Rockyn --- There are seemingly an infinite number of "admixes". All for different purposes and all with some kind of side effect. Bonding admixtures do tend to accelerate the set & cure a bit, but how much is dependent on about three thousand other factors and just about impossible to calculate with any precision. The good news is, there are other admixtures designed to offset that effect...they are called "retarders" (insert politically incorrect comment about anyone brain damaged enough to want to play with wet cement here). Retarders will slow the cure and, to some extent, the initial set. Once again, the actual rate of change is subject to change, depending on many factors, but testing and timing your particular formulation will yield relevant factors that you can depend on. You will likely have to track down a concrete specialty supplier or you may be able to "beg" some from a local pre-mix company. To my knowledge, all the commercial retarders are sugar-based, but I would advise against trying to simply add sugar to your mix. It's fine as a topical or surface retarder for exposing aggregate, but a whole 'nuther animal when mixed into the batch. Stick with a "store-bought" retarder designed for the purpose and you'll avoid a lot of headaches. As for an example of the effect they can produce, my "neat Portland paste" can solidify and harden within a couple of hours, but with a commercial retarder added, I have been able to work it soft and semi-set for about 24 hours. But experimenting and keeping good notes is the only way to tell what it will do for you. And don't get too carried away. Too much of it and the mix may never set. Best of luck and "Keep Austin Weird".