Cement Replacement GGBS in Mortar

[Rdb]

Im in a long running dispute with a builder.  The mortar company have batched Ground Granulated Blast Furnace (GGBS) at the 50% level;  in the name of the environment. Masonary mortar standards have limited this to 35%.
I have consulted an expert witness who is of the opinion that GGBS in mortar will not properly cure since it takes longer to harden and therefore the cement would require to be wet for longer to properly hydrate.  The evidence for this is within some tests which have been done; lack of properly hydrated GGBS granules.  High levels of GGBS work well with concrete because it can be kept wet.
The mortar itself is soft.
Any other opinions from anyone having knowledge in this area as to acceptability of this?  I cant help but feel ita going to be a far more frequent occurance than  lack of cement in the future.

[New Home Expert]

This is serious and you are quite right to be worried.
It has got little to do with the environment and more to do with cost.
cement is expensive, whereas waste products are virtually free.

I am helping a Bellway buyer in his battle with the NHBC who has weak mix mortar falling out of his brickwork. He is being thwarted at every attempt by Bellway, the NHBC and Marshalls who manufactured the mortar.

It is quite complicated. He is currently awaiting an allegedly 'independent inspection' report and recommendations based on the latest series of mortar samples taken away to be analysed.
The mortar mix in question has GGBS in it, referred to as "cement substitute"

I suggest you contact (PM) the original poster PSE and read this thread:
Soft mortar joints

[Rdb]

Thanks for the advice