## 1 Introduction  
Masonry has been used as a common building material worldwide for many centuries. Masonry is a composite of block units bonded together with mortar. The most effective use of masonry building can be found in load-bearing structures. The manufacturing of masonry units consumes significant amounts of resources and energy. This has added considerable pressure on the construction industry to reduce energy consumption associated with masonry production. Accordingly, many developed countries applied the energy conservation concept in the building technology. This concept can be achieved by introducing alternative building materials that have a low impact on the environment. The use of thermal insulation materials in the production of masonry is one of the most effective ways for green building technology [1; 2].  
A number of studies were carried out in this area, and it is thought that there are many parameters which influence the thickness of an insulator, such as building type, shape, construction materials, insulation materials, and costs [3; 4; 5; 6]. In general, external insulation methods are common practice around the world. However, use of insulation blocks composed of expanded polystyrene (EPS) foam, which are used to replace the external insulation of buildings, becomes more popular with the intention of thermal insulation. EPS is composed of small, white, and interconnected beads and offers superior engineering properties such as being lightweight, versatile, energy-efficient, and cost effective. Therefore, it is used as insulation material in buildings and it can be molded into many shapes to fit the required purpose [7].  
Most of the previous researches focus on lightweight concrete masonry units as good thermal insulation materials in buildings. This is because they have a lower thermal conductivity compared with normal-weight concrete. Unfortunately, masonry units made from lightweight concrete have low mechanical properties compared with normal-weight concrete [8; 9; 10; 11; 12]. Inserting insulation material such as EPS into normal-weight concrete with a special configuration of concrete masonry units (CMUs) leads to an increase in their thermal resistance without affecting their mechanical performance [13]. Recently, a new type of unreinforced masonry system was developed in Europe for use in the construction of small houses. The developed system has an energy-efficiency enclosure without concern for thermal bridges. This type of unreinforced masonry system offers significant contribution regarding the design and construction of cost-effective buildings in seismic regions [14].  
In this research, a new type of concrete masonry unit has been developed with a self-insulating feature. The developed type of self-insulating concrete masonry unit (SCMU) would be applicable for both low and medium height residential buildings in seismic area zones. The main objective of this study was to investigate the mechanical properties, namely, compression strength and shear strength, of the proposed SCMUs. The second objective of this study was to develop numerical models to predict the behavior of grouted specimens using a simplified micro-modeling technique. The successful use of SCMUs in the construction industry can have a potentially significant impact on the sustainability of masonry structures.