Abstract
The fracture response of cementitious composites containing compliant microencapsulated inclusions and its influence on the fracture process zone (FPZ) are reported. The incorporation of small amounts of phase change material (PCM) microcapsules (replacing up to 10% by volume of sand) is found to slightly improve the strength, fracture toughness, critical crack tip opening displacement (CTODc), and the strain energy release rates. Digital image correlation is used to examine the FPZ at the tip of the advancing crack, to better explain the influences of compliant microscale inclusions on energy dissipation. The FPZ widths are found to slightly increase with PCM dosage but its lengths remain unchanged. The increase in FPZ width is linearly related to the CTODc, showing that inelastic deformations of the crack-tip in the direction of crack opening are indeed influenced by microscale inclusions. It is shown that cementitious systems containing microencapsulated PCMs can be designed to demonstrate mechanical performance (including fracture) equivalent to or even better than their PCM-free counterparts, in addition to the well-described thermal performance.
Highlights
Phase change materials (PCMs) have been proposed as a means for thermal energy storage due to the large amount of heat being absorbed or released while undergoing phase change
This research article has reported the influence of microscale PCM inclusions on the fracture response and fracture process zone (FPZ) in cementitious mortars
Until a certain volume fraction of PCM-E replacing sand, the fracture toughness (KIC), critical crack tip opening displacement (CTODc) and strain energy release rate (GR) of the PCM-modified mortars are similar to or greater than those of the plain ordinary portland cement (OPC) mortar. This is in line with the strength of PCM-E modified mortars, the reasons for which have been elucidated using microstructural simulations
Summary
Phase change materials (PCMs) have been proposed as a means for thermal energy storage due to the large amount of heat being absorbed or released while undergoing phase change. The use of PCMs in building elements (i.e., non-structural components such as insulation, and recently in load-bearing roofs and walls) is studied as a means to improve the indoor thermal comfort and building energy efficiency [1,2,3,4,5,6,7]. A previous study [8] has presented evidence of the beneficial influence of microencapsulated PCMs in mitigating thermal cracking in cementitious systems. A recent study has investigated the influence of two different types of microencapsulated PCMs on the microstructure and strength of cementitious systems [9] where it was shown that the constitution and properties of the shell and the size distribution of the microencapsulated particles significantly influences the mechanical properties
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