OpenHW3 – An open-source, low-cost temperature-controlled orbital shaker

The current lack of standardized testing methods to assess the binding isotherms of ions in cement and concrete research leads to uncontrolled variability in these results. In this study, an open-source and low-cost apparatus, named OpenHW3, is proposed to accurately measure the binding isotherms of ions in various cementitious material systems. OpenHW3 provides two main options, a temperature-controlled orbital shaker, as well as an option to retrofit a commercial orbital shaker for temperature control. The effectiveness of these device options is validated via comparison with conventional binding isotherms experiments. The binding isotherm results were comparable to conventional Waterbath shakers, while providing more reliable results compared to horizontal commercial shakers. It also provided accurate temperature control between 25 °C and 75 °C. The results here are critical for allowing open access to scientific equipment, and providing high-quality binding isotherm data for reliable service life models of urban infrastructure assets throughout the world.