Appendix E 



MICROSTRUCTURE EXAMINATION OF CONCRETE 



by 



Prof. P. K. Mehta 



University of California, Berkeley 



The results of a microstructure 

 examination of the concrete samples 

 listed in Table E-1 are summarized 

 below. 



Aggregate pieces from the concrete 

 were carefully separated as much as 

 possible before crushing and grinding the 

 remainder of the sample for x-ray 

 diffraction analysis. All x-ray diffraction 

 analysis work was conducted at 40 kV, 35 

 mA Cu ka . 



There was no evidence of unhydra- 

 ted cement compounds in any of the 

 specimens. This showed that the cement 

 was more or less completely hydrated. 

 All the samples showed substantial 

 amounts of calcium hydroxide, thus 

 indicating that the hardened cement 

 pastes were undamaged in every case. 

 Since large peaks due to quartz and 



feldspar emanating from sand were also 

 present, it was not possible to make any 

 estimate of the relative quantities of 

 calcium hydroxide in the different 

 specimens. Concrete samples no. A, B, 

 and C showed small peaks due to ettrin- 

 gite. In no case were peaks large enough 

 to draw any conclusions. Concrete 

 sample no. A (piece from wall of sphere 

 no. 12) differed only in one respect from 

 the others. It showed two small peaks, 

 2.5'f A and 2.16 A, which are possibly due 

 to the presence of calcium carboalumi- 

 nate hydrates. However, these peaks are 

 not very large, and all major peaks due 

 to carboaluminate hydrates were not 

 present. Therefore, it is concluded that 

 the concrete has remained essentially 

 unaltered. 



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