The Grey Relation Entropy (GRE) theory is used to analyze the sensitive pore size that affects the compressive strength of concrete. The relationship between the strength and pore structure is revised based on the sensitivity coefficient. The revised model is used to calculate the compressive strength of concrete. In order to verify the validity of the proposed model, the calculated results are compared with experimental ones, showing satisfactory agreement with a larger correlation than existing methods.

Mixing microcapsules encapsulating asphalt recycling agents into asphalt can effectively enhance its self-healing performance and alleviate the brittle cracking of pavements due to asphalt aging. In practical engineering applications, microcapsules should have good thermal stability, mechanical properties, and uniform dispersion in asphalt or asphalt concrete, for the effective self-healing of micro-cracks which occur as pavements age. The self-healing performance of microcapsule-containing asphalt is affected by several factors. First, the thermal stability, mechanical properties, and dispersibility of microcapsules in the asphalt were investigated by thermogravimetric analysis, nanoindentation tests, and fluorescence microscopy. Then, the effects of the microcapsules’ content, temperature, time, degree of damage, and self-healing times on the self-healing performance of microcapsule-containing asphalt were investigated through two-stage fatigue loading tests. The results show that the microcapsules have good thermal stability, mechanical properties, and dispersibility. They will not thermally decompose when mixing the asphalt concrete, nor will they fracture in the early stages of a pavement’s lifetime, or agglomerate in the asphalt. Mixing microcapsules in asphalt effectively improves its self-healing performance. The self-healing index of microcapsule-containing asphalt increases and then decreases with the increase in microcapsule content. It also increases as the temperature and length of time increases, but it decreases as the degree of damage worsens, and thus, the self-healing time increases.