The invention provides a low-density, high-strength concrete composition, which is self-compacting and lightweight, with a low weight-fraction of aggregate to total dry raw materials, and a highly homogenous distribution of an absorptive lightweight aggregate such as glass microspheres and, optionally, polymer beads, as well as the methods for providing the composition or components. Lightweight concrete formed by the disclosed concrete composition have low density, high strength-to-weight ratios, and high R-value. The concrete has strength like that ordinarily found in structural lightweight concrete. The concrete, at the density ordinarily found in structural lightweight concrete, has a higher strength and, at the strength ordinarily found in structural lightweight concrete, a lower density.

It is disclosed the use of amorphous silica reagent produced from serpentine as pozzolane additive material, and more particularly a concrete mixture, such as high performance and ultra-high performance concrete, comprising a hydraulic binder; sand; aggregates, chemical admixture, mineral admixture as silica fume and an amorphous silica reagent (AmSR), wherein the AmSR is admixed for example with General Use Portland Cement and provides synergistic effect when combined with silica fume.