Hydraulic cement panel with low density core and fiber reinforced high density surface layers

Claim 1

A NAILABLE, STRUCTURAL PANEL PARTICULARLY ADAPTED FOR USE IN AREAS OF EXPOSURE TO MOISTURE, SAID PANEL COMPRISING CENTRAL CORE OF SUBSTANTIAL LENGTH AND WIDTH COMPRISED THROUGHOUT ITS THICKNESS OF INORGANIC LIGHTWEIGHT AGGREGATE AND HYDRAULIC CEMENT, SAID CORE BEING CHARACTERIZED BY THE PRESENCE OF A MULTIPLICITY OF VOIDS AND CELLS WHICH CONFER ON THE CORE AN AVERAGE UNIT WEIGHT NOT SUBSTANTIALLY EXCEEDING 130 POUNDS PER CUBIC FOOT. A LAYER OF HIGH TENSILE STRENGTH FIBROUS MATERIAL DISPOSED CLOSELY ADJACENT THE CORE AT THE TWO OPPOSED FACES THEREOF AND A LAYER OF BONDING MATERIAL CONSISTING OF AT LEAST 50% HYDRAULIC CEMENT, SAID LAYER BEING SUBSTANTIALLY THINNER THAN SAID CORE, RELATIVELY LOW IN VOIDS AND OF HIGH UNIT WEIGHT RELATIVE TO SAID CORE AND AT LEAST PARTIALLY PENETRATING THE VOIDS AND FILLING THE SURFACE IRREGULARITIES AT THE FACE OF SAID CORE THEREBY BONDING THE RESPECTIVE FIBROUS LAYERS TO THE OPPOSED SURFACES OF THE CORE TO FORM AN INTEGRAL STRUCTURE.