- Email: [email protected]
A new type of light magnesium cement foamed material
October 2002
Materials Letters 56 (2002) 353 – 356 www.elsevier.com/locate/matlet
A new type of light magnesium cement foamed material Ji Yunsong Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 20050, China Accepted 12 December 2001
Abstract By introducing an inorganic foamer, a new type of magnesium cement with high strength and water resistance is applied as the base material to prepare successfully a series of light magnesium cement foamed materials with excellent properties and a density of 0.15 – 0.60 g/cm3 by the process of foaming, compacting, solidifying and lastly gelating as well as forming the closed porosity materials. After measuring systematically the properties of light magnesium cement foamed materials, the phase compositions are studied by means of the XRD patterns. The results are discussed and concluded. D 2002 Published by Elsevier Science B.V. Keywords: Foamed material; Foamer; Magnesium cement
1. Introduction Although magnesium oxychloride cement features the following properties: quick hardening, high strength, elastic, excellent fire-proofing, good mixed compatibility with many materials, its application scope is limited greatly by the resolvability of it in the water [1]. A lot of internal and external scholars have long been devoted to the study of improving the water-resistance of magnesium oxychloride. By means of improving the composition design and introducing the efficient water-resisting additives, the water-resistance problem has been solved successfully. In order to develop the new application of the water-resisting magnesium cement in the field of building materials, the magnesium cement with high strength, excellent water resistance and fire-proofing is applied as the base material, along with introducing the inorganic foamer, to prepare successfully a series of magnesium cement foamed materials with the
following excellent properties: light, heat preservation, heat insulation, sound insulation, incombustibility and with density of 0.15 – 0.60 g/cm3 by the process of foaming, compacting, solidifying and lastly gelating as well as forming the closed porosity materials after a lot of experiments and testing comparisons. According to the different requirements for the density, it can be used as light wall board material, thermal insulation material, sound insulation ceiling material as well as heat preservation material for building top-storey, featuring with the excellent prospect of application.
2. Experiments 2.1. Raw materials Light calcinated magnesium oxide with the size of 120 mesh, magnesium chloride solution prepared by
0167-577X/02/$ - see front matter D 2002 Published by Elsevier Science B.V. PII: S 0 1 6 7 - 5 7 7 X ( 0 2 ) 0 0 4 8 4 - 6
354
J. Yunsong / Materials Letters 56 (2002) 353–356
Table 1 Chemical constituent (%) and iodine number of light calcinated magnesium MgO
CaO
Fe2O3
Al2O3
Loss of weight
Iodine noa (mg g 1)
79.18
1.47
0.78
1.09
12.72
13.20
a
Milligrams of iodine absorbed by 1 g MgO.
the magnesium chloride with appropriate water, and the additives prepared by industrial phosphoric acid with phosphate as well as completed-inorganic foamer, along with the SP milk as the foam-stabilization agent are applied. The main chemical constituent of light calcinated magnesium oxide and magnesium chloride are listed individually in the following Tables 1 and 2 (all the chemical constituent and content appeared in this article are quality fraction). 2.2. Preparation of light magnesium oxychloride cement with high strength The raw materials of magnesium oxychloride cement with certain proportion are mixed completely into the pastes, introducing the inorganic foamer and foam-stabilization agent, entering the mold for foaming and compacting, solidifying and gelating under the condition of room temperature ( > 15 jC) after two homogeneous mixing. The samples should be cultivated in the air after drawing off the mold. 2.3. Properties measuring of light magnesium oxychloride cement with high strength The samples with standard bending strength and compressive strength were prepared for measuring individually the bending strength, compressive strength and thermal conductivity on the INSTRON Strength Apparatus of England and the Thermal Conduction Apparatus of Japan. 2.4. Phase composition of light magnesium oxychloride cement with high strength XRD patterns of light magnesium oxychloride cement harder solid was measured by means of XRD Apparatus of 12 KW (CuKa).
3. Results and discussion 3.1. Composition design of magnesium oxychloride cement in the MgO –MgCl2 – H2O system It is well known that the main hydrates are 5 Mg(OH)2MgCl28H2O (abbreviated to ‘‘phase 5’’) and 3 Mg(OH)2MgCl28H2O (abbreviated to ‘‘phase 3’’) after the hardening of magnesium oxychloride cement pastes under room temperature. The study of Matkovic and Young [2] shown that the phase 5 is the main contributed one for the hardening and producing strength of magnesium oxychloride cement. Standard formation heat and other related thermodynamics data of phase 5 and phase 3 was applied to calculate the following standard formation free energy of them, according to the formula of calculation for the standard free energy supplied by Rogic and Matkovic [3]: ðDG298 Þphase 5 ¼ 3387:95 KJ=mol ðDG298 Þphase 3 ¼ 2557:07 KJ=mol In accordance with the thermodynamics principle of chemical reaction [4], the forming process of phases 5 and 3 in the MgO –MgCl2 – H2O system reads as follows. First, MgO should be dissolved in MgCl2 solution to form Mg2 + and OH ion; then phases 5 and 3 should be produced by the reaction of Mg2 +, Cl ion and H2O. Meanwhile, it can be shown that under the certain condition, phase 5 can also transfer into phase 3. Therefore, in order to form the stable structure and avoid producing the phase 3 as well as control the phase 5 transferring into phase 3 as can as possible in the MgO – MgCl2 – H2O system, the content of MgCl2 should be controlled seriously and the gelatinous Mg(OH)2 with a certain quantities should be existed. Also, in consideration of the existence of part MgO with low-activity and nonresolved MgCO3 in light calcinated MgO, the content
Table 2 Main chemical constituent (%) of magnesium chloride Mg2 +
Cl
Fe2O3
Al2O3
Na2O
CaO
SO42
11.93
34.80
0.01
0.02
0.35
0.02
2.82
J. Yunsong / Materials Letters 56 (2002) 353–356
Fig. 1. Ternary Phasegraphy and composition designing area of MgO – MgCl2 – H2O. (A) Phase 5 (38:18:44), 5Mg(OH)2MgCl2 8H2O. (B) Phase 3 (29:23:48), 3Mg(OH)2MgCl28H2O.
of MgO and H2O should be higher than the once which are necessary for the formation of phase 5. As a result, the scope listed by the dotted line in the MgO – MgCl2 –H2O Ternary Phasegraphy (Fig. 1) is selected for the composition design of this article. 3.2. Standard samples performance of light magnesium oxychloride cement The standard samples performance of light magnesium oxychloride cement are listed in the Table 3. With the drop in sample density, the bending strength, the bending strength in the water, compressive strength and thermal conductivity appeared linear decrease along with the regular increase of a average aperture. That the density of materials was mainly
355
subject to the introduction quantities of the foamer has been found in the experiments. Also the dimensions of the aperture were controlled by the mixing time after introducing the foamer on the condition of the fixed introducing quantities of the foamer. It shows in the experiments that the longer the mixing time is, the bigger and more homogeneous the dispersing degree of the foamer is, the smaller the average aperture is. However, if the mixing time is too long, the air bubble will be spilled ceaselessly with the mixing, result in the complete decrease of the bubble quantity and the increase of density and thermal conductivity. Therefore, it is the key of the preparation for the light magnesium cement materials with excellent quality that the mixing time after introducing the foamer should be controlled seriously. Additionally, that the average aperture was deeply affected by the size of MgO raw materials has been also found. Under the same density of 0.5 g/cm3, the average aperture derived from MgO with the size of 80 mesh is about two times bigger than the one with the size of 120 mesh. 3.3. Phase composition of light magnesium oxychloride cement harden solid Fig. 2 is the XRD pattern of light magnesium oxychloride cement harder solid. The phase composition of it can be obtained by the analysis of Fig. 2, namely, it mainly consists of phase 5 (characteristic peak d = 7.430, 7.420, 4.130), a few unresolved MgCO3, a few MgO without reaction, and trace Mg2P2O7 (characteristic peak d = 3.030, 2.975, 4.140), without finding the existence of phase 3 (characteristic peak d = 8.14,
Table 3 The performance of the light magnesium oxychloride cement standard samples Density (g cm3)
Bending strengtha (MPa)
Bending strengthb (MPa)
Compressive strengthc (MPa)
Thermal conductivityd [KJ(m h C) 1]
Average aperture (mm)
0.55 – 0.60 0.45 – 0.50 0.30 0.25 0.20 0.15
1.80 – 2.40 1.40 – 1.80 0.95 0.73 0.54 0.43
1.40 – 1.70 1.10 – 1.40 0.73 0.61 0.41 0.33
4.0 – 4.5 2.6 – 3.5 1.0 – 1.6 0.8 – 1.1 0.4 – 0.6 0.3 – 0.4
0.896 0.708 0.490 0.394 0.361 0.315
0.1 – 0.2 0.2 – 0.4 0.5 – 1.0 1.0 – 1.2 1.5 – 2.0 2.0 – 4.0
a b c d
4 4 4 cm samples. 4 4 4 cm samples, after soaking in water with 48 h. 5 5 6 cm samples. 4 2 18 cm samples.
356
J. Yunsong / Materials Letters 56 (2002) 353–356
Fig. 2. XRD pattern of light magnesium oxychloride cement.
3.87, 2.46). It shows that the phase composition of light magnesium oxychloride cement has not changed after introducing the inorganic foamer. Mg2P2O7 will form the gelating status in this structure for the reason that it is the chemical compound without dissolving in water, although the content of it is very small, but it still the one of the reason of the increase of water-resistance for the magnesium oxychloride cement.
0.60 g/cm3 prepared successfully is a kind of green building materials with brilliant prospect, which can be applied as light wall board material, sound insulation ceiling material, thermal insulation material used under low temperature, thermal insulation material as well as heat preservation material for building top.
References 4. Conclusions It is available on the process and technology for the preparation of light magnesium cement foamed materials that the water-resisting magnesium oxychloride cement with high strength and excellent fire-proofing performance is applied as the basic materials, along with introducing the inorganic foamer and the foamstabilization agent. A series of light magnesium cement foamed materials with the density of 0.15 –
[1] C.A. Sorrel, C.R. Armstrong, Reactions and equilibria in magnesium oxychloride cements, J. Am. Ceram. Soc. 59 (1 – 2) (1976) 51. [2] B. Matkovic, J.F. Young, Microstructure of magnesium oxychloride cements, Nature (London), Phys. Sci. 246 (1973) 70. [3] V. Rogic, B. Matkovic, Phase in magnesium oxychloride cements, Cement (Zagreb) 16 (1972) 61. [4] J. Yunsong, et al, Influence of the additive on the microstructure and performance of the new water-resisting magnesium cement, J. Inorg. Mater. 10 (2) (1995) 241.
Materials Letters 56 (2002) 353 – 356 www.elsevier.com/locate/matlet
A new type of light magnesium cement foamed material Ji Yunsong Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 20050, China Accepted 12 December 2001
Abstract By introducing an inorganic foamer, a new type of magnesium cement with high strength and water resistance is applied as the base material to prepare successfully a series of light magnesium cement foamed materials with excellent properties and a density of 0.15 – 0.60 g/cm3 by the process of foaming, compacting, solidifying and lastly gelating as well as forming the closed porosity materials. After measuring systematically the properties of light magnesium cement foamed materials, the phase compositions are studied by means of the XRD patterns. The results are discussed and concluded. D 2002 Published by Elsevier Science B.V. Keywords: Foamed material; Foamer; Magnesium cement
1. Introduction Although magnesium oxychloride cement features the following properties: quick hardening, high strength, elastic, excellent fire-proofing, good mixed compatibility with many materials, its application scope is limited greatly by the resolvability of it in the water [1]. A lot of internal and external scholars have long been devoted to the study of improving the water-resistance of magnesium oxychloride. By means of improving the composition design and introducing the efficient water-resisting additives, the water-resistance problem has been solved successfully. In order to develop the new application of the water-resisting magnesium cement in the field of building materials, the magnesium cement with high strength, excellent water resistance and fire-proofing is applied as the base material, along with introducing the inorganic foamer, to prepare successfully a series of magnesium cement foamed materials with the
following excellent properties: light, heat preservation, heat insulation, sound insulation, incombustibility and with density of 0.15 – 0.60 g/cm3 by the process of foaming, compacting, solidifying and lastly gelating as well as forming the closed porosity materials after a lot of experiments and testing comparisons. According to the different requirements for the density, it can be used as light wall board material, thermal insulation material, sound insulation ceiling material as well as heat preservation material for building top-storey, featuring with the excellent prospect of application.
2. Experiments 2.1. Raw materials Light calcinated magnesium oxide with the size of 120 mesh, magnesium chloride solution prepared by
0167-577X/02/$ - see front matter D 2002 Published by Elsevier Science B.V. PII: S 0 1 6 7 - 5 7 7 X ( 0 2 ) 0 0 4 8 4 - 6
354
J. Yunsong / Materials Letters 56 (2002) 353–356
Table 1 Chemical constituent (%) and iodine number of light calcinated magnesium MgO
CaO
Fe2O3
Al2O3
Loss of weight
Iodine noa (mg g 1)
79.18
1.47
0.78
1.09
12.72
13.20
a
Milligrams of iodine absorbed by 1 g MgO.
the magnesium chloride with appropriate water, and the additives prepared by industrial phosphoric acid with phosphate as well as completed-inorganic foamer, along with the SP milk as the foam-stabilization agent are applied. The main chemical constituent of light calcinated magnesium oxide and magnesium chloride are listed individually in the following Tables 1 and 2 (all the chemical constituent and content appeared in this article are quality fraction). 2.2. Preparation of light magnesium oxychloride cement with high strength The raw materials of magnesium oxychloride cement with certain proportion are mixed completely into the pastes, introducing the inorganic foamer and foam-stabilization agent, entering the mold for foaming and compacting, solidifying and gelating under the condition of room temperature ( > 15 jC) after two homogeneous mixing. The samples should be cultivated in the air after drawing off the mold. 2.3. Properties measuring of light magnesium oxychloride cement with high strength The samples with standard bending strength and compressive strength were prepared for measuring individually the bending strength, compressive strength and thermal conductivity on the INSTRON Strength Apparatus of England and the Thermal Conduction Apparatus of Japan. 2.4. Phase composition of light magnesium oxychloride cement with high strength XRD patterns of light magnesium oxychloride cement harder solid was measured by means of XRD Apparatus of 12 KW (CuKa).
3. Results and discussion 3.1. Composition design of magnesium oxychloride cement in the MgO –MgCl2 – H2O system It is well known that the main hydrates are 5 Mg(OH)2MgCl28H2O (abbreviated to ‘‘phase 5’’) and 3 Mg(OH)2MgCl28H2O (abbreviated to ‘‘phase 3’’) after the hardening of magnesium oxychloride cement pastes under room temperature. The study of Matkovic and Young [2] shown that the phase 5 is the main contributed one for the hardening and producing strength of magnesium oxychloride cement. Standard formation heat and other related thermodynamics data of phase 5 and phase 3 was applied to calculate the following standard formation free energy of them, according to the formula of calculation for the standard free energy supplied by Rogic and Matkovic [3]: ðDG298 Þphase 5 ¼ 3387:95 KJ=mol ðDG298 Þphase 3 ¼ 2557:07 KJ=mol In accordance with the thermodynamics principle of chemical reaction [4], the forming process of phases 5 and 3 in the MgO –MgCl2 – H2O system reads as follows. First, MgO should be dissolved in MgCl2 solution to form Mg2 + and OH ion; then phases 5 and 3 should be produced by the reaction of Mg2 +, Cl ion and H2O. Meanwhile, it can be shown that under the certain condition, phase 5 can also transfer into phase 3. Therefore, in order to form the stable structure and avoid producing the phase 3 as well as control the phase 5 transferring into phase 3 as can as possible in the MgO – MgCl2 – H2O system, the content of MgCl2 should be controlled seriously and the gelatinous Mg(OH)2 with a certain quantities should be existed. Also, in consideration of the existence of part MgO with low-activity and nonresolved MgCO3 in light calcinated MgO, the content
Table 2 Main chemical constituent (%) of magnesium chloride Mg2 +
Cl
Fe2O3
Al2O3
Na2O
CaO
SO42
11.93
34.80
0.01
0.02
0.35
0.02
2.82
J. Yunsong / Materials Letters 56 (2002) 353–356
Fig. 1. Ternary Phasegraphy and composition designing area of MgO – MgCl2 – H2O. (A) Phase 5 (38:18:44), 5Mg(OH)2MgCl2 8H2O. (B) Phase 3 (29:23:48), 3Mg(OH)2MgCl28H2O.
of MgO and H2O should be higher than the once which are necessary for the formation of phase 5. As a result, the scope listed by the dotted line in the MgO – MgCl2 –H2O Ternary Phasegraphy (Fig. 1) is selected for the composition design of this article. 3.2. Standard samples performance of light magnesium oxychloride cement The standard samples performance of light magnesium oxychloride cement are listed in the Table 3. With the drop in sample density, the bending strength, the bending strength in the water, compressive strength and thermal conductivity appeared linear decrease along with the regular increase of a average aperture. That the density of materials was mainly
355
subject to the introduction quantities of the foamer has been found in the experiments. Also the dimensions of the aperture were controlled by the mixing time after introducing the foamer on the condition of the fixed introducing quantities of the foamer. It shows in the experiments that the longer the mixing time is, the bigger and more homogeneous the dispersing degree of the foamer is, the smaller the average aperture is. However, if the mixing time is too long, the air bubble will be spilled ceaselessly with the mixing, result in the complete decrease of the bubble quantity and the increase of density and thermal conductivity. Therefore, it is the key of the preparation for the light magnesium cement materials with excellent quality that the mixing time after introducing the foamer should be controlled seriously. Additionally, that the average aperture was deeply affected by the size of MgO raw materials has been also found. Under the same density of 0.5 g/cm3, the average aperture derived from MgO with the size of 80 mesh is about two times bigger than the one with the size of 120 mesh. 3.3. Phase composition of light magnesium oxychloride cement harden solid Fig. 2 is the XRD pattern of light magnesium oxychloride cement harder solid. The phase composition of it can be obtained by the analysis of Fig. 2, namely, it mainly consists of phase 5 (characteristic peak d = 7.430, 7.420, 4.130), a few unresolved MgCO3, a few MgO without reaction, and trace Mg2P2O7 (characteristic peak d = 3.030, 2.975, 4.140), without finding the existence of phase 3 (characteristic peak d = 8.14,
Table 3 The performance of the light magnesium oxychloride cement standard samples Density (g cm3)
Bending strengtha (MPa)
Bending strengthb (MPa)
Compressive strengthc (MPa)
Thermal conductivityd [KJ(m h C) 1]
Average aperture (mm)
0.55 – 0.60 0.45 – 0.50 0.30 0.25 0.20 0.15
1.80 – 2.40 1.40 – 1.80 0.95 0.73 0.54 0.43
1.40 – 1.70 1.10 – 1.40 0.73 0.61 0.41 0.33
4.0 – 4.5 2.6 – 3.5 1.0 – 1.6 0.8 – 1.1 0.4 – 0.6 0.3 – 0.4
0.896 0.708 0.490 0.394 0.361 0.315
0.1 – 0.2 0.2 – 0.4 0.5 – 1.0 1.0 – 1.2 1.5 – 2.0 2.0 – 4.0
a b c d
4 4 4 cm samples. 4 4 4 cm samples, after soaking in water with 48 h. 5 5 6 cm samples. 4 2 18 cm samples.
356
J. Yunsong / Materials Letters 56 (2002) 353–356
Fig. 2. XRD pattern of light magnesium oxychloride cement.
3.87, 2.46). It shows that the phase composition of light magnesium oxychloride cement has not changed after introducing the inorganic foamer. Mg2P2O7 will form the gelating status in this structure for the reason that it is the chemical compound without dissolving in water, although the content of it is very small, but it still the one of the reason of the increase of water-resistance for the magnesium oxychloride cement.
0.60 g/cm3 prepared successfully is a kind of green building materials with brilliant prospect, which can be applied as light wall board material, sound insulation ceiling material, thermal insulation material used under low temperature, thermal insulation material as well as heat preservation material for building top.
References 4. Conclusions It is available on the process and technology for the preparation of light magnesium cement foamed materials that the water-resisting magnesium oxychloride cement with high strength and excellent fire-proofing performance is applied as the basic materials, along with introducing the inorganic foamer and the foamstabilization agent. A series of light magnesium cement foamed materials with the density of 0.15 –
[1] C.A. Sorrel, C.R. Armstrong, Reactions and equilibria in magnesium oxychloride cements, J. Am. Ceram. Soc. 59 (1 – 2) (1976) 51. [2] B. Matkovic, J.F. Young, Microstructure of magnesium oxychloride cements, Nature (London), Phys. Sci. 246 (1973) 70. [3] V. Rogic, B. Matkovic, Phase in magnesium oxychloride cements, Cement (Zagreb) 16 (1972) 61. [4] J. Yunsong, et al, Influence of the additive on the microstructure and performance of the new water-resisting magnesium cement, J. Inorg. Mater. 10 (2) (1995) 241.