recycling of construction and demolition waste materials: a chemical–mineralogical appraisal

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Waste Management 25 (2005) 149–159

Recycling of construction and demolition waste materials:a chemical–mineralogical appraisal

G. Bianchini *, E. Marrocchino, R. Tassinari, C. Vaccaro

Department of Earth Sciences, University of Ferrara, Corso Ercole I D�Este n.32, 44100 Ferrara, Italy

Accepted 7 September 2004

Abstract

Building activity is currently demanding remarkable amounts of inert materials (such as gravel and sand) that are usually pro-

vided by alluvial sediments. The EU directives and Italian Legislation are encouraging the re-use of construction and demolition

waste provided by continuous urban redevelopment. The re-utilisation of building waste is a relatively new issue for Italy: unfor-

tunately the employment of recycled inert materials is still limited to general bulk and drainage fills, while a more complete re-eval-

uation is generally hampered by the lack of suitable recycling plants. In this paper, chemical–mineralogical characterization of

recycled inert materials was carried out after preliminary crushing and grain-size sorting. XRF and XRD analysis of the different

grain-size classes allowed us to recognise particular granulometric classes that can be re-utilised as first-order material in the building

activity. Specifically, the presented chemical–mineralogical appraisal indicates that the recycled grain-size fraction 0.6–0.125 mm

could be directly re-employed in the preparation of new mortar and concrete, while finer fractions could be considered as compo-

nents for industrial processing in the preparation of cements and bricks/tiles.

� 2004 Elsevier Ltd. All rights reserved.

1. Introduction

Building activity is currently demanding remarkable

amounts of inert materials (such as gravel and sand) that

are usually provided by alluvial sediments. The direct

quarrying of sediments from rivers modifies river-profilesand their equilibrium, and is consequently forbidden by

law. At the same time, excavation of palaeo-river depos-

its could also induce environmental problems, as the

hydrological and hydrogeological framework of the area

is often modified.

Quarrying inert materials from rocky formations in

hilly/mountainous areas is also perceived as dangerous

for the environment, as it alters the landscape andpotentially triggers stability problems.

0956-053X/$ - see front matter � 2004 Elsevier Ltd. All rights reserved.

doi:10.1016/j.wasman.2004.09.005

* Corresponding author. Tel.: +39 532 293740; fax: +39 532 210161.

E-mail address: [email protected] (G. Bianchini).

For these reasons, the Italian Legislation is encourag-

ing the re-use of construction and demolition waste

(hereafter named C&D as proposed by Poon et al.,

2001) provided by continuous urban redevelopment,

an approach which must be promoted in order to face

the pressing landfill shortage problem.The use of recycled aggregates is also promoted by

the EU which, in the framework of an environmental

protection and waste management policy, has provided

guidelines for common strategies for a correct re-use

of C&D (DG ENV. E.3, 2000).

SomeEUcountries (Germany,UK,Netherlands) have

already developed a suitable program of building waste

recycling, while in others (such as Italy, France, Spain)the amount of recycled inert material is still limited, and

does not exceed 10% (Corinaldesi, 2002; Bressi, 2003).

As concerns Italy, re-utilisation of C&D materials is

hampered by the scarcity of suitable plants for size

reduction and sorting of waste material, and its employ-

ment is limited to general bulk and drainage fills.

mailto:[email protected]

150 G. Bianchini et al. / Waste Management 25 (2005) 149–159

In order to improve this situation greater attention

should be paid to on-site sorting, as emphasised by Poon

(1997) and Poon et al. (2001). Accordingly, through a

grain-size sorting, we studied the C&D waste sampled

in a landfill in Ferrara (NE Italy) during two different

periods (February and September 1997).The different grain-size fractions were investigated

through X-ray fluorescence (XRF) and X-ray diffrac-

tometry (XRD) analyses to evaluate their chemical

and mineralogical composition, providing data that

should be considered in order to develop correct recy-

cling strategies.

2. C&D plant in Ferrara – sampling approach

Sampling was performed in two different periods

(February and September 1997) to evaluate possible

temporal variations in the composition of the deposited

materials (Alberti, 1998).

In the investigated C&D plant the inert material is di-

vided in two different masses:

� The first consists of the original raw material arriving

at the landfill (called TQ), and appears characterised

by extremely variable grain-size and composition

(bricks and terracotta, concrete, asphalt) processed

by a preliminary separation of undesired material

(plastic, metal, wood, paper).

� The second consists of material crushed and furtherdivided in three different grain size classes: 80–40

mm, 40–10 mm (hereafter named MD), <10 mm

(hereafter named FN).

During February two samples were collected from

the first mass of material (TQ1-Feb, TQ2-Feb), and

Table 1

Average composition of construction and demolition waste materials in a F

Components TQ1-Feb

First sampling – february

Bricks and terracotta materials 45%

Concrete 20%

Wood 3%

Metals 4%

Plastic, paper and rubber 2%

Asphalt

Incoherent fine materials from mortars and concretes 26%

Components TQ3-Sept

Second sampling – september

Bricks and terracotta materials 35%

Concrete 40%

Wood 2%

Metals 2%

Plastic, paper and rubber 1%

Asphalt 5%

Incoherent fine materials from mortars and concretes 15%

two from the masses that had been crushed and sorted

(MD1-Feb, FN1-Feb); during September one sample

was collected from the first mass (TQ3-Sept) and some

others from the sorted fractions (MD2-Sept, MD3-Sept,

FN2-Sept). A brief description of these samples is pro-

vided in Table 1, where the relative proportion of theconstituting components is reported. The relatively high

amount of brick fragments is an intrinsic peculiarity of

Ferrara, typically characterised by ‘‘brick and mortars’’

as the dominant building technique.

3. Methods

Each sample was subsequently ground and sieved in

laboratory, obtaining the following grain-size fractions,

classified according to the Wentworth (1922) size limits

and terminology:

>4 mm,

4–2 mm (fine gravel),

2–0.6 mm (coarse sand),0.6–0.125 mm (medium sand),

0.125–0.075 mm (fine sand),

<0.075 mm.

The amount of material (wt%) obtained from each

sample after laboratory grinding and sieving is reported

in Table 2 and Fig. 1.

XRF analysis was carried out (utilising a PhilipsPW1400 spectrometer) on the different grain-size frac-

tions of each sample, to investigate their chemical com-

positions in terms of major element (SiO2, TiO2, Al2O3,

Fe2O3, MnO, MgO, CaO, Na2O, K2O, P2O5 expressed

in wt%) and trace element (Pb, Zn, Ni, Co, Cr, V, Th,

expressed in parts per million) components.

errara landfill

TQ2-Feb MD1-Feb FN1-Feb

30% 50% 45%

40% 35% 40%

2%

5%

1%

2% 5%

20% 10% 15%

MD2-Sept MD3-Sept FN2-Sept

47% 48% 45%

35% 32% 45%

3% 5%

15% 15% 10%

Table 2

Result of laboratory grinding and sieving: wt% of the different grain-size fractions of each sample

Grain-size (mm) TQ1-Feb TQ2-Feb MD1-Feb FN1-Feb TQ3-Sept MD3-Sept MD2-Sept FN2-Sept

>4 33.6 34.6 63.0 13.5 20.8 35.4 24.1 13.9

4–2 Fine gravel 13.2 9.3 7.4 10.4 12.2 14.6 10.7 11.4

2–0.6 Coarse sand 16.3 16.2 8.8 28.2 18.4 15.5 21.8 23.3

0.6–0.125 Medium sand 30.8 27.4 15.0 41.2 40.9 25.8 36.9 44.5

0.125–0.075 Fine sand 2.8 6.0 3.1 3.3 5.5 4.9 4.3 4.1

<0.075 3.3 6.4 2.6 3.4 2.2 3.8 2.1 2.8

Total 100 100 100 100 100 100 100 100

0

10

20

30

40

50

60

70

>4 mm Fine Gravel Coarse Sand Medium Sand Fine Sand <0,075 mm

Wt

%

TQ 1-Feb

TQ 2-Feb

MD1-Feb

FN1-Feb

February

0

10

20

30

40

50

60

70

>4 mm Fine Gravel CoarseSand Medium Sand Fine Sand <0,075 mm

Wt

%

TQ 3-Sept

MD3-Sept

MD2-Sept

FN2-Sept

September

Fig. 1. Result of laboratory grinding and sieving: wt% distribution of the different grain-size fractions of each sample.

G. Bianchini et al. / Waste Management 25 (2005) 149–159 151

XRD was performed with a Philips PW1860/00 dif-

fractometer, using graphite-filtered Cu Ka radiation

(1.54 A) to recognise the constituent mineralogical

phases. Diffraction patterns were collected in the 2hangular range 5–50�, with a 5 s/step (0.02� 2h).

4. Results and discussion

In order to investigate the best way of re-using the

considered recycled inert materials processed, both

XRD and XRF analysis results for different grain-size

fractions of various samples are considered.

XRD analysis (Table 3; Fig. 2) shows that the sepa-

rated C&D fractions are constituted by different

amounts of quartz, calcite, dolomite, feldspar, musco-

vite/illite chlorite, and minor amounts of calcium–alu-

minium–iron hydroxides and hydrous silicates (typicalof cement materials) and gehlenite and wollastonite

(typical of bricks and terracotta). Hazardous minerals

such as amianthus (asbestos) have not been recorded.

Even though this investigation does not permit a

Table 3

XRD mineralogical investigation of different grain-size fractions of samples TQ1, TQ3, MD3, FN1

Mineralogical phases >4 mm 4–2 mm 2–0.6 mm 0.6–0.125 mm 0.125–0.075 mm <0.075 mm

TQ1

Qz *** *** *** **** **** ****Feld * * * ** * *Cal *** *** *** ** ** **Dol **** *** *** ** ** **Phyll * * * * ** **Wo + Ghl * * * * * *

TQ3

Qz **** **** **** **** **** ***Feld * * * ** ** *Cal *** ** ** ** ** **Dol *** ** ** ** ** **Phyll * * * * ** **Wo + Ghl * * * * * *

MD3

Qz *** *** **** **** **** ***Feld * * * ** * *Cal *** *** *** ** *** ***Dol *** *** *** ** ** **Phyll * * * ** ** **Wo + Ghl * * * * * *

FN1

Qz **** **** **** **** **** ***Feld * * * ** * *Cal *** *** *** ** ** **Dol *** *** *** ** ** **Phyll * * * ** ** **Wo + Ghl * * * * * *

Mineral abbreviations: Qz, quartz; Calc, calcite; Dol, dolomite; Feld, feldspars; Phyll, phyllosilicates; Wo, wollastonite; Ghl, gehlenite. ****, very

abundant; ***, abundant; **, scarce; *, traces.

Fig. 2. Selected XRD patterns of medium sand fractions (0.6–0.125 mm). Abbreviations: Qz, quartz; Feld, feldspar; Calc, calcite; Dol, dolomite; Chl,

chlorite; Mu, muscovite/illite; Wo, wollastonite.


Table 4

Major (wt%) and trace elements (ppm) concentration of the different grain-size fractions of each sample

mm >4 4-2 fine

gravel

2-0.6

Coarse

sand

0.6-0.125

Medium

sand

0.125-0.075

Fine sand

<0.075 >4 4-2 fine

gravel

2-0.6

Coarse

sand

0.6-0.125

Medium

sand

0.125-0.075

Fine sand

<0.075

TQ1-Feb TQ2-Feb

TQ1 A TQ1 B TQ1 C TQ1 D TQ1E TQ1 F TQ2 A TQ2 B TQ2 C TQ2 D TQ2 E TQ2 F

SiO2 38.57 34.01 47.32 60.20 39.96 36.64 30.99 25.15 37.18 57.13 46.51 40.34

TiO2 0.29 0.24 0.28 0.30 0.41 0.42 0.16 0.17 0.24 0.30 0.51 0.50

Al2O3 7.26 6.04 7.64 8.75 8.39 8.60 5.55 4.50 6.51 8.55 9.07 8.93

Fe2O3 2.87 2.94 2.95 2.82 3.72 3.86 1.82 1.43 2.09 2.66 3.68 3.68

MnO 0.11 0.14 0.12 0.10 0.14 0.14 0.07 0.06 0.08 0.09 0.12 0.12

MgO 5.27 5.09 3.75 2.78 2.91 3.14 7.71 8.97 6.12 3.37 3.81 4.21

CaO 21.74 23.96 17.64 11.60 20.76 22.04 23.32 26.52 21.57 12.61 16.67 19.15

Na2O 0.86 0.71 1.08 1.53 0.92 0.82 0.96 0.55 0.93 1.48 1.23 1.09

K2O 1.43 1.10 1.57 1.84 1.58 1.60 1.35 0.90 1.48 1.87 1.77 1.72

P2O5 0.15 0.21 0.21 0.17 0.35 0.42 0.72 0.29 0.67 0.60 1.17 1.41

LOI 21.44 25.55 17.45 9.92 20.85 22.31 27.35 31.44 23.13 11.33 15.45 18.84

Totale 100 100 100 100 100 100 100 100 100 100 100 100

Pb* 29 90 97 86 50 50 46 15 126 125 171 98

Zn* 221 190 154 108 172 189 34 34 85 105 177 211

Ni 47 47 68 69 78 86 22 21 37 56 69 73

Co 7 7 10 9 13 14 3 4 6 10 11 12

Cr 60 59 93 113 116 114 25 28 52 91 117 107

V 48 41 45 47 63 69 29 31 39 44 61 65

Th 5 4 7 1 7 7 6 5 5 5 7 8

TQ3-Sept MD2-Sept

TQ3 A TQ3 B TQ3 C TQ3 D TQ3 E TQ3 F MD2 A MD2 B MD2 C MD2 D MD2 E MD2 F

SiO2 34.12 47.43 47.68 58.87 43.03 41.39 38.65 39.62 48.27 54.42 42.85 42.10

TiO2 0.25 0.36 0.39 0.36 0.53 0.54 0.29 0.32 0.36 0.38 0.54 0.53

Al2O3 6.40 8.07 9.31 9.62 10.88 10.40 7.26 7.92 9.15 9.59 10.85 10.55

Fe2O3 2.65 3.60 3.67 3.16 4.52 4.35 3.09 3.44 3.41 3.31 4.36 4.24

MnO 0.11 0.12 0.11 0.10 0.14 0.14 0.12 0.12 0.11 0.10 0.13 0.13

MgO 4.77 3.68 3.63 3.16 3.48 3.48 4.67 4.32 3.63 3.28 3.49 3.48

CaO 22.78 18.03 17.49 11.71 18.34 18.73 22.80 21.53 16.95 14.10 18.68 18.66

Na2O 0.80 0.87 0.99 1.53 0.86 0.88 0.94 0.87 1.09 1.38 0.87 0.90

K2O 1.05 1.50 1.79 1.89 1.80 1.70 1.31 1.48 1.80 1.92 1.86 1.77

P2O5 0.31 0.66 0.76 0.50 0.95 0.76 0.21 0.26 0.31 0.27 0.49 0.49

LOI 26.77 15.69 14.18 9.10 15.47 17.63 20.66 20.13 14.92 11.24 15.89 17.16

Totale 100 100 100 100 100 100 100 100 100 100 100 100

Pb* 25 89 129 112 84 99 39 29 51 53 62 70

Zn* 68 122 147 108 189 201 175 89 149 115 170 179

Ni 46 73 87 76 88 89 50 62 83 77 89 93

Co 8 10 12 12 14 13 9 10 12 11 14 13

Cr 56 96 120 123 139 123 66 82 129 122 144 129

V 40 54 59 49 80 79 42 50 57 55 80 80

Th 6 3 5 5 6 7 4 2 3 8 6 11

(continued on next page)

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153

Table 4 (continued)

mm >4 4-2 fine

gravel

2-0.6

Coarse

sand

0.6-0.125

Medium

sand

0.125-0.075

Fine sand

<0.075 >4 4-2 fine

gravel

2-0.6

Coarse

sand

0.6-0.125

Medium

sand

0.125-0.075

Fine sand

<0.075

MD1-Feb FN1-Feb

MD1 A MD1 B MD1 C MD1 D MD1 E MD1 F FN1 A FN1 B FN1 C FN1 D FN1 E FN1 F

SiO2 42.95 45.71 49.15 53.60 45.66 42.41 37.45 41.25 49.84 59.56 50.41 48.46

TiO2 0.37 0.49 0.47 0.42 0.52 0.54 0.32 0.35 0.42 0.38 0.55 0.57

Al2O3 8.77 11.27 10.96 10.11 10.12 10.31 7.35 8.42 9.86 9.59 10.32 10.56

Fe2O3 3.58 4.32 4.25 3.63 4.22 4.48 3.09 3.41 3.88 3.30 4.24 4.28

MnO 0.12 0.12 0.12 0.11 0.12 0.13 0.11 0.11 0.11 0.10 0.12 0.12

MgO 4.63 4.22 3.95 3.31 3.45 3.60 4.99 4.84 3.59 3.00 3.52 3.73

CaO 19.24 15.39 14.60 13.97 16.87 18.01 22.47 18.89 14.44 10.65 13.95 14.47

Na2O 1.06 0.91 1.03 1.27 1.03 0.90 0.85 0.92 1.11 1.50 1.23 1.17

K2O 1.60 2.04 2.04 2.00 1.84 1.88 1.24 1.49 1.83 1.89 1.81 1.80

P2O5 0.23 0.50 0.50 0.43 0.54 0.61 0.21 0.22 0.29 0.23 0.34 0.37

LOI 17.45 15.03 12.93 11.16 15.63 17.13 21.92 20.10 14.63 9.80 13.50 14.48

Totale 100 100 100 100 100 100 100 100 100 100 100 100

Pb* 90 185 124 49 66 77 102 92 109 47 48 47

Zn* 88 186 128 107 140 160 62 78 126 121 159 163

Ni 67 100 98 84 97 107 56 64 85 79 94 98

Co 10 17 15 13 16 15 9 11 12 11 15 13

Cr 87 136 136 128 142 143 71 80 119 126 166 142

V 59 83 79 62 82 86 52 58 70 58 78 81

Th 8 8 7 4 8 10 5 8 6 5 9 9

MD3-Sept FN2-Sept

MD3 A MD3 B MD3 C MD3 D MD3 E MD3 F FN2 A FN2 B FN2 C FN2 D FN2 E FN2 F

SiO2 41.09 39.24 43.16 53.30 42.10 41.54 35.44 39.70 47.34 55.62 45.05 44.51

TiO2 0.39 0.38 0.38 0.36 0.50 0.54 0.28 0.35 0.39 0.38 0.57 0.57

Al2O3 8.85 9.00 9.25 9.04 10.58 10.72 6.89 8.01 9.09 9.49 11.46 11.07

Fe2O3 3.63 3.62 3.59 3.17 4.29 4.46 2.91 3.16 3.57 3.27 4.48 4.28

MnO 0.15 0.14 0.12 0.10 0.13 0.13 0.11 0.11 0.11 0.10 0.13 0.12

MgO 5.11 4.51 3.91 3.28 3.46 3.52 5.49 4.56 3.89 3.35 3.72 3.77

CaO 20.72 21.83 19.94 15.32 20.01 19.42 23.14 20.74 16.45 12.74 16.65 16.71

Na2O 0.97 0.90 1.02 1.30 0.90 0.91 0.82 0.94 1.14 1.43 0.96 1.00

K2O 1.60 1.66 1.82 1.82 1.80 1.80 1.24 1.50 1.79 1.92 1.97 1.82

P2O5 0.19 0.20 0.21 0.21 0.37 0.37 0.25 0.39 0.43 0.33 0.56 0.57

LOI 17.31 18.51 16.61 12.09 15.87 16.59 23.45 20.55 15.82 11.36 14.45 15.57

Totale 100 100 100 100 100 100 100 100 100 100 100 100

Pb* 34 28 96 59 64 57 24 42 51 57 68 77

Zn* 76 73 90 85 130 144 58 85 124 110 149 157

Ni 77 77 77 74 93 98 52 65 77 73 89 90

Co 10 9 11 10 15 16 8 11 12 11 15 13

Cr 106 100 101 121 133 132 72 91 106 114 147 133

V 58 59 62 58 80 84 44 55 61 53 83 83

Th 7 7 7 7 8 10 4 5 9 7 7 9

* Semi-quantitative analyses.

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0

10

20

30

40

50

60

70


TQ1-Feb

TQ2-Feb

TQ3-Sept

SiO2

CaO

Wt %

Al2O3

Fe2O3

Variations in the TQ samples

0

10

20

30

40

50

60


MD1-Feb

MD2-Sept

MD3-Sept

Al2O3

Fe2O3

Wt %

Variations in the MD samples

SiO2

CaO

0

10

20

30

40

50

60

70


FN1-Feb

FN2-Sept

SiO2

CaO

Al2O3

Fe2O3

Wt

%

Variations in the FN samples

Fig. 3. Diagrams reporting SiO2, CaO, Al2O3, Fe2O3 variations in the grain-size fractions of each sample. Samples grouped according to the

collecting strategy: TQ (a) represents original raw material arriving at the landfill. MD (b) and FN (c) represent material after ‘‘in situ’’ crushing and

sorting (MD = 4–1 cm; FN = <1 cm).


quantitative determination of the mineral abundance,

the relative heights of the different peaks suggest that

quartz is more abundant in the sand fractions, and phyl-

losilicates, such as illite/muscovite and chlorite tend to

increase in the fraction characterised by finer grain-size.

XRF chemical composition of the separated fractions

obtained from the starting samples is shown in Table 4

and Fig. 3, highlighting compositional variations

induced by the sorting process. It can be observed

that, in all the investigated samples, a peak of SiO2

0

3

6

9

12

15

18

TQ

2AT

Q2B

MD

2AFN

2AFN

1A

TQ

3AT

Q1B

TQ

2CT

Q2D

TQ

1DT

Q3D

MD

1D

MD

3DFN

2DFN

1DT

Q2E

MD

2BFN

2BM

D1A

FN1B

TQ

3BT

Q1C

TQ

3CM

D2C

FN2C

FN1C

MD

3AM

D3B

MD

3C

TQ

1FT

Q1E

TQ

2FT

Q3E

MD

2EFN

2EFN

1EM

D3E

TQ

3FM

D2F

MD

3FFN

2FM

D1B

MD

1FM

D1E

MD

1CFN

1F

Dis

sim

ilari

ty

Euclidean distance

TQ

1A

MD

2D

Fig. 4. Cluster analysis dendrogram highlighting ‘‘medium sands’’ (labels ending with D) as a quite homogeneous group. ‘‘Fine sands’’ and fraction

<0.075 mm (labels ending with E and F, respectively) also seem to be homogeneous groups.


concentration characterises the medium sands (0.6–0.125

mm) fraction. An antithetic behaviour is shown by CaO,

characterised by a negative peak corresponding to the

medium sand fraction. On the other hand, Al2O3 and

Fe2O3 contents within each sample appear roughly con-

stant, regardless of the considered grain-size fraction.

Transition metals such as Ni, Co, Cr, V, Zn, Pb tend

to increase in the finer fraction, as they are plausiblytrapped by clay minerals that are more abundant in

the <0.075 mm fraction.

Statistical evaluation of these chemical data through

a cluster analysis shows that hierarchical grouping is

based on grain-size class; this approach is useful to re-

duce the multi-dimensionality of the data to two-dimen-

sional data that can be easily visualized and plotted, and

to highlight similarities between different samples. Inparticular, Euclidean distance-cluster analysis demon-

strates that sorting and sieving leads to a progressive

homogenisation (Fig. 4).

Considering the different grain-size fractions, it can be

envisaged that the medium sands (0.6–0.125 mm) repre-

sent a homogeneous group, showing analogies with nat-

ural sediments of comparable grain-size. In particular, if

compared with natural sands from the Ferrara area (Fig.5), these recycled inert materials are richer in CaO and

poorer in Al2O3–K2O. This simply means that the 0.6–

0.125 mm fraction of the recycled inert samples contains

more carbonate and/or more calcium-bearing alumin-

ium–iron hydroxides and hydrous silicates, and less clay

minerals than the natural sands of the area.

The content of hazardous elements, such as the tran-

sition metals of these recycled inert samples, is compara-

ble to or even lower than that recorded in the natural

sands (Fig. 5). These elements are not associated with

meta-stable phases, as they are plausibly concentrated

within the clay fraction. This suggests, in turn, that these

harmful elements cannot be easily leached and released

in solution (this statement should be verified with properleaching tests as proposed by Trankler et al., 1996 and

Wahlstrom et al., 2000).

Chemical analyses of finer fractions (0.125–0.075

mm; <0.075 mm) are also quite homogeneous and,

if calculated on anhydrous basis, reveal a comparative

enrichment in Al2O3. This suggests that these fractions

could be employed as a raw material component in

cement preparation. To test this hypothesis, chemicalcompositions of the 0.125–0.075 mm and <0.075 mm

fractions have been included in the phase diagram

for the system CaO–Al2O3–SiO2, in which components

that make up cements are easily represented (Fig. 6).

It has to be noted that suitable composition for the

cement preparation, enclosed in the sub-triangle C3S,

C2S, C3A (Manning, 1995), could be obtained by

blending �40% of the considered recycled inert mate-rials with �60% of lime. The same C&D fine-fractions

could also be considered by the ceramic industry –

although not matching the starting requirements for

preparation of bricks and tiles – to provide compo-

nents for compositional corrections of other raw

materials (Fig. 7).

9

9,5

10

10,5

11

11,5

12

12,5

Al 2O3 (wt %)

2,5

3,0

3,5

4,0

4,5

5,0

Fe2O3 (wt %)

8

10

12

14

16

18

20

CaO (wt%)

30

40

50

60

70

80

90

100

110

120

Ni (ppm)

4

6

8

10

12

14

16

18

Co (ppm)

80

90

100

110

120

130

140

150

Cr (ppm)

2,0

2,1

2,1

2,2

2,2

2,3

2,3

2,4

2,4

2,5

60 62 64 66 68

K2O (wt %)

0

1

2

3

4

5

6

7

8

9

60 62 64 66 68

Th (ppm)

SiO 2 (wt %) SiO 2 (wt %)

Fig. 5. Binary diagrams of Al2O3 (wt%), CaO (wt%), Fe2O3 (wt%), K2O (wt%), Ni (ppm), Co (ppm), Cr (ppm), Th (ppm) vs. SiO2 in which the

recycled inert material with grain-size between 0.6 and 0.125 mm is compared with natural sands of the Ferrara area (unpublished authors� data).Symbols: ¤, recycled inert material with grain-size between 0.6 and 0.125 mm; h, natural sandy sediments.


CaO Al2O3

C2S

C3S

C3A

Suitable compositions forthe Cement industry

Average composition ofrecycled inert materials

SiO2

Fig. 6. Ternary diagrams describing the system CaO–Al2O3–SiO2,

reporting the composition of mineral phases typically recognised in

cements: tricalcium silicate (alite; C3S), dicalcium silicate (belite; C2S)

and tricalcium aluminate (C3A). In accordance with Manning (1995),

raw material compositions required for cement preparation are

included in the sub-triangle C3S–C2S–C3A. Similar compositions can

be achieved by blending lime (�60%) with compositions comparable to

those of the recycled inert fractions 0.125–0.075 mm and <0.075 mm.

Symbols: · = recycled inert fractions 0.125–0.075 mm and <0.075 mm;

� = average composition of the recycled inert fractions 0.125–0.075

mm and <0.075 mm; * = phases classically recognised in cements;

} = lime composition; dotted line = mixing calculation.

Fig. 7. Fe2O3–(Na2O + K2O)–(CaO + MgO) triangular diagram

reporting compositions of the analysed recycled C&D materials

(· = C&D fractions 0.125–0.075 mm and <0.075 mm) as well as

compositional field typical of terracotta (Bianchini et al., 2002 and

references therein).


5. Conclusions

This study indicates that, through an opportune

crushing and sorting operation for C&D material, it is

possible to obtain grain-size fractions with roughly

homogenous chemical and mineralogical composition.

In particular, chemical–mineralogical characterisa-

tion of different grain-size classes, obtained through lab-

oratory sieving of C&D waste material, has allowed usto recognise a particular grain-size fraction (0.6–0.125

mm) that can be directly re-utilised as first-order mate-

rial in the building-related activities. In particular, this

fraction could be employed in the preparation of new

mortar and concrete. Similar applications have already

been tested (Zakaria and Cabrera, 1996; Limbachiya

et al., 2000; Sagoe-Crentsil et al., 2001; Ajdukiewicz

and Kliszczewicz, 2002; Corinaldesi and Morioni,

2002; Olorunsogo and Padayachee, 2002) and appear

to provide excellent results especially if coupled with

the introduction of polypropylene fibers (Mesbah andBuyle-Bodin, 1999; Corinaldesi et al., 2002).

The finer fractions could be used for direct mortar

preparation only if the fraction of ‘‘cocciopesto’’ (i.e.,

fragments of bricks, tiles and terracotta) is relevant,

thus providing material characterised by a significant

pozzolanic attitude (Baronio et al., 1997; Corinaldesi

et al., 2002; Zendri et al., 2004). This could only be ob-

tained with a careful differentiation of the initial C&Dmaterials that has to be preliminarily performed on-site

(directly at the landfill). Within the investigated C&D

materials, XRD analysis reveals that ‘‘cocciopesto’’

materials (evidenced by minerals such as ghelenite, wol-

lastonite, mullite) are diluted by other components,

while phyllosilicates (that can induce swelling/shrinkage

processes) are significantly represented thus precluding

utilization for mortar preparation. In this light, thesefine recycled fractions would require an industrial

treatment (e.g., sintering process) to be re-utilised; as

to the ceramic industry, these materials do not have

a composition totally fitting the requirements for the

preparation of bricks and tiles, but can be utilised for

compositional correction of other raw materials. Simi-

larly, we also propose a possible reuse of these fine

fractions in cement preparation, after suitable mixingwith lime and subsequent calcination process. In that

case, cement prepared with recycled fine fractions could

be subsequently employed to bind the coarser fractions

(gravel/cobbles) in the preparation of molded blocks

(Poon et al., 2002) that would represent building ele-

ments prepared entirely with recycled components.

Acknowledgements

Profs. L. Beccaluva and F. Siena are kindly acknowl-

edged as the promoters of this research and for their

helpful discussion. The authors are also grateful to the

anonymous Referees for the useful suggestions reported

in their constructive reviews, and to Prof. C.S. Poon for

the careful editorial comments which ultimately led to asignificant improvement of the paper.

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