Properties of lightweight high calcium fly ash geopolymer concretes containing recycled packaging foam

Construction and Building Materials 94 (2015) 408–413

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Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat

Properties of lightweight high calcium fly ash geopolymer concretes containing recycled packaging foam Patcharapol Posi a, Charoenchai Ridtirud a, Chatchavan Ekvong a, Duangchai Chammanee a, Khuanchai Janthowong a, Prinya Chindaprasirt b,⇑ a b

Dept. of Civil Engineering, Faculty of Engineering, Rajamangala University of Technology Isan Khon Kaen Campus, Khon Kaen 40000, Thailand Sustainable Infrastructure Research and Development Center, Dept. of Civil Engineering, Faculty of Engineering, Khon Kaen University, Khon Kaen 40002, Thailand

h i g h l i g h t s  Lightweight geopolymer (LG) block was fabricated from high calcium fly ash and recycled foam aggregate.  LG with NH = 5–15 molars, NS/NH = 0.33–3, liquid/ash = 0.5–1, curing at 25–60 °C, aggregate content = 0.85–1.05 %wt. were tested. 3

 Low densities of 1000–1300 kg/m and 28-day compressive strengths of 4.0–11.2 MPa were obtained.

a r t i c l e

i n f o

Article history: Received 5 February 2015 Received in revised form 23 May 2015 Accepted 12 July 2015 Available online 16 July 2015 Keywords: Geopolymer Recycled foam Lightweight geopolymer concrete Thermal conductivity

a b s t r a c t In this research, the properties of lightweight geopolymer concretes containing recycled packaging foam were studied. The recycled foam was crushed to sizes of 2.35–4.75 mm and used as lightweight aggregate. Compressive strengths and densities with liquid alkaline/ash ratios of 0.5–1.0, sodium silicate/NaOH ratios of 0.33–3.0, NaOH concentrations of 5–15 molars, curing temperatures at 25 and 60 °C, and foam contents of 0.85–1.05 %wt. were tested. In addition, the thermal conductivities of geopolymer blocks were determined. Results showed that the lightweight geopolymer blocks of densities of 1000–1300 kg/m3, with satisfactory strength and low thermal conductivity can be made. This gave a twofold advantageous viz. the use of low carbon footprint fly ash geopolymer and the reuse of packaging foam. Ó 2015 Elsevier Ltd. All rights reserved.

1. Introduction The production of Portland cement is an energy intensive operation and releases a large amount of green house gas to the atmosphere, which accounts for about 5% of green house gas produced annually [1]. Therefore, new cementitious material using silica and alumina activated in a high alkali solution was developed to supplement Portland cement [2]. This new material is geopolymer or alkali-activated binder [3]. In Thailand, the lignite important coal mine and large power plant are located in Mae Moh district, Lampang province. The annual output of fly ash from this source is 3 million tons. A substantial amount is not utilized and is deposited at the landfill site. This fly ash contains high calcium content. It also contains high amount of silica and alumina and is used successfully in making geopolymer binder with adequate strength and excellent durability characteristics [4–6]. ⇑ Corresponding author. E-mail address: [email protected] (P. Chindaprasirt). http://dx.doi.org/10.1016/j.conbuildmat.2015.07.080 0950-0618/Ó 2015 Elsevier Ltd. All rights reserved.

The construction of building and structures in Thailand and other countries relies heavily on Portland cement products. The structural members, walls and panels are made of Portland cement [7] and the problems of the weight of structural members and wall panels are of great concern [8]. In order to reduce the weight of structure, lightweight construction materials in the form of lightweight concrete block or wall using cast-in-place lightweight concrete have been developed. The purpose of this work is to reduce the dead load of structure resulting in lighter structures and also with reduced cement content. Lightweight concretes (LC) is usually defined as concretes with unit weight less than 1840 kg/m3 [9]. The low unit weights LC of 400–1200 kg/m3 are for block production and the high unit weights of 1300–1840 kg/m3 are for structural concrete [10]. The LC are classified into three types viz., LC with lightweight aggregate, LC with large voids, and LC with no fine aggregate [11]. LC with lightweight aggregate are mostly used for masonry due to high strength and good sound and thermal insulation properties from the air void in lightweight aggregate [12]. Both natural and synthesized lightweight aggregates are used in the manufacturing

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of LC. The common natural lightweight aggregates are pumice, perlite, and diatomite; and the synthesized ones are expanded clay and sintered fly ash [13]. Polystyrene foam (PSF) is a thermoplastic polymer with a closed cellular structure [14]. A large amount of PSF materials is now being used as food container and industrial product packaging. As a result, this foam in huge amount is now a waste and need special attention or proper disposal [15]. If burnt, they pollute the atmosphere or if discarded at landfill sites, it took a very long time to decompose. PSF has interesting properties such as low unit weight (less than 300 kg/m3), good thermal insulation, hydrophobicity, and chemical resistance [14,16]. There have been a number of studies on the use of PSF for making lightweight concretes [14–18]. The PSF dosage and water to cement ratio are important parameters affecting the density and strength of the lightweight concrete. The low density lightweight of 1050 kg/m3 was successfully fabricated with the emphasis on strengthening the cement paste matrix with the aids of silica fume and plasticizer [16,17]. Thus, in this research, high calcium fly ash geopolymer paste was used as a new binder for making lightweight concrete containing used packaging foam as lightweight aggregate. This would give a twofold advantageous viz. the use of low carbon footprint fly ash geopolymer instead of Portland cement and the reuse of packaging foam to reduce the burden of waste disposal.

Table 1 Chemical composition of materials (by weight). Chemical compositions (%)

Fly ash

SiO2 Al2O3 Fe2O3 CaO K2O TiO2 Na2O P2O5 MgO LOI

45.23 19.95 13.15 15.50 2.15 0.39 0.52 0.81 2.02 0.88

2. Experimental program 2.1. Materials Materials used in this research consisted of lignite fly ash from Mae Moh power station in the north of Thailand, sodium silicate with 15.32% Na2O, 32.87% SiO2, and 51.8% water, and 5, 10, and 15 molars (M) NaOH and recycle packaging foam (RF). The RF was the discarded packaging foam from the household electricity appliances. The foam was broken into 3.0–4.0 cm pieces by hand and then crushed using a food blender. The crushed foam was sieved to obtain the size of 2.36–4.75 mm as shown in Fig. 1 and used as fine aggregate. Chemical compositions of fly ash determined using X-ray fluorescence (XRF) technique are shown in Table 1 and its X-ray diffraction (XRD) is shown in Fig. 2. The sum of SiO2, Al2O3 and Fe2O3 was over 75% which was in accordance which ASTM C618 [18], however, the CaO content was high indicating a high calcium fly ash. The XRD analysis showed mainly amorphous phase with some peaks of crystalline phases of magnetite, magnesioferrite, dachiardite, and calcium aluminum oxide. The fly ash was 30% retained on sieve No. 325 (45 lm) with median particle size of 18.6 lm and Blaine fineness of 2800 cm2/g. It consists mainly of spherical particles with smooth surface as shown in Fig. 3. The physical properties of materials are shown in Table 2. The RF has particle sizes between 2.36 and 4.75 mm with unit weight of 215 kg/m3 and water absorption of 225%. River sand with specific gravity of 2.61 and fineness modulus of 2.65 was used as normal fine aggregate.

Fig. 2. XRD patterns of fly ash. A-Magnetite: Fe3O4; C-Magnesioferrite: Fe2MgO4; DDachiardite: Na1.1K.7Ca1.7Al5.2Si18.8O48 (H2O)12.7; N-Calcium Aluminum Oxide: CaAl2O4.

2.2. Mix proportion 2.2.1. Mix compositions Five series of mixes were used to test the effects of liquid alkaline/ash ratios (series A), sodium silicate/NaOH ratios (series B), concentration of NaOH (series C), temperature of curing (series D), and volume of foam (Series E). The details of mixes are shown in Table 3.

Fig. 3. SEM of fly ash.

Table 2 Physical properties of materials. Materials

Fly ash

Sand

Recycled foam

Specific gravity Median particle size (lm) Particle size (mm) Fineness modulus Density (kg/m3) Water absorption (%)

2.52 18.6 – – – –

2.61 – – 2.65 1360 1.17

– – 2.36–4.75 – 215 225

2.2.2. Details of mixing Constant sand to fly ash ratio of 1.00 was used for all mixes. The mixing was done in a pan mixer with the following steps:

Fig. 1. Lightweight aggregates from recycled foam.

– NaOH solution and fly ash were mixed for 5 min. – Sand was added and mixed for 5 min.

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Table 3 Weight ratios of lightweight geopolymer concrete mixes. Series

L/A ratio

NS/NaOH ratio

NaOH (M)

Curing temp. (°C)

Aggregate % by weight

A B C D E

0.5, 0.6, 0.7, 0.8, 0.9, 1.0 0.7 0.7 0.7 0.7

1.00 0.33, 0.67, 1.00, 1.50, 3.00 1.00 1.00 1.00

10 10 5, 10, 15 10 10

40 40 40 25, 40, 60 40

1.05 1.05 1.05 1.05 0.85, 0.90, 0.95, 1.00, 1.05

Compressive Strength (MPa)

1200

5.0

1100

0.0

0.50

0.80

0.90

1.00

compressive strength

1000

1250

density

1200 10.0

1150 1100

5.0

1050 0.0

3.1. Compressive strength and density

0.70

Fig. 4. Compressive strength and density at 28 days of lightweight geopolymer concretes at various L/A ratios (series A).

Compressive Strength (MPa)

3. Results and discussions

0.60

Liquid/ Fly Ash

15.0

2.3.2. Thermal conductivity The thermal conductivity of concrete was measured using portable heat transfer analyzer ISOMET2114. This analyzer is based on ASTM D5930-09 [22] method for finding thermal conductivity of plastics by means of a transient line-source technique. Similar device was successfully used for testing of cementitious materials [23–25]. The 100  100  100 mm cube specimens were used for this test. The tests were performed on the oven-dried samples at the age of 28 days and the report results were the average of three samples.

1300

density

10.0

2.3. Details of test 2.3.1. Compressive strength and density The density of concrete was determined at the ages of 28 days using the compressive strength specimens as described in ASTM C138/C138M-14 [21]. The compressive strength was tested after the density determination. The cube specimens were tested to determine the compressive strength in accordance with ASTM C109/C109M-13 [19]. The report results were the average of three samples.

compressive strength

Density (kg/m³)

The fresh lightweight geopolymer concretes were placed into 50 mm and 100 mm cube molds in accordance with ASTM C109/C109M-13 [19]. This standard is for cement mortars and was used since samples could be considered as mortars as the maximum aggregate size of the lightweight concrete was 4.75 mm which was similar to that of fine aggregate as specified by ASTM C33/C33M-13 [20]. The specimens were covered with damp cloth and plastic sheet to prevent moisture loss and placed in a 25 °C controlled room for 1 h [5]. The specimens were then transferred to oven curing at 25, 40, and 60 °C for 48 h. Finally, the specimens were demolded and wrapped with plastic sheet and stored in a 25 °C controlled room.

15.0

Density ( kg/m³)

– Sodium silicate solution (NS) was added and mixed for 5 min. – Aggregate was added and mixed for 1.5 min.

0.33

0.67

1.00

1.50

3.00

1000

NS/ NH 3.1.1. Liquid alkaline/ash ratio The results of compressive strength of geopolymer lightweight concrete with various liquid alkaline/ash ratios are shown in Fig. 4. The compressive strength decreased with the increasing liquid alkaline/ash ratios. The 28-day compressive strength of samples with liquid alkaline/ash ratios of 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0 were 11.2, 8.3, 6.4, 5.3, 4.0, and 4.3 MPa, respectively. The increase in liquid to ash ratio increased the inter-particle distance of the solid particle and thus increased the workability and reduced the strength of the geopolymer [4]. High liquid content also produced mixture which was very workable and prone to segregation and bleeding with substantial shrinkage. The increase in liquid content reduced the concentration of silica and alumina in the solution and hence the rate of geopolymerization was also reduced [6]. The compressive strength thus decreased due to the excess liquid similar to Portland cement concretes [7,26–28]. 3.1.2. Sodium silicate/NaOH ratio The results of compressive strength of lightweight geopolymer concrete with various NS/NaOH ratios are shown in Fig. 5. The 28-day compressive strengths of concretes with NS/NaOH ratios of 0.33, 0.67, 1.00, 1.50, and 3.00 were 5.1, 5.9, 6.4, 6.0, and 5.5 MPa, respectively. The optimum compressive strength of 6.4 MPa was obtained with NS/NaOH ratio of 1.00. An increase in NS/NaOH ratio from 0.33 to 1.00 increased the strength of

Fig. 5. Compressive strength and density at 28 days of lightweight geopolymer concrete at various NS/NaOH ratios (series B).

concrete. The increase in strength in this range of NS/NaOH ratio was due to the increased silica content of mixture. However, when the NS/NaOH ratio was increased to 1.5, the strength started to drop due to the difficulty in compaction [4]. The density of geopolymer concrete increased with increasing NS/NaOH from 0.33 to 1.00 due to the increase in NS content as the density of NS was higher than that of NaOH. Similar trend of result was reported for the normal weight high calcium fly ash (HCFA) geopolymer mortars. The compressive strengths of mortars with high NS/NaOH ratios of 1.5 and 3.0 were reduced compared to that with NS/NaOH ratio of 1.0 [5,29]. 3.1.3. Concentration of NaOH solution The results of the effects of NaOH solution concentrations on compressive strength are shown in Fig. 6. The concentration of NaOH solution had an influence on the strength of geopolymer but the influence was rather small. The compressive strength of mortar with 10 M NaOH solution was slightly higher than those of 5 and 15 M NaOH concretes. An increase in the concentration of NaOH solution from 5 M to 10 M resulted in the increase in compressive strengths from 5.3 MPa to 6.4 MPa. The increase in

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1200 10.0 1100 5.0 1000

0.0

900 5.00

10.00

15.00

NaOH (M) Fig. 6. Compressive strength and density at 28 days of lightweight geopolymer concrete at various concentrations of NaOH solution (series C).

concentration of NaOH in this range helped the leaching of silica and alumina from the source material and thus increased the geopolymerization reaction [4,30]. In addition, calcium oxide from high calcium fly ash reacted with silicate compounds and formed CSH similar to the hydration of Portland cement [30–32]. The CSH products co-existed with the geopolymer gel and contributed to the strength development [32]. However, an increase in the concentration of NaOH solution from 10 M to 15 M resulted in no further increase in compressive strength. The 28-day compressive strength with concentration of NaOH solutions of 15 M was 6.3 MPa. Approximately the same or even a slight drop in strength at high NaOH concentration was due to the excessive hydroxide ions causing aluminosilicate gel precipitation at the very early stages [7,32–34]. In this case, no increase in strength could also be in part due to the lower density of concrete compared with that of concrete with 10 M NaOH. The slight drop in density of geopolymer concrete was from the reduced compactability of the mix with increased concentration of NaOH. 3.1.4. Temperature of curing The results of compressive strengths of lightweight geopolymer concretes with various temperatures of curing are shown in Fig. 7. The optimum temperature of curing was 40 °C and the maximum strength of 6.4 MPa was obtained. An increase in temperature of curing from 25 °C to 40 °C resulted in the increase in compressive strength. The increase in temperature of curing to 40 °C enhanced the geopolymerization and increased the compressive strength [5,7,35,36]. However, temperature curing at 60 °C lowered the strength of lightweight concrete. The 28-day compressive strength with temperature of curing of 25, 40, and 60 °C were 4.5, 6.4, and 5.1 MPa, respectively.

compressive strength

1200 10.0 1100 5.0 1000

0.0

25.00

40.00

60.00

3.1.5. Foam content The results of compressive strengths of lightweight geopolymer concretes with various foam contents are shown in Fig. 8. The compressive strength decreased with the increasing foam content. The 28-day compressive strength with RF contents of 0.85, 0.90, 0.95, 1.00, and 1.05 %wt. were 9.5, 7.4, 6.5, 6.5, and 6.4 MPa, respectively. This was accompanied by the weight of the samples of 1340, 1250, 1285, 1220 and 1200 kg/m3, respectively as also shown in Fig. 8. The recycled foam is normally weaker than the geopolymer matrix and the increased amount thus reduced the strength of geopolymer lightweight concrete [7,40–42]. The density decreased with the increase in RF content as the density of RF was only 215 kg/m3 compared with that of geopolymer concrete of 2030 kg/m3. The porosity of RF is high and thus it is not strong [14]. The incorporation of foam at the dosage of 1.05% by weight was able to reduce the density of concrete to approximately 1200 kg/m3. Similar finding of reduction in strength with increasing foam content was reported for lightweight geopolymer concrete [43]. 3.2. Thermal conductivity The results of thermal conductivity of oven-dried lightweight geopolymer concrete with various foam contents are shown in Fig. 9. The thermal conductivity decreased with the increasing foam contents as expected. For example, the values of thermal conductivity at the age of 28-day with volumes of foam of 0, 0.85, 0.90, 0.95, 1.00, and 1.05 were 0.77, 0.35, 0.33, 0.30, 0.29 and 0.27 W/mK, respectively. The thermal conductivity values of lightweight aggregate foamed geopolymer concrete were reported to be 0.47–0.58 W/mK [43] and those of metakaolin geopolymers were 0.55–0.65 W/mK and increased to 0.91 W/mK with the addition

15.0

1300

density

Density (kg/m³)

Compressive Strength (MPa)

15.0

Temperature curing at 60 °C should increase the intrinsic strength of the matrix. However, the density of lightweight concrete cured at 40 °C was 1210 kg/m3 and reduced to 1130 kg/m3 when cured at 60 °C. Previous researches also indicated that the density of foam lightweight concrete reduced with the increase in curing temperature due to the expansion of matrix under heat curing [37,38]. The reduction in strength with curing at temperature of 60 °C was due to the reduced density resulted from the increase in porosity of lightweight geopolymer concrete under heat curing. The strength of normal weight geopolymers cured at high temperature could also be reduced due to the loss of moisture from samples [5,39]. The porous microstructure of lightweight geopolymer allowed heat to penetrate into the sample more easily and facilitated the evaporation or migration of moisture from the interior of the sample.

900

compressive strength

1400

density

1300 10.0 1200 5.0 1100

0.0

0.85

0.90

0.95

1.00

1.05

Density (kg/m³)

1300

density

Compressive Strength (MPa)

compressive strength

Density (kg/m³)

Compressive Strength (MPa)

15.0

1000

Temp (°C)

Foam (%)

Fig. 7. Compressive strength and density at 28 days of lightweight geopolymer concrete at various curing temperatures (series D).

Fig. 8. Compressive strength and density at 28 days of lightweight geopolymer concrete at various foam contents (series E).

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0.800

References

density

0.600

1600

0.400

1400

0.200

1200

Density (kg/m³)

K (w/m.k)

K

1000

0.000 0.00

0.85

0.90

0.95

1.00

1.05

Foam (%) Fig. 9. Thermal conductivity at 28 days of lightweight geopolymer concrete at various foam contents (series E).

of quartz sand [44]. These values were comparable to the obtained results of 0.27–0.35 W/mK for lightweight geopolymer concretes and 0.77 W/mK for normal weight geopolymer concrete. It should be noted here that the samples in this test were oven-dried at 110 °C for 24 h. The thermal conductivity reduced by more than half with the incorporation of recycled foam. The thermal conductivity decreased with the decreasing density as the thermal conductivity depended on the density of geopolymer lightweight concrete [13]. The increase in porosity of the system resulted in the lowering of thermal conductivity [45,46]. 4. Conclusion Based on the obtained data, the following conclusions can be drawn: (1) The compressive strength decreased with the increasing liquid alkaline/ash ratios and volume of foam due to the excess liquid and porosity effect to low compressive strength. (2) There were optimum level of NS/NaOH ratio, NaOH concentration and curing temperature. The optimum NS/NaOH ratio was 1.00 as compressive strength of 6.4 MPa. The optimum concentration of NaOH solution was 10 M and temperature of curing was 40 °C for maximum compressive strength. (3) The volume of foam had significant effects on strength, density and thermal properties of lightweight geopolymer concrete. The increase in the volume of foam decreased the strength, density and thermal conductivity of the lightweight concrete. (4) The results showed that the lightweight geopolymer concrete with 28-day compressive strength of 4.0–11.2 MPa, densities of 1000–1300 kg/m3, and thermal conductivities of 0.52–0.69 W/mK could be made.

Acknowledgments This work was financially supported by the Higher Education Research Promotion and National Research University Project of Thailand, Office of the Higher Education Commission, through the Advanced Functional Materials Cluster of Khon Kaen University, and Khon Kaen University and the Thailand Research Fund (TRF) under the TRF Senior Research Scholar Contract No. RTA5780004. The support of the Siam Research and Innovation Co., Ltd. and the Dept. of Civil Engineering, Faculty of Engineering, Rajamangala University of Technology Isan Khon Kaen Campus is also acknowledged here.

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