stock 0.005-inch (0.13-mm) thick and waterproofed, 

 using standard procedures. These procedures used 

 normal preparation steps for applying gages to metal 

 and then were waterproofed using General Electric 

 Clear RTV 109. This waterproofing approach works 

 successfully under hydrostatic pressure loadings 

 equivalent to thousands of feet of head. A second 

 type of electrical resistant gage used was a self- 

 encapsulated, waterproof, weldable gage. 



(2) The objective was to apply these waterproof gages to 

 the wet concrete surface with an adhesive of sufficient 

 bonding strength that strain in the parent material is 

 transferred through the epoxy adhesive, through the 

 shim stock material, to the gage. To check the accu- 

 racy of these shim-stock mounted gages, a control test 

 was conducted on an aluminum tube loaded in uniaxial 

 compression. Seven pairs of gages were mounted on 

 the aluminum cylinder; each gage in a pair was diamet- 

 rically opposite the other gage. The test consisted of 

 three pair of single wire gages mounted with Eastman 

 9-10, two pair of foil gages on brass shim stock 

 mounted with EPY-150, one pair of foil gages on brass 

 shim stock mounted with Eastman 9-10, and one pair of 

 foU gages on brass shim stock mounted with Hysol EA 

 934. Eastman 9-10 is an excellent adhesive in a dry 

 environment, so it was used in this test as a control. 

 The results showed that gages mounted on brass shim 

 stock registered accurate strains . The different glue 

 systems did not affect the results . 



(3) In the first method of mounting foil gages on brass 

 shim stock to the wet-concrete specimens, an under- 

 water curing adhesive developed at CEL (Ref 17) was 



46 



