclable concrete or the low temperature decomposition of cement hydrates of the cement paste. Continued heating of the cement paste showed a rapid and extensive reaction of the free lime to form intermediate calcium silicate and aluminate phases such as belite, gehlenite, mayenite, and ye'elimite. The combination of free lime was less rapid in the dominantly limestone‐rich recyclable concrete. Similarly, subsequent melt and clinker phase formation (1250°C and higher) occurred more rapidly in the hydrated cement paste, indicating a positive contribution of cement hydrates to raw meal burnability. Reactions below typical cement clinkering temperatures were enhanced (1) by the intimate mixing of lime, silicate, and aluminate components in the hydrated cement and (2) by the elevated sulfate content that acted as flux and belite mineralizer. Lime formed in the thermal decomposition of portlandite (±450°C) was partially carbonated to calcite at temperatures below the onset of calcite decarbonation (±650°C).

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