Temperature changes driven by hydration reactions and environmental loading cause thermal cracking of restrained concrete elements.This work describes the use of microencapsulated phase change materials (PCMs) as a means to mitigate such thermal cracking.Special attention is paid to quantify: heat absorption and release,the development of unrestrained/restrained thermal stresses and strains and the mechanical properties including:compressive strength, elastic modulus and fracture behavior.Significantly, PCMs incorporated in cementitious systems absorb and release heat, which scales as a function of their dosage and enthalpy of phase change.In the case of both restrained and unrestrained conditions and for equal temperature change, the thermal deformation and stresses developed are noted to be similar to a plain cement system independent of the PCM dosage.However, PCM additions are noted to reduce the rate of deformation and stress development so long as the phase transition is active.Furthermore, while the presence of PCMs depresses the compressive strength and elastic modulus (in increasing proportion with dosage), the fracture toughness is impacted to a lesser degree.However, by rational design, and for intermediate PCM dosages, equivalence of both elastic modulus and fracture toughness can be maintained.For the 1 st time, these studies highlight an innovative means of exploiting (solid-liquid) phase transitions to control thermal stress evolutions and cracking in restrained concrete elements.