Study on Modification of Alkali-Free Liquid Accelerator of Mine-Used Wet-Mix Shotcrete

Table 4

1 d and 28 d compressive strength of the modified accelerator and standard deviation of compressive strength.

Types	Compressive strength and standard deviation
	SWF^a (%)	1 d^b (MPa)	σ^c (%)	28 d^d (MPa)	σ^e (%)
Accelerator A	0	9.1	0.36	38.7	3.45
	1	8.9	0.45	38.8	1.74
	2.5	8.4	1.01	34.5	2.35
	5	7.8	1.06	30.9	1.46
Accelerator B	0	8.6	0.41	35.3	2.31
	1	8.9	0.67	36.4	1.57
	2.5	8.1	0.55	39.6	1.88
	5	7.2	0.79	39.1	2.03
Accelerator C	0	8.8	0.63	31.1	3.12
	1	8.4	0.48	30.7	2.94
	2.5	8.5	1.23	30.6	2.12
	5	8.1	0.44	29.9	1.56

^aThe SWF volume range is from 0% to 5% of the accelerator mass fraction; ^bthe 1 d compressive strength of the modified accelerator; ^cthe standard deviation of 1 d compressive strength; ^dthe 28 d compressive strength of the modified accelerator; ^ethe standard deviation of 28 d compressive strength.