The field of In Situ Resource Utilisation (ISRU) is expanding rapidly with a particular focus on developing ISRU technologies and applications to support a longer-term surface exploration of the Moon. In this respect, microwave sintering is proposed to be one of the potential fabrication methods for developing a 3D printing technique for construction processes on the Moon. Thus, understanding the behaviour of lunar regolith, available at different locations on the Moon (e.g. mare versus highlands regions), under microwave heating is crucial for developing an optimal method for microwave sintering. As the availability of real lunar regolith on Earth is highly limited, developing an appropriate numerical model of microwave heating behaviour of lunar regolith is urgently required. In this paper, three representative lunar regolith samples (selected from the database of Apollo sample collections) with pre-defined material properties have been simulated under seven input powers and three specimen sizes. This paper discusses the outcomes of these simulations and the potential contribution of the model for developing a desired 3D printing technique utilising microwave sintering of lunar regolith.