# Fracture Evolution and Mechanical Properties of Mortar Containing Different Inclusions
## 1 Introduction  
Inclusions are commonly found in geo-materials such as rock and coal as well as artificial structures such as concrete buildings [1, 2], tunneling [3, 4], and mining roadways [5, 6]. In underground environments, a dyke intrusion into sedimentary rock can create an inclusion that is denser and stronger than the surrounding material. Backfilling [7, 8, 9] and side-entry retaining [10, 11, 12] with the filling of engineering materials are widely used mining techniques that can generate an inclusion softer than the surrounding rock. In civil engineering, concrete structures generally contain different inclusions, such as aggregate [13, 14], wood [1, 15], and embedded materials [16].  
The existence of inclusions will have a significant influence on the mechanical properties and failure characteristics of the whole natural or artificial structure, as inclusions can change the stress distribution and cracking process. Hence, it is highly worthwhile to study the influence of inclusions on the overall fracture evolution and mechanical properties. Few researchers have studied the influence of inclusions through experimental and numerical studies. [PERSON] et al. [17] studied the influence of the shape and number of inclusions on the cracking behavior of prismatic gypsum subjected to a uniaxial compression load. Based on the experimental results conducted by [PERSON] et al., [PERSON] et al. [5] extended the numerical manifold method (NMM) to investigate the strength and cracking of samples containing either one or double cylinder inclusions under a uniaxial compression load. However, theNMM model cannot obtain a satisfying prediction of the cracking behavior of samples containing stiff inclusions. [PERSON] et al. [18] studied the effects of different filling materials (Gypsum, Cement, and Resin) on the mechanical properties and crack behavior of sandstone samples with a single filled flaw under a uniaxial compression load. [PERSON] et al. [19] performed uniaxial compression tests on sandstone samples containing single inclusions with various properties, including stiffness and shape. Most research has focused on the effect of the shape, number, and distribution of inclusions on crack mechanical properties and the cracking behavior of rock, concrete, mortar, or gypsum samples. More work needs to be conducted on the effect of inclusions with different strengths and elasticities on the crack evolution and mechanical properties of samples.  
Digital image correlation (DIC) is a kind of non-contacting method that can achieve deformation measurements and stress intensity evaluations by performing a digital image analysis of observed objects [20]. DIC has been widely used to analyze the fracture and crack propagation of concrete [21; 22] and rock [23] due to its advantages of non-contact, full-field measurement, simple devices, and strong anti-interference. [PERSON] et al. [24] incorporated DIC techniques into three-point bending tests for notched concrete beams, which were reinforced with various strengthening systems, identifying failure at characteristic stress points. Similarly, [PERSON] et al. [25; 26] utilized DIC techniques to uncover the fracture behavior of rock samples containing cavities under both quasi-static and dynamic-loading conditions. These researches demonstrated that DIC can be successfully applied to analyze the fracture evolution of geo-materials and concrete.  
In this study, mortar samples containing cylindrical inclusions of varying properties are tested under a uniaxial compression load to study the effect of inclusions on the fracture evolution and mechanical properties of samples using the DIC method. This research aims to understand the impact of inclusions on the mechanical characteristics and failure features of mortar. The presence and characteristics of inclusions are critical in many engineering applications, making this study significant for enhancing material designs and predicting structural performance.