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Smart casting of concrete structures by active control of rheology

Periodic Reporting for period 3 - SmartCast (Smart casting of concrete structures by active control of rheology)

Reporting period: 2019-10-01 to 2021-03-31

Concrete production processes do not take full advantage of the rheological potential of fresh cementitious materials, and are still largely labour-driven and sensitive to the human factor. The ERC Advanced Grant project 'SmartCast' proposes a new concrete casting concept to transform the concrete industry into a highly automated technological industry. Currently, the rheological properties of the concrete are defined by mix design and mixing procedure without any further active adjustment during casting. The goal of the 'SmartCast' project is the active control of concrete rheology during casting, and the active triggering of early stiffening of the concrete as soon as it is put in place. The ground-breaking idea to achieve this goal, is to develop concrete with actively controllable rheology by adding admixtures responsive to externally activated electromagnetic frequencies. Inter-disciplinary insights are important to achieve these goals, including inputs from concrete technology, polymer science, electrochemistry, rheology and computational fluid dynamics. In the short term, achieving the active control of the pumping slip layer will have an immediate impact on concrete industry, as this can be applied on pump trucks without interfering with the elements to be cast. In the longer term, making possible concrete casting with active control of flow and stiffening will be a totally new paradigm for concrete industry. Moving from ‘passively’ relying on evolving properties of fresh concrete, to ‘actively’ controlling rheology and stiffening will revolutionize concrete industry and bring quality levels to higher standards. The developed active rheology control will also provide a fundamental basis for the development of future-proof 3D printing techniques in concrete industry. For society, it will mean more reliable construction, with less damage cases and less failures, while better preserving the environment (reduced carbon footprint, reduced noise and vibration levels, reduced exposure of technicians to safety and health risks).
Three different and promising routes of newly developed responsive polymers have been identiefied, of which two have led to experimentally confirmed breakthrough results. Because of the ongoing protection of Intellectual Properties Rights, the fundamental research progress achieved has not been disclosed yet in full detail yet. However, a patent application has been submitted, and is now entering the national phase. In parallel to the polymer routes, a fall-back route is also followed, studying the effect of electromagnetic fields on the rheological behaviour of cement paste with existing additional materials. Also in this route, breakthrough results have been obtained with nano magnetic particles (nMP) and with fly ash particles. While serving as a fall-back option at the materials level, these research actions fully contribute to the success of the main polymer routes by enabling the advancement and improvement of the special test set-ups with control features.

Besides the fundamental material developments, experimental set-ups for rheometry in specific field conditions (electromagnetic signal, electrochemical signal), formwork tightness investigations and pumping studies have been installed. The small pumping system (SPS) for studies at paste and mortar level has been equipped with advanced monitoring systems, including Ultrasound Velocity Profiling (UVP) and Electrical Impedance Tomography (EIT), and external control features.

A first critical internal evaluation workshop was organized on 1 October 2018. A second critical evaluation workshop was organized on 20 April 2021. In spite of some initial delay caused by recruitment efforts, and some more recent delays due to the covid-19 pandemia, the SmartCast project is progressing very well. Clear breakthrough results have been obtained. Further upscaling is ongoing. Due to the covid-19 pandemia, the end date of the project has been extended to 31 March 2022.
In current practice, concrete rheology cannot be actively controlled during processing and casting. The flowability of concrete is to a very large extent determined by its mix design and mixing procedure, without relevant means to intervene during casting. SmartCast is going beyond this state of the art, and develops concrete with actively controllable rheology, in order to automate and optimize formwork-based concrete casting operations. In short terms, SmartCast intends to develop Active Rheology Contol (ARC) and Active Stiffening Control (ASC) of cementitious materials. The main and groundbreaking route consist of the development of newly designed responsive polymers that can be added to the concrete in view of enabling active rheology control. Finally, it is expected that SmartCast will enable following control options:
- Active control of the slip layer in pumping pipes, substantially reducing pumping pressures,
- Active control of concrete rheology during flow in formworks,
- Active control of formwork leakage,
- Active stiffness triggering of the fresh concrete once it is in final position.
In spite of the many remaining challenges, a good application opportunity might be given by digital fabrication methods, including 3D printing. Within the relatively limited volume of a printing head, it will be more practical and realistic to provide control signals to modify the rheology of the fresh cementitious material when moving from pumping line to printed layer. As the rheological requirements in a pumping pipe and for a printed layer are significantly different, an active control of the material properties in the printing head would be a very efficient approach. Finding solutions to the remaining challenges will lead to marvelous opportunities in general, and for 3D printing more particularly.
Concrete pumping and casting on-site