Research has been done at the Mines Branch for the purpose of producing concretes with high strength at early ages at a price competitive with conventional concrete or cheaper. Expensive monomers that require high pressure to impregnate the concrete were ruled out. Instead, simple and effective procedures for using cheaper materials such as sulfur were sought. Some of the results obtained up to now are given here. The work has resulted in a new type of high-strength concrete made from lean, two-day old conventional concrete, using sulfur infiltration technique. In the laboratory the method has consisted of moist-curing fresh concrete specimens for 24 hours, drying them at 250 degrees F for 24 hours, immersing them in molten sulfur under vacuum for two hours, releasing the vacuum and soaking them for an additional half hour, then removing them from the sulfur to cool. They are tested one to two hours later. In a simplified version of the above process, vacuum is eliminated and immersion time is molten sulfur is increased to four hours. Phenomenal increases have been obtained in the mechanical and elastic properties of sulfur-infiltrated specimens. The compressive strengths increased about ninefold over those of the reverence moist cured specimens, which were about 1000 psi. A corresponding increase was observed in the flexural strength of the infiltrated test prisms. Sulfur-infiltrated concrete should have applications in pavements, bridge decks, and many precast products.