Construction and Building Materials 38 (2013) 987–993
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Effects of waste-glass fineness on sintering of reservoir-sediment aggregates I.J. Chiou a,⇑, C.H. Chen b a
Graduate School of Materials Applied Technology, Department of Environmental Technology and Management, Taoyuan Innovation Institute of Technology, No. 414, Sec. 3, Jhongshan E. Rd., Jhongli, Taoyuan 320, Taiwan, ROC b Department of Social and Regional Development, National Taipei University of Education, No. 134, Sec. 2, Heping E. Rd., Taipei City 106, Taiwan, ROC
h i g h l i g h t s " Fine waste glass can smooth the surface of aggregates and decrease the pore size. " When glass fineness is > 150 lm, it’s suitable to sinter lightweight aggregates. " When glass fineness is < 150 lm, it’s suitable to sinter normal weight aggregates. " When glass fineness increased, alkali-silica reactivity of aggregates decreased.
a r t i c l e
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Article history: Received 13 June 2012 Received in revised form 19 August 2012 Accepted 20 September 2012 Available online 3 November 2012 Keywords: Reservoir sediment Fineness Sinter Aggregate Durability
a b s t r a c t During sintering, waste-glass can reduce sintering temperature. Therefore, this study uses reservoir sediments blended with waste-glass with different degrees of fineness to investigate how waste-glass fineness affects the sintering behaviors and material characteristics of reservoir-sediment aggregates. Analytical results show that fine waste-glass powder smoothed the surface of reservoir-sediment aggregates and decreased the aggregate’s pore size. Moreover, the maximum failure point loading increased to 75.9%. When waste-glass fineness was >150 lm, this glass is suitable for sintering lightweight reservoirsediment aggregates with a specific gravity of <1.8. Conversely, when waste-glass fineness was <150 lm, this glass was suitable for sintering reservoir-sediment aggregates with normal weights and a specific gravity exceeding 1.8. Waste-glass fineness affects the lightweight characteristics of reservoir-sediment aggregates more significantly than do volatile organic compounds. Adding finer waste-glass into reservoir sediment positively affects the chemical-corrosion resistance and potential alkali-silica reactivity of the reservoir-sediment aggregates. Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction According to statistics from Taiwan’s Environmental Protection Administration, Executive Yuan, Taiwan produced 3,610,000 metric tons of garbage in 2011. However, the amount of recycled waste-glass containers was 238,334 metric tons, accounting for roughly 6.6% of all garbage. Moreover, the amount of glass sent for recycling increases annually. Glass, a non-crystallized inorganic matter, is cooled in its molten state. The major of raw materials used to produce glass are silica sand, limestone, soda, waste-glass, flux, and coloring agents. The components in glass are sodium carbonate, potassium carbonate, calcium lime, magnesium oxide, aluminum oxide, and silicon oxide. Waste-glass containers can be re-used in concrete aggregates [1–7], in glass ceramics [8–10], as pozzolanic materials [11], as artificial stone [12], and in colored glass. ⇑ Corresponding author. Fax: +886 3 4372193. E-mail address:
[email protected] (I.J. Chiou). 0950-0618/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.conbuildmat.2012.09.042
According to data compiled by Taiwan’s Water Resources Agency, Ministry of Economic Affairs (2006), the amount of sediment in reservoirs is adversely affected by poor soil and water conservation in upstream catchment areas. Currently, reservoir sediment reached 17% of water level. That is, 10 l of water contains about 2 l of sediment. This is mainly caused by natural collapse, over exploitation, and soil erosion by typhoons. Taking the Shihman Reservoir in Taoyuan County as an example, up to 2011, the accumulative reservior sediment has reached to 93,860,000 m3, and the annual average to 1,920,000 m3. To extend the lifetime of reservoirs, large amounts of money were spent to dredge Taiwan’s reservoirs. In 2007, roughly 5,000,000 m3 of sediment was cleaned out of the reservoirs. Most reservoir sediment was illite and chlorite, and mainly contained silt (particle sizes of 0.005–0.075 mm) and clay (particle sizes 6 0.005 mm). The chemical composition of reservoir sediment was SiO2 (59–77%), Al2O3 (8–18%) and Fe2O3 (4–6%). Moreover, traces of such substances as CaO, MgO, Na2O, and K2O [13] were found. Reservoir sediment is typically re used as fill, construction materials,
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hydraulic materials, geo-materials, eco-materials, and agricultural materials. Notably, reservoir sediment can replace clay when sintering artificial aggregates [14–16], be used in lightweight aggregates [17–19], and be used in self-compacting lightweightaggregate concrete [20] and high performance lightweight-aggregate concrete [21]. The temperature for sintering reservoir-sediment aggregates must reach 1150–1200 °C [17–19]. By adding SiO2, sintering temperature can be reduced [22]. The sodium content in waste-glass influences melting flow and the gas cartridge package during sintering to produce lightweight aggregates. As the amount of waste-glass added to matrix increases, water absorption of aggregates decreases [7]. Using waste-glass (<600 lm) significantly reduces concrete expansion due to the alkali-silica reaction [6]. To conserve energy, this work investigates the sintering behaviors and characteristics of reservoir-sediment aggregates by adding waste-glass with different degrees of fineness, and proposes the application strategy. 2. Materials and methods 2.1. Materials Reservoir sediment and waste-glass were used as raw materials in this work. Reservoir sediment was obtained from the Shih-man Reservoir in Taoyuan County, and waste-glass powder was acquired from a glass container recovery plant. The waste-glass powder was added into reservoir sediment partially for producing reservoir-sediment aggregates. Reservoir sediment was dried, ground, and screened (through a No. 50 sieve (0.3 mm), yielding dried reservoir-sediment powder. The reservoir-sediment powder contained 2.3% sandstone, 36.8% silt, and 60.9% clay. The specific gravity of reservoir-sediment powder is 2.72. Moisture and ash content in the reservoir-sediment powder were as high as 32.38% and 63.93% respectively, and combustible content of the reservoir-sediment powder was 3.69%. The amount of SiO2 in the reservoir sediment was 60.9%, followed by Al2O3 at 25.2%, and Fe2O3 at 5.55%. Loss of ignition was 17.65% (Table 1). The waste-glass was dried, ground, and screened through No. 50 sieve (0.3 mm), yielding dried glass powder. The specific gravity of this waste-glass powder was 2.47. The waste-glass powder contained 74.0% SiO2, followed by CaO + MgO at 9.66%, Na2O at 8.23%, and Al2O3 at 6.01%. Loss of ignition was 1.23% (Table 1). 2.2. Experimental According to a previous experiment [22,23], a mixture with a weight ratio of 80% reservoir-sediment powder to 20% waste-glass powder was used in this work (i.e., 80:20). Taking the fineness of waste-glass powder as an experimental variable, four waste-glass powders with different degrees of fineness were used: >300 lm (i.e., >No. 50 sieve), 150–300 lm (i.e., Nos. 50–100 sieve), 75–150 lm (i.e., Nos. 100–200 sieve) and <75 lm (i.e.,
electronic gauge. Then, the same 10 pellets of each mixing proportion were sintered, and measured the particle sizes with the same way to calculate the particle size change before and after sintering. Additionally, 10 pellets of reservoir-sediment aggregates were randomly picked from each mixing proportion and proceeded the failure point loading test. The chemical stability of reservoir-sediment aggregates was tested for three solutions, the nitric acid solution, hydrocyanic acid solution and sodium hydroxide solution (i.e., 0.54 M HNO3, pH = 0.89; 0.54 M HCl, pH = 0.99; and 1.32 M NaOH, pH = 11.35).
3. Results and discussion 3.1. Particle size and physical properties of reservoir-sediment aggregates Via the changes in particle sizes, the behaviors of the reservoirsediment aggregates during sintering were determined (Table 2). When the fineness of the added waste-glass powder was >300 lm (i.e., did not pass through a No. 50 sieve) and 150–300 lm (i.e., Nos. 50–100 sieve), the expansion rate of each particle in the reservoir-sediment aggregates was in the ranged of +4.55–10.22% (mean, +7.39%) and +3.60–9.21% (mean, +6.41%) respectively. Moreover, average shrinkage of each particle in the reservoir-sediment aggregates was in the range of 2.95% to 1.15% (mean, 2.05%) and 3.47% to 2.34% (mean, 2.91%) when the added waste-glass powder had a fineness of 75–150 lm (i.e., Nos. 100– 200 sieve) and <75 lm (i.e.,
300 lm, 150–300 lm, 75–150 lm and <75 lm, was 1.65, 1.74, 1.83, and 1.87, respectively. As the fineness of waste-glass powder increased, the specific gravity of reservoir-sediment aggregates increased. That is, the fineness of waste-glass powder was positively correlated with the specific gravity of reservoir- sediment aggregates (Fig. 2). Water absorption of reservoir-sediment aggregates was 0.58– 2.98% (Table 2). Water absorption of reservoir-sediment aggregates with waste-glass powder at four different degrees of fineness, >300 lm, 150–300 lm, 75–150 lm, and <75 lm was 0.58%, 1.00%, 2.47%, and 2.98%, respectively. Water absorption of pure reservoir-sediment aggregates was 1.60%, indicating that as the fineness of waste-glass powder decreased, water absorption of the reservoir-sediment aggregates increased. That is, the fineness of waste-glass powder was positively correlated with the water absorption of reservoir-sediment aggregates (Fig. 2).
Table 1 Chemical compositions of raw materials. Raw materials
SiO2
Al2O3
Fe2O3
CaO + MgO
K2O
Na2O
S2O
P 2 O5
LOI
Reservoir sediment Sewage sludge Waste-glass
60.9 36.2 74.0
25.2 14.4 6.01
5.55 9.15 0.33
0.92 9.47 9.66
3.49 2.49 0.83
1.22 – 8.23
0.34 11.0 0.20
– 15.0 –
17.65 56.40 1.23
LOI: Loss of ignition.
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(A) >#50 (Before fired)
(a) >#50 (>300µm)
(B) 150–300µm (Before fired)
(b) 150–300µm (After fired)
(C) 75–150µm (Before fired)
(c) 75–150µm (After fired)
(D) <75µm (Before fired)
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(d) <75µm (After fired)
Fig. 1. Appearance change of reservoir-sediment aggregates (RS80WG20, 1100 °C/10 min).
The standard deviation and coefficient of variation (CV) were 22.34–44.36 kgf and 9.93–20.48%, respectively. The failure point loading of pure reservoir-sediment aggregates were 372.4 ± 67.9 kgf, demonstrating that adding waste-glass powder reduces sintering temperature; however, failure point loading of reser-
voir-sediment aggregates also decreased significantly. The failure point loading of reservoir-sediment aggregates positively correlated with the fineness of waste-glass powder (Fig. 3). This was because very fine waste-glass powder made particles and particles tight more closely during sintering due to a lower energy barrier,
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Table 2 Effects of waste-glass fineness on the characteristics of reservoir-sediment aggregates. Characteristics
RS100
RS80WG20
RS80WG20
RS80WG20
RS80WG20
Waste-glass fineness Particle change during sintering (%) Dry specific gravity Water absorption (%) Failure point loading (kgf) Weight loss during sintering (%) Chemical-corrosion resistance NaOH (%) HNO3 (%) H2SO4 (%) Potential alkali-silica reactivity Sc (mmol/L) Rc (mmol/L) Sc/Rc BET surface area (m2 g 1)
– 3.21 2.56 1.60 372.4 ± 67.9 9.25
>300 lm +7.39 1.65 2.98 170.40 ± 34.89 4.28
150–300 lm +6.41 1.74 2.47 225.00 ± 22.34 4.07
75–150 lm 2.05 1.83 1.00 279.2 ± 36.33 4.55
<75 lm 2.91 1.87 0.58 299.6 ± 44.36 4.50
0.14 0.15 0.11
0.13 0.14 0.10
0.09 0.04 0.07
0.07 0.03 0.06
0.05 0.01 0.02
54.18 245 0.22 –
63.4 130 0.49 0.0151
70.4 160 0.44 0.0324
54.8 170 0.32 0.0589
41.6 145 0.29 0.0775
and thus, the inner structure of the artificial aggregates compacted. As demonstrated (Figs. 2 and 3), the dry specific gravity was positive correlated with the failure point loading. 3.2. Durability of reservoir-sediment aggregates Chemical-corrosion resistance and the potential alkali-silica reactivity were used to evaluate the chemical stability of reservoir-sediment aggregates. The reservoir-sediment aggregates were immersed into the three solutions (i.e., 0.54 M HNO3, 0.51 M HCl, and 1.32 M NaOH) at 80 °C for 2 h. Weight loss was then measured (Table 2). Weight loss of reservoir-sediment aggregates with 20% waste-glass powder added to 0.54 M HNO3, 0.51 M HCl, and 1.32 M NaOH was 0.05–0.13%, 0.01–0.14% and 0.02–0.10%, respectively. However, weight loss of pure reservoir-sediment aggregates in 0.54 M HNO3, 0.51 M HCl, and 1.32 M NaOH was 0.14%, 0.15% and 0.11%, respectively. This analytical finding indicates that reservoir-sediment aggregates with 20% waste-glass powder had better chemical-corrosion resistance than pure reservoir-sediment aggregates. As the fineness of the glass-powder increased, chemical-corrosion resistance of reservoir-sediment aggregates increased. The potential alkali-silica reactivity of reservoir-sediment aggregates were evaluated using the Chemical Method Judgment Chart based on the amount of dissolved silica (Sc) and amount of depleted alkali (Rc). Reactivity was classified as harmful, potentially harmful, or harmless (Fig. 4). The Sc/Rc of reservoir-sediment aggregates was 0.29–0.49, and that of pure reservoir-sediment aggregates was 0.22. Both are much less than 1.0. Reactivity of both pure reservoir-sediment aggregates and reservoir-sediment aggregates with 20% waste-glass powder were in the harmless
Fig. 2. Dry specific gravity and water absorption of reservoir-sediment aggregates.
Fig. 3. Failure Point loading of reservoir-sediment aggregates.
zone (Fig. 4). Additionally, as the fineness of the waste-glass powder increased, the Sc/Rc of reservoir-sediment aggregates decreased. However, the Sc/Rc of reservoir-sediment aggregates with added waste-glass powder was higher than that of pure reservoir-sediment aggregates, indicating that the potential alkali-silica reactivity of reservoir-sediment aggregates was enhanced. However, the potential alkali-silica reactivity of reservoir-sediment aggregates reduced gradually as the fineness of the wasteglass powder increased. 3.3. Appearance and microstructures of reservoir-sediment aggregates The appearance change of reservoir-sediment aggregates before and after sintering (Figs. 1 and 5). Many glassy educts separated out onto the surface of reservoir-sediment aggregates, which were added to waste-glass powder with particle sizes exceeding 150 lm. The surface of educts was rough and water absorption of reservoir-sediment aggregates was 2.47–2.98% (Figs. 1a, 5a; 1b, 5b). Conversely, glassy educts were still separated out onto the surface of reservoir-sediment aggregates, which were added to waste-glass powder with the fineness of 75–150 lm. However, the surface of educts became smooth (Figs. 1c, 5c, 1d, 5d) when the fineness of added waste-glass powder was <75 lm. The surface of the reservoir-sediment aggregates became significantly smooth and glossy, and water absorption of reservoir-sediment aggregates was 60.58% (Figs. 1d and 5d). Scanning electronic microscopy (SEM) was applied to examine the holes and to identify the pore distribution on and in the reser-
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0.0151 m2 g 1, 0.0324 m2 g 1, 0.0589 m2 g 1, 0.775 m2 g 1 individually (Table 2). This explains why inner pore diameters and the fineness of added waste-glass powder were negatively correlated. The inner structure of reservoir-sediment aggregates was generally regular, and pore diameters were distributed uniformly (Figs. 6A–D and 6a–d). 4. Conclusions
Fig. 4. Potential alkali-silica reactivity of reservoir-sediment aggregates.
voir-sediment aggregates (Figs. 5a–d, 6A–D and 6a–d). The largest pore diameters on the reservoir-sediment aggregates, which were added to waste-glass powder with fineness of >300 lm, 150– 300 lm, 75–150 lm, and <75 lm were 2.0 mm, 1.0 mm, 0.6– 0.7 mm and 0.2 mm, respectively. This means that as the fineness of added waste-glass powder increased, the number of holes that shrank and closed increased. This effect and the fineness of added waste-glass powder were negatively correlated. On the other hand, SEM micrographs show that the pore distribution in the reservoirsediment aggregates, which were added to waste-glass powder with fineness of >300 lm, 150–300 lm, 75–150 lm and <75 lm was 237–378 lm, 156–202 lm, 117–153 lm and 94–124 lm, respectively. And, the corresponding BET surface area is
(1) During sintering, as the fineness of waste-glass powder added to reservoir-sediment aggregates decreased, the amount of glassy educts that separated out increased, and the surface of educts was irregular and rough. Conversely, as the fineness of waste-glass powder added to reservoirsediment aggregates increased, the degree of smoothness and glassiness of reservoir-sediment aggregate surfaces increased. (2) When the particle size of added waste-glass powder was <150 lm, particle size of aggregates declined, and aggregates produced had normal weights. When aggregate pellets were sintered at 1100 °C, particle size of reservoirsediment aggregates added with the waste-glass powder with fineness >150 lm increased and, thus, lightweight aggregates were produced. However, when the fineness of added waste-glass powder was <150 lm, particle size of reservoir-sediment aggregates declined, and reservoir-sediment aggregates produced had normal weights. (3) As the fineness of added waste-glass powder increased, specific gravity, failure point loading and chemical-corrosion resistance of reservoir-sediment aggregates increased. Concurrently, water absorption, particle size of reservoir-sediment aggregates declined.
(a) >300µm, ×100
(b) 150–300µm, ×100
(c) 75–150µm, ×100
(d) <75µm, ×100
Fig. 5. SEM micrographs on reservoir-sediment aggregates(RS80WG20, 1100 °C/10 min).
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(A) >300µm, ×100
(a) >300µm, ×300
(B) 150–300µm, ×100
(b) 150–300µm, ×300
(C) 75–150µm, ×100
(c) 75–150µm, ×300
(D) <75µm, ×100
(d) <75µm, ×300
Fig. 6. SEM micrographs in reservoir-sediment aggregates (RS80WG20, 1100 °C/10 min).
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(4) The potential alkali-silica reactivity of reservoir-sediment aggregates increased, but all in the harmless zone, when 20% of waste-glass powder was added to the reservoir-sediment aggregates. However, as the fineness of waste-glass powder increased, the potential alkali-silica reactivity of aggregates decreased.
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