Activated Alumina Sludge as Partial Substitute for Fine Aggregates in Brick Making

Prafulla Pokharaa,d,1, Aravinth S. S. Ekamparamb,1, Akhilendra B. Guptac, Durgesh C. Raib, Abhas Singha,b†

a Environmental Engineering and Management Programme, Indian Institute of Technology Kanpur, Uttar Pradesh, India 208016b Department of Civil Engineering, Indian Institute of Technology Kanpur, Uttar Pradesh, India 208016c Department of Civil Engineering, Malaviya National Institute of Technology Jaipur, Rajasthan, India 302017d General Stores Depot, South East Central Railway, Raipur, Chhattisgarh, India 492008

Supporting Information

This document contains 8 figures (Figs. S1 – S8) and 7 tables (Tables S1 – S7)

† Corresponding author phone: +91-512-259-7665, fax: +91-512-259-7395, email: abhas@iitk.ac.in1 The first two authors should be considered joint first authors as they contributed equally to this work.

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Figure S1. Map of India showing locations from where the activated alumina (AA) sludge was obtained (Jhunjhunu, Rajasthan) and utilized in making bricks (brick kiln in Chaubepur near Kanpur, Uttar Pradesh). Also are indicated the AA-based water treatment plants (A-D) and an AA regeneration plant (E), from where the AA-sludge was obtained.

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Figure S2. Dried activated alumina (AA) sludge

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Figure S3. Core samples of bricks (0 % and 10 % sludge).

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10 % brickI II

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0 % brick III

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Figure S4. Structural ,non-structural and leaching tests performed on manufactured sludge-clay bricks; (a) compression strength test; (b) prism compression test; (c) flexural strength test (d) efflorescence test by soaking bricks in a water column of 25 mm height; (e) thermal conductivity test; and (f) TCLP test on powdered brick.

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Figure S5. SEM images of activated alumina sludge at different magnifications (a and b) and of (c) conventional fired brick (0 % sludge-clay) and (d) sludge-mixed fired brick (10 % sludge-clay).

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10 μm10 μm

1 μm10 μm

(a) (b)

(c) (d)

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Procedure for extraction of residual chloride and sulfate from clay soil and AA sludge

The procedure recommended by the Texas Department of Transportation [1] was followed as

per the details below. Pre-weighed amounts (300 g) of pulverized (< 425 μm) sludge and soil

samples were dried at 60 °C and cooled in a desiccator. A part of each sample (30 g) was

mixed with 300 mL of ultrapure water (resistivity 18.2 MΩ.cm) in a 1000 mL beaker. The

suspension was covered with watch glass and kept on a hot plate at 66 ± 11 °C with magnetic

stirrer rotated at 300 rpm. After 15-18 h, the suspension was vacuum-filtered through a

1.22 μm filter and the filtrate was collected in a 500 mL volumetric flask. Any sample

residue in the beaker was rinsed out by continuously washing with hot ultrapure water at

66 °C until the sample in the beaker was found to be free from chloride. Absence of chloride

was tested by adding 2 drops of filtrate into dilute AgNO3 solution; formation of a white

precipitate indicates presence of chloride. The filtrate was cooled down to room temperature

and the volumetric flask was made up to 500 mL with ultrapure water. This final collected

water was termed as sample extract, which was analysed by ion chromatography (IC) for

dissolved chloride and sulphate.

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Table S1. Comparison of various oxide percentages computed in targeted sludge-clay bricks with recommended values

 S. No.

 Oxide

Weight %RecommendedClay Soila AA- Sludgea Bricksb

5 % sludge 10 % sludge1 SiO2 69 12 65.8 62.9 50-60

2 Al2O3 19 26 19.3 19.6 20-303 CaO 1 7 1.5 1.8 104 Fe2O3 6 3 5.5 5.3 <7

5 MgO 3 4 3.2 3.3 1

6 K2O 3 0 3.1 3.0  

7 Na2O 1 21 2.4 3.4  

8 P2O5 0 0 0.1 0.1  

9 TiO2 1 0 0.7 0.7  10 NiO 0 0 0.0 0.0  11 MnO 0 0 0.1 0.1  

a quantified using X-ray fluorescence spectroscopy (XRF)b calculated for the desired clay and sludge proportions using quantified clay soil and sludge weight % obtained from XRF

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1E-3 0.01 0.1

0

20

40

60

80

100 AA Sludge

Clay Soil

% F

iner

Particle diameter (mm)

Clay Silt

% Finer less than 2 m

Fine Sand

Figure S6. Particle size distribution of activated alumina (AA) sludge and clay soil using Mastersizer

Table S2. Gradation of clay soil and activated alumina sludge

S. No. Material D60 D30 D10 Cub Cc

b

(mm)a

1 Clay soil 0.05 0.02 0.005 10 1.6

2 Activated alumina sludge 0.04 0.02 0.006 6.67 1.67

aD60;D30;D10 are the sizes of the particle at 60, 30 and 10 percent finer on the particle size distribution graph. b

Cu=D60 /D10; C c=D302 /D10D60

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Estimation of flow index of clay soil used in brick manufacturing

Flow index of clay soil was estimated following the detailed procedure provided in [2]

1.00 1.25 1.50 1.75

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Wat

er c

onte

nt (W

in %

)

log10 (No. of blows)

Y = -13.079*X + 48.58

Figure S7. No. of blows as a function of water content

Calculation:

Flow index = Slope of the water content versus number of blows plot [2] = 13.08

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Statistical t test

From each category (0 % and 10 %), two bricks were chosen and 3 cores each of 2 cm

diameter were carved out from samples using core cutter (Fig. S3). For gas pyconometry

analysis, cylinders of ~ 2 cm dia and 5 cm height were further made from the cores earlier.

Pooled variance and statistic -t can be calculated [3] as follows

s2=(n1−1 ) s1

2+(n2−1 ) s22

(n1+n2−2)

and

t=x1−x2

s √ 1n1

+ 1n2

where t has n1+n2−2 degrees of freedom and

t critical value at p=0.05

Table S3. Statistical t test on porosity measurements on two different bricks

Brick Porosity (%)

No. of measurement

s s2 DOF |t| t critical Result0 % 31.9 ± 2.8 17 6.1 33 10.4 2.0 Failed10 % 40.6 ± 2.1 18

H0: No significant difference in porosity between 0 % and 10 % sludge-clay brick; s2 – pooled estimate of variance; DOF: degree of freedom; t – statistic t; error bars indicate standard deviations of the means

Table S4. Statistical t test on bulk density measurements on two different bricks

Brick Bulk density (g/cm3)

No. of measurement

s s2 DOF |t| t critical Result0 % 1.93 ± 0.07 6 0.007 10 4.9 2.2 Failed10 % 1.69 ± 0.09 6

H0: No significant difference in bulk density between 0 % and 10 % sludge-clay brick; s2 – pooled estimate of variance; DOF: degree of freedom; t – statistic t; error bars indicate standard deviations of the means

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Load Calculations for Masonry Wall

6 m

6 m

0.23 m

Brick wall

3 m

6 m

AA

Section A - A

15 kN/m

Figure S8. Plan of the brick walled load bearing structure with reinforced concrete slab (RCC).

Table S5. Total load calculation for masonry wall

S. No. Member

Unit Weight Load(kN/m3) (kN)

1 Reinforced Concrete Slab (RCC) 25 3 m (width) x 0.2 m (thickness) x 6 m

(length) x 25 kN/m3 = 90 kN

2 Brick Masonry 22 3 m (height) x 0.23 m (thickness) x 6 m (length) x 22 kN/m3 = 91.08 kNTotal Load = 181.08 kN

Assuming that this load is applied per unit area, the total load = 181.08 kN/m2 (0.181 MPa).

The compressive strength of 10 % sludge-clay brick = 5400 kN/m2 (5.4 MPa) (from Fig.

5a). However, the total load from the structure (0.181 MPa) << compressive strength of

brick (5.4 MPa). Hence, 10 % sludge – clay brick is well recommended.

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Table S6. EDX elemental composition on manufactured sludge-clay bricks

ElementsSludge- clay bricks (mass %)

0 % a 10 % b

Si 14.2 ± 7.1 21.4 ± 8.5

Fe 13.2 ± 15.2 4.1 ± 1.4

Al 6.1 ± 2.5 9.1 ± 4.3

Ca 1.3 ± 1.3 2.1 ± 1.3

Na 1.7 ± 0.9 1.3 ± 0.6

Mg 1.9 ± 1.1 1.9 ± 1.5

K 1.3 ± 1.0 1.2 ± 0.4

F 0.3 ± 0.4 0.7 ± 0.6a obtained from measurements at 11 spots on specimenb obtained from measurements at 7 spots on specimen

Table S7. Statistical t tests on F, Ca and Al measurements on two different bricks

Element Brick Mass (%) No. of measurements s2 DOF |t| t critical Result

F 0 % 0.3 ± 0.4 11 0.2 16 1.8 2.1 Passed10 % 0.7 ± 0.6 7

Ca 0 % 1.3 ± 1.3 11 1.6 16 1.3 2.1 Passed10 % 2.1 ± 1.3 7

Al 0 % 6.1 ± 2.5 11 10.8 16 1.8 2.1 Passed10 % 9.1 ± 4.3 7

H01: No significant difference in fluorine concentration between 0 % and 10 % sludge-clay brick; H02: No significant difference in calcium concentration between 0 % and 10 % sludge-clay brick; s – pooled estimate; H03: No significant difference in aluminum concentration between 0 % and 10 % sludge-clay brick; s – pooled estimate; DOF: degree of freedom; t – statistic t; (see supporting information for pooled standard deviation and t value calculation)

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Table S8. Performance comparison of acid-resistant bricks

S. No. Characteristic Sludge proportion0 % 5 % 10 %

1 Water absorption % NC NC NC

2 Flexural strength kg/cm2 NC NC NC

3 Compressive strength kg/cm2 NC NC NC

4 Resistance to acid (loss in weight %) Class I Class II NC

5 Resistance to wear (average in mm) NA NA NA

6 Warpage (mm) NC NC NC

*According to IS 4860 – 1968; NA – tests were not conducted; NC- not complies (i.e., neither class I nor Class II)

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Table S9. Comparison of mineralogical composition of materials used for brick making

Clay Soila AA- Sludgea Clay soilb Al-filter dustbM

iner

al P

hase

s

Quartz Quartz Quartz MgAl2O4

Al(OH)3 Al(OH)3 Illite K3.2Na0.8Cl4

Muscovite Calcite Calcite KAlSi3O8

Kaolinite Al

Montmorillonite Al2O3

Microcline K2NaAlF6

Hematite NaCl

BaFe1.5Al0.5O4

aused in this study; b used in Bonet-Martinez et al. (2018) [4]

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References

[1] TDT, Test procedure for determining chloride and sulfate contents in soil, Texas Department of Transportation, Texas, 2005, p. 11.

[2] IS 2720 (Part 5) : 1985 (Reaffirmed 2006), Indian standard method of test for soils Part 5 : determination of liquid and plastic limit, Bureau of Indian Standards, New Delhi.

[3] Miller J. N., Miller J. C., Statistics and chemometrics for analytical chemistry, Pearson Education Limited2010.

[4] Bonet-Martínez E., Pérez-Villarejo L., Eliche-Quesada D., Castro E., Manufacture of sustainable clay bricks using waste from secondary aluminum recycling as raw material, Materials (2018) 11(12) 2439.

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