Influence of Reactive Alumina and Calcined Alumina on properties of Free Flowing Castables

doi:10.19691/j.cnki.1004-4493.2021.03.002

China's Refractories ›› 2021, Vol. 30 ›› Issue (3): 7-10.DOI: 10.19691/j.cnki.1004-4493.2021.03.002

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Influence of Reactive Alumina and Calcined Alumina on properties of Free Flowing Castables

Christian DÜNZEN^*()

Nabaltec AG, Schwandorf 92421, Germany

Online:2021-09-15 Published:2021-11-26
Contact: Christian DÜNZEN
About author:Dr. Christian Dünzen was born in 1982 in Germany. He studied ceramics engineering from 2003 to 2007 at the University of Applied Sciences in Koblenz, and then he achieved his Ph.D in 2017 at the Technical University of Clausthal-Zellerfeld. He has been working at Nabaltec AG since 2007. Since 2017, he has been working as the Head of Department R & D/Technical Service.

Reactive alumina is a well-established group of raw materials for refractory castables to improve their rheological behavior. In this article the influence of bimodal reactive alumina and standard (<325#) calcined alumina on workability, packing density and strength of alumina based castables is examined. It will be shown that there is a significant effect on water demand and apparent density of the castable, which is depending on the percentage of reactive alumina on the one hand and on the type of reactive alumina on the other hand. The effect of the alumina on setting time and cold crushing strength has shown to be insignificant in this set of experiments.

Key words: reactive alumina, refractory castables, calcined alumina, rheological behavior

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Christian DÜNZEN. Influence of Reactive Alumina and Calcined Alumina on properties of Free Flowing Castables[J]. China's Refractories, 2021, 30(3): 7-10.

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URL: http://www.cnref.cn/EN/10.19691/j.cnki.1004-4493.2021.03.002

http://www.cnref.cn/EN/Y2021/V30/I3/7

Figures/Tables 11

Table 1 Castable formulations according to the first variation

Formulation /mass%		1	2	3	4
TA	3 - 6 mm	24	24	24	24
	1 - 3 mm	16	16	16	16
	0.5 - 1 mm	15	15	15	15
	<0.5 mm	7	8	11	11
	<0.3 mm	5	6
	<325#	12	14	15	15
CAC		3	3	5	5
CA		5	7	8	12
RA		13	7	6	2
PAE /[g · (100 g)^-1] (extra adding)		0.1	0.1	0.1	0.1

Table 1 Castable formulations according to the first variation

Formulation /mass%		1	2	3	4
TA	3 - 6 mm	24	24	24	24
	1 - 3 mm	16	16	16	16
	0.5 - 1 mm	15	15	15	15
	<0.5 mm	7	8	11	11
	<0.3 mm	5	6
	<325#	12	14	15	15
CAC		3	3	5	5
CA		5	7	8	12
RA		13	7	6	2
PAE /[g · (100 g)^-1] (extra adding)		0.1	0.1	0.1	0.1

Table 2 Physical and chemical properties of used CA and RA grades, according to the second variation

	Matrix A		Matrix B		Matrix C
	CA (<325#)	RA	CA (<325#)	RA	CA (<325#)	RA
	No. 315	No. 530	No. 115 TC	No. 660	No. 115 TC	No. 652
D₁₀/µm	0.8	0.3	1.0	0.4	1.0	0.5
D₅₀/µm	3.2	1.6	4.5	1.9	4.5	3.1
D₉₀/µm	8.5	5.0	13	5.0	13	5.5
S_spec./(m² · g^-1)	1.2	4.0	0.9	2.8	0.9	2.6
Al₂O₃/mass%	99.6	99.8	99.6	99.8	99.6	99.8
Na₂O /mass%	0.30	0.10	0.30	0.10	0.30	0.10
SiO₂ /mass%	0.02	0.02	0.01	0.02	0.01	0.02

Table 2 Physical and chemical properties of used CA and RA grades, according to the second variation

	Matrix A		Matrix B		Matrix C
	CA (<325#)	RA	CA (<325#)	RA	CA (<325#)	RA
	No. 315	No. 530	No. 115 TC	No. 660	No. 115 TC	No. 652
D₁₀/µm	0.8	0.3	1.0	0.4	1.0	0.5
D₅₀/µm	3.2	1.6	4.5	1.9	4.5	3.1
D₉₀/µm	8.5	5.0	13	5.0	13	5.5
S_spec./(m² · g^-1)	1.2	4.0	0.9	2.8	0.9	2.6
Al₂O₃/mass%	99.6	99.8	99.6	99.8	99.6	99.8
Na₂O /mass%	0.30	0.10	0.30	0.10	0.30	0.10
SiO₂ /mass%	0.02	0.02	0.01	0.02	0.01	0.02

Fig. 1 Particle size distributions of CA-grades

Fig. 2 Particle size distributions of RA-grades

Table 3 Castable properties achieved with matrix A

Formulation	1	2	3	4
Water demand /[mL · (100 g)^-1]	3.8	3.9	4	4.4
Spreading /%	125	110	120	115
Setting time /min	600	440	170	415
CCS_{110 °C} /MPa	73	109	97	83
Apparent density_{110 °C} /(g · cm^-3)	3.31	3.25	3.26	3.25

Table 3 Castable properties achieved with matrix A

Formulation	1	2	3	4
Water demand /[mL · (100 g)^-1]	3.8	3.9	4	4.4
Spreading /%	125	110	120	115
Setting time /min	600	440	170	415
CCS_{110 °C} /MPa	73	109	97	83
Apparent density_{110 °C} /(g · cm^-3)	3.31	3.25	3.26	3.25

Table 4 Castable properties achieved with matrix B

Formulation	1	2	3	4
Water demand /[mL · (100 g)^-1]	4.0	4.2	4.4	5.2
Spreading /%	110	120	110	110
Setting time /min	220	210	180	340
CCS_{110 °C} /MPa	61	59	74	70
Apparent density_{110 °C} /(g · cm^-3)	3.29	3.25	3.20	3.18

Table 4 Castable properties achieved with matrix B

Formulation	1	2	3	4
Water demand /[mL · (100 g)^-1]	4.0	4.2	4.4	5.2
Spreading /%	110	120	110	110
Setting time /min	220	210	180	340
CCS_{110 °C} /MPa	61	59	74	70
Apparent density_{110 °C} /(g · cm^-3)	3.29	3.25	3.20	3.18

Table 5 Castable properties achieved with matrix C

Formulation	1	2	3	4
Water demand /[mL · (100 g)^-1]	4.6	4.8	5.0	5.2
Spreading /%	100	105	110	110
Setting time /min	590	590	610	590
CCS_{110 °C} /MPa	54	52	79	67
Apparent density_{110 °C} /(g · cm^-3)	3.22	3.20	3.17	3.15

Table 5 Castable properties achieved with matrix C

Formulation	1	2	3	4
Water demand /[mL · (100 g)^-1]	4.6	4.8	5.0	5.2
Spreading /%	100	105	110	110
Setting time /min	590	590	610	590
CCS_{110 °C} /MPa	54	52	79	67
Apparent density_{110 °C} /(g · cm^-3)	3.22	3.20	3.17	3.15

Fig. 3 Water demand of test castables in dependence of reactive alumina content

Fig. 4 Apparent density of test castables in dependency of water demand

Fig. 5 Influence of matrix on water demand of test castables

Fig. 6 Influence of matrix on apparent density of test castables

References 6

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[3]	D. R. Dinger, J. E. Funk, Particle packing, part III: discrete versus continuous particle sizes. Interceram, 1992, 41(5):332-334.
[4]	Ritwik Sarkar. Effect of alumina fines on high alumina self-flow low cement castables. International Ceramic Review, 2013, 63(3):113-116.
[5]	Chabas E., Ulrich C., Caneri P. Improving flowability of low-cement castable refractories using fine-ground alumina. American Ceramic Society Bulletin, 2013, 92(3):23-24.
[6]	R. Kockegey-Lorenz, A. Buhr, D. Schmidtmeier, Z. Tian, D. Zacherl, S. Chatterjee, J. Dutton. The value of additives in refractory castables—part 1: castables without silica fume. Proceedings of UNITECR 2015, Austria, 2015: 232.

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