To improve the structural integrity of concrete, which method can be adopted?

Adding fibers during mixing is a widely recognized method to improve the structural integrity of concrete. Fibers, such as steel, fiberglass, or polypropylene, enhance the concrete by increasing its tensile strength, reducing cracks, and improving ductility. When these fibers are distributed throughout the concrete mix, they act as reinforcements that help in mitigating shrinkage cracks and improving impact resistance. This makes the concrete more robust under various stress conditions, thereby enhancing its overall durability and longevity.

The other options do not effectively contribute to structural integrity in the same way. For instance, removing excess aggregate may affect the balance of the mix, potentially leading to weaknesses. Reducing the curing time can lead to insufficient hydration of the cement, negatively impacting strength development. Increasing the air content can improve workability and freeze-thaw resistance, but too much air can weaken the concrete, compromising its structural integrity. Thus, adding fibers during mixing is the most effective method to enhance the structural characteristics of concrete.