This book introduces epoxy resin (diglycidyl ether of bisphenol A) without any hardener as self-healing materials. Epoxy-modified mortars using an epoxy resin without any hardener are prepared with various polymer-cement ratios, subjected to initial wet/dry curing plus long term dry curing and tested for strength properties. The fundamental properties such as workability, influence of curing, strengths, strength development, porosity, permeability and water absorption are investigated. The self-healing function and hardening of epoxy resin are evaluated by preloading and drying of specimens, chemical analysis, and ultrasonic pulse velocity test.