Foam Glass Development Using Glass Cullet and Fly Ash or Rice Husk Ash as the Raw Materials

Parinya Chakartnarodom1, a, and Pitcharat Ineure2 1Department of Materials Engineering, Faculty of Engineering, Kasetsart University, Chatuchak,

Bangkok, Thailand, 10900

2Glass Bridge Co. Ltd., Wang Thonglang, Bangkok, Thailand,10310

afengpryc@ku.ac.th

Keywords: foam glass, glass cullet, fly ash, rice husk ash, recycle

Abstract. The aim of this work is to study the recycling of glass cullet (waste glass), fly ash, and

rice husk ash as the foam glass which is alkaline resistant and has the properties better than the light

weight brick (autoclaved aerated concrete), including higher compressive strength, lower degree of

water absorption, and lower density, with the competitive production cost. The foam glasses were

prepared by mixing the ground glass cullet/ash mixtures with calcium carbonate (foaming agent) at

1 wt% and sodium silicate solution (binder) at 10 wt%, and then compacted into the rectangle

shapes (30 cm × 30 cm × 7cm) which were fired at 650 oC for 30 min, and then for 1 hour at 750,

800, 850, or 900 °C. The sources of glass cullet were art glass factory and glass window industry.

The percentages of ash in the ground glass cullet/ash (fly ash or rice husk ash) mixtures were 20,

40, and 60 wt%. The results showed that the foam glass that was made from 80wt% window glass/

20wt% fly ash and fired at 750 °C had the most suitable properties for being produced

commercially. The compressive strength, density, and degree of water absorption of this foam glass

were 59.9 kg/cm2, 421 kg/m

3, and 2.1 % respectively. By compared with properties of the light

weight bricks (G2-type and G4-type autoclaved aerated concrete), 80wt% window glass/ 20wt% fly

ash foam glass has higher compressive strength and lower degree of water absorption than G2-type

and G4-type. For density, this foam glass has the density lower than G4-type but similar to G2-type.

Furthermore, as of September 2013, the total production cost (materials, labor, energy, etc.) of this

foam glass is about 16 baht per piece (20 cm × 60 cm × 7.5 cm) which is 12.5 to 43.75% lower than

the wholesale price of a light weight brick (18-23 baht per piece for G2-type and G4-type

autoclaved aerated concrete).

Introduction

Glass is a silicate- based material made from the natural occurring materials such as sand, soda

ash, and lime stone. Due to its wide variety of compositions, glass has many applications. For

example, borosilicate glass has high content of SiO2 and Al2O3. Therefore, borosilicate glass is

chemically resistant and commonly used as laboratory ware. There are many tons of waste glass

generated each year as either manufacturing waste (rejected or broken products) or post-consumer

waste (e.g. bottle and jars, broken glass ware, and light bulb). According to [1], each year in the

UK, 600,000 tons of glass bottles are thrown out from pubs, clubs, hotels, restaurants and cafes.

Although glasses can be recycled, there are some limitations such as glass composition or color that

do not meet the standard, hygienic condition, and costs (e.g. labor, and transportation cost).

Fly ash is the waste from the coal -fired power plant. The major chemical compositions of fly

ash are SiO2, Al2O3, and Fe2O3. There is 40,000 tons of fly ash generated each day only from

Maemoh power plant in Lampang, Thailand. Currently, fly ash is commonly used as a pozzolanic

material for the concrete to reduce the use of Portland cement and improve concrete properties such

as workability and durability in some environments. [2]-[4] Beside coal, some power plants use the

biomass such as rice husk as the fuel which finally yield rice husk ash as the waste. The

compositions of rice husk ash are mainly SiO2 and the trace amount of CaO, MgO, K2O, and Na2O.

Key Engineering Materials Vol. 608 (2014) pp 73-78Online available since 2014/Apr/17 at www.scientific.net© (2014) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/KEM.608.73

All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,www.ttp.net. (ID: 128.42.202.150, Rice University, Fondren Library, Houston, USA-12/11/14,08:18:09)

Currently, rice husk ash is also used as a pozzolanic material which also improves the properties of

concrete while reduce the use of Portland cement. [5]-[6]

The foam glass is a construction material having the wide variety of properties including high

compressive strength, low density, low water absorption, vapor tight, incombustible, pest proof,

acid resistant, dimensionally stable, and easy to cut [7]. Some of these properties are similar to the

light weight brick (autoclaved aerated concrete block). Normally, foam glass can be produced by

mixing ground glass cullet (waste glass) and foaming agent such as calcium carbonate and then

fired at the proper temperature for sintering and foaming. All types of glass cullet (composition and

color) can be used as the raw material. The proper temperature for sintering depends on the

softening point and the glass transition temperature or the viscosity of the mixture. For foaming

step, the firing temperature is commonly between 750-1,000 oC. According to [8] and [9], the

parameters that affect the physical and mechanical properties of the foam glass are chemical

composition of the glass cullet, particle sizes of the raw materials, and firing condition. Moreover, it

was found that foam glass can also be produced by the mixture containing ground glass cullet and

fly ash and yields the foam glass having compressive strength and density similar to lightweight

brick. [9]-[12]

The objectives of this work are to study the recycling of glass cullet (waste glass) from either art

glass factory or glass window industry, fly ash, and rice husk ash as the foam glass and study the

optimum production parameters (glass/ash ratio, and firing condition) that yield the foam glass that

is alkaline resistant (compatible with the cement) and have the compressive strength, density, and

water absorption ability better than the lightweight brick (autoclaved aerated concrete block) with

the competitive production cost.

Experimental Procedure

Specimen Preparation. The glass cullet from either art glass factory or glass window industry

were cleaned and coarse ground by the crusher until the particle size of the ground glass cullet was

not greater than 2 cm. After that, the coarse ground glass cullet was further fine ground for 8 hours

by the ball mill and then sieved by 100 -mesh sieve. Next, the fine ground cullet was mixed with the

ash which was either fly ash or rice husk ash. The compositions of the ash in the glass cullet/ash

mixture were 20, 40, and 60 wt%. Then, the glass cullet/ash mixtures were mixed with calcium

carbonate (CaCO3) as the foaming agent at 1 wt% and sodium silicate solution as the binder at 9

wt%. After that, the mixtures were molded into a rectangular shape having the density 1000 kg/m3

(1 g/cm3) and the dimensions 30 cm by 30 cm by 7cm. Later, the as-molded specimens were fired in

two steps including sintering step and foaming step. For sintering step, the specimens were fired at

650 oC for 30 min. For the foaming step, the specimens were fired for 1 hour at 750, 800, 850, or

900 oC. Figure 1 shows the steps for specimen preparation.

Figure 1 Specimen preparation.

74 Traditional and Advanced Ceramics

Raw materials and Specimen Characterization. The raw materials were characterized for their

composition by using x-ray fluorescence spectrometer (XRF). The compressive strength, bulk

density, and degree of water absorption of the foam glasses were measured by using the standard

test methods listed on Table 1. For alkaline resistant test, the foam glasses were soaked in the

Ca(OH)2 solution 1 N for 28 days to observe their percent weight loss.

Table 1 Standard test methods for compressive strength, bulk density, and water absorption.

Properties Standard Test Method

Compressive strength EN 826 Standard

Bulk density EN 1602 Standard

Degree of water absorption ASTM C240 standard

Results and Discussions

Table 2 shows the compositions of the raw materials used in this work and Figure 2 shows the

cross-section view of the foam glass which is porous and the pores appear as the closed-pore. From

Fig. 3 (a) and (b), the compressive strength and the density of the foam glasses increased with the

increasing of temperature for the foaming step. However, from Fig. 3 (c), there was no correlation

between the temperature and the degree of water absorption of the foam glasses. Table 3 shows the

general properties of the light weight brick (G2-type and G4-type autoclaved aerated concrete)

including compressive strength, density, and degree of water absorption. The maximum and

minimum values of these properties are shown on Fig. 3 as the dash lines.

For alkaline resistant, from Fig. 4, the increasing of ash content (fly ash or rice husk ash)

reduce the percent weight loss of the foam glass. Thus, both fly ash and rice husk ash can increase

the alkaline resistant of the foam glass. Because rice husk ash has higher content of SiO2 than fly

ash, the foam glasses that use rice husk ash as a raw material have higher alkaline resistant (lower

percent weight loss) than the foam glasses that use fly ash as a raw material. Moreover, the alkaline

resistant of window glass is higher than art glass because window glass has higher content of Al2O3

but lower content of ZnO than art glass. It was found that if the percent weight loss was higher than

1wt%, when the foam glass was coated with the cement, the cement would peel off. From Fig. 4,

only foam glasses made from window glass/ash mixture have the percent weight loss less than 1

wt%.

To select the optimum production parameters for the foam glass, the following requirements

should be met: (1) the foam glass should have good alkaline resistant, (2) the energy required for

the production should be lowest, and (3) the compressive strength of the foam glass should be

greater than the light weight brick while the density and degree of water absorption should be lower

or similar. From Fig. 4, for good alkaline resistant, the foam glass should be made from window

glass. Furthermore, from Fig. 3, only the foam glass made from 80wt% window glass/ 20wt% fly

ash and fired at 750 oC has met the requirements. Table 4 shows the cost of the raw materials and

the energy for the production of foam glass. To produce a piece of the selected foam glass having

the dimension 20 cm × 60 cm × 7.5 cm (the regular size of light weight brick sold in the market), it

will cost about 16 baht per piece. Normally, the construction materials are sold in bulk and the

profit is about 10 to 15% of the production cost. The general wholesale price as of September 2013

of the light weight brick (G2 and G4-type autoclaved aerated concrete) is about 18-23 baht. By

selling the selected foam glass at the same price of the light weight brick, the profit for the

manufacturer is 12.5 to 43.75%. Therefore, the production parameters, which is the most

competitive in this work, is 80wt% window glass/ 20wt% fly ash and the firing temperature for

foaming step 750 oC.

Key Engineering Materials Vol. 608 75

Table 2 Composition of the raw materials. Art glass is the glass from art glass factory and window

glass is the glass from glass window industry.

Raw

Materials SiO2 TiO2 Al2O3 ZrO2 B2O3 Na2O K2O CaO MgO ZnO P2O5 MnO Fe2O3

Art glass 73.45 0.02 0.61 - 0.72 18.34 - 5.13 0.07 0.37 - - 0.02

Window

glass 71.12 0.03 1.33 0.25 - 13.31 0.21 8.71 4.72 - - - 0.10

Fly ash 59.83 22.67 1.34 0.09 - 0.47 1.27 3.08 0.86 - - 5.00

Husk ash 82.19 0.05 0.25 - - 0.43 0.92 0.75 0.43 0.16 0.85 0.48

Figure 2 The cross-section view of foamglass after firing.

(a)

(b)

76 Traditional and Advanced Ceramics

Figure 3 Properties of the foam glasses (a) compressive strength (b) density (c) water absorption.

The horizontal dash lines represent the range of properties of the light weight brick (G2 and G4 type

of autoclaved aerated concrete). F = fly ash, R = rice husk ash, A = art glass, W = window glass

Table 3 Properties of the light weight brick (G2-type and G4-type autoclaved aerated concrete).

Foam glass type Compressive Strength (kg/cm2) Density (kg/m

3) Water Absorption (%)

G2-type 25 400-500 34-36

G4-type 50 600-700 30

Figure 4 The % weight loss of foam glass fired at 750 oC and then soaked in Ca(OH)2 solution 1 N

for 28 days.

Table 4 Cost for the production of foam glass as of September 2013.

Raw Material Price (Baht/kg) Raw Material Price (Baht/kg)

Art glass cullet 0.48 Foaming agent 3.96

Window glass cullet 4.76 Binder (10 wt% Sodium

silicate solution)

2.62

Fly ash and husk ash 0.96

Average energy cost (LPG) (Baht/ kg batch) 2.92

Operation cost (labor, transportation, marketing) 20% of the summation of raw material

cost and energy cost

Summary

The results showed that the foam glass that was made from 80wt% window glass/ 20wt% fly ash

and fired at 750 °C had the most suitable properties for being produced commercially because it had

(c)

Key Engineering Materials Vol. 608 77

good alkaline resistant, and compared with the light weight brick (G2 and G4-type autoclaved

aerated concrete), this foam glass had higher compressive strength, lower degree of water

absorption, and similar density as G2-type but lower than G4-type. As of September 2013, the total

production cost (materials, labor, energy, etc.) of this foam glass is about 16 baht per piece (20 cm

× 60 cm × 7.5 cm) which is 12.5 to 43.75% lower than the wholesale price of a light weight brick

(18-23 baht per piece for G2 and G4-type autoclaved aerated concrete).

Acknowledgements

The authors would like to thank Faculty of Engineering, Kasetsart University for partially funded

this research, and Department of Materials Engineering, Kasetsart University, and Glass Bridge Co.

Ltd. for the supporting of scientific equipment. Materials Innovation Center of Kasetsart University

is also acknowledged.

References

[1] Glass recycling information sheet. [cited August 2013; Available from:

http://dl.dropboxusercontent.com/u/21130258/resources/InformationSheets/Glass.htm.

[2] Maemoh power plant, [cited August 2013; Available from:

http://maemoh.egat.com/index_maemoh.php.

[3] Pollution Control Department, Ministry of Natural Resources and Environment [cited;

Available from: http://www.pcd.go.th/info_serv/pol_suc_ash.html.

[4] Durability of Fly Ash Concrete. [cited; Available from: http://www.rdi.ku.ac.th/techno_ku60/

res-84/index84.html.

[5] V. Ramasamy. Compressive Strength and Durability Properties of Rice Husk Ash Concrete,

KSCE Journal of Civil Engineering 16 (2012) 93-102

[6] R. N. Krishna. Rice Husk Ash – An Ideal Admixture for Concrete in Aggressive Environments,

37th

Conference on Our World in Concrete & Structures (2012) Singapore

[7] P. Ineure, Glass Bridge Co. Ltd

[8] R. G. C. Beerkens and H. de Waal, Mechanism of oxygen diffusion in glass melts containing

variable-valence ions, J. Am. Ceram. Soc. 73 (1990) 1857-1861

[9] A. C.Steiner. Foam Glass Production from Vitrified Municipal Waste Fly Ashes. PhD thesis,

Eindhoven University of Technology, 2006.

[10] H. R. Fernandes, D. U. Tulyaganov, J. M. F. Ferreira. Preparation and Characterization of

Foams from Sheet Glass and Fly Ash using Carbonates as foaming agents, Ceramics

International. 35 (2009) 229-235.

[11] B. Chen, Z. Luo, A. Lu. Preparation of Sintered Foam Glass with High Fly Ash Content,

Materials Letters. 65 (2011) 3555-3558.

[12] B. Chen, K, Wang, X. Chen, A. Lu. Study of Foam Glass with High Content of Fly Ash

using Calcium Carbonate as Foaming Agent, Materials Letters. 79 (2012) 263-265.

78 Traditional and Advanced Ceramics

Traditional and Advanced Ceramics 10.4028/www.scientific.net/KEM.608 Foam Glass Development Using Glass Cullet and Fly Ash or Rice Husk Ash as the Raw Materials 10.4028/www.scientific.net/KEM.608.73

DOI References

[5] V. Ramasamy. Compressive Strength and Durability Properties of Rice Husk Ash Concrete, KSCE

Journal of Civil Engineering 16 (2012) 93-102.

http://dx.doi.org/10.1007/s12205-012-0779-2 [8] R. G. C. Beerkens and H. de Waal, Mechanism of oxygen diffusion in glass melts containing variable-

valence ions, J. Am. Ceram. Soc. 73 (1990) 1857-1861.

http://dx.doi.org/10.1111/j.1151-2916.1990.tb05235.x [10] H. R. Fernandes, D. U. Tulyaganov, J. M. F. Ferreira. Preparation and Characterization of Foams from

Sheet Glass and Fly Ash using Carbonates as foaming agents, Ceramics International. 35 (2009) 229-235.

http://dx.doi.org/10.1016/j.ceramint.2007.10.019 [11] B. Chen, Z. Luo, A. Lu. Preparation of Sintered Foam Glass with High Fly Ash Content, Materials

Letters. 65 (2011) 3555-3558.

http://dx.doi.org/10.1016/j.matlet.2011.07.042 [12] B. Chen, K, Wang, X. Chen, A. Lu. Study of Foam Glass with High Content of Fly Ash using Calcium

Carbonate as Foaming Agent, Materials Letters. 79 (2012) 263-265.

http://dx.doi.org/10.1016/j.matlet.2012.04.052