Will the concrete industry soon be asked to supply air-entrained concretes of 6,000 psi and greater strengths? Architects and engineers have all ready begun routinely requesting and obtaining non-air-entrained concrete compressive strengths of magnitudes that 10 years ago were considered unrealistic if not impossible. Inevitably, the industry will also be asked consistently to supply air-entrained concrete of 6,000 psi or greater. Actual mix materials, proportions and production practices may be limited or even virtually dictated by materials available, standard practices or project specification. However, the concrete producer must use all the flexibility available if he is to obtain consistent high strengths and the proper level of air entrainment. Each material, including cement, aggregates, pozzolans, admixtures and water, must be carefully examined in light of mix requirements. Mix design is normally a matter of establishing the most efficient proportions of materials to achieve the desired strength, air content and workability. There are two nearly universal proportioning limitations for high-strength concrete. One is a clump range between two and one-half and 3 and one-half inches for concrete mixes in truck mixers. The other is use of the lowest practical water-cements ratio, preferably . 30 to .40.