Circularity is often treated as a design principle or strategic ambition to improve resource efficiency, but in practice, many of its claims remain unverified and untraceable. Existing assessment methods typically focus on intended design strategies or modelled impacts, rather than demonstrating real-world outcomes. This paper introduces the concept of evidence-based circularity assessment as an alternative approach for shifting from intention to actionable outcome. Drawing on an analogy of two contrasting ‘circular’ coffee pod systems, it illustrates how the credibility of circularity claims depends on the presence of verifiable evidence, coordinated infrastructure, and traceable processes. Building on these insights, the paper proposes a conceptual framework for assessing circularity, structured around three interdependent elements: proof, process, and persuasion. Finally, the paper explores how these principles can be applied in the built environment, where supporting systems are needed to track, evaluate, and realize circular material flows. The approach aspires to support more transparent, accountable, and adaptive forms of circularity assessment in complex real-world settings.

When concrete is subjected to sustained load, it first deforms elastically and then continues to deform with time. The stress-induced time-dependent deformation is, by definition, creep. Creep plays an important role in view of the serviceability, durability and sometimes even the safety of concrete structures. Prediction of the long-term creep is still a challenge. Apart from the time-dependent deformation, the microstructure, strength and elasticity of concrete are also continuously changing under sustained load. This will, in turn, have an influence on the creep deformation. Micro-cracking has been detected experimentally by acoustic emission techniques during creep tests for concrete loaded at different stress levels. It could contribute to both an extra deformation and a reduction in the strength and elasticity. This is somehow contradictory to the experimental observation that there is an extra increase in strength (and elastic modulus) of concrete under sustained load, especially at low and medium stress levels, compared to load-free concrete. There must be another phenomenon during the creep process that "resolves" this contradiction. Despite a few theories which have been proposed in the paste to explain the extra increase in strength of concrete under sustained load, the mechanism behind this phenomenon has not been fully understood yet. Besides, how this extra increase in strength influences the long-term creep deformation has rarely been studied. In this research self-healing is considered as a promising mechanism to explain the extra increase in strength of concrete under sustained load. The main aim of this research is to study the effect of micro-cracking and self-healing on the long-term creep and strength development of concrete under sustained load and to gain a better understanding of the behaviour of concrete under sustained load.

In order to gain a better understanding of the interaction between creep and micro-cracking during long-term creep process, a theoretical study was performed. An existing lattice model was modified to take creep into account. Based on the model, the micro-cracking in the creep process was simulated on a three-phase concrete sample under sustained compressive load (30% of compressive strength). The effect of on-going hydration and self-healing were considered in this process and inserted in the modified lattice model. This paper contains preliminary results of numerical simulations of an on-going study. The results show that continuous micro-cracking contributes to an extra deformation and degradation of mechanical properties, even though the on-going hydration is involved. The effect of self-healing in the damage zone leads to a decrease in the extra deformation and also to the recovery of the compressive strength and elastic modulus.