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Project Title:

“Green Integrated Structural Elements for Retrofitting and New Construction of Buildings”

Deliverable No D6.1

Deliverable Title Processed raw materials as precursors for synthesizing geopolymer matrix

Work Package and Task Number

Work Package 6 Task 6.1

Participants: 1- UBRUN 2- CID 3- LEITAT 4- NTUA 5- CETRI

6- EXERGY 7- ALCN 8- STRESS 9- UAVR 10- ARTIA 11- NRGIA 12- COLL 13- COOLH 14- ACCIO

Sign off Name Date Approved

Originator NTUA 30/03/2018

Work Package leader ALCN 30/03/2018

Tech Lead NTUA 30/03/2018

Coordinator UBRUN 30/03/2018

1 Enter a cross (X) in the appropriate cell.

Dissemination Level 1

PU Public X

PP Restricted to other programme participants (including the Commission Services)

RE Restricted to a group specified by the consortium (including the Commission Services)

CO Confidential, only for members of the consortium (including the Commission Services)

HORIZON 2020 SPECIFIC PROGRAMME: Nanotechnologies, Advanced Materials,

Advanced Manufacturing and Processing, and Biotechnology

THEME: [EEB-04-2016]

GRANT AGREEMENT NO: 723825

Ref. Ares(2018)1754134 - 30/03/2018

Green INSTRUCT - Contract No: 723825 EEB-04-2016

Copyright ©, Green INSTRUCT 2016 - THIS DOCUMENT IS UNCONTROLLED WHEN PRINTED Page 1

DISCLAIMER

This document contains the description of the Green INSTRUCT project findings, work and

products. Certain parts of it might be under partner Intellectual Property Right (IPR) rules.

Therefore, prior to using its content please contact the consortium coordinator for approval. E-mail:

[email protected] .

Should you feel that this document harms in any way the IPR held by you as a person or as a

representative of an entity, please do notify us immediately.

The authors of this document have taken all available measures in order for its content to be

accurate, consistent and lawful. However, neither the project consortium as a whole nor the

individual partners that implicitly or explicitly participated in the creation and publication of this

document hold any sort of responsibility that might occur as a result of using its content.

This document has been produced with the assistance of the European Union. The content of this

document is the sole responsibility of the Green INSTRUCT consortium and can in no way be

taken to reflect the views of the European Union.

mailto:[email protected]



Table of Contents

1 Project Summary ............................................................................................................................... 3

2 Glossary of Terms ............................................................................................................................. 4

2.1 Definitions .................................................................................................................................. 4

2.1.1 Additional Definitions ......................................................................................................... 4

3 Description of Work ........................................................................................................................... 5

3.1 Technical Objectives .................................................................................................................. 5

4 Raw Materials .................................................................................................................................... 6

4.1 Selection .................................................................................................................................... 6

4.2 Characterization ......................................................................................................................... 8

4.2.1 Chemical characterization ................................................................................................. 8

4.2.2 Mineral characterization ..................................................................................................... 8

4.2.3 Particle size ...................................................................................................................... 10

4.3 Pre-treatment of the raw materials .......................................................................................... 10

5 Evaluation of Geopolymerization Potential ...................................................................................... 13

5.1 Test procedure ......................................................................................................................... 13

5.2 Results ..................................................................................................................................... 14

6 Synthesis of Geopolymers ............................................................................................................... 17

6.1 Preliminary tests ...................................................................................................................... 17

6.2 Brick based geopolymers ........................................................................................................ 19

6.3 Preparation of lightweight geopolymers .................................................................................. 22

7 Waste Glass Activation Solution ...................................................................................................... 25

8 Conclusions ..................................................................................................................................... 28

9 References ...................................................................................................................................... 29

10 Acknowledgment ......................................................................................................................... 30



1 Project Summary

The Green INSTRUCT project will develop a prefabricated modular structural building block that is superior

to conventional precast reinforced concrete panels by virtue of its reduced weight, improved acoustic and

thermal performance and multiple functionalities. The Green INSTRUCT block consists of over 70% of CDW

in weight.

The Green INSTRUCT project will:

(i) achieve sustainability and cost savings through CDW sourced materials and C2C;

(ii) develop efficient, robust, eco-friendly and replicable processes;

(iii) to enable novel cost efficient products and new supply chains;

(iv) (iv) develop a building block that renders refurbished or new buildings safe and energy

efficient; and

(v) safeguard a comfortable, healthy and productive environment.

They can be achieved by defining the structural, thermal and acoustic performance of our final product to

be competitive to similar products in the market. The types and sources of CDW are carefully identified,

selected and processed while the supply chain from the sources, processing, fabrication units to assembly

site of the whole modular panel will be optimized.

The project is guided by a holistic view through building information modelling and optimal overall

performance. This includes considering the life cycle analysis, weight, structural performance, thermal and

acoustic insulation, connectivity among modular panels and other structural/non-structural components as

well as the compatibility of different internal parts of the each modular panel. In order to homogenize the

production process, all individual elements are fabricated by extrusion which is a proven cost effective,

reliable, scalable and high yield manufacturing technique. The concept, viability and performance of

developed modular panels will be verified and demonstrated in two field trials in test cells.



2 Glossary of Terms

Acronym Meaning

CDW Construction and Demolition

Waste

GI Green INSTRUCT

EPS Expanded Polystyrene

XPS Extruded Polystyrene

PU Polyurethane Foam

XRD X-ray Diffraction

XRF X-ray Fluorescence

AAS Atomic Absorption

Spectroscopy

ICP-OES Inductive Coupled Plasma

Optical Emission

Spectroscopy

Definitions 2.1

Words beginning with a capital letter shall have the meaning defined either herein or in the Rules or in the

Grant Agreement related to the Project.

Additional Definitions 2.1.1

Project: Project refers to the Green INSTRUCT project funded from the European Union’s Horizon 2020

research and innovation programme under Grant Agreement 723825.

Geopolymerization: chemical process which involves the reaction between aluminosilicate precursors

and alkali silicate solution and the conversion of the precursor into a three-dimensional inorganic

amorphous or structured material.

Geopolymer: The product of geopolymerization.

Activation Solution: An alkali silicate solution which is mixed with an aluminosilicate precursor and

activates the reactions of geopolymerization process.

Alkali silicates: Chemical compounds which consist of alkali metals (Na or K), silicon and oxygen and are

widely used in geopolymerization process.

Precursor: Starting material.



3 Description of Work

The geopolymer layer is an essential part of the GI technology since it will serve as a supporting structural

element increasing the impact resistance and the overall resilience of the integrated modular building

block.

The main scopes of the Deliverable 6.1 are the identification and processing of the most suitable CDW

materials that can be applied in the production of CDW precursors for the geopolymer matrix

development. All these materials were characterized and appropriately processed prior to their use.

Ceramic wastes such as bricks and tiles are the second most abundant material in Construction and

Demolition Wastes. These wastes contain high amounts of SiO2 and Al2O3 in amorphous phase and

therefore are promising materials for geopolymerization.

Traditionally, the geopolymerization of the aluminosilicate precursors takes place by activation through an

alkaline solution which contains alkali silicates. However, the production of such reagents is energy and

resources consuming. The utilization of waste glass as precursor for the production of the activation

solution will solve these issues and thus will contribute to the circular economy principle.

Lightweight building elements generally exhibit improved thermal insulation and relatively good strength.

The main benefits by the application of these elements are associated with the reduction of the total load

of the structure making savings in foundations and reinforcement as well as the improved thermal

properties. In order to develop a low density geopolymer layer, lightweight aggregates in the form of CDW

expanded polystyrene (EPS), extruded polystyrene (XPS) and Polyurethane Foam (PU) can be incorporated

into the matrix.

Technical Objectives 3.1

The aim of this Deliverable is to select, characterize and develop the appropriate processing of CDWs that

can be used as raw materials for the geopolymer matrix. Bricks, tiles, glass, expanded polystyrene (EPS),

extruded polystyrene (XPS) and polyurethane foam (PU) were provided by NRGIA and tested, by NTUA, as

precursors for the geopolymer synthesis. All these materials were characterized and appropriately

processed prior to their use.

Deliverable 6.1 comprises the following stages:

Selection of suitable raw materials: bricks and tiles were selected due to their high SiO2 and Al2O3

content. EPS, XPS and PU were added in the geopolymers in order to reduce their weight. Glass was

tested as an alternative precursor for the activation solution.

Characterization of raw materials: the characterization was performed by means of XRF (chemical

composition), XRD (mineral composition) and Laser granulometry (particle size distribution).

Pretreatment of raw materials: bricks and tiles were ground (d50 = 20μm) prior to their use in order to

accelerate the geopolymerization reactions. Waste glass was ground (< 56 μm) in order to facilitate the

dissolution. EPS, XPS and PU were chopped and sieved in order to get particles with a size between 1

and 4 mm which was found to be the most appropriate for satisfactory dispersion in the geopolymeric

matrix.

Measurement of the degree alkali dissolution: the geopolymerization potential of bricks and tiles was

evaluated through alkaline dissolution tests and strength measurements of the final products.

Synthesis of geopolymers: reference and lightweight geopolymer specimens were prepared and

evaluated on the basis of their density and mechanical strength (EN 196-1)

Conversion of CDW glass into water glass solution: the effect of glass/NaOH and H2O/NaOH ratios as

well as the effect of temperature, pressure and time on the conversion yield of glass was measured.



4 Raw Materials

Selection 4.1

The geopolymerization process, in general, starts with a chemical reaction between an aluminosilicate

precursor material and an alkali silicate solution at ambient or slightly elevated temperature, leading to the

conversion of the precursor material into a three-dimensional inorganic amorphous or structured material

[1]. The reactants are from alkali metal hydroxide/silicate solution (often referred to as the chemical

activator) and finely ground aluminosilicate-rich precursor material. The chemical activator is prepared by

mixing the alkali metal hydroxide/silicate with water. Then, the aluminosilicate precursor and the activation

solution are mechanically mixed to form homogenous slurry. The slurry is shaped/formed by molding or

extrusion to the desired shape and dimensions. The material is finally cured at temperatures below 100C.

Figure 4.1 presents the geopolymer preparation process.

Figure 4.1 Flow sheet of geopolymer synthesis

The precursor used in the geopolymer technology needs to have a significant amount of silicon and

aluminium, preferably in an amorphous state. The aluminosilicate precursor is usually an industrial mineral,

waste or by-product. Commonly used precursors include fly ash, ground granulated blast-furnace slags,

ferrous slags, and metakaolin. In the GI project, the aluminosilicate precursor of choice for the geopolymer

matrix development is originating from CDW materials. The major part of CDWs contains concrete and

ceramic waste such as bricks and tiles. Here, the ceramic wastes were selected as the most promising

candidates for geopolymerization since they have high amounts of SiO2 and Al2O3. Furthermore, the parent

materials of such wastes are treated at high temperatures (~1000oC) at their production stage and

therefore have a higher degree of disorder i.e. are more amorphous which is advantageous for

geopolymerization. On the other hand, concrete is well known for its low geopolymerization potential [2-4]

since it contains low amounts of Al2O3. Also, the abundant calcium silicate phases generated from the

hydration of cement are not soluble in alkaline media.

In the GI project, four different brick waste precursors and one tile waste precursor were tested as raw

materials for the development of the geopolymer matrix. The first two brick precursors (B1, B2a and B2b)

are batches rejected from the production line of the brick industry since they did not conform to the quality

control standards. The third brick precursor (B3) as well as the tile precursor (T) originate from construction

and demolition activities. All the aluminosilicate waste precursors were provided by NRGIA. Figure 4.2

shows waste brick and tile precursors used in the GI project.



(a)

(b)

Figure 4.2 Waste (a) brick and (b) tile precursors applied in the GI project

Traditionally, the successful activation of an aluminosilicate precursor is carried out by the application of a

solution containing alkali silicates as an extra source of silicon ions promoting the geopolymerization

reactions. However, the production process of such silicates demands the heat treatment of the raw

materials (a mixture of sodium carbonate and silica salts) at elevated temperatures of around 1300°C,

which reduces the advantages of using geopolymers as environmentally friendly alternatives to traditional

cementitious materials. Waste materials such as CDW glass can also be valorized as supplementary source

of silica in alkali activated materials to minimize the adverse energy demand and CO2 emissions of the

industrial production of sodium silicate, also known as water glass. In the GI project, we explore the

feasibility of using waste glass as a potential alkaline activator for the geopolymer matrix development. This

demands the design and development of an experimental setup which includes the hydrothermal

treatment of the waste glass. The precursor of waste glass (G) utilized in the GI project was provided by the

partner NRGIA (Figure 4.3).

Figure 4.3 CDW glass precursor provided by NRGIA

Lightweight building elements generally exhibit improved thermal insulation at a small trade-off with

strength. The main benefits by the application of these elements are associated with the reduction of the

total load of the structure making savings in foundations and reinforcement as well as the improved

thermal properties. Such elements usually consist of a cementitious binder and a lightweight aggregate

(polystyrene beads, expanded perlite etc.). In the GI project, the reduction of the geopolymer matrix

density will be carried out by the incorporation of lightweight additives in the raw materials mixes such as

CDW expanded polystyrene (EPS), CDW extruded polystyrene (XPS) and CDW polyurethane foam (PU). The



precursors of the lightweight additives were provided by the partner NRGIA and are presented in Figure

4.4.

(a)

(b)

(c)

Figure 4.4 CDW (a) EPS, (b) XPS and (c) PU foam provided by NRGIA

Characterization 4.2

Chemical characterization 4.2.1

The CDW aluminosilicate precursors (bricks and tiles) were characterized by means of X-ray fluorescence

spectroscopy (XRF) in order to determine their chemical composition. The content of SiO2 and Al2O3 in the

CDW precursors is a crucial factor in the geopolymer technology and generally high contents of the

aforementioned oxides tend to provide good geopolymerized materials. The chemical composition of the

raw materials (Table 4.1) shows that the selected CDW precursors could provide sufficient amounts of Si

and Al ions needed for the geopolymerization reactions. It must be noted that batches B2a and B2b came

from the same precursor and their behavior was very similar. For clarity reasons, from this point on, B2

refers to B2a or B2b.

The Table 4.1 also presents the chemical composition of the waste glass. As stated before waste glass from

demolition activities will be utilized in the preparation of the activation solution of the geopolymer

synthesis and thus will increase the CDW content of the final product. The utilized waste glass belongs to

soda – lime glasses typical used in the fabrication of windowpanes.

Table 4.1 Chemical composition of the CDW precursors

WASTE SiO2 Al2O3 Fe2O3 CaO MgO K2O Na2O SO3 TiO2 P2O5 Cl L.O.I.

B1 51.31 14.62 8.45 6.33 8.10 2.28 0.57 0.44 0.66 0.08 0.04 3.97

B2a 69.66 16.23 7.21 0.42 2.11 2.92 0.28 - 0.79 0.07 - 0.16

B2b 65.99 18.38 4.79 2.09 1.89 2.85 1.96 - 0.72 0.12 - 0.86

B3 78.92 10.76 4.41 0.89 1.12 1.85 0.87 - 0.59 0.11 - 0.29

T 57.42 15.93 5.96 7.43 3.22 3.39 0.79 0.17 0.67 0.13 0.03 4.70

G 71.35 - - 10.10 3.80 - 14.28 - - - - 0.47



Mineral characterization 4.2.2

Figure 4.5 presents the XRD patterns of the waste brick precursors. XRD analysis showed that the mineral

composition of the waste brick precursors is similar and contain quartz as the most predominant mineral

constituent while phases such as albite, diopside, hematite, carbonates, microcline and muscovite are also

present in lower amounts. The brick precursors B2 and B3 seems to be more crystallized than the B1 brick

precursor. Furthermore, B2 and B3 precursors do not contain carbonate and muscovite phases. The

amorphous phase content of the B1, B2 and B3 precursors was calculated at 38.9, 35.6 and 19.6%,

respectively.

Figure 4.5 XRD patterns of the waste brick precursors

Figure 4.6 shows the XRD pattern of the tile waste. As in the case of the brick wastes the main mineral

phase of the tile material is quartz while phases such albite, diopside and hematite are also present in

lower intensities. The amorphous phase content of tile waste was calculated at 39.5%.

Figure 4.6 XRD pattern of waste tile precursor

5 10 15 20 25 30 35 40 45 50 55 60 65 70

Inte

nit

y (

arb

.un

its

)

2θ (ο)

1

1

1

232

2,6 7

11 11

B1

14

5

1116

788

B2

B312 4

1: Quartz, 2: Albite, 3: Diopside, 4: Hematite, 5:Calcite , 6: Microcline, 7: Potassium - calcium Carbonate, 8: Muscovite

5 10 15 20 25 30 35 40 45 50 55 60 65 70

Inte

nit

y (

arb

.un

its)

2θ (ο)

1

1

1

3

2

11 11

T1

4 11122 3

1: Quartz, 2: Albite, 3: Diopside, 4: Hematite



Figure 4.7 presents the XRD pattern of the waste glass. This soda – lime glass is predominately amorphous

(74.7%), also containing quartz as the main crystalline phase.

Figure 4.7 XRD pattern of waste glass precursor

Particle size 4.2.3

The particle size of the CDW materials precursors utilized in the development of the geopolymer matrix is

presented in Table 4.2. It is noted that these particle size values are referred to the raw materials as

received prior to their processing i.e. milling or grinding.

Table 4.2 Particle size of the as-received CDW materials

CDW material Particle size

Brick

precursors 150 – 200 μm

Tile precursor 150 – 200 μm

Waste glass 1 – 3 mm

EPS 1 – 10 mm

XPS 1 – 20 mm

PU foam < 50 mm

Pre-treatment of the raw materials 4.3

The particle size distribution of the aluminosilicate precursor is a crucial factor in the geopolymer

technology. It is essential to grind the raw material to certain fineness in order to maximize the active

surface of particles leading to the acceleration of the geopolymerization reactions. Therefore, waste brick

and tile precursors were pulverized prior to their use to obtain a mass median particle diameter (d50) of 20

10 15 20 25 30 35 40 45 50 55 60 65 70

Inte

nit

y (

arb

.un

its)

2θ (ο)

1

G

1

1: Quartz



μm. This fineness is in the typical range for raw materials used in the industrial formulation of cementitious

materials. Waste glass was pulverized and then sieved prior to its alkaline treatment to obtain a powder

with particle size lower than 56 μm. The particle size distribution and characteristics of the CDW precursors

are shown in Figure 4.8 and Error! Reference source not found. , respectively.

(a)

(b)

(c)

(d)

(e)

Figure 4.8 Particle size distributions of waste precursors: (a) B1, (b) B2, (c) B3 (d) T and (e) G

Particle Diameter (µm.)

Volume (%)

0

10

0

10

20

30

40

50

60

70

80

90

100

0.1 1.0 10.0 100.0 1000.0


Volume (%)

0

10

0

10

20

30

40

50

60

70

80

90

100

0.1 1.0 10.0 100.0 1000.0


Volume (%)

0

10

0

10

20

30

40

50

60

70

80

90

100

0.1 1.0 10.0 100.0 1000.0


Volume (%)

0

10

0

10

20

30

40

50

60

70

80

90

100

0.1 1.0 10.0 100.0 1000.0


Volume (%)

0

10

0

10

20

30

40

50

60

70

80

90

100

0.1 1.0 10.0 100.0 1000.0



Table 4.3 Particle size fractions of the CDW raw materials used

B1 B2 B3 T G

d90 (μm) 89.0 106.5 83.6 79.8 169.1

d50 (μm) 14.0 20.6 26.9 20.9 50.0

The reduction of the geopolymer matrix density will be carried out by the incorporation of CDW lightweight

additives (EPS, XPS or PU) in the raw materials mixes. However, due to their wide particle size distribution,

the as received lightweight agents were cut by an appropriate cutting machine and then sieved to obtain a

particle size in the range of 1 – 4 mm.



5 Evaluation of Geopolymerization Potential

Geopolymerization is a complex process (Figure 5.1) and its exact mechanism is not yet fully understood,

but it is believed to consist of four main stages: (1) the surface dissolution of Al and Si in a highly alkaline

solution, (2) the diffusion of the dissolved species through the solution, (3) the polycondensation of the Al

and Si complexes with the added silicate solution that involves the gelation and reorganization of the

matrix and (4) the hardening of the gel that results in the final geopolymeric product. Stages (2) to (4)

cannot be monitored since the procedures cannot be stopped and the products cannot be isolated.

Therefore, the dissolution stage is the only one that can be quantitatively studied. Yet, as it is indicated by

the proposed mechanisms, the extent of aluminosilicate precursors’ dissolution is crucial since the amount

of Si and Al initially dissolved is substantial for the following polycondensation. Thus, dissolution studies can

be used for the initial evaluation of the geopolymerization potential of the aluminosilicate materials

selected for the geopolymer matrix development.

Figure 5.1 Conceptual model for geopolymerisation and microstructure changes [1]

In the alkali dissolution tests, the studied variables were the kind of aluminosilicate precursor (brick or tile

waste) and the alkali metal ion (Na or K) in the solution.

Test procedure 5.1

0.5 (± 0.0001) g of solid paste was mixed with 20 ml of alkaline solution under continuous stirring. The

concentration of the NaOH and KOH solutions as well as the dissolution time was kept constant at 10 M

and 24 h, respectively [5]. After filtering, the liquid part was diluted to 250 ml, the pH was adjusted to pH <

1 by adding concentrated HCl acid and Atomic Absorption Spectroscopy (AAS) was used to determine the Al



and Si concentrations. The solid part was examined by means of XRD in order to evaluate the effect of Al

and Si leaching on the structure of the precursor.

Results 5.2

Table 5.1 presents the concentration of Al and Si in the solutions (10M NaOH or KOH) in relation to the

precursor (CDW bricks and tiles). These values are the measured concentrations, after the leaching of 0.5 g

of the solid material and the dilution of the liquid to 250 ml. Figures 5.2 and 5.3 present the percentage of

dissolved Al and Si after leaching, for 24 h, in 10 M NaOH and 10 M KOH, respectively. Since the precursors

have a varying content of Al and Si, Figure 5.2 and Figure 5.3 present the percentage of the total Al and Si of

the precursor that has been dissolved. In this way, it was possible to evaluate how extensively the

precursor has been affected by the attack of the alkaline solution.

Table 5.1 Extent of Al and Si dissolution in alkali media

CDW material 10 M NaOH 10 M KOH

Si (ppm) Al (ppm) Si (ppm) Al (ppm)

B1 37.10 14.66 29.3 9.69

B2 79.30 23.99 47.6 12.22

B3 51.40 8.79 32.67 6.55

T 27.10 11.20 18.60 6.22

The results of the alkaline dissolution experiments showed that waste bricks and tiles are adequately

susceptible to alkaline dissolution and, therefore, both types of precursor possess good geopolymerization

potential. Nonetheless, the brick wastes showed a greater alkaline dissolution than the tile waste in both

NaOH and KOH. For both brick and tile waste, the degree of dissolution was determined to be higher in

NaOH than in KOH solution due to the smaller size and higher mobility of sodium ions and therefore their

ability to penetrate easier in the aluminosilicate precursor [6]. Amongst the three precursors of brick waste,

variations in the alkaline dissolution rates revealed the diversity of chemical composition, which would

ultimately affect the geopolymerization potential. In particular, the Si and Al dissolution rates present the

following order among the brick precursors: B2 > B1 > B3. This is closely related to the amorphous phase

content of each brick precursor. Bricks with high amorphous contents (B1 and B2) are able to be dissolved

more easily by the alkali ions than the more crystallized bricks (B3). However, it must be noted, that the

leaching behavior of Al and Si cannot predict by itself the quality of the final geopolymers. Further

experiments concerning the preparation and properties of geopolymers from these raw materials have to

be conducted.



Figure 5.2 Dissolved Al and Si after leaching, for 24 h, in 10 M NaOH (% w/w)

Figure 5.3 Dissolved Al and Si after leaching, for 24 h, in 10 M KOH (% w/w)

Figure 5.4 presents the XRD patterns of the B1 and T materials and their solid residues after leaching in 10

M NaOH for 24 h. The solid residues of both waste bricks and tiles contain the same crystalline phases as

the precursors but in lesser amounts as indicated by the decrease of the corresponding peaks. The same

behavior was observed for the B2 and B3 raw materials.

0

2

4

6

8

10

12

14

BRICK1 BRICK2 BRICK3 TILE

Dis

so

lve

d E

lem

en

t(%

w/w

)

Sample

Si

Al

0.0

2.0

4.0

6.0

8.0

10.0

BRICK1 BRICK2 BRICK3 TILE

Dis

so

lve

d E

lem

en

t(%

w/w

)

Sample

Si

Al



Figure 5.4 XRD patterns of precursors and solid residues

a: B1, b: solid residue of B1 after leaching in 10 M NaOH for 24 h, c: T,

d: solid residue of T after leaching in 10 M NaOH for 24 h

5 10 15 20 25 30 35 40 45 50 55 60 65 70

Inte

nsit

y (

arb

.un

its)

2θ (ο)

1

1

1

2 6,2

2

2

7

11

1

4

8,1

c

a

1

4

1

11

b

d

55,4 3

1: Quartz, 2: Albite, 3:Calcite, 4: Muscovite, 5: Microcline, 6: Diopside, 7: Potassium - calcium Carbonate, 8: Maghemite



6 Synthesis of Geopolymers

The synthesis of geopolymers involves a chemical reaction between aluminosilicate material and sodium

silicate solution (known as the activation solution) in a highly alkaline environment. The first step of the

geopolymer synthesis involves the preparation of the activation solutions by dissolving NaOH (> 99%, CAS:

1310-73-2) anhydrous pellets in distilled water and adding soluble Si in the form of SiO2 solution (50% in

H2O, colloidal dispersion, CAS: 7631-86-9). The activation solutions were stirred for 1 h prior to use, to allow

for equilibrium. Then, the raw materials (waste brick or tile) and the activation solution were mechanically

mixed (standard mortar mixer: Controls 65-L0005) to form a homogenous slurry which was transferred to

50x50x50 mm cubic molds and mildly vibrated. The specimens were left at room temperature for 2 h and

then were cured at 80oC for 48h [7]. Compression tests were carried out on a Toni-technik uniaxial testing

press, 7 days after the specimen preparation (loading rate 1.5 kN/s, according to EN196-1). For each sample

synthesis, three specimens were prepared and tested under compression. Figure 6.1 presents the flow

chart of the experimentation.

Figure 6.1 Flow sheet of geopolymer synthesis

Factors, such as the mineral and chemical composition of raw materials, the curing conditions and the

ratios of precursors strongly affect the structure and properties of geopolymers. Therefore, the

optimization of the synthesis is mndatory prior to any development of geopolymeric material.

In order to evaluate the efficiency of brick and tile wastes on the preparation of geopolymers, preliminary

tests concerning the synthesis and the properties of geopolymers from CDWs were performed. These tests

were performed by the method of changing “one factor at a time”. The studied parameters were the molar

ratio [Si]/Na2O which determines the amount of soluble silicon in the activation solution, the molar ratio

Na/Al related to the alkalinity of the initial solution and the mass ratio solid/liquid2 which affects the

workability of the pastes. The value range of the examined parameters ([Si]/Na2O = 0 – 4.15, Na/Al = 0.5 –

2.0 and solid/liquid = 2.8 – 4.2) was based on our previous work on the production of fly ash based

geopolymers [7].

Preliminary experiments 6.1

Table 6.1 presents the preliminary experiments of the geopolymer synthesis based on B1 and T wastes

performed by changing “one factor at a time” along with their compressive strength and density. It is

obvious that the values of the strength measurements are highly dispersed (0.5-16.4 MPa) indicating that

2 Solid refers to the sum of aluminosilicate precursor, NaOH and SiO2 (from SiO2 reagent) masses.



the selected factors have a significant effect on the mechanical behaviour of the produced geopolymers.

The results showed that both precursors can be geopolymerized but to a different degree. Overall, the brick

waste geopolymer samples attained higher compressive strength compared to the tile waste geopolymer

samples, confirming that its higher Si and Al dissolution degree did indeed increase the geopolymerization

potential. As shown in Table 6.1 the brick-based geopolymers exhibit a three times higher compressive

strength than tile-based geopolymers.

From the perspective of material availability, the waste brick is the most abundant aluminosilicate CDW

material, offering a higher opportunity of recycling and reuse [8]. For the aforementioned reasons of both

mechanical strength and material availability, the CDW brick was chosen as the aluminosilicate material for

the development of the geopolymer layer.

Table 6.1 Preliminary experiments of brick (B1) and tile (T) waste geopolymers

Experiment [Si]/R2O Na/Al Solid/liquid Compressive Strength

(MPa)

Density (g/cm3)

B1_1 0.00 1.0 3.6 10.8 ± 0.2* 1.85 ± 0.01*

B1_2 1.05 1.0 3.6 16.4 ± 0.3 1.94 ± 0.01

B1_3 2.05 1.0 3.6 12.2 ± 0.6 1.91 ± 0.01

B1_4 1.05 0.5 3.6 7.2 ± 0.9 1.94 ± 0.01

B1_5 1.05 1.5 3.6 1.9 ± 0.1 1.64 ± 0.00

B1_6 1.05 2.0 3.6 0.5 ± 0.1 1.57 ± 0.01

B1_7 1.05 1.0 2.8 11.4 ± 0.8 1.74 ± 0.02

B1_8 1.05 1.0 3.4 15.3 ± 0.5 1.91 ± 0.01

T1 0.00 0.5 3.6 2.5 ± 0.2 1.83 ± 0.01

T2 0.00 1.0 3.6 1.9 ± 0.1 1.71 ± 0.02

T3 1.05 0.5 3.6 1.1 ± 0.2 1.86 ± 0.00

T4 1.05 1.0 3.6 1.4 ± 0.0 1.89 ± 0.05

T5 4.15 0.5 3.6 5.4 ± 1.0 1.83 ± 0.09

* Standard deviation of the measurements. Three specimens for each experiment were prepared and tested (compressive strength and density).

When the value varies by more than ±10% from the mean, these results are discarded and new specimens are prepared.

In Figure 6.2, the effect of the molar ratio [Si]/Na2O (a), Na/Al (b) and mass ratio solid/liquid (c) on the

compressive strength values of waste brick geopolymers is presented. The results in Fig. 6.2(a) revealed

that the presence of soluble Si in the activation solution favors the production of geopolymers with

enhanced mechanical properties. The soluble Si reacts with the Al of the raw material which is dissolved at

the early stages of the dissolution process and forms oligomers which are polymerized to geopolymer

structures [9]. The positive effect of the soluble Si on the mechanical properties has an upper limit

([Si]/Na2O = 1.05). At higher values, a reduction of the compressive strength is observed. It seems that a

high soluble Si concentration in the activation solution slows down the dissolution of the Si from the

aluminosilicate precursor by shifting the dissolution reaction to the left, and therefore delays the

geopolymerization reactions.



As observed from Fig. 6.2(b,), the increase of alkalinity is initially beneficial for the development of

compressive strength, since the alkali metals help the dissolution of the raw material and provide charge

balance in the geopolymer network [9]. However, considerably high amounts of alkali metals do not further

dilute the raw material, nor are incorporated to the matrix, on the contrary they favor the formation of

carbonate phases which cause deterioration of the mechanical properties.

Finally, the effect of the water content (solid/liquid) on the geopolymerization of waste brick was

evaluated. With the increase of the solid/liquid ratio in Fig. 6.2(c), compressive strength also increases,

probably due to the increase of alkalinity in the activation solution. Solid/liquid ratios higher than 3.6 led to

limited workability and mixing problems of the pastes.

(a)

(b)

(c)

Figure 6.2 Effect of the synthesis factors on the compressive strength of brick waste geopolymers

[Si]/Na2O (a), Na/Al (b) and Solid/Liquid (c)

Brick based geopolymers 6.2Variations in the firing conditions, the raw materials composition as well as the recycling process of the

brick precursors result in variability in the chemical, physical and mineralogical properties of the brick

geopolymer precursors. This variability has a great impact on the reactant mixture as well as the

performance of the geopolymers. In this regard, we tested two additional brick waste precursors to explore

the effect of diverse brick precursor composition on the mechanical properties of the produced

geopolymers. After the examination of B1 precursor in the previous chapter, two other brick precursors

provided from NRGIA and originating from the production line (B2) and construction activities (B3) were

8

10

12

14

16

18

0 1.05 2.05

Co

mp

r. S

tre

ng

th (

MP

a)

[Si]/Na2O

0

4

8

12

16

20

0.5 1 1.5 2

Co

mp

r. S

tre

ng

th (

MP

a)

Na/Al

10

12

14

16

18

2.8 3.4 3.6

Co

mp

r. S

tre

ng

th (

MP

a)

Solid/Liquid



tested for their geopolymerization potential. Table 6.2 and Table 6.3 show the experiments performed for

the B2 and B3 precursors along with the compressive strength and density values.

Table 6.2 Tests performed for B2 precursor along with compressive strength and density values

Sample Na/Al [SiO2]/Na2O Solid/Liquid Compressive

Strength (MPa) Density (g/cm3)

B2_1 0.6 1.00 3.8 1.9 ± 0.4 1.88 ± 0.02

B2_2 0.6 1.50 3.8 4.0 ± 0.5 1.81 ± 0.03

B2_3 0.6 2.00 3.8 5.5 ± 0.3 1.67 ± 0.03

B2_4 0.8 1.00 3.8 5.9 ± 0.2 1.73 ± 0.02

B2_5 0.8 4.00 3.3 0.4 ± 0.0 1.94 ± 0.02

B2_6 0.9 1.00 3.1 11.9 ± 1.2 1.63 ± 0.02

B2_7 0.9 1.50 3.8 9.4 ± 0.6 1.98 ± 0.01

B2_8 0.9 2.00 3.8 12.2 ± 0.4 1.75 ± 0.01

B2_9 1.0 0.75 2.8 1.5 ± 0.2 1.90 ± 0.02

B2_10 1.0 3.00 3.4 14.2 ± 0.8 1.79 ± 0.04

B2_11 1.1 1.10 3.4 5.8 ± 0.4 1.97 ± 0.01

B2_12 1.2 1.00 2.7 3.9 ± 0.3 1.83 ± 0.00

B2_13 1.2 1.50 3.8 17.9 ± 1.1 1.91 ± 0.02

B2_14 1.2 2.00 3.8 22.5 ± 0.4 1.88 ± 0.02

B2_15 1.3 1.00 2.6 0.6 ± 0.0 1.99 ± 0.02

B2_16 1.3 1.60 4.2 37.3 ± 1.3 2.12 ± 0.02

B2_17 1.3 2.30 3.8 28.6 ± 1.4 1.89 ± 0.00

Table 6.3 Tests performed for B3 precursor along with compressive strength and density values

Sample

Na/Al [SiO2]/Na2O Solid/Liquid

Compressive


B3_1 0.90 1.0 3.5 3.3 ± 0.2 1.86 ± 0.00

B3_2 0.90 1.5 3.8 3.2 ± 0.5 1.86 ± 0.01

B3_3 0.90 2.0 3.8 2.4 ± 0.4 1.89 ± 0.03

B3_4 1.35 1.0 3.1 0.4 ± 0.0 1.89 ± 0.04

B3_5 1.35 1.5 3.8 5.5 ± 0.3 1.88 ± 0.02

B3_6 1.35 2.0 3.8 10.0 ± 0.4 1.86 ± 0.01

B3_7 1.80 1.0 2.7 0.5 ± 0.2 1.96 ± 0.01

B3_8 1.80 1.5 3.8 8.6 ± 0.8 1.91 ± 0.02

B3_9 1.80 2.0 3.8 13.0 ± 0.3 1.92 ± 0.01



Table 6.4 presents a summary of the optimum conditions in terms of compressive strength reached for the

three tested brick precursors, along with similar density values. It is obvious that all batches show

satisfactory geopolymerization potential by producing compact geopolymers and achieving relatively high

compressive strength values. However, the three brick batches exhibit a large variation in the

geopolymerization potential showing that the variability of the raw materials composition seriously affects

the geopolymer mechanical properties.

Table 6.4 Optimum synthesis conditions and final product properties of the geopolymers

Brick precursor [Si]/Na2O Na/Al Solid/Liquid Compressive


B1 1.05 1.0 3.6 16.4 ± 0.3 1.94 ± 0.01

B2 1.60 1.3 4.2 37.3 ± 1.3 2.12 ± 0.02

B3 2.00 1.8 3.8 13.0 ± 0.3 1.92 ± 0.01

Hence, the major challenge in the design of the GI geopolymer panel is to minimize the variability of the

final products properties resulting from the different sources of brick waste. For this purpose, it was

decided to develop a fast and reliable method to optimize the geopolymerization conditions, taking into

account the chemical and mineral composition of the CDWs. The optimization of the geopolymer synthesis

was achieved by the implementation of a multifactorial experimental designing model that involves

conducting a minimum number of experiments with the statistical evaluation of their results. The

optimization was based on the requirements of the final product (density and strength). This was carried

out in Task 6.2 and the results will be presented in Deliverable 6.2 (Final Geopolymer Layer) and the report

of Milestone 7 (Prototype of Geopolymer Matrix from CDWs).

Figure 6.3 presents specimens prepared from different waste brick precursors by applying the optimum

conditions.

(a)

(b)

(c)

Figure 6.3 Specimens prepared with the optimum synthesis conditions for (a) B1, (b) B2 and (c) B3



Preparation of lightweight geopolymers 6.3In the GI project, three types of lightweight agents provided by NRGIA were applied for the reduction of the

geopolymer matrix density: CDW expanded polystyrene (EPS), CDW extruded polystyrene (XPS) and CDW

polyurethane foam (PU). In all cases, the preparation of lightweight samples followed the same procedure

as the reference geopolymers. The lightweight materials were premixed with the aluminosilicate precursor

prior to the addition of the activation solution. The aluminosilicate precursor applied for these tests was

the B2 precursor. The preparation of the lightweight geopolymers was based on the optimum synthetic

parameters of the B2 reference geopolymers: [Si]/Na2O = 1.60, Na/Al = 1.3, T = 80oC and t = 48 h. Table 6.5

shows the incorporation range of lightweight agents into the geopolymer matrix tested in the GI project.

Table 6.5 Incorporation range of the applied lightweight agents

Agent Incorporation Range (% per brick weight)

EPS 1.0 – 3.0

XPS 3.0 – 4.5

PU 1.0 – 6.0

Figure 6.4 presents the effect of CDW EPS incorporation on the compressive strength and density of the

geopolymers. As it was expected, the incorporation of expanded polystyrene in the geopolymeric matrix

favors the production of lightweight materials by reducing their density. However, this reduction is

accompanied with a more intense decrease of the compressive strength values. For example, the addition

of 3% wt. of EPS lowers the density by 47%, with the reduction of strength being much higher (86%).

Despite the low percentage of expanded polystyrene, its volume fraction in the geopolymer is high (~ 75%)

and the dilution of binding matrix causes severe decrease in compressive strength. The lightweight

geopolymer containing 3% wt. EPS exhibits 7.6 MPa and 1.04 g/cm3 of compressive strength and density,

respectively.

Figure 6.4 Compressive strength and density of geopolymers containing EPS

37.3

19.5

15.0

7.6

2.12

1.49

1.25

1.04

0.0

0.5

1.0

1.5

2.0

2.5

0

10

20

30

40

50

0 1 2 3

Ap

p.

den

sit

y (

g/c

m3)

Co

mp

. str

. (M

Pa)

EPS (% wt.)

Compr. Str. (MPa)

App. Density (g/cm3)



In the case of CDW XPS geopolymers, slightly higher amounts of lightweight material are needed to achieve

similar density values as with EPS. However, satisfactory values of mechanical strength are obtained. Figure

6.5 presents the dependence of compressive strength and density by the incorporation of XPS.

Figure 6.5 Compressive strength and density of geopolymers containing XPS

The effect of PU Foam incorporation to the compressive strength and density of the geopolymer products is

presented in Figure 6.6. Contrary to EPS and XPS effect, the introduction of PU foam particles inside the

geopolymer matrix did not yield any considerable reduction on the final density of the products. For

example, the introduction of 6% wt. PU led to a reduction of density by only 25% when the compressive

strength was reduced by 75%. This phenomenon is possibly connected to the nature of PU material and its

processing for size reduction. The chopped particles of PU foam show a higher tendency to be compressed

during the stages of mixing and molding resulting in lower volume fractions inside the matrix in relation to

the EPS and XPS particles.

Figure 6.6 Compressive strength and density of geopolymers containing PU

37.3

10.18.1 6.6

2.12

1.41

1.301.16

0.0

0.5

1.0

1.5

2.0

2.5

0

10

20

30

40

50

0.0 3.0 3.5 4.0

Ap

p.

den

sit

y (

g/c

m3)

Co

mp

. str

. (M

Pa)

XPS (% wt.)

Compr. Str. (MPa)App. Density (g/cm3)

37.3 36.6

30.427.5

14.2

9.1 9.1

2.12

1.90 1.83 1.78 1.751.64 1.57

0.0

0.5

1.0

1.5

2.0

2.5

0

10

20

30

40

50

60

0 1 2 3 4 5 6

Ap

p.

Den

sit

y (

g/c

m3)

Co

mp

. str

. (M

Pa)

PU (% wt.)

Compr. Str. (MPa)App. Density (g/cm3)



The aforementioned results showed that EPS and XPS (but not PU) materials can be applied as effective

density reducing agents in the development of a lightweight geopolymer matrix with sufficient mechanical

strength. The incorporation of EPS and XPS led to the development of lightweight geopolymers with density

in the range of 1.0 – 2.0 g/cm3 and compressive strength 6.6 – 37.3 MPa. Typical specimens of 3% wt.

lightweight geopolymers developed by the incorporation of EPS, XPS and PU are shown in Figure 6.7.

a

b

c

Figure 6.7 Lightweight geopolymers containing 3% wt. EPS (a), XPS (b) and PU (c)

As mentioned before, the chemical and mineral composition of brick precursors show a wide variation due

to the variation of raw materials, production line and possible failures during the industrial processing. This

variation must be taken into account when geopolymeric products are to be developed. Figure 6.8 presents

a photo of the lightweight geopolymer (2% wt. EPS) from brick precursor B3 which exhibited expansion

issues during the geopolymerization. (This is attributed to local reductive conditions during the firing

process of the bricks which lead to the formation of metallic elements (e.g. Fe). These elements react with

the activation solution, during geopolymerization, releasing H2 gas and causing expansion of specimens.

Figure 6.8 Lightweight geopolymer showing expansion



7 Waste Glass Activation Solution

In the GI project we explore the feasibility of using waste glass as a potential alkaline activator for the

geopolymer matrix development instead of the traditional chemical reagents and thus maximizing the CDW

content of the geopolymer layer and lowering the cost of its production.

The waste glass utilized for the preparation of sodium silicate solutions was supplied by NRGIA. The glass

was crushed, ground and sieved to obtain a fineness < 56 μm prior to its use. The chemical composition of

glass was evaluated by XRF analysis (4.2.1 Chemical characterization).

The dissolution process was carried out by hydrothermal treatment of the waste glass powder in sodium

hydroxide solutions. The variables studied to determine the solubility of the waste glass in highly alkaline

media were: (a) the alkalinity of the sodium hydroxide solution expressed as (a) the molar ratio of

NaOH/SiO2, (b) the water content expressed as the molar ratio of H2O/SiO2, and (c) the conditions

(temperature, time and pressure) of the waste glass hydrothermal processing. Table 7.1 presents the trials

performed in order to achieve the maximum glass conversion. The selection of the ranges of the

parameters was based on previous studies on glass dissolution [10-12].

At the end of each test, filtration, washing and separation of the liquid and solid phases were carried out. A

sodium silicate rich liquid phase and a solid phase containing a mixture of a new phase essentially

composed of calcium silicate and particles of unreacted glass were always obtained. Then, the liquid phases

were analyzed for their SiO2 and Na2O contents by ICP-OES. The solid residues were characterized by XRD

while their SiO2, CaO, Na2O, MgO and Al2O3 content was measured through XRF analysis. The flow sheet of

glass hydrothermal treatment and characterization is presented in Figure 7.1.

Table 7.1 Trials performed to produce water glass solutions

Sample NaOH/SiO2 H2O/SiO2 T(oC) t(h) P (atm)

G1 1 23 150 24 1

G2 2 23 150 24 1

G3 4 23 150 24 1

G4 4 23 100 24 1

G5 2 23 150 24 20

G6 4 23 150 24 30

G7 4 23 200 24 20

G8 4 23 150 8 30

G9 1 9 150 48 1

G10 1 23 150 96 1

G11 0 23 200 24 40



Figure 7.1 Flow sheet of the waste glass treatment

The results obtained from the alkaline treatment of waste glass are presented in Table 7.2. In particular,

the Table shows the Si and Na quantities measured in the liquid products by ICP-OES, the SiO2/Na2O molar

ratio of the liquid products as well as the conversion yield defined as the molar fraction of SiO2 and Na2O

sum in liquid products to the SiO2 and Na2O sum in the initial mixtures ((SiO2+Na2O)liquid/(SiO2+Na2O)initial).

Table 7.2 Results of the hydrothermal treatment trials

Sample Si

(mg) Na (mg)

SiO2 (mole) Na2O (mole) SiO2/Na2O

(liquid)

Conversion

Yield

(%) Initial Liquid Initial Liquid

G1 1869.0 5492.8 0.2029 0.0665 0.1418 0.1195 0.56 54%

G2 2480.0 5922.5 0.1220 0.0883 0.1446 0.1288 0.69 81%

G3 3970.0 17250.0 0.2447 0.1413 0.5309 0.3752 0.38 67%

G4 1467.5 10925.0 0.1220 0.0522 0.2655 0.2376 0.22 75%

G5 1202.5 5807.5 0.1220 0.0428 0.1446 0.1263 0.34 63%

G6 1052.0 9246.0 0.1220 0.0375 0.2655 0.2011 0.19 62%

G7 1189.5 10677.8 0.1220 0.0423 0.2655 0.2322 0.18 71%

G8 1305.0 10867.5 0.1220 0.0465 0.2655 0.2364 0.20 73%

G9 560.3 3892.6 0.2029 0.0199 0.1418 0.0847 0.24 30%

G10 2241.8 5844.3 0.2029 0.0798 0.1418 0.1271 0.63 60%

G11 88.5 241.5 0.1220 0.0032 0.0237 0.0053 0.60 6%

The results obtained by the performed trials showed that the treatment of waste glass using the following

parameters (G2 sample): NaOH/SiO2 = 2, H2O/SiO2 = 23, T = 150oC, t = 24 h and P = 1 atm maximizes the

glass conversion to silicate solution. In particular, 81% of solid SiO2 and Na2O in glass is dissolved. The

resulting liquid phase is a sodium silicate rich aqueous product with a SiO2/Na2O molar ratio close to 0.7.

The application of this silicate solution as the activation solution of the geopolymer synthesis (optimum

conditions: SiO2/Na2O = 1.0, Na/Al = 1.0) increases the CDW content of the geopolymer product from 82%

to 88% wt. It must be noted that, the highest amount of CDW that can be achieved in the geopolymer



synthesis is 91% wt. since the introduction of NaOH in the starting solution is essential for the evolution of

the geopolymerization reactions as well as the conversion of waste glass to sodium silicate solutions.

The solid residues of the glass treatment were characterized by XRD. Figure 7.2 presents the XRD patterns

of selected solid residues. In any case, the residues contain a mixture of calcium silicates and quartz from

unreacted glass particles.

Figure 7.2 XRD patterns of waste glass and selected solid residues

In conclusion, a process was developed and optimized for the conversion of waste glass into water glass

that can be applied as the activation solution of the geopolymer synthesis (Figure 7.3). The highest

conversion rate of glass to water glass was found to be close to 81% wt.

Figure 7.3 Optimized processing of CDW glass

10 15 20 25 30 35 40 45 50 55 60 65 70

Inte

nsit

y (

arb

.un

its)

2θ (ο)

1

11

1

1 1

Glass

1

2

3 111

G5

G4

G6

1: Calcium Silicates,2: Quartz, 3:Sodium Calcium Silicate

1

12 2



8 Conclusions

The main target of the Deliverable 6.1 is to identify the most promising CDW materials that can be applied

as precursors for the successful development of the geopolymer matrix. In particular, six different CDW

materials (tiles, bricks, EPS, XPS, PU and glass) were tested and four of them (bricks, EPS, XPS, glass) are

found to be suitable for the development of lightweight geopolymer construction elements. All these

materials were characterized and appropriately processed to meet the requirements of geopolymer

synthesis.

CDW bricks and tiles were selected as the aluminosilicate precursors since they are abundant CDW

materials and possess high SiO2 and Al2O3 content crucial for the geopolymerization reactions. Brick-based

geopolymers exhibit three times higher compressive strength than tile-based geopolymers and therefore

bricks are the raw material of choice for the development of the geopolymeric panel layer.

Four different batches of CDW bricks were tested and all of them showed satisfactory, however varied

geopolymerization potential. It was decided to develop a fast and reliable method to optimize the

geopolymerization conditions of each batch, taking into account its own chemical and mineral composition.

This was carried out on Task 6.2 and the results will be presented on Deliverable 6.2 (Final Geopolymer

Layer) and the achievement of Milestone 7 (Prototype of Geopolymer Matrix from CDWs).

The incorporation of CDW based lightweight agents was tested for the delivery of a lightweight geopolymer

matrix. The incorporation of EPS or XPS (but not PU) in geopolymers leads to considerable reduction of the

final density, lowering also the mechanical strength of the final products. Lightweight geopolymers with

density in the range 1.0 – 2.0 g/cm3 and compressive strength 6.6 – 37.3 MPa were prepared.

A hydrothermal processing for the conversion of glass into water glass that can be used as the activation

solution, was developed and optimized. This processing involves the grinding of waste glass, its dissolution

in alkaline media (Glass/NaOH = 1.1 and H2O/NaOH = 5.2) at 150oC for 24h, the filtration and the

condensation of the liquid part. The highest conversion rate of glass to water glass was found to be close to

81% wt.

In conclusion, bricks, EPS or XPS glass from CDWs can be valorized through their transformation to

geopolymers that can serve as the structural layer in the GI panel. The content of CDWs in this geopolymer

is 88% by mass.



9 References

1. Duxson, P., Fernandez-Jimenez, A., Provis, J.L., Lukey, G.C., Palomo, A., van Deventer, J.S.J.:

Geopolymer technology: the current state of the art. J. Mater. Sci. 42, 2917–2933 (2007)

2. Komnitsas, K., Zaharaki, D., Vlachou, A., Bartzas, G., Galetakis, M.: Effect of synthesis parameters on

the quality of construction and demolition wastes (CDW) geopolymers. Adv. Powder Technol. 26(2),

368–376 (2015)

3. Allahverdi, A., Najafi Kani, E.: Construction Wastes as Raw Materials for Geopolymer Binders. Inter.

J. Civ. Eng. 7(3), 154-160 (2009)

4. Pathak, A., Kumar, S., Vinay Kumar Jh.: Development of Building Material from Geopolymerization

of Construction and Demolition Waste (CDW). Trans. Ind. Ceram. Soc. 7(3), 133-137 (2014)

5. Panagiotopoulou, Ch., Kontori, E., Perraki, Th., Kakali, G.: Dissolution of aluminosilicate minerals

and by-products in alkaline media. J. Mater. Sci. 42(9), 2967–2973 (2007)

6. Hu, X.U., Van Deventer, J.S.J.: The geopolymerisation of alumino-silicate minerals. Int. J. Miner.

Process. 59(3), 247-266 (2000)

7. Panagiotopoulou, Ch., Tsivilis, S., Kakali, G.: Application of the Taguchi approach for the

composition optimization of alkali activated fly ash binders. Constr. Build. Mater. 91, 17-22 (2015)

8. Oikonomou, N.D.: Recycled concrete aggregates. Cem. Concr. Compos. 27(2), 315–318 (2005)

9. Duxson, P., Mallicoat, S.W., Lukey, G.C., Kriven, W.M., van Deventer J.S.J.: The effect of alkali and

Si/Al ratio on the development of mechanical properties of metakaolin-based geopolymers. Coll.

Surf. A: Physicochem Eng. Asp. 292(1), 8–20 (2007)

10. Keawthun, M., Krachodnok, S., Chaisena, A.: Conversion of waste glasses into sodium silicate

solutions. Int. J. Chem. Sci. 12(1), 83-91(2014)

11. Torres-Carrasco, M., Palomo, J.G., Puertas, F.: Sodium silicate solutions from dissolution of glass

wastes. Statistical analysis Mater. Constr. 64(314), 1-14(2014)

12. Puertas, F., Torres-Carrasco, M.: Use of glass waste as an activator in the preparation of alkali-

activated slag. Mechanical strength and paste characterization. Cement Concr. Res. 57, 95-

104(2014)



10 Acknowledgment

This project has received funding from the European

Union’s Horizon 2020 research and innovation

programme under grant agreement No 723825.

Disclaimer

The Horizon 2020 project has been made possible by a financial contribution by the European Commission

under Horizon 2020 research and innovation programme. The publication as provided reflects only the

author’s view. Every effort has been made to ensure complete and accurate information concerning this

document. However, the author(s) and members of the consortium cannot be held legally responsible for

any mistake in printing or faulty instructions. The authors and consortium members reserve the right not to

be responsible for the topicality, correctness, completeness or quality of the information provided. Liability

claims regarding damage caused by the use of any information provided, including any kind of information

that is incomplete or incorrect, will therefore be rejected. The information contained in this document is

based on the author’s experience and on information received from the project partners.

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