Page 390 - Handbook of Thermal Analysis of Construction Materials

368 Chapter 9 - Non-Portland Cement Binders and Concrete

Portland cement is an accelerator for CAC and vice versa. The
effect of proportions of each component on setting time is illustrated in Fig.
4. Ternary blends of portland blast-furnace cement and CAC also have an
acceleratory effect.

Figure 4. The setting times of mixtures of high alumina cement (HAC) and ordinary
portland cement. [21]

The long-term strength and chemical resistance of CAC is affected
by the addition of portland cement and chemical admixtures. [21] Calcium
chloride retards CAC, the opposite of its effect on portland cement.
Strength reduction is also a consequence of its use. Retarding action is
provided by inorganic compounds such as phosphates, lead salts, and borax,
and organic compounds that include cellulose products, starch, glycerine,
sugars, flour, and cosein. Most sulfates in small amounts retard the set of
CAC but concentrations between 0.5 and 1.0% produce quick setting.
Plasticizing agents, e.g., alkyl aryl sulfonates, secondary alkyl
sulfates, or their sodium salts, are used to overcome the harshness of
many CAC concrete mixes. [21] Workability can be improved with
calcium lignosulfonate addition; larger doses, however, promote excessive