An admixture for making a high-strength concrete with any type of water, including potable water, freshwater, saltwater, brackish water, reclaimed water or any other non-potable water. The admixture consists of basalt fibers, graphene nanoplatelets, calcium sulfide, calcium chloride, magnesium oxide and nanoclays. The admixture can be added to the cement to supplement it to increase the overall compressive strength, or the amount of cement used can be reduced by the amount of admixture added to shorten cure times. A concrete mix can also be prepared by replacing the calcium chloride with silica fume, reducing the amount of cement used, and introducing locally sourced aggregates, coarse and fine, to yield Ultra High Performance Concrete. Products made from the concrete incorporating the admixture have increased compression strength, improved cure times, reduced water consumption and corrosion, increased durability and workability, drastically reduced freeze-thaw effects, and superior crack control.