We at our plant intend to utilise high sulphate resistant cement for oil well cement. To produce low viscosity and slow-setting slurry we need to know the type of most suitable retarder and friction reducing additive to be used with SRC.

The key to producing oil well cement lies in the testing and meeting of the API performance specification. A high sulphate resisting cement with low C₃A content may well be a good starting point. Lignosulphonate is likely to be a useful retarder and friction reducing agent for this application.

I wish to know which are the problems we may face if we start using phosphogypsum as a set retarder in manufacturing OPC. Currently, we are adding 3.5 per cent of natural gypsum in the finish mill.

I recommend that you conduct trials with the phosphogypsum replacing natural gypsum, however there is reported experience from India and South Africa that this can be done. I would recommend researching the work conducted by the University of Pretoria in conjunction with Pretoria Portland Cement in South Africa.