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Compressive strength and resistance to chloride penetration of mortars using ceramic waste as fine aggregate
Construction and Building Materials 26 (2012) 96–101
Contents lists available at ScienceDirect
Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Compressive strength and resistance to chloride penetration of mortars using ceramic waste as fine aggregate Hiroshi Higashiyama a,⇑, Fumio Yagishita a, Masanori Sano a, Osamu Takahashi b a b
Department of Civil and Environmental Engineering, Kinki University, 3-4-1, Kowakae, Higashiosaka, Osaka 577-8502, Japan The Kanden L&A Company, Ltd., 1-3-12, Shinmachi, Nishi-ku, Osaka 550-0013, Japan
a r t i c l e
i n f o
Article history: Received 25 December 2010 Received in revised form 16 April 2011 Accepted 27 May 2011 Available online 21 June 2011 Keywords: Ceramic waste Mortar Compressive strength Chloride penetration
a b s t r a c t This paper presents the results of experimental investigation on compressive strength and resistance to chloride ion penetration of mortars made of ceramic waste as fine aggregate. The ceramic waste of electrical insulators provided from an electric power company in Japan has been crushed and ground to produce fine aggregates for mortars in this study. In the process of crushing and grounding, ceramic powder is discharged as a by-product. The effects of mixing with the ceramic powder in mortars have been also investigated. Compression tests of mortars are conducted at 7, 28 and 91 days curing. Moreover, the resistance to chloride ion penetration of mortars has been determined by two methods: the spraying of a 0.1 N silver nitrate solution and the X-ray fluorescence spectrometry. The compressive strength of mortar made of the ceramic waste aggregate increases and the resistance to chloride ion penetration is significantly higher in comparison with mortar made of the river sand. It is also confirmed that a partial replacement of cement by the ceramic powder up to 20% by weight is effective with respect to the compressive strength and the resistance to chloride ion penetration. Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction Industrial wastes have continued to increase due to the continued demands of resource use. With increasing restrictions on landfills, industries have to find effective ways for recycling their wastes and by-products. From the viewpoint of the sustainable society, recycle of ceramic wastes from ceramic industries and electric power companies is one of the most important purposes as the global environmental problem. In the year 2009, electric power companies in Japan have discharged ceramic wastes of 3300 t from The Tokyo Electric Co. Inc. [1] and 3100 t from The Kansai Electric Co. Inc. [2]. Some researchers in the world have investigated the effects of using ceramic wastes, such as blocks, bricks, roof tiles, sanitary ware or electrical insulators, as aggregates and/or pozzolanic admixtures in mortar and concrete. There are a number of studies on mechanical properties of mortar or concrete made of ceramic wastes as aggregates [3–13]. The pozzolanic reactivity of ceramic powders from ceramic roof tiles or ceramic electrical insulators has been confirmed [9–11]. Several authors [5–7,12,13] have also investigated on permeability, abrasion resistance, and chloride ion penetration depth of concrete with crushed ceramic wastes.
⇑ Corresponding author. Tel.: +81 6 6721 2332; fax: +81 72 995 5192. E-mail address: [email protected] (H. Higashiyama). 0950-0618/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.conbuildmat.2011.05.008
Compressive strength increased and chloride ion penetration depth significantly reduced with the increase in crushed ceramic percentages [6]. However, the effects and mechanical properties on ceramic wastes of electrical insulators provided from electric power industries in mortar and concrete are still limited [4,10,13]. In the present study, the ceramic waste of electrical insulators provided from an electric power company in Japan was used as fine aggregate in mortar. The ceramic powder produced in the process of crushing and grounding of the ceramic waste was also used with a partial replacement of cement or as an admixture. The aim of this investigation is to study the compressive strength and the resistance to chloride ion penetration of mortars containing the ceramic waste aggregate and powder. 2. Experimental programs 2.1. Materials Ceramic electrical insulators as shown in Fig. 1 were broken by a hammer into smaller pieces with 50–100 mm length. These pieces were crushed using a specially assembled crushing machine into under 30 mm particle size. These ceramic particles had very sharp edges like a knife edge, which were still dangerous to supply as aggregates for mortar and concrete. Therefore, the ceramic particles were ground by an originally developed grinding machine with a 160 L capacity such as Los Angeles abrasion testing machine (Fig. 2). The relation between the particle edge width and grinding time [14] is given in Fig. 3. The safety shape of particle, which has the particle edge width of greater than 0.5 mm, is sufficiently obtained by grinding for 45–60 min. The grain size distribution of ceramic waste fine aggregate
97
H. Higashiyama et al. / Construction and Building Materials 26 (2012) 96–101
100
Passing (%)
80
60
40
Ceramic
20
River sand 0 0.075
0.15
0.3
0.6
1.2
2.5
5.0
10.0
Sieve size (mm)
Fig. 1. Ceramic electrical insulator.
Fig. 4. Grain size distributions of ceramic waste aggregate and river sand. The chemical composition of ceramic waste from electrical insulators is presented in Table 1. Maximum particle size, specific gravity, water absorption, and fineness modulus of the ceramic waste aggregate and the river sand are presented in Table 2. In this study, the particle size ranging from 5.0 to 0.075 mm was used as fine aggregate and that with smaller than 0.075 mm was employed as a partial replacement of cement or as an admixture. The cement used was an ordinary Portland cement (specific gravity: 3.15, specific surface area: 3360 cm2/g). 2.2. Mixture proportions A constant water to cement ratio (W/C) of 0.5 by weight and sand to cement ratio (S/C) of 2.0 by weight were chosen as the basic mixture proportion of mortar. Mixture proportion ratios by weight are summarized in Table 3. A partial replacement of cement by the ceramic powder with the particle size smaller than 0.075 mm was at 10%, 20% or 30% of cement by weight and the addition of ceramic powder to mortars was also at 10%, 20% or 30% of cement by weight. The river sand was mixed in saturated surface-dry condition. On the other hand, the ceramic waste aggregate and powder were mixed in air-dry condition owing to lower water absorption. 2.3. Specimens preparation and test procedures Fig. 2. An originally developed grinding machine.
after grinding for 60 min is shown in Fig. 4 with that of river sand and Japanese Industrial Standards (JIS A 5005). The grain size distribution of ceramic waste aggregate used was adjusted to correspond with that of the river sand for specimens of compression tests in order to provide a direct comparison of their effects on the compressive strength. The ceramic waste aggregate of mortar for the chloride ion penetration test, however, was supplied without making an adjustment of the grain size distribution.
2.3.2. Pore size distribution test The pore size distribution test was performed using a mercury intrusion porosimeter. The samples were obtained from each broken cylinder of 50 mm diameter and 100 mm height after 28 days curing. Pore volume of pore size ranging from 0.01 to 10 lm was measured. Specimens, S-1, G-1, GI-2 and GE-2 shown in Table 3, were chosen considering the results of compression test.
Particle edge width (mm)
0.7
Safety shape area
0.6
2.3.1. Compression test For each mixture, five cylindrical specimens of 50 mm diameter and 100 mm height were cast to determine the compressive strengths after 7, 28 and 91 days curing. The specimens were covered with a plastic waterproof sheet for 24 h after casting and then were demolded and cured in water at 20 ± 2 °C of room temperature until the test age. Compressive load was applied by using a 500 kN capacity universal testing machine and loading speed was a constant of 0.6 N/mm2/s. Only the specimens at 28 days curing were attached two strain gauges on the side surface to determine the elastic modulus.
0.5
2.3.3. Chloride ion penetration test In this study, the chloride ion penetration test referred to the procedures described in the literature [6,15,16] was conducted. Mortar cylinders of 100 mm diameter and 200 mm height were demolded after 24 h of casting and cured in water at 20 ± 2 °C of room temperature for 7 days. After that, they were cut into 150 mm height with the 50 mm end discarded and were left to dry in laboratory condition for 24 h before application of epoxy coating. The specimens were
0.4 0.3 0.2 0.1
Table 1 Chemical composition of ceramic waste from electrical insulators.
0 0
15
30
45
60
Grinding time (min) Fig. 3. Particle edge width and grinding time.
Chemical composition (%)
75 SiO2
Al2O3
Fe2O3
CaO
MgO
Na2O
K2O
TiO2
70.9
21.1
0.81
0.76
0.24
1.47
3.57
0.33
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H. Higashiyama et al. / Construction and Building Materials 26 (2012) 96–101
Table 2 Physical properties of ceramic waste aggregate and river sand. Physical properties
Ceramic waste
River sand
Maximum size (mm) Specific gravity Water absorption (%) Finess modulus
5.0 2.30 0.47 3.74
5.0 2.59 1.73 2.39
Table 3 Mixture proportion ratios of mortars (by weight). Specimen
W
C
S
Ceramic powder
Fine aggregate
S-1 G-1 GI-1 GI-2 GI-3 GE-1 GE-2 GE-3
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
2.0 2.0 1.8 1.6 1.4 2.0 2.0 2.0
4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0
– – 0.2 0.4 0.6 0.2 0.4 0.6
RS CWA CWA CWA CWA CWA CWA CWA
W is water, C is cement, S is fine aggregate, RS is river sand, CWA is ceramic waste aggregate.
epoxy-coated leaving only one sawn surface free of coating and were fully immersed in a 5.0% NaCl solution for 3 months and 6 months in hermetic tanks at 20 ± 2 °C of room temperature as shown in Fig. 5. Specimens, S-1, G-1, GI-2 and GE-2, were chosen as well as the pore size distribution test. At each age, after spraying of a 0.1 N silver nitrate solution on a cross section of split mortar [17], white silver chloride precipitation was measured by a caliper at three points (mid and its both sides apart from 25 mm) as shown in Fig. 6. Furthermore, to determine the concentration and penetration depth of chloride ion, mortar powder samples taken from five drilled holes (in 10 mm depth increments) were analyzed by using the X-ray fluorescent spectrometer (OURSTEX 101FA) which can accurately measure the chloride ion concentration of 0.1 kg/m3.
3. Results and discussion
of specimens made of the ceramic waste aggregate and powder except for a replacement ratio of 30% at earlier age became higher at each age. The compressive strengths of GI series decreased gradually with the increase of a replacement ratio except for a replacement ratio of 30% at 28 days curing. However, differences of the compressive strengths of GI series in comparison with that of specimen G-1 became smaller at long curing age. From these results, it might be said that the ceramic powder has the pozzolanic reactivity. Furthermore, the compressive strengths of GE series with an addition of the ceramic powder increased slightly with the increase of its amount at each age. In addition, since the elastic modulus of the ceramic waste aggregate itself from electrical insulators is considerably high, the elastic modulus of the specimens made of the ceramic waste aggregate tested were relatively higher than that of the specimen made of the river sand (Table 4). 3.2. Pore size distribution It is well known that the compressive strength and chloride diffusion of hardened cement paste depend on the porosity and pore size distribution [18–20]. The relations between the pore volume and pore diameter ranging from 0.01 to 10 lm at 28 days curing in comparison with specimen S-1 made of the river sand are given in Fig. 8. Pore volume ranging from 0.03 to 1.0 lm of pore diameter in mortars containing the ceramic waste aggregate decreases than that of specimen S-1. Furthermore, the histogram of cumulative pore volume ranging from 0.05 to 2.0 lm of pore diameter, which highly correlates with chloride ion ingress [20], is given in Fig. 9. Each cumulative pore volume of specimens G-1, GI-2, and GE-2 decreases by 30%, 28%, and 43% in comparison with that of specimen S-1. These results are in agreement with the results of increasing the compressive strength as presented in Fig. 7. Consequently, it can be said that mortars made of the ceramic waste aggregate lead to superior durability concerning not only the chloride ion penetration but also water absorption and vapor permeability.
3.1. Compressive strength
3.3. Resistance to chloride ion penetration
The results of compressive strengths of mortars at 7, 28 and 91 days curing and the elastic modulus at 28 days curing are summarized in Table 4. The histogram of compressive strengths at 7, 28 and 91 days curing is also shown in Fig. 7. In comparison with specimen S-1 made of the river sand, the compressive strengths
3.3.1. Chloride ion penetration depth The split surfaces of specimens (focused around white silver chloride precipitation), after spraying a 0.1 N silver nitrate solution, are shown in Fig. 10. The white silver chloride penetration depth (lower side of Fig. 10) in all the specimens was clearly visible
5 % NaCl solution
Fig. 5. Immersion of mortars in a 5.0% NaCl solution.
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H. Higashiyama et al. / Construction and Building Materials 26 (2012) 96–101
Pore volume (ml/g)
0.008
S-1 0.006
G-1
0.004 0.002 0 0.001
0.01
0.1
1
10
Pore diameter ( µm)
(a) G-1 Fig. 6. Measured positions of white silver chloride precipitation.
Pore volume (ml/g)
0.008
2
Compressive strength (N/mm )
100 80
7 days 28 days 91 days
60
S-1 0.006
GI-2
0.004 0.002 0 0.001
40
0.01
0.1
1
10
Pore diameter ( µm)
20
(b) GI-2 0 GI-1
GI-2
GI-3
GE-1
GE-2
GE-3
Fig. 7. Compressive strengths of mortars.
Table 4 Compressive strengths and modulus of elasticity. Specimen
S-1 G-1 GI-1 GI-2 GI-3 GE-1 GE-2 GE-3
Compressive strength (N/mm2)
Elastic modulus (kN/mm2)
7 days
28 days
91 days
28 days
31.8 38.3 34.7 33.3 25.9 34.8 34.4 36.3
51.6 58.7 57.2 53.1 32.6 61.5 62.8 67.4
58.0 70.3 71.4 66.5 62.3 77.1 81.5 83.7
26.4 30.1 30.8 31.7 28.2 34.8 34.5 35.7
and almost uniformly distributed. The results of chloride ion penetration depths at each immersion age are presented in Table 5. It can be seen that the chloride ion penetration depths of mortars containing the ceramic waste aggregate were considerably less than that of mortar made of the river sand at each immersion age. The difference of chloride ion penetration depth between mortars containing the ceramic waste aggregate with a replacement by or an addition of the ceramic powder was insignificant. Researchers [18–20] state that the chloride diffusion is strongly dependent on the porosity of hardened cementitious matrixes. As shown in Figs. 8 and 9, the pore volume in mortars containing the ceramic waste aggregate was lower than that of mortar made of the river sand. The chloride ion penetration depth correlates well with the cumulative pore volume. 3.3.2. Chloride ion concentration Total chloride ion profiles of specimens determined by the Xray fluorescence spectrometry at each immersion age are given
0.008
Pore volume (ml/g)
G-1
S-1 0.006
GE-2
0.004 0.002 0 0.001
0.01
0.1
1
10
Pore diameter ( µm)
(c) GE-2 Fig. 8. Pore volume and pore diameter at 28 days of curing.
in Fig. 11. At both 3 months and 6 months immersion, the chloride ion in specimen S-1 penetrated into a greater depth from the ex-
Cumulative pore volume (ml/g)
S-1
0.02
0.015
0.01
0.005
0
S-1
G-1
GI-2
GE-2
Fig. 9. Histogram of cumulative pore volume ranging from 0.05 to 2.0 lm of pore diameter.
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H. Higashiyama et al. / Construction and Building Materials 26 (2012) 96–101
S-1
G-1
GI-2
GE-2
GI-2
GE-2
3 months immersion
S-1
G-1 6 months immersion
Fig. 10. Split surface of specimens after sprayed a 0.1 N silver nitrate solution.
Table 5 Chloride penetration depths. Chloride ion penetration depth (mm)
S-1 G-1 GI-2 GE-2
3 months
6 months
12.3 7.2 7.3 6.0
18.4 7.6 6.1 6.5
Chloride ion content (kg/m 3)
Specimen
20
S-1 G-1
15
GE-2 10
5
0
10
20
30
40
50
Depth from sufrace (mm)
GI-2 GE-2
(a) 3 months immersion
10 20
S-1 5
0
0
5
10
15
20
25
30
Depth from sufrace (mm)
(a) 3 months immersion 20
Chloride ion content (kg/m 3)
GI-2
0
S-1
GI-2 GE-2
10
5
0
10
20
30
40
50
Depth from sufrace (mm)
(b) 6 months immersion
10
Fig. 12. Curve fitting by Eq. (1) of total chloride profiles.
5
0
G-1
15
0
G-1 GI-2 GE-2
15
Chloride ion centent (kg/m 3)
Chloride ion content (kg/m 3)
20
S-1 G-1
15
0
10
20
30
Depth from sufrace (mm)
(b) 6 months immersion Fig. 11. Total chloride profiles.
40
50
posed surface than that in the other specimens. It can be seen that specimens G-1, GI-2 and GE-2 exhibited a better resistance to the chloride ion penetration than specimen S-1. These results correspond to the white silver chloride penetration depths shown in Fig. 10 and Table 5. Although the chloride ion concentration of specimen GI-2 was greater than that of specimens G-1 and GE-2 at 3 months immersion, those chloride ion profiles expressed almost the same profiles at 6 months immersion. Both the apparent chloride diffusion coefficient and the surface chloride concentration for each specimen at each immersion age
H. Higashiyama et al. / Construction and Building Materials 26 (2012) 96–101 Table 6 Apparent chloride diffusion coefficients. Specimen
3 months 3
S-1 G-1 GI-2 GE-2
6 months 2
C0 (kg/m )
D (cm /year)
C0 (kg/m3)
D (cm2/year)
23.63 34.34 30.24 32.85
4.85 0.92 1.67 0.93
22.91 26.31 29.78 32.80
2.70 0.67 0.58 0.46
were determined by fitting Eq. (1) to the corresponding measured chloride ion profiles for a relative comparison on the resistance to chloride ion penetration. The chloride concentration C (x, t) is given by
x Cðx; tÞ ¼ C 0 1 erf pffiffiffiffiffiffiffiffiffi 2 Dt
101
(3) From the results of the spraying a 0.1 N silver nitrate solution and the X-ray fluorescence spectrometry, the ceramic waste aggregate and powder used in mortars significantly restrains chloride ion penetration. The chloride ion penetration depths of mortars made of the ceramic waste aggregate and powder were about half and one third of that made of the river sand at 3 months and 6 months immersion, respectively. Apparent chloride ion diffusion coefficients of mortars made of the ceramic waste aggregate and powder significantly decreased in comparison with mortar made of the river sand. Consequently, it is concluded that mortars made of the ceramic waste aggregate and powder lead to superior durability concerning the chloride ion ingress.
ð1Þ
where, C (x, t) is the chloride concentration (kg/m3) at depth x (cm) and time t (year), C0 is the surface chloride concentration (kg/m3), D is the apparent chloride diffusion coefficient (cm2/year), and erf is the error function. From the results of the curve fitting by Eq. (1), the apparent chloride diffusion coefficient and the surface chloride concentration for each specimen at each immersion age are determined as shown in Fig. 12 and Table 6. The apparent chloride diffusion coefficients of all the specimens decreased with the immersion period (Table 6). The apparent chloride diffusion coefficients of mortars containing the ceramic waste aggregate were much lower than that of specimen S-1 made of the river sand. In comparison with specimen G-1, an addition of the ceramic powder with respect to the resistance to chloride ion penetration had only a minor effect in this study. It was revealed that mortars containing the ceramic waste aggregate from electrical insulators exhibit a higher performance against the chloride ion penetration as well as using ceramic bricks, tiles or sanitary ware [6,7,12]. Further studies, however, are needed for a better understanding of this chloride resistance of mortars made of the ceramic waste aggregate with respect to the chloride binding properties. 4. Conclusions This study investigated the compressive strength and resistance to chloride ion penetration of mortars made of the ceramic waste from electrical insulators as fine aggregate and powder. The following conclusions can be drawn. (1) No harmful influence with respect to the compressive strength of mortar made of the ceramic waste aggregate was found. On the contrary, the compressive strength of mortars made of the ceramic aggregate and powder except for a replacement ratio of 30% at earlier age became higher than that of mortar made of the river sand at each age. It is concluded that the ceramic waste aggregate investigated herein can be supplied as fine aggregate for mortar. (2) The pore volume distribution ranging from 0.03 to 1.0 lm of pore diameter in mortars made of the ceramic waste aggregate and powder at 28 days curing decreased than that of mortar made of the river sand.
References [1]. [2] . [3] de Brito J, Pereira AS, Correia JR. Mechanical behavior of non-structural concrete made with recycled ceramic aggregates. Cem Concr Compos 2005;27:429–33. [4] Senthamarai RM, Manoharan PD. Concrete with ceramic waste aggregate. Cem Concr Compos 2005;27:910–3. [5] Correia JR, de Brito J, Pereira AS. Effects on concrete durability of using recycled ceramic aggregates. Mater Struct 2006;39:169–77. [6] Binici H. Effect of crushed ceramic and basaltic pumice as fine aggregates on concrete mortars properties. Constr Build Mater 2007;21:1191–7. [7] Pacheco-Torgal F, Jalali S. Reusing ceramic wastes in concrete. Constr Build Mater 2010;24:832–8. [8] Torkittikul P, Chaipanich A. Utilization of ceramic waste as fine aggregate within Portland cement and fly ash concretes. Cem Concr Compos 2010;32:440–9. [9] Ay N, Ünal M. The use of waste ceramic tile in cement production. Cem Concr Res 2000;30:497–9. [10] Hata H, Nakashita A, Ohmura T, Itou H. Strength development of concrete containing granulated abandonment insulator. Proc Jpn Concr Inst 2004;26(1):1683–8 [in Japanese]. [11] Lavat AE, Trezza MA, Poggi M. Characterization of ceramic roof tile wastes as pozzolanic admixture. Waste Manage 2009;29:1666–74. [12] Gomes M, de Brito J. Structural concrete with incorporation of coarse recycled concrete and ceramic aggregates: durability performance. Mater Struct 2009;42:663–75. [13] Senthamarai RM, Manoharan PD, Gobinath D. Concrete made from ceramic industry waste: Durability properties. Constr Build Mater 2011;25:2413–9. [14] Sano M, Tobi N, Takahashi O, Sakai K. Study on recycling crushed insulator to safe shaped aggregate. J Jpn Inst Aggr Technol 2009;41(163):117–25 [in Japanese]. [15] Meck E, Sirivivatnanon V. Field indicator of chloride penetration depth. Cem Concr Res 2003;33:1113–7. [16] Chindaprasirt P, Chotithanorm C, Cao HT, Sirivivatnanon V. Influence of fly ash fineness on the chloride penetration of concrete. Constr Build Mater 2007;21:356–61. [17] Otsuki N, Nagataki S, Nakashita K. Evaluation of AgNO3 solution spray method for measurement of chloride penetration into hardened cementitious matrix materials. ACI Mater J 1992;89(6):587–92. [18] Odler I, Robler M. Investigation on the relationship between porosity, structure and strength of hydrated Portland cement paste. (I) Effect of porosity. Cem Concr Res 1985;15:320–30. [19] Robler M, Odler I. Investigation on the relationship between porosity, structure and strength of hydrated Portland cement paste. (II) Effect of pore structure and of degree of hydration. Cem Concr Res 1985;15:401–10. [20] Matsushita H, Sagawa Y, Kawabata Y. The effect of microstructure on strength and durability of mortar incorporating recycled fine aggregate. J JSCE Div E 2006;62(1):230–42 [in Japanese].
Contents lists available at ScienceDirect
Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Compressive strength and resistance to chloride penetration of mortars using ceramic waste as fine aggregate Hiroshi Higashiyama a,⇑, Fumio Yagishita a, Masanori Sano a, Osamu Takahashi b a b
Department of Civil and Environmental Engineering, Kinki University, 3-4-1, Kowakae, Higashiosaka, Osaka 577-8502, Japan The Kanden L&A Company, Ltd., 1-3-12, Shinmachi, Nishi-ku, Osaka 550-0013, Japan
a r t i c l e
i n f o
Article history: Received 25 December 2010 Received in revised form 16 April 2011 Accepted 27 May 2011 Available online 21 June 2011 Keywords: Ceramic waste Mortar Compressive strength Chloride penetration
a b s t r a c t This paper presents the results of experimental investigation on compressive strength and resistance to chloride ion penetration of mortars made of ceramic waste as fine aggregate. The ceramic waste of electrical insulators provided from an electric power company in Japan has been crushed and ground to produce fine aggregates for mortars in this study. In the process of crushing and grounding, ceramic powder is discharged as a by-product. The effects of mixing with the ceramic powder in mortars have been also investigated. Compression tests of mortars are conducted at 7, 28 and 91 days curing. Moreover, the resistance to chloride ion penetration of mortars has been determined by two methods: the spraying of a 0.1 N silver nitrate solution and the X-ray fluorescence spectrometry. The compressive strength of mortar made of the ceramic waste aggregate increases and the resistance to chloride ion penetration is significantly higher in comparison with mortar made of the river sand. It is also confirmed that a partial replacement of cement by the ceramic powder up to 20% by weight is effective with respect to the compressive strength and the resistance to chloride ion penetration. Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction Industrial wastes have continued to increase due to the continued demands of resource use. With increasing restrictions on landfills, industries have to find effective ways for recycling their wastes and by-products. From the viewpoint of the sustainable society, recycle of ceramic wastes from ceramic industries and electric power companies is one of the most important purposes as the global environmental problem. In the year 2009, electric power companies in Japan have discharged ceramic wastes of 3300 t from The Tokyo Electric Co. Inc. [1] and 3100 t from The Kansai Electric Co. Inc. [2]. Some researchers in the world have investigated the effects of using ceramic wastes, such as blocks, bricks, roof tiles, sanitary ware or electrical insulators, as aggregates and/or pozzolanic admixtures in mortar and concrete. There are a number of studies on mechanical properties of mortar or concrete made of ceramic wastes as aggregates [3–13]. The pozzolanic reactivity of ceramic powders from ceramic roof tiles or ceramic electrical insulators has been confirmed [9–11]. Several authors [5–7,12,13] have also investigated on permeability, abrasion resistance, and chloride ion penetration depth of concrete with crushed ceramic wastes.
⇑ Corresponding author. Tel.: +81 6 6721 2332; fax: +81 72 995 5192. E-mail address: [email protected] (H. Higashiyama). 0950-0618/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.conbuildmat.2011.05.008
Compressive strength increased and chloride ion penetration depth significantly reduced with the increase in crushed ceramic percentages [6]. However, the effects and mechanical properties on ceramic wastes of electrical insulators provided from electric power industries in mortar and concrete are still limited [4,10,13]. In the present study, the ceramic waste of electrical insulators provided from an electric power company in Japan was used as fine aggregate in mortar. The ceramic powder produced in the process of crushing and grounding of the ceramic waste was also used with a partial replacement of cement or as an admixture. The aim of this investigation is to study the compressive strength and the resistance to chloride ion penetration of mortars containing the ceramic waste aggregate and powder. 2. Experimental programs 2.1. Materials Ceramic electrical insulators as shown in Fig. 1 were broken by a hammer into smaller pieces with 50–100 mm length. These pieces were crushed using a specially assembled crushing machine into under 30 mm particle size. These ceramic particles had very sharp edges like a knife edge, which were still dangerous to supply as aggregates for mortar and concrete. Therefore, the ceramic particles were ground by an originally developed grinding machine with a 160 L capacity such as Los Angeles abrasion testing machine (Fig. 2). The relation between the particle edge width and grinding time [14] is given in Fig. 3. The safety shape of particle, which has the particle edge width of greater than 0.5 mm, is sufficiently obtained by grinding for 45–60 min. The grain size distribution of ceramic waste fine aggregate
97
H. Higashiyama et al. / Construction and Building Materials 26 (2012) 96–101
100
Passing (%)
80
60
40
Ceramic
20
River sand 0 0.075
0.15
0.3
0.6
1.2
2.5
5.0
10.0
Sieve size (mm)
Fig. 1. Ceramic electrical insulator.
Fig. 4. Grain size distributions of ceramic waste aggregate and river sand. The chemical composition of ceramic waste from electrical insulators is presented in Table 1. Maximum particle size, specific gravity, water absorption, and fineness modulus of the ceramic waste aggregate and the river sand are presented in Table 2. In this study, the particle size ranging from 5.0 to 0.075 mm was used as fine aggregate and that with smaller than 0.075 mm was employed as a partial replacement of cement or as an admixture. The cement used was an ordinary Portland cement (specific gravity: 3.15, specific surface area: 3360 cm2/g). 2.2. Mixture proportions A constant water to cement ratio (W/C) of 0.5 by weight and sand to cement ratio (S/C) of 2.0 by weight were chosen as the basic mixture proportion of mortar. Mixture proportion ratios by weight are summarized in Table 3. A partial replacement of cement by the ceramic powder with the particle size smaller than 0.075 mm was at 10%, 20% or 30% of cement by weight and the addition of ceramic powder to mortars was also at 10%, 20% or 30% of cement by weight. The river sand was mixed in saturated surface-dry condition. On the other hand, the ceramic waste aggregate and powder were mixed in air-dry condition owing to lower water absorption. 2.3. Specimens preparation and test procedures Fig. 2. An originally developed grinding machine.
after grinding for 60 min is shown in Fig. 4 with that of river sand and Japanese Industrial Standards (JIS A 5005). The grain size distribution of ceramic waste aggregate used was adjusted to correspond with that of the river sand for specimens of compression tests in order to provide a direct comparison of their effects on the compressive strength. The ceramic waste aggregate of mortar for the chloride ion penetration test, however, was supplied without making an adjustment of the grain size distribution.
2.3.2. Pore size distribution test The pore size distribution test was performed using a mercury intrusion porosimeter. The samples were obtained from each broken cylinder of 50 mm diameter and 100 mm height after 28 days curing. Pore volume of pore size ranging from 0.01 to 10 lm was measured. Specimens, S-1, G-1, GI-2 and GE-2 shown in Table 3, were chosen considering the results of compression test.
Particle edge width (mm)
0.7
Safety shape area
0.6
2.3.1. Compression test For each mixture, five cylindrical specimens of 50 mm diameter and 100 mm height were cast to determine the compressive strengths after 7, 28 and 91 days curing. The specimens were covered with a plastic waterproof sheet for 24 h after casting and then were demolded and cured in water at 20 ± 2 °C of room temperature until the test age. Compressive load was applied by using a 500 kN capacity universal testing machine and loading speed was a constant of 0.6 N/mm2/s. Only the specimens at 28 days curing were attached two strain gauges on the side surface to determine the elastic modulus.
0.5
2.3.3. Chloride ion penetration test In this study, the chloride ion penetration test referred to the procedures described in the literature [6,15,16] was conducted. Mortar cylinders of 100 mm diameter and 200 mm height were demolded after 24 h of casting and cured in water at 20 ± 2 °C of room temperature for 7 days. After that, they were cut into 150 mm height with the 50 mm end discarded and were left to dry in laboratory condition for 24 h before application of epoxy coating. The specimens were
0.4 0.3 0.2 0.1
Table 1 Chemical composition of ceramic waste from electrical insulators.
0 0
15
30
45
60
Grinding time (min) Fig. 3. Particle edge width and grinding time.
Chemical composition (%)
75 SiO2
Al2O3
Fe2O3
CaO
MgO
Na2O
K2O
TiO2
70.9
21.1
0.81
0.76
0.24
1.47
3.57
0.33
98
H. Higashiyama et al. / Construction and Building Materials 26 (2012) 96–101
Table 2 Physical properties of ceramic waste aggregate and river sand. Physical properties
Ceramic waste
River sand
Maximum size (mm) Specific gravity Water absorption (%) Finess modulus
5.0 2.30 0.47 3.74
5.0 2.59 1.73 2.39
Table 3 Mixture proportion ratios of mortars (by weight). Specimen
W
C
S
Ceramic powder
Fine aggregate
S-1 G-1 GI-1 GI-2 GI-3 GE-1 GE-2 GE-3
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
2.0 2.0 1.8 1.6 1.4 2.0 2.0 2.0
4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0
– – 0.2 0.4 0.6 0.2 0.4 0.6
RS CWA CWA CWA CWA CWA CWA CWA
W is water, C is cement, S is fine aggregate, RS is river sand, CWA is ceramic waste aggregate.
epoxy-coated leaving only one sawn surface free of coating and were fully immersed in a 5.0% NaCl solution for 3 months and 6 months in hermetic tanks at 20 ± 2 °C of room temperature as shown in Fig. 5. Specimens, S-1, G-1, GI-2 and GE-2, were chosen as well as the pore size distribution test. At each age, after spraying of a 0.1 N silver nitrate solution on a cross section of split mortar [17], white silver chloride precipitation was measured by a caliper at three points (mid and its both sides apart from 25 mm) as shown in Fig. 6. Furthermore, to determine the concentration and penetration depth of chloride ion, mortar powder samples taken from five drilled holes (in 10 mm depth increments) were analyzed by using the X-ray fluorescent spectrometer (OURSTEX 101FA) which can accurately measure the chloride ion concentration of 0.1 kg/m3.
3. Results and discussion
of specimens made of the ceramic waste aggregate and powder except for a replacement ratio of 30% at earlier age became higher at each age. The compressive strengths of GI series decreased gradually with the increase of a replacement ratio except for a replacement ratio of 30% at 28 days curing. However, differences of the compressive strengths of GI series in comparison with that of specimen G-1 became smaller at long curing age. From these results, it might be said that the ceramic powder has the pozzolanic reactivity. Furthermore, the compressive strengths of GE series with an addition of the ceramic powder increased slightly with the increase of its amount at each age. In addition, since the elastic modulus of the ceramic waste aggregate itself from electrical insulators is considerably high, the elastic modulus of the specimens made of the ceramic waste aggregate tested were relatively higher than that of the specimen made of the river sand (Table 4). 3.2. Pore size distribution It is well known that the compressive strength and chloride diffusion of hardened cement paste depend on the porosity and pore size distribution [18–20]. The relations between the pore volume and pore diameter ranging from 0.01 to 10 lm at 28 days curing in comparison with specimen S-1 made of the river sand are given in Fig. 8. Pore volume ranging from 0.03 to 1.0 lm of pore diameter in mortars containing the ceramic waste aggregate decreases than that of specimen S-1. Furthermore, the histogram of cumulative pore volume ranging from 0.05 to 2.0 lm of pore diameter, which highly correlates with chloride ion ingress [20], is given in Fig. 9. Each cumulative pore volume of specimens G-1, GI-2, and GE-2 decreases by 30%, 28%, and 43% in comparison with that of specimen S-1. These results are in agreement with the results of increasing the compressive strength as presented in Fig. 7. Consequently, it can be said that mortars made of the ceramic waste aggregate lead to superior durability concerning not only the chloride ion penetration but also water absorption and vapor permeability.
3.1. Compressive strength
3.3. Resistance to chloride ion penetration
The results of compressive strengths of mortars at 7, 28 and 91 days curing and the elastic modulus at 28 days curing are summarized in Table 4. The histogram of compressive strengths at 7, 28 and 91 days curing is also shown in Fig. 7. In comparison with specimen S-1 made of the river sand, the compressive strengths
3.3.1. Chloride ion penetration depth The split surfaces of specimens (focused around white silver chloride precipitation), after spraying a 0.1 N silver nitrate solution, are shown in Fig. 10. The white silver chloride penetration depth (lower side of Fig. 10) in all the specimens was clearly visible
5 % NaCl solution
Fig. 5. Immersion of mortars in a 5.0% NaCl solution.
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H. Higashiyama et al. / Construction and Building Materials 26 (2012) 96–101
Pore volume (ml/g)
0.008
S-1 0.006
G-1
0.004 0.002 0 0.001
0.01
0.1
1
10
Pore diameter ( µm)
(a) G-1 Fig. 6. Measured positions of white silver chloride precipitation.
Pore volume (ml/g)
0.008
2
Compressive strength (N/mm )
100 80
7 days 28 days 91 days
60
S-1 0.006
GI-2
0.004 0.002 0 0.001
40
0.01
0.1
1
10
Pore diameter ( µm)
20
(b) GI-2 0 GI-1
GI-2
GI-3
GE-1
GE-2
GE-3
Fig. 7. Compressive strengths of mortars.
Table 4 Compressive strengths and modulus of elasticity. Specimen
S-1 G-1 GI-1 GI-2 GI-3 GE-1 GE-2 GE-3
Compressive strength (N/mm2)
Elastic modulus (kN/mm2)
7 days
28 days
91 days
28 days
31.8 38.3 34.7 33.3 25.9 34.8 34.4 36.3
51.6 58.7 57.2 53.1 32.6 61.5 62.8 67.4
58.0 70.3 71.4 66.5 62.3 77.1 81.5 83.7
26.4 30.1 30.8 31.7 28.2 34.8 34.5 35.7
and almost uniformly distributed. The results of chloride ion penetration depths at each immersion age are presented in Table 5. It can be seen that the chloride ion penetration depths of mortars containing the ceramic waste aggregate were considerably less than that of mortar made of the river sand at each immersion age. The difference of chloride ion penetration depth between mortars containing the ceramic waste aggregate with a replacement by or an addition of the ceramic powder was insignificant. Researchers [18–20] state that the chloride diffusion is strongly dependent on the porosity of hardened cementitious matrixes. As shown in Figs. 8 and 9, the pore volume in mortars containing the ceramic waste aggregate was lower than that of mortar made of the river sand. The chloride ion penetration depth correlates well with the cumulative pore volume. 3.3.2. Chloride ion concentration Total chloride ion profiles of specimens determined by the Xray fluorescence spectrometry at each immersion age are given
0.008
Pore volume (ml/g)
G-1
S-1 0.006
GE-2
0.004 0.002 0 0.001
0.01
0.1
1
10
Pore diameter ( µm)
(c) GE-2 Fig. 8. Pore volume and pore diameter at 28 days of curing.
in Fig. 11. At both 3 months and 6 months immersion, the chloride ion in specimen S-1 penetrated into a greater depth from the ex-
Cumulative pore volume (ml/g)
S-1
0.02
0.015
0.01
0.005
0
S-1
G-1
GI-2
GE-2
Fig. 9. Histogram of cumulative pore volume ranging from 0.05 to 2.0 lm of pore diameter.
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H. Higashiyama et al. / Construction and Building Materials 26 (2012) 96–101
S-1
G-1
GI-2
GE-2
GI-2
GE-2
3 months immersion
S-1
G-1 6 months immersion
Fig. 10. Split surface of specimens after sprayed a 0.1 N silver nitrate solution.
Table 5 Chloride penetration depths. Chloride ion penetration depth (mm)
S-1 G-1 GI-2 GE-2
3 months
6 months
12.3 7.2 7.3 6.0
18.4 7.6 6.1 6.5
Chloride ion content (kg/m 3)
Specimen
20
S-1 G-1
15
GE-2 10
5
0
10
20
30
40
50
Depth from sufrace (mm)
GI-2 GE-2
(a) 3 months immersion
10 20
S-1 5
0
0
5
10
15
20
25
30
Depth from sufrace (mm)
(a) 3 months immersion 20
Chloride ion content (kg/m 3)
GI-2
0
S-1
GI-2 GE-2
10
5
0
10
20
30
40
50
Depth from sufrace (mm)
(b) 6 months immersion
10
Fig. 12. Curve fitting by Eq. (1) of total chloride profiles.
5
0
G-1
15
0
G-1 GI-2 GE-2
15
Chloride ion centent (kg/m 3)
Chloride ion content (kg/m 3)
20
S-1 G-1
15
0
10
20
30
Depth from sufrace (mm)
(b) 6 months immersion Fig. 11. Total chloride profiles.
40
50
posed surface than that in the other specimens. It can be seen that specimens G-1, GI-2 and GE-2 exhibited a better resistance to the chloride ion penetration than specimen S-1. These results correspond to the white silver chloride penetration depths shown in Fig. 10 and Table 5. Although the chloride ion concentration of specimen GI-2 was greater than that of specimens G-1 and GE-2 at 3 months immersion, those chloride ion profiles expressed almost the same profiles at 6 months immersion. Both the apparent chloride diffusion coefficient and the surface chloride concentration for each specimen at each immersion age
H. Higashiyama et al. / Construction and Building Materials 26 (2012) 96–101 Table 6 Apparent chloride diffusion coefficients. Specimen
3 months 3
S-1 G-1 GI-2 GE-2
6 months 2
C0 (kg/m )
D (cm /year)
C0 (kg/m3)
D (cm2/year)
23.63 34.34 30.24 32.85
4.85 0.92 1.67 0.93
22.91 26.31 29.78 32.80
2.70 0.67 0.58 0.46
were determined by fitting Eq. (1) to the corresponding measured chloride ion profiles for a relative comparison on the resistance to chloride ion penetration. The chloride concentration C (x, t) is given by
x Cðx; tÞ ¼ C 0 1 erf pffiffiffiffiffiffiffiffiffi 2 Dt
101
(3) From the results of the spraying a 0.1 N silver nitrate solution and the X-ray fluorescence spectrometry, the ceramic waste aggregate and powder used in mortars significantly restrains chloride ion penetration. The chloride ion penetration depths of mortars made of the ceramic waste aggregate and powder were about half and one third of that made of the river sand at 3 months and 6 months immersion, respectively. Apparent chloride ion diffusion coefficients of mortars made of the ceramic waste aggregate and powder significantly decreased in comparison with mortar made of the river sand. Consequently, it is concluded that mortars made of the ceramic waste aggregate and powder lead to superior durability concerning the chloride ion ingress.
ð1Þ
where, C (x, t) is the chloride concentration (kg/m3) at depth x (cm) and time t (year), C0 is the surface chloride concentration (kg/m3), D is the apparent chloride diffusion coefficient (cm2/year), and erf is the error function. From the results of the curve fitting by Eq. (1), the apparent chloride diffusion coefficient and the surface chloride concentration for each specimen at each immersion age are determined as shown in Fig. 12 and Table 6. The apparent chloride diffusion coefficients of all the specimens decreased with the immersion period (Table 6). The apparent chloride diffusion coefficients of mortars containing the ceramic waste aggregate were much lower than that of specimen S-1 made of the river sand. In comparison with specimen G-1, an addition of the ceramic powder with respect to the resistance to chloride ion penetration had only a minor effect in this study. It was revealed that mortars containing the ceramic waste aggregate from electrical insulators exhibit a higher performance against the chloride ion penetration as well as using ceramic bricks, tiles or sanitary ware [6,7,12]. Further studies, however, are needed for a better understanding of this chloride resistance of mortars made of the ceramic waste aggregate with respect to the chloride binding properties. 4. Conclusions This study investigated the compressive strength and resistance to chloride ion penetration of mortars made of the ceramic waste from electrical insulators as fine aggregate and powder. The following conclusions can be drawn. (1) No harmful influence with respect to the compressive strength of mortar made of the ceramic waste aggregate was found. On the contrary, the compressive strength of mortars made of the ceramic aggregate and powder except for a replacement ratio of 30% at earlier age became higher than that of mortar made of the river sand at each age. It is concluded that the ceramic waste aggregate investigated herein can be supplied as fine aggregate for mortar. (2) The pore volume distribution ranging from 0.03 to 1.0 lm of pore diameter in mortars made of the ceramic waste aggregate and powder at 28 days curing decreased than that of mortar made of the river sand.
References [1]