Patent ID: 8415009

Claim:
An engineered composite building material comprising: a cementitious substrate having a pre-determined porosity; and a sub-surface region formed in the substrate, said sub-surface region comprising a cement-polymer matrix configured to reduce moisture absorption of the building material, wherein the cement-polymer matrix comprises a polymeric impregnating agent chemically bonded to hydroxyl functional groups in the substrate, wherein the thickness of the sub-surface region is controlled by the viscosity of the impregnating agent and the porosity of the cementitious substrate, the impregnating agent having a viscosity of less than about 500 cps at 25° C., wherein the impregnating agent is deposited in the pores and interstices in the cementitious substrate of the sub-surface region, thereby causing the porosity of the sub-surface region to be less than the pre-determined porosity of the cementitious substrate.