Difficult to place and finish. Too much sand requires excessive water which may lead to cracking and excessive shrinkage. Will produce concrete that cracks more easily. Typically a 4000psi mix should be used for concrete that is subject to freeze thaw conditions. Work with your producer to find the mix that is right for your job.
Firm subsoil is generally adequate.
Sand or stone base assists in providing uniformity and drainage. Wire mesh is not necessary, unless specified. Nylon fibers can also be used. Do not use rakes to distribute concrete because it will cause segregation of components. Do not drop the concrete more than 4' from its final location to prevent aggregate segregation.