I'm new to bricklaying, and am in the process of building a low level garden wall that's about 10m long. I have access to a mixer and I've found that if I mix the mortar at 1:4 with some plasticizer it begins to stiffen after about 2 hours. Is it OK to add a little more water and keep using the mortar a little longer as I understand I could be using a 1:6 mix?
Thanks for any advice.