What are the key considerations for high-strength concrete (HSC) mix design?

HSC (strength > 60 MPa) requires: very low w/c ratio (0.25-0.35) achieved with superplasticizers, high-quality aggregates with good strength and bond, optimized gradation including fine materials, silica fume or other pozzolans to fill voids and enhance paste strength, and careful quality control. HSC has higher elastic modulus but lower ductility. Special considerations include early-age cracking due to autogenous shrinkage, thermal cracking, and potential explosive spalling under fire.