Self-healing efficiency of concrete containing engineered aggregates

This paper presents the results from a new approach for self-healing concrete. Conventional macro-capsules such as those made of glass cannot resist the harsh mixing process of concrete and require changes to conventional preparation methods. Here, a new encapsulation method; namely, engineered aggregates (EAs) were developed and tested, which do not require any changes to concrete preparation methods. EAs were shown to resist the conventional concrete mixing methods and effectively deliver healing agents when cracks appear in concrete. The mechanical properties of the produced self-healing concrete were examined by performing uniaxial compression, split tensile, and four-point bending tests. The self-healing efficiency of the concrete with EAs containing different healing agents (polyurethane, super glue, sodium silicate, magnesium oxidate) was determined based on split tensile, water absorption and water permeability tests. It was seen that more than 50% of the original strength and stiffness could be regained after self-healing. It was also found that the water permeability could be reduced by a factor 102 to 104 due to autonomous crack healing. Although some further research is still necessary concerning functional life of encapsulated healing agents and healing of cracks less than 50 & mu;m, self-healing EA concrete was shown to be a novel approach that could lead to changes in the concrete industry.