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Eingeladener Vortrag
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Introduction of a monitoring system for Bingham fluids in additive manufacturing with concrete
(2022)
Freeform additive manufacturing of concrete structures is a rising technology in civil engineering with several fascinating advantages. Nonetheless, to ensure reliability and structural integrity, standards and quality control are required in the future to bring this technology into the market. As the concrete is manufactured continuously, continuous quality control of the printing process is also required, i.e. comprehensive process monitoring. At BAM, a test rig will be installed, enabling the printing of concrete structures with a maximum size of 2 m x 1 m x 1 m (l x w x h). Here, process monitoring is the focus of the test rig. In this study, we show the results of the first pump tests, including the measurement of several parameters such as temperature and pressure along the supply system, i.e. from the concrete pump to the printer head.
Introduction of a monitoring system for Bingham fluids in additive manufacturing with concrete
(2022)
Freeform additive manufacturing of concrete structures is a rising technology in civil engineering with several fascinating advantages. Nonetheless, to ensure reliability and structural integrity, standards and quality control are required in the future to bring this technology into the market. As the concrete is manufactured continuously, continuous quality control of the printing process is also required, i.e. comprehensive process monitoring. At BAM, a test rig will be installed, enabling the printing of concrete structures with a maximum size of 2 m x 1 m x 1 m (l x w x h). Here, process monitoring is the focus of the test rig. In this study, we show the results of the first pump tests, including the measurement of several parameters such as temperature and pressure along the supply system, i.e. from the concrete pump to the printer head.
Long-term completely embedded sensor systems offer innovative possibilities for structural health monitoring of concrete structures. Measuring of relevant parameters, e.g., temperature, humidity, or indication of corrosion can be performed with low energy sensors. This allows to implement passive RFID sensor systems without cable connection and battery, which are power supplied exclusively by the electromagnetic field from the external reader device. To evaluate characteristics and conditions of this concept, a systematical investigation of the transmission characteristics with variation of relevant parameters, as communication frequency, installation depth, type of concrete, moisture content, etc. is currently carried out in an interdisciplinary research project at BAM. First results are presented in this paper.
Long-term completely embedded sensor systems offer innovative possibilities for structural health Monitoring of concrete structures. Measuring of relevant parameters, e.g., temperature, humidity, or indication of corrosion can be performed with low energy sensors.
This allows to implement passive RFID sensor systems without cable connection and battery, which are power supplied exclusively by the electromagnetic field from the external Reader device. To evaluate characteristics and conditions of this concept, a systematical Investigation of the transmission characteristics with variation of relevant parameters, as communication frequency, installation depth, type of concrete, moisture content, etc. is currently carried out in an interdisciplinary research project at BAM. First results are presented in this paper.
We have compared the performance of the typical Darr and CM moisture testing techniques, which are destructive with several non-destructive testing techniques on two types of floor screeds. In case of cement based screeds these destructive tests failed to deliver reliable results. Moreover, our measurements indicate significantly different drying and moisture transport behavior for the investigated cement based and calcium-sulphate based screeds. Whereas we have strong with depth decreasing moisture gradients in the CT material, we observe in the penetrated volumes of our ndt methods basically no clear moisture gradient in the CA samples. The findings with ndt methods could be supported by moisture gradient studies with nuclear magnetic resonance measurements.
Eight different screed types are tested including two different sample heights of 35 and 70 mm. The moisture of the four cement based and four sulphate based screeds are monitored during hydration and evaporation. All samples are stored in a climatic chamber at 23° C and 50 % relative humidity. Embedded sensors like temperature arrays, humidity sensor arrays, and multi-ring electrodes are embedded in the samples to yield a detailed moisture evolution with high depth resolution. Furthermore, nuclear magnetic resonance is used to quantify the water content at different depths. This multi-sensor approach allows a comprehensive monitoring of the moisture and its gradient in the different screed samples. This yields a deeper insight into the hydration, moisture convection, and diffusion processes.
Eight different screed types are tested including two different sample heights of 35 and 70 mm. The moisture of the four cement based and four sulphate based screeds are monitored during hydration and evaporation. All samples are stored in a climatic chamber at 23◦ C and 50 % relative humidity. Embedded sensors like temperature arrays, humidity sensor arrays, and multi-ring electrodes are embedded in the samples to yield a detailed moisture evolution with high depth resolution. Furthermore, nuclear magnetic resonance is used to quantify the water content at different depths. This multi-sensor approach allows a comprehensive monitoring of the moisture and its gradient in the different screed samples. This yields a deeper insight into the hydration, moisture convection, and diffusion processes.
To quantify the moisture in concrete, RFID based humidity sensors are embedded. Passive high frequency, ultra-high frequency RFID tags as well as active Bluetooth sensors are tested. After concreting, all sensors measure the corresponding relative humidity to monitor the concrete moisture. Two case studies are performed, embedding in an existing construction, i.e. the duraBASt test bridge, and embedding in cement based mortar in the laboratory. As basis for robust and long-life sensors in alkaline concrete, different casing materials are tested. Furthermore, signal strength measurements and their sensitivity to different moisture levels are performed.
To quantify the moisture in concrete, RFID based humidity sensors are embedded. Passive high frequency, ultra-high frequency RFID tags as well as active Bluetooth sensors are tested. After concreting, all sensors measure the corresponding relative humidity to monitor the concrete moisture. Two case studies are performed, embedding in an existing construction, i.e. the duraBASt test bridge, and embedding in cement based mortar in the laboratory. As basis for robust and long-life sensors in alkaline concrete, different casing materials are tested. Furthermore, signal strength measurements and their sensitivity to different moisture levels are performed.
Um den Feuchtegehalt von Fußbodenestrich vor der Verlegung von Holz- oder anderen
Bodenbelägen zu bestimmen, werden zerstörende Prüfverfahren wie die Calcium-Carbid
Methode (CM) oder das thermogravimetrische Darr-Verfahren eingesetzt. Diese liefern
jedoch einmalig nur punktuelle Informationen und sind je nach Estrichtyp auch störanfällig.
Zusammen mit Partnern aus Forschung und Industrie wurde an der BAM ein Ringversuch
durchgeführt, dessen Ziel es war, verschiedene nach Möglichkeit zerstörungsfreie oder –
arme Prüfverfahren hinsichtlich ihrer Genauigkeit und Sensitivität vor allem im Bereich der
Belegereife zu testen. Hier dargestellt sind die Ergebnisse aufgenommen an einer
Calciumsulphat-Estrich Probe vom Typ Knauf FE80 Largo mit drei Verfahren, die auch
Aussagen über die Feuchtegradienten in die Tiefe zulassen. Die Proben wurden bei
Konstant-Normklima mit T=23 °C und rH=50 % zur Trocknung gelagert.