Thermal Conductivity Tests on 3D printed cob - data

Work was carried out to investigate the thermal properties of 3D printed Cob, a monolithic earth construction technique based on robotically extruded subsoil and locally available organic fibres.  The results of the 3D printed samples are compared with traditionally-constructed Cob material of the same dimensions. The assessment has revealed strong potential for 3D printed cob as compared to its manually constructed counterparts in terms of thermal conductivity. Moreover, the testing process has helped in identifying several challenges in the 3D printing process of cob and the assessment of its thermal properties.

To establish the thermal performance of the specimens, a series of conductivity tests were undertaken using a heat flow meter ( Net- zsch HFM 446 ). This machine is based on ASTM C518, ASTM C1784, ISO 8301, JIS A1412, DIN EN 12664, and DIN EN 12667 Method and Technique for the Characterization of Insulation Materials. The Netzsch was chosen because it takes a larger sample size and uses additional external thermocouples in conjunction with the hot and cold plates. This makes it suitable for measuring denser, more random materials like cob. The experiment tested four specimens of 3d printed cob, hence, there are four data files included in this submission.

The heat flow meter generates results in the form of a Microsoft Excel file, comprising five sheets. The first sheet includes the properties of the tested specimen, such as size, density and weight. It also includes the summary of test settings and result in the setpoints and results table. The setpoint temperature refers to the assigned temperature of both the cold and hot plates. The difference in temperature (delta) between both plates was kept at 20 degrees Celsius. This difference is essential to achieve equilibrium state and therefore understanding the heat flow over time through the volume of the specimen. Second column of the table shows the measured temperature by the thermocouples during the whole process. The table then shows the achieved thermal conductivity and thermal resistance at each setpoint. This data generation repeats at each set point in the table. The average can be taken to show the mean thermal conductivity. The second and third sheet show the detailed progress of heat transfer versus time in seconds to reach the equilibrium state. Columns in these sheets refers to essential factors in the process such as time, set point number, physical state of the specimen surface ( fine, rough), temperature of upper plate, temperature of lower plate, mean temperature on plates, temperature measured at upper thermocouple, temperature measured at lower thermocouple, average measured temperature and the heat flow per cm/sec. Fourth and fifth sheets further represent the previous relation between temperature and thermal energy versus time as charts.

Research results based upon these data are published at https://doi.org/10.1080/00038628.2019.1606776