Effect of Ball Milling Time on the Performance of Phosphorous Building Gypsum

Table 4

Comparison of ball milling PBG with national standards.

Performance index	Untreated PBG	PBG after 50 min of ball milling	“Building gypsum” (GB/T 9775-2008) (level 1)
Fineness (0.2 mm square hole sieve residue) (%)	2	0.2	≤10
Initial setting time (min)	6.73	4.5	≥3
Final setting time (min)	14.9	8.87	≤30
Flexural strength at 2 h (MPa)	2.28	3.41	≥3.0
Compressive strength at 2 h (MPa)	4.29	7.78	≥5.0