Small sections of typical panels can be seen in Figure 1. The 

 panel section on the left is set in a simulated footing. The sections 

 shown contain 1 inch of polyurethane foam at mid-thickness; 2 by 2-inch 

 no. 14 galvanized mesh forms the reinforcing on both sides of the foam. 

 The two mats of fabric, one on each side of the foam, are tied together 

 by single no. 14 wires welded to each mat and placed at 45 degrees from 

 the plane of the mat to provide shear strength. About 1 inch of portland 

 cement plaster or mortar is then applied to both sides of the panel to 

 complete the construction. After the concrete has hardened, a finish 

 coat of stucco (including color) may be applied. 



Plastered or mortared panels will shrink when drying (i.e., when 

 used in a typical wall or roof). If the shrinkage, which is a shortening 

 in length due to loss of water, is restrained or resisted by reinforcement, 

 tensile stresses develop in the material which can exceed its tensile 

 strength, resulting in a crack. Steel reinforcing tends to hold cracks 

 "closed," but moisture can penetrate as a vapor; heat and cold also find 

 their way through. In an insulated wall or roof panel, water vapor can, 

 and often does, condense in the insulation, thus reducing its insulation 

 efficiency by increasing its thermal conductivity. The purpose of using 

 shrinkage-compensating cement in the plaster (or mortar) is to provide 

 enough induced compressive stresses in the hardened plaster to prevent 

 shrinkage cracking, thus making the resultant construction more energy 

 efficient. 



EXPERIMENTAL PROGRAM 



Descriptions of the test panels and conditions in the research 

 program undertaken to provide crack-free, sandwich-type insulated, 

 expansive concrete walls and roofs follow. 



Cement: Type K, Shrinkage-Compensating 



Cement content: 5.5 bags/cu yd 



Sand/cement ratio: 3.5/1; 3.0/1 



Panel size: (1) 2 by 4 feet; (2) 1 by 2 feet 



Panel thickness: approximately 3 inches 



Insulation thickness: 1 inch 



Strain measurement: (1) mechanical strain gage 



(2) embedded resistance strain gage 



Number of panels: Twenty-one 



INSTRUMENTATION 



At the outset of the experimental program, it was planned to measure 

 expansion strain and subsequent shrinkage with a mechanical strain gage 

 on reference points cast into the wet concrete after construction of the 

 panels. In addition, reference points were soldered to the mesh rein- 

 forcing at selected locations to measure steel movement. Later in the 

 program, embeddable resistance strain gages were also used. 



