Determination of Fracture Parameters of Lime-Pumice Composites Using the Double-K Fracture Model

Abstract

Experimental studies on concrete beams have demonstrated that there are three distinct phases of crack development in cement-based materials: the initiation of cracks, stable crack growth, and unstable fracture. In light of these phases, the Double-K model necessitates two fracture parameters, specifically the unstable stress intensity factor and the initiation stress intensity factor, to effectively simulate the fracture-dominated failure of concrete structures. Particularly, the initiation fracture toughness is crucial in the assessment of certain structures, including nuclear power plants, reservoirs, and water-resource facilities. Roman mortars are considered the initial type of concrete, made from lime, water, sand, and volcanic tuff, enabling the construction of structures that have lasted for nearly two millennia, with prominent examples such as the Pantheon and the Colosseum. The Pantheon temple remains in use as an exhibition hall in the present day. In this study, beams and square prismatic samples featuring three different initial crack lengths were created to determine the fracture characteristics of lime-pumice mixtures containing various aggregate sizes (4 and 16 mm) and subjected to three-point bending tests at fracture test days (28 and 90). The two-parameter model and the double-K fracture model were employed for simulating the results of the fracture test.