Page 404 - Handbook of Thermal Analysis of Construction Materials

382 Chapter 9 - Non-Portland Cement Binders and Concrete

Figure 8. Compressive strength vs time for seven phosphate cement concretes made with
ammonium phosphate solution. [66]

The concrete mixes contained 22.5 parts solution to 100 parts
aggregate; the aggregate contained 80% sand and 20% dead burnt magne-
sia, and the phosphate solutions all contained approximately 10% ammo-
niacal nitrogen and 34% P O . The pH ranged from 5.8 to 6.3, and the
2 5
specific gravity was approximately 1.39. The polyphosphate contents of the
solutions varied from 55 to 76.5%. Concretes made with phosphate solu-
tions containing < 58% polyphosphate have greater strengths below 14 days
than concretes made with phosphate solutions containing > 58%
polyphosphate. Also, the rate of strength development from 2 to 3 days is
greater for the concretes containing < 58% polyphosphate. At 28 days, the
compressive strengths of those concretes made with phosphate solutions
containing > 58% polyphosphate are generally higher.
The compressive strength and setting time (Gillmore needle ASTM
C266-74) for several phosphate-cement concretes containing different
amounts of polyphosphate in ammonium phosphate solutions are plotted in
Fig. 9. At 2 hours, 24 hours, and 7 days the compressive strength increases