The method of calorimetry chosen for experimentation is semi-adiabatic as the sample environment is insulated with polystyrene, which has a density of 20 kg/m³ and a thermal conductivity of 0.042. Each sample is contained in a polystyrene flask which is then placed into a polystyrene enclosure for further insulation. A ‘fully’ adiabatic calorimeter would have been preferred as eliminating heat exchange between the sample and the environment is vitally important in accurately approximating the actual heat of hydration produced by the mixture. However due to time constrains and the complexity of the system a simpler method was pursued. Furthermore due to budget constrains an ‘off the self’ calorimeter was not plausible.

 

The setup of the semi-adiabatic calorimeter is based on the guidelines defined in the ASTM draft standard (2012) and advice obtained from Dale Bentz of the National Institute of Standards and Technology (NIST, USA). The experiment took place under laboratory conditions where the temperature (20°C ±2) and relative humidity (not less than 50%) was controlled. All materials and instrumentation used were acclimatized to the experimental environment before batching and data logging commenced. Mixtures were monitored separately and two temperature profiles were developed from two 650g samples (e.g. M1A- PC and M1B - PC). For each of the three mixtures the temperatures of an inert sample and two hydrating samples were monitored over 24 h, during which time the environmental conditions were kept constant. The sample mixing procedure was identical to that followed for the standard consistence and setting time tests, which is outline in SANS 50196-3:2006. An image of the semi-adiabatic calorimeter that was constructed can be see in the image below.