166 ILLINOIS ACADEMY OF SCIENCE 



Combination of lightness with considerable strength is a 

 desirable property for a material to be used in floors for light 

 loads on considerable spans. In such cases the weight of the 

 building material may be the largest part of the load. 



With this in mind, tests were made to determine the be- 

 havior of reinforced gypsum beams, both rectangular and T- 

 shaped. At first the importance of giving gypsum specimens 

 a chance to dry not being fully appreciated, the first and sec- 

 ond series of beams were tested before they were entirely dry 

 and without knowing just how much moisture they contained. 

 The showing made by these beams was creditable, but in view 

 of the marked increase in compressive strength and bond 

 strength with increased drying (See Figs. 4 and 8), it is ap- 

 parent that the results of the earlier beam tests may be mis- 

 leading in some respects. They gave the impression that a 

 means of developing the tensile stress by anchorage rather 

 than bond would be essential, but the later development of 

 a bond stress of 500 pounds per square inch, or possibly more, 

 in thoroughly dry pull-out specimens, made from a mixture 

 having the standard consistency, makes it appear that for po- 

 sitions not exposed to the weather or to wetting, anchorage 

 may not be more necessary for a gypsum beam than for a re- 

 inforced concrete beam. However it must be recognized that 

 there are few places where occasional wetting may not be 

 possible. Mechanical would generally be an advantage for 

 either reinforced gypsum or reinforced concrete. 



The form of the T-beam tested is shown in Fig. 9. The 

 main results of the tests are given in Table 2. Measurements 

 of deformation in the reinforcement and in the gypsum were 

 taken at the gage lines shown in Fig. 9. It is of interest that 

 the compression in the flange was substantially uniform 

 throughout the width of the flange of the T-beam, also that 

 the deformations on a section at the center of the span were 

 approximately proportional to their distance from the neutral 

 axis. Diagrams showing these phenomena for one of the 

 beams are shown in Fig. 9. 



The tests here discussed point toward the suitability of gyp- 

 sum for use in certain reinforced work and suggest possibili- 

 ties which have not been entirely investigated. Certain diffi- 

 culties also have been encountered, but for most of these, fur- 

 ther investigation has already offered a satisfactory solution. 



