... . We offer Grey Portland Cement 42.5 N/R, same price for N or R. It conforms to International Standards, ... 5 N or R Chemical Composition: Silicon Dioxide (SIO2)21,00Aluminium Oxide (AL203)5,30Ferric Oxide (FE203)3,30Calcium Oxide (CAO)65,60Magnesium Oxide ... (MGO)1,10Sulphur Oxide (SO3)2,70Loss ...