Accelerators

Cement setting times can be adjusted with accelerators.  Accelerators speed up the time required for a cement slurry to become hardened in a reaction process that shortens WOC (Wait On Cement) time and provides faster drill out, thus saving rig time.  This reaction process is known as cement hydration whereby water induces chemical reactions that ultimately lead to bonding. Accelerators essentially speed the reaction with water, which in turn reduces (a) thickening time and/or increases (b) early compressive strength development after set.  Accelerators that cause both effects can be considered "total" and those producing only one effect can be called "partial".   Most known accelerators are total.  A useful partial accelerator would increase strength without altering thickening time.

Calcium Chloride (CaCl2) Additive
Decreases thickening time, increases early strength, and shortens time spent waiting on cement.
Cal-Seal™ 60 Accelerator
Can be blended with Portland cements to shorten setting time and improve the expansion characteristics of Portland cements.
Potassium Chloride (KCl)
Formation clays and shales swell in the presence of fresh water, adversely affecting production and zonal isolation. Potassium chloride (KCl) helps prevent this swelling.
Sodium Chloride (NaCl) Accelerator
A crystalline solid additive used in oilwell cementing applications in salt zones that acts as an accelerator at low concentration and as a retarder in high concentration.