Table A-4. Expected Intensity Peaks [12] From X-Ray Diffraction Analysis 

 of Concrete Attacked and Unattacked by Seawater 



Diffraction Angle (2d) 







at Intensity Peak 



Material 



Remarks 



(deg) 









Concrete Attacked by Sulfates 



n Seawater 



9.1 



Ettringite, 





15.8 



3CaOAl203 3CaS04 32H20 





11.2 



Hydrocalumite, 

 CaigAli8(OH)54C03 21H20 



May not be present. 



11.7 



Gypsum, CaS042H20 



Very soluble, may not be present. 



29.4 



Calcite, CaCOj 



Due to carbonation. 



26.2 



27.2 



Aragonite, CaCOj 



Formed at cold temperatures, 

 may not be present. 



Concrete Unattacked 



18.1 

 34.1 



Lime, Ca(0H)2 



Created from hydrated cement. 



broad peak 

 -28-33 



Tobermorite gel 



Created from hydrated cement. 



32.3 



CjS 



Traces of unhydrated cement, 



32.7 



CjS andC2S 



usually hard to see in older 



33.1 



CjA 



concrete. 



29.4 



Calcite, CaCOj 



Due to carbonation. 



10.5 







20.9 



Aggregates 



Some of the larger peaks from the 



26.6'' 





aggregate. 



27.8 







" Quartz aggregate. 



23 



