High-Strength, High-Density Concrete,

No new technology is necessary to produce adequately uniform concrete with unit weights of 225 to 235 lb per cu ft and 90-day strengths of 10,000 to 12,000 psi. It is necessary to control the water-cement ratio of the concrete vigilantly, and to use efficient mixers, thorough consolidation by vibration, and forms designed to resist the pressures developed by the fresh concrete. While no new technology is required, careful adherence to every aspect of the best practices in production and control is absolutely essential. High-density aggregates that are tough, well graded, and of good particle shape are more expensive than many concrete aggregates in commercial use. In this respect they differe only in degree from many other aggregates of high quality. The single greatest cause for the difference in cost between a shield constructed with concrete of normal unit weight and one constructed of high-strength, high-density concrete like those described is the excellent construction practice and rigorous control required to achieve the high-strength, high-density concrete.