Patent ID: 7658794

Claim:
A formulation used to form a building material, comprising: an hydraulic binder in the form of cement; about 5% to 80% of the formulation by weight of the hydraulic binder; not greater than about 80% of the formulation by weight of an aggregate; water; cellulose fibers, wherein the cellulose fibers comprise greater than about 4% of the formulation by weight; and a low density additive, wherein the low density additive comprises volcanic ash, hollow ceramic microspheres, or combinations thereof, the composition of the low density additive is different from the composition of the aggregate, the low density additive is incorporated into the formulation in a quantity sufficient to lower the density of the building material to about 1.2 g/cm 3 or less, and said quantity of low density additive maintains the moisture expansion of the building material at a level of about 0.17% or less.