Specimens with 5 different IBA replacement amount of 0%, 5%,10%, 15%, and 20%(wt) were prepared. Before the specimens were made, the raw materials went through Atterberg limits to derive their plasticity limits so that proper mixing water quantities could be determined. In the process of fabrication, proper compositions of clay, IBA were uniformly mixed in a shaft clay mixer first, and the mixtures were kneaded with a de-airing vacuum pug mill to reduce extra interior pores. Next, the well-kneaded mixtures were placed in a mold with the size of 12 * 6*1 cm3 and compressed by a pressing machine with a normal pressure of 34.32 ± 0.5 MPa to produce the specimens. Specimen were then kilned at 4 different temperatures, 1000℃,1050℃,1100℃, and 1150℃. Based on the mixture and kilned temperatures, 20 sets of specimens were made. Each set of specimens had 30 tile samples ready for a series of tests, including shrinkage, weight loss on ignition, specific gravity, water absorption, bending strength, wear resistance, SEM, EDS, XRD, and NMR..
3.1 Atterberg limits
The plastic limits obtained from plastic limit tests for different mix designs were used to study the effects of the various IBA replacements on the amount of water applied at each mix design. Figure 3 shows the results of the plastic limit at different amounts of IBA replacement. Because the IBA was characterized as porous material with high water absorption. As shown in the figure, the plastic limits increased first and then decreased with the increasing amount of the IBA replacement. When applied IBA to the floor tiles, the water used in the mixing process was increased. Moreover, IBA was characterized as hydrophobic non-plastic material. After the amount of IBA replacement reached to 10%, the plastic limit reduced with the increasing amount of the IBA replacement.
3.1 Shrinkage
Figure 4 shows results of the shrinkage for floor tiles contained with different amounts of IBA replacement firing at various kiln temperatures. A study by (Valle-Zermeño et al 2016) suggested that when the particle size was small, the diffusion became better and the neck effect grew fast leading to a better compaction for ceramic tiles. Because the particle sizes of IBA were larger than that of clay, the particles were hard to mixed uniformly inside the structure of floor tiles. Hence, the shrinkage of the floor tiles reduced with the increasing amount of the IBA replacement within the kiln temperature of 1000-1100oC. Moreover, Figure 5 shows the shrinkage and expansion of the floor tile specimens at different kiln temperature. When the kiln temperature increased, the pores among particles were pushed and compacted by the thermal force driven from heat in the floor tile specimens. The shrinkage of the tile specimens reduced first and then expanded with the increasing of the kiln temperature, as shown in the figure 5. The highest shrinkage of the floor tile specimens was 5.25% at the initial stage of firing temperature of 1000oC. When the kiln temperature reached to 1100oC, the highest shrinkage of the tile specimens was observed. It suggests that the interior of the floor tile specimens was completely compacted. Finally, as the kiln temperature increased 50oC more, melting of the tile body was noticed and entrapped air was wrapped by glass film. As a result, the tile body was expanded, which comply with the pioneering study at Imperial College (Cheesman et al. 2003). Another study by (Bernd and Carl 1997) suggested that the expansion of tile body was reduced if the tile specimens contained with large amount of CaO. It was also possible that the shrinkage of tile specimens could be turned from negative to positive with the amount of IBA replacement increased at kiln temperature of 1150oCn (Bijen 1986).
3.2 Weight loss on ignition
Figure 5 shows results of the weight loss on ignition for floor tiles contained with different amounts of IBA replacement firing at various kiln temperatures. Because IBA contained with large amount of organic and non-organic matters and heavy metals in which were easily burned or become fugitive emissions at high kiln temperature. The weight loss on ignition of floor tile specimens increased with increasing amount of IBA replacement. Although the weight loss on ignition increased with the increasing of the kiln temperature, the increment of weight loss on ignition became less with the increasing amount of IBA replacement.
3.3 Specific gravity
Figure 6 shows results of the specific gravity for floor tiles contained with different amounts of IBA replacement firing at various kiln temperatures. Because the IBA contained with CaCO3 leading to an increase of pore volume inside the tile body, the specific gravity of the floor tile specimens reduced with the increasing amount of IBA replacement within the kiln temperature of 1000-1100oC. As the kiln temperature reached to 1150oC, the specific gravity increased with the increasing amount of IBA replacement. The high kiln temperature could result in a rearranging of particle in the interior structure of the floor tile specimens, producing compaction of tile body, and pore volume circularized and vanished. The specific gravity of the tile specimens reduced with the increasing kiln temperature within the kiln temperature of 1000-1100oC. At kiln temperature of 1100oC, the pores in the tile body were circularized and vanished leading to a more compact interior structure of floor tile and apparent increase of specific gravity was observed. However, as the kiln temperature reached to 1150oC, the tile body became to melt and foam and pores were produced in the interior of specimens leading to a decrease on the specific gravity.
3.4 Water absorption
Figure 7 shows results of the water absorption for floor tiles contained with different amounts of IBA replacement firing at various kiln temperatures. Bernd and Carl [1997] pointed out that the carbonates in the tile body could increase the water absorption of tile specimens. IBA contained with large amount of CaCO3 in which characterized as carbonate. The water absorption of floor tile specimens increased with increasing amount of IBA replacement, as shown in the Figure 7. Moreover, pores in the interior structure of tile specimens were gradually circularized and vanished driven by the thermal force from heat. As a result, the interior structure became compact. The water absorption of floor tile specimens contained with IBA replacement reduced with the increasing of kiln temperature. When the kiln temperature reached to 1150oC, the surface of the floor tile specimens became shiny and water was hard to penetrate into tile specimens. Hence, the water absorption for floor tile specimens firing at kiln temperature of 1150oC was close to zero, as also shown in Figure 7 and Figure 8.
3.5 Bending strength
Figure 9 shows results of the bending strength for floor tiles contained with different amounts of IBA replacement firing at various kiln temperatures. Because IBA was a porous material, the porosity of the floor tile specimens increased with increasing amount of IBA replacement. This increasing of porosity could affect the interior structure of tile specimens. The bending strength of floor tile specimens reduced with increasing amount of IBA replacement, as shown in the Figure 9. Moreover, high kiln temperature could reduce pores in the tile specimens leading to a more compact interior structure of floor tile specimens. The bending strength of floor tile specimens containing with IBA replacements increased with increasing kiln temperature within the range of 1000-1100oC, as shown in the Figure 9. However, when kiln temperature reached to 1150oC, foam was produced in the tile specimens and the bending strength of tile specimens reduced, as shown in the Figure 9, while Figure 10 shows the cross section of the tile specimens.
3.6 Wear resistance
Figure 11 shows results of the wear resistance for floor tiles contained with different amounts of IBA replacement firing at various kiln temperatures. Because IBA was a porous material, the compaction of floor tile specimens became less with increasing amount of clay replaced by IBA firing at the same kiln temperature. Hence, the amount of wear for tile specimens increased with increasing amount of IBA replacement. Moreover, the thermal force from heat could produce more compact interior structure for floor tile specimens. The amount of wear for tile specimens reduced with increasing kiln temperature with the range of 1000-1100oC, as shown in the Figure 11. However, when kiln temperature reached to 1150oC, melting of the tile specimens was observed and foam was produced in the tile specimens. Hence, the amount of wear for tile specimens firing at 1150oC was more than that firing at 1100oC, as shown in the Figure 11 and 12.
3.7 SEM analysis
Figures 13 and 14 show SEM images for floor tiles contained with 0 and 20% IBA replacements firing at various kiln temperatures, respectively, while Figures 15 shows SEM images for floor tiles containing different amount of IBA replacements firing at kiln temperature of 1150oC. The images were magnified at 5000 times. Because IBA contained with CaCO3 in which decomposed into CaO and CO2 at high kiln temperature. As a result, pores would be increased by the addition of IBA replacement. The SEM images show that holes in the interior structure of floor tile specimens increased with increasing amount of IBA replacement firing at the same kiln temperature. As stated above, the interior structure of the floor tile specimens became more compact at kiln temperature of 1100oC driven by the thermal force from heat, as shown in the Figure 13 and 14. The pores reduced and strength increased. Hence, the largest bending strength and least amount of wear were obtained for tile specimens firing at kiln temperature of 1100oC. Moreover, when kiln temperature reached to 1150oC and passed over the melting point of tile specimens, the floor tile specimens began to melt and foam was formed with holes produced. Hence, the bending strength of the tile specimens reduced at kiln temperature of 1150oC.
3.8 EDS analysis
Figure16 shows results obtained from EDS analysis for floor tiles contained with different amounts of IBA replacement firing at kiln temperature of 1150oC. The main and trace chemical elements in the floor tile specimens contained with different amount of IBA replacement were O, Mg, Al, Si, K, Ca, and Fe, and C, Na, Ti, and Zr, respectively. The main chemical elements in the floor tile specimens were little affected by kiln temperature. Moreover, there were no apparent differences on main chemical elements for floor tile specimens contained with different amount of IBA replacement as the kiln temperature increased. As stated above, the main chemical element of IBA was Ca and the amount of Si was less in IBA. The amount of Si in floor tile specimens decreased with increasing amount of IBA replacement firing at the same kiln temperature.
3.9 XRD analysis
Table 4 shows results obtained from XRD analysis for floor tiles contained with different amounts of IBA replacement firing at various kiln temperatures. The main component in floor tile specimens was SiO2. The IBA contained with CaCO3. When the amount of IBA replacement increased, the amounts of productions of CaSiO3 and Ca(Al2Si2O8) produced from SiO2 with CaO and Al2O3 increased, as shown in the Table 4. As discussed above, the bending strength of floor tile specimens decreased with increasing amount of IBA replacement. It suggests that the amounts of CaSiO3 and Ca(Al2Si2O8) increased with the increasing amount of IBA replacement may lead to a decrease on bending strength of tile specimens. Moreover, the amount of production of MgSiO3 produced from SiO2 and MgO increased with the increasing kiln temperature resulting in an increase of bending strength of floor tile specimens within the temperature of 1000-1100oC. However, as the kiln temperature reached to 1150oC, more amount of Ca(Al2Si2O8) was produced and the bending strength of tile specimens reduced.
Figure 17 shows SEM images for floor tiles contained with 0% IBA replacements firing at kiln temperatures of 1000-1150oC. The red arrow in the figure pointed to the crystal products of SiO2 and Al2O3 in the interior structure of floor tile specimens. The amount of crystal products reduced with increasing of kiln temperature. It suggests that the tile body structure became compact as the kiln temperature increased. Figure 18 shows SEM images for floor tiles contained with 5-20% of IBA replacement firing at kiln temperature of 1150oC. When part of clay replaced by IBA, impurities were observed on the images of tile specimens. It suggests from EDS analysis that the impurities were Ca related compounds because IBA contained with large amount of Ca element. The Ca related compounds increased with increasing amount of IBA replacement.
Table 4 XRD analysis for floor tiles
Temperature
|
IBA %
|
SiO2
|
AlPO4
|
CaSiO3
|
MgSiO3
|
Ca(Al2Si2O8)
|
K(AlSi3O8)
|
1000℃
|
0%
|
54.9
|
1.2
|
4.4
|
16.5
|
16.3
|
6.8
|
10%
|
56.4
|
0.3
|
7.7
|
9.0
|
21.8
|
4.8
|
20%
|
36.9
|
0.4
|
10.2
|
24.8
|
20.9
|
6.8
|
1050℃
|
0%
|
45.8
|
1.9
|
10.4
|
14.1
|
15.4
|
12.4
|
10%
|
54.2
|
0.1
|
5.8
|
20.0
|
17.0
|
2.9
|
20%
|
55.8
|
0.7
|
-
|
-
|
43.5
|
-
|
1100℃
|
0%
|
84.3
|
2.7
|
13.0
|
-
|
-
|
-
|
10%
|
52.7
|
1.2
|
-
|
25.0
|
15.1
|
6.1
|
20%
|
37.0
|
1.6
|
-
|
41.3
|
20.1
|
-
|
1150℃
|
0%
|
65.3
|
2.0
|
8.0
|
15.5
|
9.2
|
-
|
10%
|
40.2
|
1.2
|
-
|
-
|
21.2
|
10.6
|
20%
|
33.7
|
1.4
|
-
|
-
|
45.5
|
19.3
|
3.10 NMR analysis
Figure19 shows integration result of NMR spectra analysis for floor tiles contained with different amounts of IBA replacement firing at kiln temperature of 1050oC. Qx stands for the location of Si in the tetrahedral structure. Q0 is the location of the un-connecting Si atom in the tetrahedral structure with chemical shifts between -68 and -76ppm. Q1 is at the location connecting to one Si atom with chemical shifts between -76 and -82ppm. Q2 has chemical shifts between -82 and -88ppm. Q3 has chemical shifts between -88 and -98ppm. Q4 is at the location connecting to four Si atoms with chemical shifts between -98 and -129ppm (He and Hu 2007). The values of Q4 after integration decreased with increasing amount of IBA replacement. Because the IBA contained with less amount of Si than that of clay, the amount of silicate became less with insufficient Si atom in the tile specimens. Moreover, the less amount of silicate lead to the decrease of bending strength for tile specimens in which conformed with the results obtained from bending strength tests.
3.11 Quality summary for floor tile
Table 5 shows the quality requirements for ceramic floor tiles contained with IBA and SSA replacements. The qualified rate for bending failure loading decreased with increasing amount of IBA replacement. Because IBA was a material with large porosity, the amount of IBA replacement increased resulted in an increase of porosity for floor tile specimens and reduction on qualified rate for tile specimens. Moreover, the high kiln temperature improved the compaction of floor tile specimens. The qualified rate of bending failure loading for tile specimens increased with increasing kiln temperature. At kiln temperature of 1100oC, the bending failure loadings for floor tile specimens contained with different amount of IBA replacement met the requirement set by the standards. In general, the floor tile specimens contained with different amount of IBA replacement firing at various kiln temperature met the requirement for type III water absorption set by the standards. As for type Ia, Ib, and II water absorption, the qualified rates were improved by increasing kiln temperature. Because the IBA contained with CaCO3 in which decomposed into CaO and CO2 and formed air bubbles at high kiln temperature, the qualified rate of water absorption decreased with increasing amount of IBA replacement. Table 6 shows the floor tile specimens with different mix designs met the requirements set by the standard. As shown in the table, the tile specimens contained with 5% IBA replacement firing at kiln temperature of 1050-1150oC met the requirements set for the exterior ceramic floor tile standards. Moreover, the same mix design of tile specimens firing at kiln temperature of 1100oC met the requirements for the interior floor tile standards and the high standard of Ib water absorption requirement.
Table 5 Quality compliance summary for all tile specimens
Material
|
Temperature
(℃)
|
Judgment criteria
|
|
Interior floor tile
|
Exterior floor tile
|
Water absorption(%)
|
|
Clay
(%)
|
IBA
(%)
|
Bending strength
|
Size shrinkage
|
Bending strength
|
Size shrinkage
|
|
Ia
|
Ib
|
II
|
III
|
|
100
|
0
|
1000
|
○
|
×
|
×
|
×
|
×
|
×
|
×
|
○
|
|
1050
|
○
|
×
|
○
|
○
|
×
|
×
|
○
|
○
|
|
1100
|
○
|
×
|
○
|
×
|
×
|
○
|
○
|
○
|
|
1150
|
○
|
×
|
○
|
○
|
○
|
○
|
○
|
○
|
|
95
|
5
|
1000
|
○
|
×
|
×
|
×
|
×
|
×
|
×
|
○
|
|
1050
|
○
|
×
|
○
|
○
|
×
|
×
|
×
|
○
|
|
1100
|
○
|
○
|
○
|
○
|
×
|
○
|
○
|
○
|
|
1150
|
○
|
×
|
○
|
○
|
×
|
○
|
○
|
○
|
|
90
|
10
|
1000
|
○
|
×
|
×
|
○
|
×
|
×
|
×
|
○
|
|
1050
|
○
|
×
|
×
|
×
|
×
|
×
|
×
|
○
|
|
1100
|
○
|
×
|
○
|
×
|
×
|
×
|
○
|
○
|
|
1150
|
○
|
×
|
○
|
○
|
○
|
○
|
○
|
○
|
|
85
|
15
|
1000
|
×
|
×
|
×
|
○
|
×
|
×
|
×
|
○
|
|
1050
|
○
|
○
|
×
|
○
|
×
|
×
|
×
|
○
|
|
1100
|
○
|
×
|
○
|
×
|
×
|
×
|
○
|
○
|
|
1150
|
○
|
×
|
○
|
○
|
×
|
○
|
○
|
○
|
|
80
|
20
|
1000
|
×
|
×
|
×
|
×
|
×
|
×
|
×
|
○
|
|
1050
|
○
|
○
|
×
|
○
|
×
|
×
|
×
|
○
|
|
1100
|
○
|
×
|
○
|
×
|
×
|
×
|
○
|
○
|
|
1150
|
○
|
×
|
○
|
○
|
×
|
○
|
○
|
○
|
|
70
|
30
|
1000
|
×
|
○
|
×
|
○
|
×
|
×
|
×
|
○
|
|
1050
|
×
|
○
|
×
|
○
|
×
|
×
|
×
|
○
|
|
1100
|
○
|
×
|
○
|
×
|
×
|
×
|
○
|
○
|
|
1150
|
○
|
×
|
○
|
×
|
○
|
○
|
○
|
○
|
|
Table 6表6 Suggested applications for tiles with different IBA replacement
Material
|
Temperature
(℃)
|
Judgment criteria
(Interior floor tile / Exterior floor tile)
|
Water absorption
(Ia、Ib、II、III)
|
|
|
Clay
(%)
|
IBA
(%)
|
|
|
100
|
0
|
1050
|
Exterior floor tile
|
II、III
|
|
1150
|
Exterior floor tile
|
Ia、Ib、II、III
|
|
95
|
5
|
1050
|
Exterior floor tile
|
III
|
|
1100
|
Interior floor tile/ Exterior floor tile
|
Ib、II、III
|
|
1150
|
Exterior floor tile
|
Ib、II、III
|
|
90
|
10
|
1150
|
Exterior floor tile
|
Ia、Ib、II、III
|
|
85
|
15
|
1050
|
Interior floor tile
|
III
|
|
1150
|
Exterior floor tile
|
Ib、II、III
|
|
80
|
20
|
1050
|
Interior floor tile
|
III
|
|
1150
|
Exterior floor tile
|
Ib、II、III
|
|