Production of bricks from waste materials – A review

Construction and Building Materials 47 (2013) 643–655

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

Review

Production of bricks from waste materials – A review Lianyang Zhang ⇑ Department of Civil Engineering and Engineering Mechanics, University of Arizona, Tucson, AZ 85721, USA

h i g h l i g h t s  A wide variety of waste materials have been researched for production of bricks, including mainly fly ash and slags.  Methods for producing bricks from waste materials can be divided into 3 categories: firing, cementing and geopolymerization.  Commercial production of bricks from waste materials is still very limited due to different reasons.  Further research and development is needed to promote wide production and application of bricks from waste materials.

a r t i c l e

i n f o

Article history: Received 17 February 2013 Received in revised form 27 April 2013 Accepted 5 May 2013 Available online 10 June 2013 Keywords: Bricks Waste materials Firing Cementing Geopolymerization Sustainable development

a b s t r a c t Bricks are a widely used construction and building material around the world. Conventional bricks are produced from clay with high temperature kiln firing or from ordinary Portland cement (OPC) concrete, and thus contain high embodied energy and have large carbon footprint. In many areas of the world, there is already a shortage of natural source material for production of the conventional bricks. For environmental protection and sustainable development, extensive research has been conducted on production of bricks from waste materials. This paper presents a state-of-the-art review of research on utilization of waste materials to produce bricks. A wide variety of waste materials have been studied to produce bricks with different methods. The research can be divided into three general categories based on the methods for producing bricks from waste materials: firing, cementing and geopolymerization. Although much research has been conducted, the commercial production of bricks from waste materials is still very limited. The possible reasons are related to the methods for producing bricks from waste materials, the potential contamination from the waste materials used, the absence of relevant standards, and the slow acceptance of waste materials-based bricks by industry and public. For wide production and application of bricks from waste materials, further research and development is needed, not only on the technical, economic and environmental aspects but also on standardization, government policy and public education related to waste recycling and sustainable development. Ó 2013 Elsevier Ltd. All rights reserved.

Contents 1. 2.

3. 4.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Review of research on utilization of waste materials to produce bricks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. Production of bricks from waste materials through firing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2. Production of bricks from waste materials through cementing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3. Production of bricks from waste materials through geopolymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

⇑ Tel.: +1 520 6260532; fax: +1 520 6212550. E-mail address: [email protected] 0950-0618/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.conbuildmat.2013.05.043

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1. Introduction Bricks have been a major construction and building material for a long time. The dried-clay bricks were used for the first time in 8000 BC and the fired-clay bricks were used as early as 4500 BC [1,2]. The worldwide annual production of bricks is currently about 1391 billion units and the demand for bricks is expected to be continuously rising [3,4]. Conventional bricks are produced from clay with high temperature kiln firing or from ordinary Portland cement (OPC) concrete. Quarrying operations for obtaining the clay are energy intensive, adversely affect the landscape, and generate high level of wastes. The high temperature kiln firing not only consumes significant amount of energy, but releases large quantity of greenhouse gases. Clay bricks, on average, have an embodied energy of approximately 2.0 kWh and release about 0.41 kg of carbon dioxide (CO2) per brick [5,6]. It is also noted that there is a shortage of clay in many parts of the world. To protect the clay resource and the environment, some countries such as China have started to limit the use of bricks made from clay [7–9]. The OPC concrete bricks are produced from OPC and aggregates. It is well known that the production of OPC is highly energy intensive and releases significant amount of greenhouse gases. Production of 1 kg of OPC consumes approximately 1.5 kWh of energy and releases about 1 kg of CO2 to the atmosphere. Worldwide, production of OPC is responsible for about 7% of all CO2 generated [5,10– 12]. So the production of OPC concrete bricks also consumes large amount of energy and releases substantial quantity of CO2. In addition, the aggregates are produced from quarrying and thus have the same problems as described above for clay. For environmental protection and sustainable development, many researchers have studied the utilization of waste materials to produce bricks [8,9,13–15,17–66,80–85]. A wide variety of waste materials have been studied, including fly ash, mine tailings, slags, construction and demolition (C&D) waste, wood sawdust, cotton waste, limestone powder, paper production residue, petroleum effluent treatment plant sludge, kraft pulp production residue, cigarette butts, waste tea, rice husk ash, crumb rubber, and cement kiln dust. Different methods have been used to produce bricks from waste materials. This paper presents a state-of-the-art review of the research on utilization of different types of waste materials to produce bricks. The advantages and disadvantages of different methods for utilizing waste materials to produce bricks are described. The concerns related to production of bricks from waste materials are also discussed. 2. Review of research on utilization of waste materials to produce bricks The extensive research on utilization of waste materials to produce bricks can be divided into three general categories based on the production methods: firing, cementing and geopolymerization, as detailed below. 2.1. Production of bricks from waste materials through firing This method uses waste material(s) to substitute a portion or entire amount of clay and follows the traditional way to kiln fire the material(s) to produce bricks. Many researchers have studied the production of bricks from waste materials based on firing (see Table 1). Chen et al. [8] studied the feasibility of utilizing hematite tailings and class F fly ash together with clay to produce bricks. Brick samples were prepared by using 77–100% tailings, 0–8% fly ash and 0–15% clay. Tests were performed to determine the compressive

strength, water absorption and bulk density of brick samples prepared at different conditions. Based on the results, they recommended a tailings:fly ash:clay ratio of 84:6:10, a forming water content of 12.5–15%, a forming pressure of 20–25 MPa, and a firing temperature of 980–1030 °C for 2 h, to produce good quality bricks. Lingling et al. [9] investigated the production of fired bricks by using class F fly ash to replace clay at high volume ratios. Brick samples were prepared by mixing fly ash and clay at designed proportion, casting the mixture into bricks, drying the bricks at ambient condition for 2 days, at 60 °C for 4 h and at 100 °C for 6 h, and firing the dried bricks in an electric furnace at 100 °C/h below 500 °C, 50 °C/h from 500 °C to highest temperature (1000, 1050, or 1100 °C), and at the highest temperature for 8 h. Tests were conducted on the fired bricks to evaluate their compressive strength, water absorption, bulk density, apparent porosity, cracking due to lime, frost and frost-melting. The results showed that when high percentages of fly ash were used, a firing temperature about 1050 °C should be adopted. The fired bricks with high percentages of fly ash had high compressive strength, low water absorption, no cracking due to lime, and high resistance to frost-melting. The study also indicated that the properties of fired bricks were improved by using pulverized fly ash (i.e., by decreasing the particle size of the fly ash). Kute and Deodhar [13] studied the bricks manufactured in laboratory using class F fly ash and clay. The brick samples were prepared by mixing different amount of fly ash with clay and sufficient quantity of water, and then compressing the mixture in a mold. The molded bricks were dried in air for 2 days and then fired in a laboratory furnace respectively at 850 and 1000 °C for 24 h. Laboratory tests were conducted to evaluate the compressive strength and water absorption of the produced bricks. The results indicated that the inclusion of fly ash in general increased the compressive strength and decreased the water absorption of bricks. The highest compressive strength of 12.4 MPa (an average of eight samples) was obtained at 40% fly ash content, with the corresponding water absorption being 13.8%. Chou et al. [14,15] conducted systematic study on utilization of class F fly ash to replace part of the clay and shale in production of bricks using the conventional kiln firing procedure. Paving bricks with up to 20 vol.% of fly ash and building bricks with up to 40 vol.% of fly ash were successfully produced in commercial-scale production test runs, with the properties exceeding the ASTM commercial specifications. They also conducted leaching study on the fired bricks from commercial-scale production following US EPA Method 1320 [16]. The results indicated that the amounts of leached metals were well below the US EPA’s regulatory thresholds. Kayali [17] studied the performance of FlashBricks, bricks produced from fly ash. The bricks were produced by mixing fly ash with water and a small amount of commercially protected additive, molding the mixture, drying the formed units for 3 days, and then firing them for hours. The FlashBricks were about 28% lighter than clay bricks and had a compressive strength greater than 40 MPa. Other important performance parameters such as water absorption, modulus of rupture, bond strength and durability also exceeded those pertaining to clay bricks. Menezes et al. [18] evaluated the possibilities of using granite sawing wastes as alternative raw materials in the production of ceramic bricks and tiles. The results showed that the granite sawing wastes had physical and mineralogical characteristics that were similar to those of conventional raw materials for ceramic bricks and tiles and could be used to partially replace the conventional raw materials to produce ceramic bricks and tiles meeting the Brazilian standardizations. Lin [19] studied the utilization of municipal solid waste incinerator (MSWI) slag to partially replace clay for the production of fired

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L. Zhang / Construction and Building Materials 47 (2013) 643–655 Table 1 Studies on production of bricks from waste materials through firing. No.

Waste material (wt.%)

Brick size (mm)

Drying/firing condition

Tests conducted

Reference

1

Hematite tailings (77–100%) and class F fly ash (0–8%)

50  50 (cylinder)

Compressive strength, water absorption, bulk density

[8]

2

Class F fly ash (0, 50, 60, 70, and 80 vol.%)

60  60  25

Compressive strength, water absorption, bulk density, apparent porosity, cracking due to lime, frost and frost-melting

[9]

3

95  45  45

5

Fly ash (100%)

-

6

Granite sawing wastes (0–60%)

Various sizes

7

Municipal solid waste incinerator slag (0–40%)

50  25  50

8

Gold mill tailings (0–75%)

100  100  76

Compressive strength, water absorption Compressive strength, water absorption, leaching Compressive strength, water absorption, modulus of rupture, density, bond strength, durability Compressive strength, water absorption, modulus of rupture Compressive strength, water absorption, density, firing shrinkage, weight loss on ignition, TCLP Compressive strength, water absorption, linear shrinkage

[13]

4

Class F fly ash (0%, 20%, 40%, and 60%) Class F fly ash (0–60 vol.%)

Dried in an oven at 105 °C for 6–8 h and then fired in an electric furnace at 6 °C/min until 850–1050 °C for 2 h Dried at ambient condition for 2 days, at 60 °C for 4 h and at 100 °C for 6 h, and fired in an electric furnace at 100 °C/h below 500 °C, 50 °C/h from 500 °C to 1000, 1050 or 1100 °C, and at the highest temperature for 8 h Dried in air for 2 days and then fired in a laboratory furnace at respectively 850 and 1000 °C for 24 h Following the process of a commercial clay brick plant Dried for 3 days and then fired at 1000–1300 °C for hours

9

Kaolin fine quarry residue (50%), granulated blast-furnace slag (10– 40%), granite–basalt fine quarry residue (10–40%) Paper production residues (0%, 10%, 20%, and 30%)

50  50  50

Compressive strength, water absorption, bulk density

[21]

Compressive strength, water absorption, bulk density, apparent porosity, thermal conductivity

[22]

Compressive strength, water absorption, density, thermal conductivity, leaching Compressive strength, water absorption, density

[23]

Compressive strength, water absorption, leaching

[25]

Compressive strength, water absorption, density

[26]

Compressive strength, water absorption, density

[27]

Compressive strength, water absorption, porosity, firing shrinkage, leaching, permeability, freeze–thaw Bending strength, water absorption, open porosity, bulk density, firing shrinkage, leaching

[28]

Compressive strength, water absorption, shrinkage, leaching Compressive strength, water absorption, bulk density, apparent porosity Flexural strength, water absorption, density, apparent porosity Flexural strength, water absorption, bulk density, porosity Flexural strength, water absorption, density, open porosity, leaching

[30]

10

Various sizes

85  85  10

Fired at different temperatures between 750 and 1200 °C Air-dried at room temperature for 24 h, oven dried at 80 °C for 24 h, and finally fired at 800, 900, or 1000 °C for 6 h Dried at room temperature for 2 days, in the sun for 3 days, and then fired in an electric furnace at 750, 850, or 950 °C for 9 h Dried in an electric dryer at 80 °C for 24 h, and then fired at different temperatures of 1100, 1125, 1150 and 1175 °C at 5 °C/min and 4 h soaking time in a muffle furnace under oxidizing condition Held overnight at room temperature followed by drying at 45 °C for 1 h in an oven, then fired in an electrical furnace at 2.5 °C/min until 600 °C and then at 10 °C/min until 1100 °C, for 1 h Dried at 105 °C for 24 h, and then fired in a furnace at 1050 °C

11

Cigarette butts (0%, 2.5%, 5% and 10%)

300  100  50

12

Rice husk ash (0%, 5%, 10%, 15% and 20%)

50  50  50

13

Petroleum effluent treatment plant sludge (41%)

280  130  170

14

Kraft pulp production residue (2.5%)

15

Waste tea (5%)

33  40 (cylinder), 25  25  150 100  70  40

16

River sediments (15%)

60  220  220

17

PC and TV waste glass (<2%)

100  20  10

18

– 30  10  60

Fired in a laboratory furnace at 3 °C/min up to 950 or 1050 °C for 4 h

20

Municipal solid waste incineration fly ash (20%) Sawdust (0–10%), spent earth from oil filtration (0–30%), compost (0– 30%), or marble (0–20%) Foundry by-products (0–50%)

150  30  15

21

Waste marble powder (20–100%)

41  8  8

22

Waelz slag and waste foundry sand (20–40%)

100  80  20

23

River sediment (100% or 50%)

54  54  (5–10)

Fired in a laboratory muffle at 2 °C/min up to 850, 950 or 1050 °C for 3.5 h Fired in an electrical furnace at 5 °C/min up to at 900, 1000 or 1100 °C for 3 h Dried at 96–104 °C and fired in an industry tunnel kiln to a maximum temperature of 850 °C (heating rate 0.85 °C/min, cooling rate 1.14 °C/min, and soaking time of 1 h) Dried in an oven at temperature gradually increasing from 25 to 110 °C until no change in mass, and then fired in an electric laboratory furnace at different temperatures from 900 to

19

Dried in the sun at 30 °C for 8 days, at 105 °C for 24 h in an oven, and then fired in a furnace continuously at 250, 500, 750 °C for 2 h each and finally at 1000 °C for 2, 4 or 6 h Dried at room temperature and then fired in a coalfired Bulls trench commercial brick kiln along with usual commercial bricks at 1000–1100 °C Dried at 21 °C for 72 h and then at 105 °C in the oven, and subsequently fired at 2 °C/min until 600 °C and then at 5 °C/min until 900 °C for 30 min Dried at 21 °C for 72 h and then at 105 °C in the oven, and subsequently fired at 2 °C/min until 600 °C and then at 5 °C/min until 900 °C for 2 h Dried through a tunnel drier up to 80 °C and then fired through a tunnel kiln with a maximum temperature of 1000 °C Dried at ambient temperature in a non-controlled atmosphere for 48 h and then in an electric oven at 100 °C overnight, and finally fired in an electric chamber kiln at 100 °C/h until 900, 950 or 1000 °C for 4 h Dried at around 60 °C and then fired at 950 °C

Compressive strength, water absorption, firing shrinkage, freeze–thaw

[14,15] [17]

[18] [19]

[20]

[24]

[29]

[31]

[32] [33] [34]

[35]

(continued on next page)

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Table 1 (continued) No.

24

Waste material (wt.%)

Sugarcane bagasse ash waste (up to 20%)

Brick size (mm)

Drying/firing condition

Tests conducted

Reference

25 mm (diameter)

1000 °C with variations in heating rate and holding duration at the maximum temperature Dried at 110 °C for 24 h and then fired in an electric kiln at 1100 °C (24 h cold to cold)

Linear shrinkage, water absorption, apparent density, tensile strength

[36]

clay bricks. Brick samples were heated to temperatures between 800 and 1000 °C for 6 h at a heating rate of 10 °C/min. Physical, mechanical and leaching tests were conducted on the brick samples. The results indicated that the heavy metal concentrations in the leachate met the regulatory thresholds. Increasing the amount of MSWI slag resulted in a decrease in the water absorption rate and an increase in the compressive strength of the bricks. The absorption rate and compressive strength of the bricks sintered at 1000 °C met the Chinese National Standard (CNS) building requirements for second-class bricks. The addition of MSWI slag also reduced the degree of firing shrinkage. So the MSWI slag was suitable for partial replacement of clay in production of fired clay bricks. Roy et al. [20] studied production of bricks by mixing different amount of gold mill tailings (0–75%) with black cotton soils or red soils. The soil-tailings bricks were dried at room temperature for 2 days and in the sun for another 3 days, and then fired in an electric furnace respectively at 750, 850, and 950 °C. The fired bricks were tested to evaluate their compressive strength, water absorption and linear shrinkage. The results indicated that 65%, 75%, 50% and 45% of tailings could be used respectively with the four different types of soils studied to produce bricks that pass the criteria in terms of compressive strength, water absorption and linear shrinkage. El-Mahllawy [21] investigated the production of bricks using kaolin fine quarry residue (KFQR) combined with granulated blast-furnace slag (GBFS) and granite–basalt fine quarry residue (GBFQR). Brick specimens were prepared by mixing 50% of KFQR, 10–40% of GBFS and 10–40% GBFQR, and then placing the mixture into a 50 mm cubic mold and applying a forming pressure of 22 MPa. The formed specimens were dried in an electrical dryer at 80 °C for 24 h, and then fired at different firing temperatures of 1100, 1125, 1150 and 1175 °C at 5 °C/min firing rate and 4 h soaking time in a muffle furnace. Tests were performed to assess the physical, chemical and mechanical characteristics of the fired bricks against the requirements of the Egyptian standard specification (ESS). The results showed that the bricks containing 50% KFQR, 20% GBFQR and 30% GBFS fired at 1125 °C exhibited the most satisfying properties that meet the ESS requirements. Sutcu and Akkurt [22] studied production of porous and lightweight bricks with reduced thermal conductivity and acceptable compressive strength by using paper processing residues as an additive to earthenware bricks. Mixtures containing brick raw materials and the paper processing waste were prepared at different proportions (up to 30% by weight). The granulated powder mixtures were compressed in a hydraulic press under a pressure of 10 MPa. The pressed specimens were held overnight at room temperature followed by drying at 45 °C for 1 h in an oven, and then fired in a laboratory-type electrical furnace at a rate of 2.5 °C/min until 600 °C and subsequently at a rate of 10 °C/min until 1100 °C for 1 h. Tests were performed to evaluate the dilatometric behavior, drying and firing shrinkages, loss on ignition, bulk density, apparent porosity, water absorption, thermal conductivity, compressive strength and freeze–thaw performance of the fired brick specimens. The results indicated that the paper processing waste could be utilized together with brick raw materials to produce porous and lightweight bricks with reduced thermal conductivity and acceptable compressive strength.

Aeslina et al. [23] investigated the recycling of cigarette butts (CBs) into fired clay bricks. The CBs were disinfected by heat at 105 °C for 24 h and then mixed with soil at four different percentages. The mixture was placed in molds and compacted manually at the optimum moisture content which was found from standard compaction tests. The specimens were dried at 105 °C for 24 h, removed from the molds and fired in a furnace at 1050 °C. The fired specimens were tested for density, strength, thermal conductivity and leachate characteristics. The results indicated that cigarette butts could be regarded as a potential addition to raw materials used in the manufacturing of light fired bricks. Rahman [24] made fired bricks using clay–sand mixes with different percentages of rice husk ash. The firing durations at 1000 °C were respectively 2, 4 and 6 h. The effects of rice husk ash content on workable mixing water content, Atterberg limits, linear shrinkage, density, compressive strength and water absorption of the bricks were investigated. The results indicated that (1) the inclusion of rice husk ash increased the compressive strength of bricks, (2) the optimum firing duration was 4 h at 1000 °C, and (3) the bricks made of clay–sand–rice husk ash mixes could be used in load bearing walls. Sengupta et al. [25] studied the utilization of petroleum effluent treatment plant sludge in preparing environmentally acceptable masonry bricks in a commercial brick plant. The sludge was mixed thoroughly with soil and sand at a ratio of 0.46:1:0.12. Mixtures were homogenized and used to prepare bricks by adopting the procedure as practiced in common masonry brick manufacturing. The bricks were air dried at ambient condition to optimum moisture content and fired in a coal-fired Bulls trench commercial brick kiln along with the usual commercial bricks. The firing temperature ranged from 1000 to 1100 °C. The physical, chemical and mechanical properties of the bricks were evaluated. The results indicated that (1) the addition of the sludge reduced the requirement of process water and fuel, (2) the fired bricks containing the sludge met all the requirements of the Indian Standard Specification, and (3) most of the toxic metals were fixed in the vitrification process and the leachate values met the US EPA’s requirement for recycling of hazardous materials. Demir et al. [26] investigated the potential of utilizing kraft pulp production residues in clay bricks. Different amounts of residues were mixed with raw brick clay to produce bricks. Shaped brick samples were dried at laboratory conditions (21 °C and 40% relative humidity) for 72 h and then dried to constant weight at 105 °C in the oven. The dried samples were fired in a laboratory type electrically heated furnace at a rate of 2 °C/min until 600 °C and then at a rate of 5 °C/min until 900 °C for 30 min. The effect of including the sludge on shaping, plasticity, density, porosity, water absorption and mechanical properties were investigated. The results indicated that 2.5–5% residue additions were effective for the pore forming in clay body with acceptable mechanical properties. It was concluded that kraft pulp residues can be utilized in brick clay as an organic pore-forming agent. Demir [27] studied the utilization of processed waste tea (PWT) together with clay to produce bricks. The effects of PWT addition on the durability and mechanical properties of bricks were investigated. Due to the organic nature of PWT, pore-forming (fired body) and binding (unfired body) ability in clay body was investigated. Different amounts of PWT were added to the clay to produce

L. Zhang / Construction and Building Materials 47 (2013) 643–655

bricks. The test brick specimens were produced by the extrusion method. The specimens were tested following the standard test methods. The results indicated that the inclusion of PWT significantly increased the compressive strength of the unfired and fired brick samples. As a result, it was concluded that PWT can be utilized in unfired and fired building bricks by taking advantage of low cost and environmental protection. Samara et al. [28] investigated the use of polluted river sediments after treatment in brick production by conducting a fullscale industrial experiment at a brick factory. The polluted sediment was first stabilized by the NovosolÒ process and then introduced in the mix-design by replacing 15% of quartz sand used in normal brick production. Approximately 15,000 perforated sediment-amended bricks were produced and the bricks were subjected to different qualification tests. The results indicated that the use of treated sediment resulted in significant increase in compressive strength and firing shrinkage and decrease in porosity and water absorption. The leaching tests showed that the quantities of heavy metals leached from crushed bricks were within the regulatory limits. Dondi et al. [29] studied the feasibility of utilizing PC and TV waste glass in production of clay bricks. The results indicated that addition of up to 2% of waste glass to the clay did not bring about significant changes to the properties of bricks. For low carbonate bricks, no significant release of Pb, Ba, and Sr was observed during the firing and leaching processes. However, for high carbonate bricks, some Pb volatilization during firing and Sr leaching were observed. One main constraint for the utilization of the PC and TV waste glass is that the glass must have a particle size below the limit of the pan mills used in brick production (<1 mm). Haiying et al. [30] investigated the utilization of municipal solid waste incineration (MSWI) fly ash in production of ceramic bricks. It was found that the optimal mixture ratio of materials, MSWI fly ash:red ceramic clay:feldspar:gang sand, was 20:60:10:10, and the optimal sintering temperature was 950 °C. The results as a whole suggested that utilization of MSWI fly ash in production of ceramic bricks constituted a potential means of recycling MSWI fly ash. Eliche-Quesada et al. [31] studied the application of a variety of waste materials together with clay to produce lightweight bricks: sawdust, spent earth from oil filtration, compost and marble. Brick samples were fabricated respectively with 0–10% sawdust, 0–30% spent earth from oil filtration, 0–30% compost, and 0–20% marble. A 54.5 MPa compression pressure was applied during the molding process. The brick samples were fired in a laboratory furnace at a rate of 3 °C/min up to respectively 950 and 1050 °C for 4 h. The results showed that the bricks fired at 1050 °C had higher compressive strength, lower porosity and water absorption than those at 950 °C. The optimum amount of waste material which should be used was 5% sawdust, 15% spent earth from oil filtration, 10% compost, or 15% marble. Alonso-Santurde et al. [32] studied the production of bricks by mixing green and core foundry sand with clay in proportions 0– 50% and firing at 850–1050 °C. Brick specimens were prepared and evaluated physically and mineralogically. It was found that the clay–foundry sand bricks fired at 1050 °C had better physical property values while the mineralogy was not significantly affected. The optimum amount of foundry sand to produce bricks was found to be 35% green sand and 25% core sand. Bilgin et al. [33] investigated the usability of waste marble dust as an additive material in industrial brick. Waste marble dust and industrial brick mortar were mixed in different proportions to produce brick specimens for evaluating the effect of marble dust composition on the physico-mechanical properties of bricks. The brick specimens were pressed and sintered at three different temperatures, 900, 1000 and 1100 °C. It was found that the amount of

647

added marble dust had positive effect on the physical, chemical and mechanical properties of the produced industrial brick. Quijorna et al. [34] studied the utilization of Waelz slag and foundry sand to partially replace clay in the production of red clay bricks. A semi-scale industrial trial was conducted by incorporating 20–40% additions to produce bricks and then evaluating their physico-chemical, mechanical and environmental properties. The results indicated that the incorporation of Waelz slag and foundry sand was beneficial for improved extrusion properties during forming, lower water absorption of the sintered brick due to reduced connected porosity, significant reduction in CO2 and NOx emissions during firing, and improvements in potential leachability of some pollutants in relation to samples containing only Waelz slag or foundry sand. However, it was necessary to limit the addition of Waelz slag to less than 30% in order to meet regulatory leaching limits for Mo. Other physico-chemical and mechanical parameters were not significantly affected by the addition of these industrial by-products. Mezencevova et al. [35] conducted a laboratory-scale study to assess the feasibility of producing fired bricks by using dredged sediments as the sole raw material or as a 50% replacement for natural brick-making clay. Brick samples were produced by firing at temperatures between 900 and 1000 °C. The test results indicated that the physical and mechanical properties of the dredged sediment bricks generally complied with ASTM criteria for building bricks. Faria et al. [36] investigated the recycling of sugarcane bagasse ash waste as a method to provide raw material for clay brick production. Brick samples were produced by using up 20% of sugarcane bagasse ash waste to replace natural clay, and then tested to determine their physical and mechanical properties. It was found that the sugarcane bagasse ash waste was mainly composed of crystalline silica particles and could be used as a filler in clay bricks. 2.2. Production of bricks from waste materials through cementing This method does not need kiln firing but relies on cementing from the waste material itself or other added cementing materials. Again, many researchers have studied the utilization of waste materials to produce bricks based on cementing (see Table 2). Roy et al. [20] also used gold mill tailings to make bricks by mixing them with OPC in different proportions. The cement-tailings bricks were cured by immersing them in water for different periods of time and their compressive strengths were determined. The bricks with 20% of cement and 14 days of curing were found to be suitable. The cost analysis revealed that the cement-tailings bricks would be uneconomical compared to the soil-tailings bricks (see the related review in the previous section). Malhotra and Tehri [37] investigated the development of bricks from granulated blast furnace slag, a byproduct of the iron and steel industry. The slag was first mixed with hydrated lime and then the lime–slag mixture with Badarpur sand thoroughly. Brick specimens were made by pressing the mixture in a hydraulic machine at a pressure of 4.9 MPa and then curing the molded specimens at 270–272 °C and 95% humidity over a period of 28 days. The cured bricks were tested for compressive strength (in saturated conditions), bulk density and water absorption properties. The study revealed that good quality bricks could be produced from a slag–lime mixture and sand. Poon et al. [38] studied the production of concrete bricks and paving blocks using recycled aggregates obtained from construction and demolition (C&D) waste together with OPC and/or fly ash. A series of tests were carried out to determine the properties of the bricks and blocks prepared with and without recycled aggregates. The test results showed that the replacement of coarse and

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L. Zhang / Construction and Building Materials 47 (2013) 643–655

Table 2 Studies on production of bricks from waste materials through cementing. No. 1 2

3

4

Waste material (wt.%)

Cementing material

Brick size (mm)

Curing condition

Tests conducted

Reference

Gold mill tailings (0–75%) Granulated blast furnace slag (5–35%) Recycled aggregates (replacing 25– 100% of natural aggregates) Class F fly ash (60–90%)

OPC

100  100  76

Cured in water for different periods of time

Compressive strength

[20]

Hydrated lime

190  90  90

Cured at 95% humidity and at a temperature of 270–272 °C for 28 days

Compressive strength, bulk density, water absorption

[37]

OPC alone or both OPC and fly ash

225  105  75

Bricks: cured in air at room temperature for 28 days; Blocks: cured in a steam bath at 65 °C for 6 h and then further cured in air at room temperature until 28 days

Compressive strength, density, drying shrinkage

[38]

Calcined phosphogypsum and mineral lime Fly ash itself

220  110  75, 150  150  150 (hollow block) 200  100  55

Covered with wet gunny bags for a week and then cured in water filled tanks at 23°2 °C Cured in a moist room at 23 ± 2 °C and relative humidity not less than 95%

Compressive strength, water absorption, density, durability

[39]

[40]

Cured in a wet environment (curing chamber) at room temperature for over 2 weeks Placed in well ventilated room at ambient temperature for 24 h and then cured in water Pre-cured for about 24 h and then steamed autoclaved at pressure 0.5–2 MPa for 3– 12 h Cured at room temperature for 24 h, in lime-saturated water tank at 22 °C for 28 days, and then dried in ventilated oven at 105 °C for 24 h Cured at room temperature for 24 h, in lime-saturated water tank at 22 °C for 28 days, and then dried in ventilated oven at 105 °C for 24 h Cured at room temperature for 24 h, in lime-saturated water tank at 22 °C for 28 days, and then dried in ventilated oven at 105/115 °C for 24 h

Compressive strength, water absorption, modulus of rupture, freeze– thaw Compressive strength, water absorption, permeability, freeze–thaw, leaching Compressive strength, water absorption

5

Class C fly ash (100%)

6

Class C fly ash (100%)

Fly ash itself

200  100  55

7

Copper mine tailings (8%, 12% and 15%) Class F fly ash (50–80%)

OPC

190  90  90

Hydrated lime

45 (diameter)

OPC

105  95  75

OPC

105  95  75

OPC

Various

8

9

10

11

Wood sawdust and limestone powder (86–89%) Cotton waste and limestone powder (84–89%) Waste glass powder and limestone powder (89%)

12

Crumb rubber (0–29%)

OPC

105  100  75

13

Class F fly ash (95% and 100%)

Hydrated lime

15  65  10

14

Stockpiled circulating fluidized bed combustion ash (58.3–100%) Low-silicon tailings (83%)

OPC, lime, and/or class F fly ash

90  65  90

Fly ash, slag, clinker dust and some activators Class C fly ash itself

240  115  53

105  75  225

OPC, ground silicate cement clinker, alumina cement, or slag cement Lime

40  40  160

15

16

Limestone powder and class C fly ash (100%)

17

Sludge from dyestuff-making wastewater coagulation (33– 50%) Low SiO2 content copper tailings (0–88%) Limestone powder, class C fly ash, and silica fume (100%) Recycle paper mill waste (80–95%) Hematite tailings (70%)

18

19

20

21

Cured in air for 6 h, in lime-saturated water tank at 22 °C for 28 days, and then dried in ventilated oven at 65 °C for 48 h Put in moist chamber at 98% RH for 3 days, and then autoclaved at 125–135 °C & 0.14 MPa pressure for 4 h Placed at 23 °C and 100% RH room for 1 day, and then cured in air at room temperature for different period of time

[41–45]

[46]

Compressive strength, water absorption, unit weight, thermal conductivity Compressive strength, water absorption, flexural strength, unit weight, UPV test

[47]

Compressive strength, water absorption, flexural strength, unit weight, UPV test, thermal conductivity

[49,50]

Compressive strength, water absorption, flexural strength, unit weight, UPV test, abrasion resistance, freezing–thawing resistance, thermal conductivity Compressive strength, water absorption, flexural strength, freeze– thaw resistance, unit weight, UPV test Compressive strength, water absorption, bulk density, leaching

[51,52]

[48]

[53]

[54]

Compressive strength, water absorption density

[55]

Sealed in plastic bag for 6 h, and then cured in autoclave for certain period of time

Compressive and bending strengths, freeze–thaw resistance, dry shrinkage

[56]

Cured at room temperature for 48 h, in water tank at 22 °C for 7, 28 and 90 days, and then dried in ventilated oven at 105 °C for 24 h Cured at 20 °C in 100% humidity for 24 h, and then cured in water at 20 °C for 28 days

Compressive strength, water absorption, flexural strength, density, UPV test, thermal conductivity

[57]

Compressive strength, freeze–thaw resistance, leaching

[58]

100  100  50

Heated-up for 2 h to 170–190 °C, stayed for 5–8 h, and then cooled-down for 3 h

Compressive strength, freeze–thaw resistance

[59]

Class C fly ash and/or silica fume

225  105  75

Cured by spraying additional water on the surface at room temperature for 48 h, and then cured in water for different times

Compressive strength, flexural strength, density, water absorption, porosity, thermal conductivity

[60]

OPC

230  105  80

Solar dried

[61]

Lime

50  23 (cylinder)

Pre-cured for about 24 h, and then steam autoclaved for certain period of time

Compressive strength, water absorption, specific weight, voidage, moisture content Compressive strength, flexural strength, freeze–thaw resistance

[62]

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L. Zhang / Construction and Building Materials 47 (2013) 643–655 Table 2 (continued) No.

Waste material (wt.%)

Cementing material

Brick size (mm)

Curing condition

Tests conducted

Reference

22

CFBC fly ash (77–100%) and slag (0–20%) Waste phosphogypsum (75) Coal combustion residues (70%, 90vol.%) Fly ash, quarry dust, and billet scale (85% and 90%)

OPC or lime

50  50 (cylinder) 240  115  53 240  115  53

Cured at 25–30 °C temperature and 80–90% humidity for a certain period of time, and then autoclaved for 3–8 h Wet cured for 1 day, dried at 180 °C for 2 h, immersed in water for 1 h, and naturally cured Moistened through water spraying and covered by a black plastic sheet

Compressive strength, water absorption, dry-shrinkage, bulk density, freeze–thaw resistance Compressive strength, bending strength, water absorption, freeze– thaw resistance Compressive strength, unit weight

[63]

Covered with wet burlap overnight, and then cured in plastic storage boxes at 22 °C and 95% RH

Compressive strength, water absorption, modulus of rupture, UPV, efflorescence and durability

23

24

25

OPC and hydrated lime OPC

140  140  90

OPC

200  90  60

fine natural aggregates by recycled aggregates at the levels of 25% and 50% had little effect on the compressive strength of the brick and block specimens, but higher levels of replacement reduced the compressive strength. Using recycled aggregates as the replacement of natural aggregates at the level of up to 100%, concrete paving blocks with a 28-day compressive strength of not less than 49 MPa could be produced without the incorporation of fly ash, while paving blocks for footway uses with a lower compressive strength of 30 MPa and masonry bricks could be produced with the incorporation of fly ash. Kumar [39] investigated the production of bricks and hollow blocks using class F fly ash together with calcined phosphogypsum and mineral lime. The brick and hollow block specimens were prepared by mixing different amounts of fly ash (60–90%), calcined phosphogypsum (5–30%) and mineral lime (5–30%) and then placing the mixture in wooden molds. The molded bricks and hollow blocks were covered with wet gunny bags for a week and then transferred to water filled curing tanks at 21–25 °C. To investigate the durability, the bricks and hollow blocks were cured in an aggressive environment of sulfate solution. The cured bricks and hollow blocks were tested to evaluate their compressive strength, water absorption, density and durability. It was observed that these bricks and hollow blocks had sufficient strength for their use in low cost housing development. Li and Lin [40] studied the production of bricks by compacting class C fly ash, both high grade with LOI (loss on ignition) = 0.03% and low grade with LOI = 9.1%, mixed with water. They tested the compacted bricks to evaluate their compressive strength, modulus of rupture, freeze–thaw resistance, and water absorption. The results indicated that the bricks compacted from fly ash had higher compressive strength than ordinary commercial bricks, but lower freeze–thaw resistance. So they could be used in certain applications. Analysis was also performed on the production cost for the compacted fly ash bricks and the results showed that the cost would be less than 2 cents per brick if the capital cost for a plant with a capacity of 100,000 tons per year did not exceed 1 million dollars. Liu and his colleagues [41–45] developed a technique to produce bricks by mixing class C fly ash with approximately 10% water, compressing the mixture at a pressure higher than 6.9 MPa and then curing the formed brick in a wet environment (curing chamber) at room temperature for over 2 weeks. This method relies on the self-cementing property of class C fly ash which contains a large amount of calcium and thus does not need the usage of other cementing material. The produced bricks had high compressive strength, good water absorption property and low permeability. To enhance the freeze–thaw resistance, they added small amount (0.2% by weight) of air-entrainment chemical into the bricks. They also performed detailed environmental study

[64]

[65]

[66]

and the results indicated that the produced fly ash bricks were environmentally safe. Morchhale et al. [46] studied the production of bricks by mixing copper mine tailings with different amounts of OPC and then compressing the mixture in a mold at a pressure of 15 MPa. The molded bricks were transferred to a well ventilated room at ambient temperature for 24 h and then cured in water for different periods of time. The cured brick specimens were tested to evaluate their compressive strength and water absorption. The results indicated that the produced copper mine tailings-cement bricks satisfied the compressive strength and water absorption requirements as prescribed in Indian Standard (IS). Cicek and Tanrverdi [47] investigated the production of light weight bricks by using class F fly ash together with sand and hydrated lime. Brick samples were prepared under different conditions to study the effect of different factors. An optimum raw material composition was found to be a mixture of 68% fly ash, 20% sand and 12% hydrated lime. The optimum brick forming pressure was 20 MPa and the optimum autoclaving time and pressure were found to be 6 h and 1.5 MPa respectively. The results suggested that it is possible to produce good quality light weight bricks from fly ash. Turgut and Algin [48] studied the potential use of wood sawdust waste (WSW) and limestone powder waste (LPW) combination together with Portland cement to produce lightweight bricks. Brick samples were prepared by mixing WSW and LPW with cement at specified proportions and then compacting the mixture in a mold for 4 h under specified pressures. The molded brick samples were cured at room temperature for 24 h, in a tank filled with lime-saturated water at 22 °C for 28 days, and then dried in a ventilated oven at 105 °C for 24 h. Tests were conducted on the bricks to evaluate their compressive strength, flexural strength, unit weight, ultrasonic pulse velocity and water absorption. The results showed that the produced bricks satisfy the relevant international standards. The results also showed that the high-level replacement of WSW with LPW did not exhibit a sudden brittle fracture even beyond the failure loads, led to high energy absorption capacity, reduced the unit weight dramatically, and introduced smother surface compared to regular concrete bricks. Algin and Turgut [49] tried to use cotton waste (CW) and limestone powder waste (LPW) together with Portland cement to produce lightweight bricks. The study followed essentially the same method as used in [48] and similar conclusions were drawn (the only difference is that CW instead of WSW was used). Turgut [50] studied the thermal conductivity of the bricks produced from CW and LPW. Turgut [51,52] studied the utilization of waste glass powder (WGP) and limestone powder waste (LPW) together with a small quantity of Portland cement to produce bricks following essentially

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L. Zhang / Construction and Building Materials 47 (2013) 643–655

the same method used in [48–50]. The results indicated that the WGP used in LPW remarkably improved the compressive strength, flexural strength, modulus of elasticity, abrasion resistance, freezing–thawing resistance, and thermal conductivity of LPW bricks. Turgut and Yesilata [53] examined the potential use of crumb rubber to partially replace sand aggregate for producing low cost and lightweight composite concrete bricks with improved thermal resistance. The physico-mechanical and thermal insulation properties of the rubber-added concrete bricks were investigated. The obtained compressive strength, flexural strength, splitting strength, freeze–thaw resistance, unit weight and water absorption values met the relevant international standards. The experimental observations also revealed that high level replacement of crumb rubber with conventional sand aggregate did not exhibit a sudden brittle fracture even beyond the failure loads, led to high energy absorption capacity, reduced the unit weight dramatically, and introduced smoother surface. Chindaprasirt and Pimraksa [54] studied the properties of fly ash–lime granule unfired bricks. Granules were prepared from mixtures of fly ash and lime at fly ash to hydrated lime ratios of 100:0, 95:5 and 90:10 and then used to make unfired bricks using hydrothermal treatment at temperature of 125–135 °C and pressure of 0.14 MPa. The microstructures, mineralogical compositions, mechanical properties and environmental impact of bricks were determined. The results revealed that the strength of unfired bricks was dependent on the fineness of fly ash and was higher with an increase in fly ash fineness. The strength of the fly ash–lime granule unfired bricks was 47.0–62.5 MPa. In addition, the heavy elements, in particular Cd, Ni, Pb and Zn, were efficiently retained in the fly ash–lime granule unfired brick. Shon et al. [55] studied the utilization of stockpiled circulating fluidized bed combustion ash (SCFBCA) with OPC, lime, class F fly ash, and/or calcium chloride to manufacture compressed bricks. Brick specimens were prepared using a compaction pressure of 55.2 MPa and then placing the specimens at a 23 °C and 100% relative humidity room for 1 day before air curing at room temperature. Laboratory tests were conducted on the prepared brick specimens to determine their physical, chemical and mineralogical properties. The results indicated that SCFBCA could be used to manufacture compressed earth bricks. Zhao et al. [56] investigated production of load-bearing bricks from low-silicon tailings by pressing and autoclaving, using fly ash, slag, clinker dust and some activators as the cementing material. The tailings were mixed with the cementing material and water and then pressure molded into brick samples under a forming pressure of 20 MPa. The formed bricks were sealed with plastic bags for 6 h and then placed into autoclave for cuing for certain period of time. The results indicated that good quality bricks containing 83% of tailings could be produced, having compressive strength up to 16.1 MPa, bending strength 3.8 MPa, low drying shrinkage and good freeze–thaw resistance. Turgut [57] studied the production of masonry blocks using limestone powder (LP) waste and class C class fly ash (FA), without the addition of Portland cement. LP was mixed with FA at respectively 10%, 20% and 30% by volume, wetted and compressed under a pressure of 20 MPa in a steel mold for 1 min to produce block samples. The formed blocks were cured at room temperature for 48 h, in water tank at 22 °C for respectively 7, 28 and 90 days, and then dried in ventilated oven at 105 °C for 24 h. Tests were conducted on the produced blocks to evaluate their compressive and flexural strengths, ultrasonic pulse velocity (UPV), density, water absorption and thermal conductivity. The results indicated that masonry blocks could be produced using LP, FA and water. Liu et al. [58] explored the feasibility of using the sludge derived from dyestuff-making wastewater coagulation for producing unfired bricks. They tried four typical cements, OPC, ground clinker

of silicate cement, alumina cement, and slag cement, as the binder. The experimental results showed that the cement solidified sludge could meet all performance criteria for unfired bricks at a cement/ dry sludge/water ratio of 1:0.5–0.8:0.5–0.8. The compressive strength of alumina cement solidified sludge was the highest and exceeded 40 MPa. Fang et al. [59] studied the utilization of low SiO2 content copper tailings to partially replace sand to produce autoclaved sand– lime bricks. Brick specimens were prepared by mixing the tailings with river sand and sand powder at different proportions, pressing the mixture in a mold under a pressure of 20 MPa and autoclaving the molded bricks. The produced bricks were tested to evaluate their compressive strength and freeze–thaw durability. The results showed that the copper tailings with low content of SiO2 could be used to produce autoclaved sand–lime bricks meeting the China National Standard, if the proportion of the copper tailings in the brick batch did not exceed 50% by mass and appropriate proportions of river sand and sand powder were added to compensate for the low SiO2 content. Turgut [60] investigated manufacturing of bricks by utilizing limestone powder, class C fly ash, silica fume and water without any other components. Brick specimens were produced by mixing limestone powder, class C fly ash and silica fume with water, compacting the mixture and curing the formed units for periods of 7, 28 and 90 days. The brick specimens were tested to measure their physical and mechanical properties. The results indicated that the compressive and flexural strengths increased significantly when the silica fume content in the mixture was increased. At 20% silica fume content, the compressive strengths of the bricks after 28 and 90 days curing time reached 23 and 26.5 MPa respectively. It was also found that the production cost of the new bricks was 6.4-times lower than that of traditional fired clay bricks. Raut et al. [61] studied the utilization of recycled paper mill waste (RPMW) together with OPC to produce light weight bricks. Brick specimens were produced by mixing RPMW and cement at different proportions, compressing the mixture using a hand operated hydraulic press and then solar drying the formed bricks. The brick specimens were tested following ASTM C 67-03a standards. The results showed that bricks prepared using RPMW–cement combination was light weight, shock absorbing and met the ASTM C 67-03a compressive strength requirements. Zhao et al. [62] investigated the possibility of using hematite tailings as main raw material to produce high strength autoclaved bricks. The orthogonal test results indicated that the optimum formulation was the mixture of 70% hematite tailings, 15% lime and 15% sand and the optimum autoclave pressure and time were respectively 1.2 MPa and 6 h. The produced hematite tailings autoclaved bricks had mechanical strength and durability conforming to the China Autoclaved Lime–Sand Brick Standard (GB119451999) for MU20 autoclaved bricks. Zhang et al. [63] studied the production of autoclaved bricks from circulating fluidized bed combustion (CFBC) fly ash and slag. It was shown that autoclaved bricks could be made using 77% CFBC fly ash, 20% CFBC slag and 3% cement, exhibiting good long-term volume stability and achieving a compressive strength up to 14.3 MPa. There was no dihydrate gypsum and ettringite formation in the autoclaved brick so that the destructive expansion could be avoided. Zhou et al. [64] proposed and tested a novel process, called ‘‘hydration–recrystallization process’’, for producing non-fired bricks from waste phosphogypsum. In this process, the pressformed bricks were hot-dried at 180 °C to dehydrate gypsum into semi-hydrated gypsum, water-immersed to recrystallize gypsum crystals, and finally air-dried naturally to obtain the non-fired bricks. A series of experiments were conducted based on the novel process. The results showed that the optimal mix consisted of

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L. Zhang / Construction and Building Materials 47 (2013) 643–655 Table 3 Studies on production of bricks from waste materials through geopolymerization. No.

Waste material (wt.%)

Alkali activator

Brick size (mm)

Curing condition

Tests conducted

Reference

1

Fly ash and bottom ash (100%)

Sodium silicate solution

Cured in ambient air at 20–23 °C and RH 35–60% for 28 days

Compressive strength, water uptake, water absorption

[80]

2

Class F fly ash (100%)

Sodium silicate and sodium hydroxide solution

40  57 (cylinder), 300  140  90 190  90  50

Compressive strength, density

[81]

3

Bottom ash from circulating fluidized bed combustion (100%) Copper mine tailings (100%) Copper mine tailings (90–100%) and cement kiln dust (0–10%) Fly ash (80% and 90%) and red mud (20% and 10%)

Sodium silicate solution, sodium hydroxide solution, potassium hydroxide solution, and lithium hydroxide solution

100  100  200

Treated in oven and steam at 40, 60, 80, 100 °C for 2, 4, 6, 24, 48, 72 h, and then cured at ambient condition Cured at 40 °C and 100% humidity for different periods of time

Compressive strength

[82]

Sodium hydroxide solution

33.4  72.5 (cylinder) 33.4  72.5 (cylinder)

Cured in an oven at 60–120 °C for 7 days Cured in an oven at 90 °C for 7 days

Compressive strength, water absorption, abrasion resistance Compressive strength, water absorption, durability

[83]

I shaped block

Covered with plastic lid and cured at ambient temperature for 28 days

Compressive strength, water absorption, splitting tensile strength, flexural strength, abrasion resistance, leaching

[85]

4 5

6

Sodium hydroxide solution

1:1 Mix of sodium hydroxide solution and sodium silicate solution

75.0% phosphogypsum, 19.5% river sand, 4.0% Portland cement and 1.5% hydrated lime and the produced bricks at the optimal condition met the requirements of MU20 grade bricks in the Chinese standard (JC/T422-2007). Vinai et al. [65] studied the production of bricks using coal combustion residues (CCRs) together with cement, lateritic clayey soil and sand. 12 Dosages were tested and about 300 bricks were produced with a hand-operated press. Unconfined compressive strength (UCS) higher than 7.5 MPa was observed for bricks with 20% of laterite and 10% cement after 45 days of curing. The produced bricks showed good mechanical strength, low weight and no health threat. Shakir et al. [66] investigated the production of bricks using fly ash, quarry dust, and billet scale. The procedure for producing the bricks included mixing the constituents along with cement and water, and then forming the bricks within molds without applying pressure over them. Results of mechanical property and durability tests were promising. The optimum ratio of both billet scale to fly ash and billet scale to quarry dust was found to be 1:1. It was indicated that the bricks developed in this study could be used as an alternative to conventional bricks. 2.3. Production of bricks from waste materials through geopolymerization The different methods described above produce bricks from waste materials either using high temperature kiln firing or relying on cementing as in the OPC concrete and thus still have the drawbacks of high-energy consumption and large quantity of greenhouse gas emissions. Therefore, researchers have studied production of bricks from waste materials based on geopolymerization (see Table 3). Geopolymerization is a technology that relies on the chemical reaction of amorphous silica and alumina rich solids with a high alkaline solution at ambient or slightly elevated temperatures to form amorphous to semi-crystalline aluminosilicate inorganic polymer or geopolymer. Geopolymer possess three-dimensional silicoaluminate structures consisting of linked SiO4 and AlO4 tetrahedra by sharing all the oxygen atoms [67–74]. A general formula for the chemical composition of geopolymer is as follows:

Mþn ½—ðSiO2 Þz —AlO2 —n

ð1Þ

[84]

where M+ is an alkali cation (Na+ or K+); n is the degree of polymerization; and z is the Si/Al ratio. By tuning the Si/Al ratio (i.e., z = 1– 15, up to 300), geopolymers with different properties can be synthesized. Geopolymer not only provides performance comparable to OPC in many applications, but has additional advantages, including abundant raw material resources, rapid development of mechanical strength, good durability, superior resistance to chemical attack, ability to immobilize contaminants, and significantly reduced energy consumption and greenhouse gas emissions [72–79]. These characteristics have made geopolymer of great research interest as an ideal material for sustainable development. Freidin [80] studied production of geopolymer bricks from fly ash and bottom ash by using sodium silicate solution as the alkali activator. Small cylinder specimens were prepared at different conditions to study the effect of sodium silicate content, compaction pressure and hydrophobic additive. The specimens were cured in ambient air at temperature of 20–23 °C and RH of 35–60% for 28 days before tested. The results indicated that concrete-like building materials can be produced from mixtures of fly ash and bottom ash by using sodium silicate solution as the alkali activator. The full size blocks made from the concrete-like building materials met the requirements of Israeli Standard for conventional cement concrete blocks. Arioz et al. [81] investigated production of geopolymer bricks using class F fly ash, sodium silicate, and sodium hydroxide solution. The bricks were produced using 30 MPa forming pressure and treated at various temperatures for different hours in oven and steam. Tests were performed to determine the compressive strength and density of the fly ash-based geopolymer bricks at ages of 7, 28 and 90 days. It was found that the compressive strength of the fly ash-based geopolymer bricks ranged between 5 and 60 MPa and the effect of heat treatment temperature and duration on the density of the bricks was not significant. Chen et al. [82] studied production of geopolymer bricks using bottom ash from circulating fluidized bed combustion and four different alkali activators: sodium silicate solution, sodium hydroxide solution, potassium hydroxide solution, and lithium hydroxide solution. Brick samples were produced by first mixing the bottom ash and an alkaline solution, placing the mixture into a mold until the mold was full, and applying a force of 60 kN at the top to compress the mixture for 10 s. Then the brick was pushed out of the mold and stored at 40 °C and 100% humidity for curing. The same

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liquid to solid mass ratio of 0.3 was used for all brick samples. The results indicated that the alkali activator used has a great effect on the compressive strength of bricks. The highest 7 day compressive strength of 18.8 MPa was obtained for brick samples prepared using 10 M potassium hydroxide solution. Ahmari and Zhang [83] investigated utilization of copper mine tailings to produce geopolymer bricks by using sodium hydroxide (NaOH) solution as the alkali activator. They produced cylindrical brick specimens by using different initial water contents, NaOH concentrations, forming pressures and curing temperatures to study their effects on the physical and mechanical properties of the copper mine tailings-based geopolymer bricks. Scanning electron microscopy (SEM) imaging and X-ray diffraction (XRD) analysis were also performed to investigate the microstructure and phase composition of the mine tailings-based geopolymer bricks prepared at different conditions. The results showed that by properly selecting the preparation condition (initial water content, NaOH concentration, forming pressure and curing temperature), mine tailings-based geopolymer bricks could be produced to meet the ASTM requirements on compressive strength, water absorption, and abrasion resistance for nearly all types of applications. Ahmari and Zhang [84] studied the feasibility of using cement kiln dust (CKD) to further enhance the physical and mechanical properties and the durability of the copper mine tailings-based geopolymer bricks developed in [83]. The effects of CKD content (0–10%) on unconfined compressive strength, water absorption, and weight and strength losses after immersion in water were studied. To shed light on the mechanism for the contribution of CKD to geopolymerization, microscopic and spectroscopic techniques including scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy were used to investigate the micro/nano-structure and the elemental and phase composition of geopolymer brick specimens containing different amount of CKD. The results showed significant improvement of UCS and durability when CKD was used. Water absorption, however, slightly increased due to the hydration of Ca in the added CKD. Kumar and Kumar [85] studied the production of geopolymer paving blocks by using red mud together with fly ash. The influ-

ence of 0–40% red mud addition on the reaction, structure and properties of fly ash geopolymer was studied. An improvement in intensity of reaction was observed with the red mud addition at all replacement levels but the improvement in setting time and compressive strength was observed only in the samples containing 5–20% red mud. Structural characterization revealed that the rate of reaction was dependent on the NaOH concentration but the development of mechanical properties was related to the compact microstructure which was developed due to the combined effects of NaOH concentration, solubility of silicates and the presence of iron oxides. Based on the study results, paving blocks using 10% and 20% red mud were developed. These blocks met Indian Standard (IS) 15658 and the leached toxic metals were within permissible limits. It is noted that researchers have also studied many other types of waste materials for geopolymer production, including red mud and rice husk ash [86], fly ash and mine tailings [87], fly ash and concrete waste [88], blast furnace slag [89], and fly ash and blast furnace slag [90]. Although these studies are not specifically about brick production, the results indicate that many of these wastes are promising materials for production of geopolymer bricks. 3. Discussion It is evident from Tables 1–3 that researchers have used various types of waste materials in different proportions and adopted different methods to produce bricks. Different tests were conducted on produced bricks to evaluate their properties following the various available standards. Compressive strength and water absorption are two common parameters considered by most researchers as required by various standards. For example, Table 4 shows the ASTM specifications on minimum unconfined compressive strength (UCS) and maximum water absorption for different applications of bricks. It is noted that although many of the studied bricks made from waste materials meet the various standard requirements and a number of patents have been approved (see Table 5 for a partial list), so far commercial production and application of bricks from waste materials is still very limited. Currently, the CalStar brick from CalStar Products Inc., which is produced from 99.5% fly ash,

Table 4 ASTM specifications for different applications of bricks.

a b c d e f g h i

Title of specification

ASTM designation

Type/grade

Structural clay load bearing wall tile

C34-03

LBXa LBX LBb LB

Building brick

C62-10

SWf MWg NWh

20.7 17.2 10.3

17 22 No limit

Solid masonry unit

C126-99

Vertical coring Horizontal coring

20.7 13.8

NA NA

Facing brick

C216-07a

SW MW

20.7 17.2

17i 22i

Pedestrian and light traffic paving brick

C902-07

SX MX NX

55.2 20.7 20.7

8 14 No limit

LBX = load bearing exposed. LB = load bearing non-exposed. End construction use. Side construction use. Based on 1 h boiling water absorption. Severe weathering. Moderate weathering. Negligible weathering. Based on 5 h boiling water absorption.

Minimum UCS (MPa) 9.6c 4.8d 6.8c 4.8d

Maximum water absorption (%) 16e 16e 25e 25e

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L. Zhang / Construction and Building Materials 47 (2013) 643–655 Table 5 Patents for production of bricks from waste materials.a Patent no.

Title

Inventor/year

US20120031306

Bricks and method of forming bricks with high coal ash content using a press mold machine and variable firing trays Method to produce durable non-vitrified fly ash bricks and blocks Composition and process for making building bricks and tiles

Belden et al./2012 Fly ash

US7998268 US6440884

Liu/2011 Devagnanam/ 2002 US6068803 Method of making building blocks from coal combustion waste and related products Weyand et al./ 2000 US5366548 Volcanic fly ash and kiln dust compositions, and a process for making articles Riddle/1996 therefrom WO/1996/022952 Structural products produced from fly ash Strabala/1996 US5362319 Process for treating fly ash and bottom ash and the resulting product Johnson/1994 US5358760 Process for producing solid bricks from fly ash, bottom ash, lime, gypsum, and Furlong and calcium carbonate Hearne/1994 US4780144 Method for producing a building element from a fly ash comprising material and Loggers/1988 building element formed US4476235 Green molded product containing asbestos tailings suitable for firing Chevalier/1984 US3886244 Method for producing bricks from red mud Bayer et al./1975 a

Source material

Fly ash Clay, sludge and sand Fly ash, bottom ash, & rock mineral fines Volcanic fly ash and kiln dust Fly ash Fly ash and bottom ash Fly ash, bottom ash, gypsum, calcium carbonate, & lime Fly ash and slaked lime Asbestos tailings Red mud

Based on the search on http://www.freepatentsonline.com/.

fine aggregates, water and less than 0.5% of proprietary material, is commercially available [91]. Sanjay Kumar from CSIR, Jamshedpur, India reported in July 2012 the commercial production of around 0.5 million geopolymer bricks from steel slag, fly ash and GBFS combination [92]. The possible reasons are related to the methods for producing bricks from waste materials, the potential contamination from the waste materials, the absence of relevant standards, and the slow acceptance of waste materials-based bricks by industry and public, as detailed below. The method for producing bricks from waste materials through firing is very similar to the conventional clay brick production process. Therefore, this method can be easily executed without making major changes in the conventional clay brick production line. However, during the firing process, contaminants within the waste material may be released and cause new contaminations. Besides, making bricks through firing consumes significant amount of energy and releases large quantity of greenhouse gases. Therefore, the methods for producing bricks without firing seem to be the trend to follow in terms of energy and environmental concerns. The method for producing bricks from waste materials through cementing is based on hydration reactions similar to that in OPC to form mainly C–S–H and C–A–S–H phases contributing to strength. The cementing material can be the waste material itself or other added cementing material(s) such as OPC and lime. Since the manufacture of cementing material(s) such as OPC and lime consumes significant amount of energy and releases large quantity of greenhouse gases, the production of bricks from waste materials based on added cementing material(s) also has the drawbacks of high energy consumption and large carbon footprint. When it relies on the self cementing of waste material, the waste material has to contain a large amount of calcium (such as class C fly ash). To ensure and accelerate the reaction kinetics, the curing process usually needs to be conducted under pressurized steam at 125–200 °C in an autoclave, which translates itself into additional costs. The method for producing bricks from waste materials through formation of geopolymer is based on the relatively new geopolymerization technology which is different from the conventional

cementing technology in OPC concrete. Geopolymerization relies on the polycondensation of silica and alumina precursors and a high alkali content to attain structural strength whereas the conventional cementing depends on the presence of C–S–H and C–A–S–H phases for matrix formation and strength. Production of geopolymer bricks consumes much less energy and releases significantly lower quantity of greenhouse gases than production of conventional bricks. Besides, geopolymer bricks have favorable physical, mechanical and chemical properties. However, the utilization of alkali solutions brings about extra costs. The mild temperature required for curing in some cases also leads to additional costs for production. Although geopolymer is considered by many authors as a solution for ‘‘green’’ construction material, few studies have quantified the environmental impact of geopolymer [93,94]. Therefore, detailed environmental impact assessment of geopolymer brick production is necessary and should be compared with other brick production methods. Since most waste materials contain contaminants within them, for production of bricks from waste materials using whatever method, it is important to ensure that the contaminants within the original waste material are effectively and safely immobilized. Leaching analyses can be conducted following USEPA, ASTM and/or other standard methods to check if the leached elements meet the related standard criteria such as those listed in Table 6. For example, Cengizler [95], Tanrıverdi, [96], Ahmari and Zhang [97], and Kumar and Kumar [85] respectively studied the leaching behavior of heavy metals from fired fly ash bricks, non-fired autoclaved fly ash–lime bricks, copper mine tailings-based geopolymer bricks, and red mud/fly ash-based geopolymer blocks. The limited production and application of bricks from waste materials is also related to the absence of relevant standards and the slow acceptance by industry and public. Standardization plays an important role in disseminating knowledge, exploiting research results and reducing time to market for innovations [98]. To promote the production and application of bricks from waste materials, relevant standards should be developed. Since the existing brick manufacturers have a vested interest in the conventional

Table 6 Concentration limit on different leached elements based on different standards. Standard

USEPA DIN Greek

Concentration limit (ppm) Al

Hg

Ag

Ba

Cr

Mn

Ni

Cu

Zn

As

Se

Cd

Pb

NA NA 2.5–10.0

5.0 NA NA

5.0 NA NA

100 NA NA

5.0 NA NA

NA NA 1.0–2.0

5.0 NA 0.2–0.5

NA 2.0–5.0 0.25–0.5

NA 2.0–5.0 2.5–5.0

5.0 NA NA

1.0 NA NA

1.0 NA NA

5.0 NA NA

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brick production technology, their interest in new technologies to produce bricks from waste materials has been tepid. As mentioned earlier, most waste materials contain contaminants within them. The ‘‘waste’’ feature of the waste material and the potential for causing contamination and being unsafe adversely affect public acceptance of waste material-based bricks. To promote production and application of bricks from waste materials, more work needs to done, not only on the technical, economic and environmental aspects but also on the government policy and public education related to waste recycling and sustainable development. 4. Conclusions Based on the review of the various studies on production of bricks from waste materials, the following conclusions can be drawn:  A wide variety of waste materials have been studied for production of bricks.  The different methods studied for producing bricks from waste materials can be divided into three general categories: firing, cementing and geopolymerization. The firing and cementing (especially cementing based on added cementing materials) methods for producing bricks from waste materials still have the drawbacks of high energy consumption and large carbon footprint as the conventional brick production methods. The method for producing bricks from waste materials through geopolymerization seems to be the trend to follow in terms of energy and environmental concerns.  Although much research has been conducted, the commercial production of bricks from waste materials is still very limited. The possible reasons are related to the methods for producing bricks from waste materials, the potential contamination from the waste materials used, the absence of relevant standards, and the slow acceptance of waste materials-based bricks by industry and public.  For wide production and utilization of bricks from waste materials, further research and development is needed, not only on the technical, economic and environmental aspects but also on standardization, government policy and public education.

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