The most important factor when curbing is the quality of the mix. One of the key components of a quality mix should be the additive to prevent efflorescence.
There are several products on the market that can help with this endeavor, however the most effective and most cost effective is this one. For your standard mix, 1 to 2 oz is all it takes to prevent efflorescence.
Superior water repellency protects masonry from weather related damage
Reduced absorption enhances durability, efflorescence control & color retention
Markedly improved material flow/distribution maximizes density, strength, & product consistency
Uniquely increases water tolerance, cement efficiency, production rate, & color vibrancy
Inhibits growth of mold and mildew by virtue of slower wetting and quicker drying of concrete products
Comes in 1 gallon jugs complete with measuring pump, good for up to 128 mixes.