OFFICIAL Reactive Ground Isothermal Testing Isothermal refers to a test where the conditions are maintained at a set temperature, with a thermostat adding heat when the temperature drops below a set point and allowing heat to dissipate if the temperature exceeds a set point. The equipment required is simple and widely available, but the ability to maintain a set temperature is critical to ensuring reactions of interest are detected because heat is dissipated faster in the test than in blast holes. Figure 2 shows the reactive ground apparatus. The inset picture highlights the aluminium block, which provides good thermal conductivity and enables the test temperature to be maintained. Figure 6: Isothermal Reactive Ground Test Apparatus with inset showing detail of aluminium heating block All isothermal testing was done at Orica’s Kurri Kurri Technical Centre using the procedure described in the AEISG isothermal reactive ground test (AEISG, 2020). Two sample types were used in the study 1) a reactive ground standard developed in-house to provide consistent reproducible results across experiments and 2) reactive samples from mines that consistently displayed reactivity to AN in the absence of the above-described inhibition components in the explosive. In the standard procedure, a crushed reactive rock sample was mixed with an inhibited bulk explosive and maintained at 55 °C in a dry block heater for the duration of the test (AEISG, 2020). A thermocouple monitored the sample’s temperature for any exothermic peak greater than 2 oC from baseline, which indicates the onset of the AN-sulphide reaction. If no reaction occurs for the duration of the test, the explosive was deemed compatible (safe to sleep for the corresponding field sleep time). Following industry
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