ye thanks mark thats what i was thinking aswell about the colour hardener now and worried again about this job .
i have tried to explain this to the customer that am concerned about not using colour hardener but its like talking to a brick wall we have 3 different grey colours to choose from but she said it makes the cobbles fake looking
am in two minds to just knock this job on the head and walk away
No reason why you cant. The colour is a surface hardener as well as a colouring agent. I would give the concrete a final trowel over before you print it, as if you had a colour hardener on the surface. This will give you a better printing surface and keep it a bit more supple.
I have seen some jobs printed without colour although never tried it. The longetivity of the slab will be called in to question. lafarge's ART mix is the same principle only with integral colour in it. It is also designed to get over the longetivity issues. I am a strong advocate for colour hardeners though. Back to the question though, you can give the customer what she wants confidently.
