Lightweight concrete compositions

A method of making an optimized lightweight cementitious composition article comprising:

• identifying the desired density and strength properties of a set lightweight cementitious composition;
• determining the type, size and density of polymer beads to be expanded for use in the lightweight cementitious composition;
• determining the size and density the polymer beads are to be expanded to;
• expanding the polymer beads to form expanded polymer beads;
• dispersing the expanded polymer beads in a cementitious mixture to form the lightweight cementitious composition;
• and
• allowing the lightweight cementitious composition to set in a desired form.

A lightweight concrete composition comprising

• from 10 to 60 volume percent of a cement composition that includes type III Portland Cement;
• from 20 to 78 volume percent of expanded polymer particles having an average particle diameter of from 0.2 mm to 5 mm, a bulk density of from 0.032 g/cc to 0.56 g/cc, and an aspect ratio of from 1 to 2;
• from 15 to 35 volume percent of sand and/or fine aggregate, wherein at least a portion of the sand and/or fine aggregate has a fineness modulus of less than 2;
• from 5 to 15 volume percent coarse aggregate;
• and
• from 0.1 to 1 volume percent of one or more additives selected from anti-foam agents, water-proofing agents, dispersing agents, set-accelerators, set-retarders, plasticizing agents, superplasticizing agents, freezing point decreasing agents, adhesiveness-improving agents, colorants and combinations thereof;
• wherein the sum of components used does not exceed 100 volume percent and
• wherein after the lightweight concrete composition is set, it has a compressive strength of at least 2000 psi as tested according to ASTM C39 after seven days.