W. £ASICA et al.: CHARACTERIZATION OF RECYCLED GLASS-CEMENT COMPOSITE MECHANICAL STRENGTH
473–477
CHARACTERIZATION OF RECYCLED GLASS-CEMENT
COMPOSITE: MECHANICAL STRENGTH
KARAKTERIZACIJA KOMPOZITA, IZDELANEGA IZ
RECIKLIRANEGA STEKLA IN CEMENTA: MEHANSKA TRDNOST
Waldemar £asica, Marcin Ma³ek
*
, Zbigniew Szczeœniak, Mariusz Owczarek
Military University of Technology in Warsaw, Faculty of Civil Engineering and Geodesy, 2 gen. Sylwestra Kaliskiego, 00-908 Warsaw, Poland
Prejem rokopisa – received: 2019-07-15; sprejem za objavo – accepted for publication: 2020-02-27
doi:10.17222/mit.2019.152
The presented work summarizes the results for the mechanical strength of a recycled glass-cement composite. The composite
material was fabricated using Portland cement CEM I 52.5 N. As the aggregate, 100-% recycled glass bottles were added. The
novelty of the research was to fabricate a cement composite using only recycled glass as the aggregate. This type of glass has
many imperfections in its structure. In addition, it also contains elements used as fluxes that chemically pollute the glass. Due to
this, the described glass is very difficult to recycle and requires many pre-trial procedures before the recycling process. The final
recipe was prepared with the experimental-laboratory method, using the following aggregates: 0/2 mm of glass bottles,
0/0.2 mm of glass flour, a deflocculant based on polyacrylate and a hydrophobic additive based on surfactants. In this work,
three kinds of recycled glass-cement composite were compared (the reference one, a composite with a zeolite addition and a
composite with a fly-ash addition to the matrix). The main purpose of this research was to increase the use of difficult-to-recycle
materials such as bottle glass and fly ash in industry. After 28 days of curing, the mechanical properties including the
compressive strength, bending strength and tensile strength were widely investigated. Light micrographs of the additives were
characterized. Additionally, the thermal properties were measured. The used glass aggregates increased the mechanical strength
and thermal properties of the fabricated composites. These kinds of composites are very suitable for future applications in civil
engineering in special-building construction.
Keywords: concrete strength, recycled glass, glass-cement composite, mechanical strength
V pri~ujo~em prispevku avtorji podajajo povzetek rezultatov preiskav mehanske trdnosti kompozita, sestavljenega iz
recikliranega stekla in cementa. Kompozitni material je bil izdelan z uporabo portlandskega cementa CEM I 52,5 N. Kot agregat
so bile uporabljene samo reciklirane steklenice. Novost raziskave je v tem, da so avtorji za izdelavo steklo-cementnega kom-
pozita, kot agregata uporabili samo reciklirano steklo. Ta vrsta stekla ima mnogo napak v svoji strukturi. [e dodatno, tak{no
steklo vsebuje razli~ne vrste elementov iz talil, ki onesna`ujejo steklo. Zato je tak{no steklo zelo te`ko reciklirati, saj je
potrebno pred recikla`o izvesti ve~ preizkusov oz. predhodnih postopkov. Kon~ni recept za izdelavo kompozita so avtorji izra~u-
nali z uporabo eksperimentalnih laboratorijskih metod z vklju~itvijo: stekleni~nega drobirja velikosti do 2 mm, fluoridnega
stekla velikosti do 0,2 mm, deflokulanta (antipenilca) na osnovi poliakrilata in povr{insko aktivnih snovi, ki odbijajo vodo
(hidrofobnega dodatka na osnovi surfaktantov). V raziskavi so primerjali tri vrste izdelanih kompozitov steklo-cement s
kompozitom, ki je kot matrico vseboval zeolit z dodatkom dimni{kega pepela. Glavni namen raziskave je bil dolo~iti, kako v
industriji pove~ati uporabo trdih recikliranih materialov, kot so steklenice in dimni{ki pepel. Po 28-tih dneh su{enja, so avtorji
dolo~ili mehanske lastnosti (tla~no, upogibno in natezno trdnost) izdelanih kompozitov. Dodatno so kompozite pregledali s
svetlobnim mikroskopom in dolo~ili njihove termi~ne lastnosti. Uporabljeni stekleni agregati so pove~ali mehansko trdnost in
izbolj{ali termi~ne lastnosti izdelanih kompozitov. Ta vrsta kompozitov ima veliko mo`nosti, da bodo v prihodnje uporabljeni v
gradbeni{tvu, {e posebej za specialne gradbene konstrukcije.
Klju~ne besede: trdnost betona, reciklirano steklo, kompozit steklo-cement, mehanska trdnost
1 INTRODUCTION
Granulated glass together with ground sand may be a
partial substitute for the cement binder in an amount of
up to 15 % in relation to the planned amount of cement
in a concrete mix. Glass powder affects the strength of
concrete, not only after 28 days in relation to the re-
ference concrete, but also in the later period of concrete
maturation.
1–6
Designing ecological, self-compacting concrete pro-
vided for a new possibility of introducing waste-glass
powder into the composition of a composite. Glass pow-
der has been used in SCC (self-compacting concrete)
types that do not require additional mechanical compac-
tion, reducing the costs of the technology for concrete
and reinforced-concrete structures. Glass powder im-
proves the rheological properties of a fresh concrete mix,
allowing excellent workability – the ability to accurately
fill in the moulds and frameworks without the use of
thickening devices. Experimental studies have proved the
possibility of using a larger range of plasticizers compa-
tible with glass powder.
7–12
The use of glass waste in transparent and photo-
catalytic concrete leads to the construction of innovative
composites that purify the air of oxides and nitrogen
oxides. The literature demonstrates the influences of
purified and impurified glass in the structure of such
concrete on its photocatalytic capabilities.
13–15
Materiali in tehnologije / Materials and technology 54 (2020) 4, 473–477 473
UDK 620.1:625.843:620.17 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 54(4)473(2020)
*Corresponding author's e-mail:
marcin.malek@wat.edu.pl (Marcin Ma³ek)

The development of an ultra-high-speed composite
using glass powder is a new trend towards eco-concrete
with a compressive strength of over 220 MPa. Glass in
the powder form, more precisely, glass dust, affects the
mechanical and microstructural properties of concrete.
The concrete of this type was defined as UHPGC
(ultra-high-performance glass composite). The UHPGC
concrete has technological, economic and environmental
advantages compared to the ultra-resistant UHPC
concrete. The UHPGC concrete is more ecological due
to the reduction in the amount of cement in the compo-
sition of concrete.
16–20
2 EXPERIMENTAL PART
Portland CEM I 52.5 N white and CEM I 52.5 R grey
cements were used to make all the samples (low-alkaline
cements with a low chloride content). In addition, an
acrylate-based water-reducing agent was used. Three
recipes were prepared: the reference sample, based on
the glass aggregate, with a zeolite addition of 13.5 w/%
(Recipe 2) and with a fly-ash addition of 13.5 w/%
(Recipe 3) to improve the workability of the composite
and make it possible to include additional waste ma-
terials. All tests and sample preparations were performed
in accordance with the applicable European standards for
concrete.
2.1 A mixture of cement and glass
The cement-and-glass composite consistency test was
performed with the drop-cone method.
The pH value was tested using a pH meter with a
probe used for suspensions at 21 °C and 50-% humidity.
For the measurement, we used a high chemical glass
reactor, which was filled with a sample of a fresh
mixture of cement and glass. The sample of the mixture
was dissolved in water in a ratio of 1:2.5 (the ratio of the
mixture to water: 250 g of water and 100 g of the mix-
ture). In order to obtain a homogenous suspension, the
amount of glass was mixed with water using a magnetic
stirrer with high rotations.
An analysis of the air-pore amount was made using
the pressure method. Determination of the amount of air
pores in a sample of a fresh mix of cement and glass was
made using an 8-litre porosimeter.
2.2 Cement-glass composite after 28 days of matu-
ration
The strength of cement-and-glass samples was deter-
mined with three-point bending, compression and tensile
tests. For this purpose, standard samples were used. A
strength machine was used for the strength tests. The
transverse speed was set at 5 mm/minute. The values of
Young modulus and Poisson’s ratio were also deter-
mined.
Research was carried out in the field of determining
the basic thermal parameters. The individual thermal
parameters, i.e., the values of thermal conductivity
coefficient  , specific heat per unit of volume c
pv
and
thermal diffusivity were measured with an ISOMET
2114 meter. The density  of the material was also
measured, using precision weight and volume measure-
ments.
In addition, after the mechanical tests, the samples
were subjected to surface-structure studies in order to
determine the correctness of the choice of the vibration
time and mixing. For this purpose, an Opta-Tech trans-
mission-reflection microscope was used.
3 RESULTS AND DISCUSSIONS
The obtained samples and recycled glass aggregate
are shown in Figure 1.
In the photographs below, it can be observed that the
glass grains are sharp-edged. There are several fractions
of powder, which were subjected to a mechanical
breakage before the calculation of the recipe and then
sifted using an automatic sift device. This allowed us to
separate the fractions in the form of glass flour from the
0–2 mm aggregates.
The surface of the produced cement-glass composite,
i.e., its cross-section does not bear any signs of poorly
selected vibration time and mixing time. The particles
are evenly distributed and do not form aggregates (agglo-
merates). No places are observed where the cement is
W. £ASICA et al.: CHARACTERIZATION OF RECYCLED GLASS-CEMENT COMPOSITE MECHANICAL STRENGTH
474 Materiali in tehnologije / Materials and technology 54 (2020) 4, 473–477
Figure 1: a) Recycled-glass surface and b) cross-section of obtained
glass-cement composite

W. £ASICA et al.: CHARACTERIZATION OF RECYCLED GLASS-CEMENT COMPOSITE MECHANICAL STRENGTH
Materiali in tehnologije / Materials and technology 54 (2020) 4, 473–477 475
Figure 3: Mechanical-strength comparison for investigated glass-cement composites (A – bending strength, B – tensile strength, C – compressive
strength, D – Poisson’s ratio,E–Y oung’s modulus)
Figure 2: Basic properties of mortars (A – poresB–av erage values of the slump test,C–pHv alues)

not bonded. This is a sign of a well-prepared sample,
which undoubtedly has a large impact on the final pro-
perties of the prepared glass-cement composite.
The basic parameters such as the pore amount, slump
test and pH value compared for the investigated glass-
cement composite samples are presented in Figure 2.
The above graphs show that Recipe 2 with the addi-
tion of zeolite is characterized by the highest pH value
(12.66) and a drop of the Abrams cone to the level above
50 mm. This is evidenced by the fact that this sample
represents the S2 consistency. The remaining products
are characterized by the S1 consistency. The highest pore
content is shown by the reference-recipe sample amount-
ing to 4 %.
Mechanical-strength comparisons involving the
bending strength, tensile strength, compressive strength,
Poisson’s ratio and Young’s modulus are shown in Fig-
ure 3.
According to the following graphs, the Recipe 1 sam-
ple shows the highest mechanical resistance among all
the cement-glass composites produced. Because 13.5 %
of zeolite was used for its production, it allowed for its
better sealing, thus increasing the resistance to compres-
sion, bending and stretching during splitting. The addi-
tion of fly ash, in the Recipe 2 sample, also increased the
strength of the obtained concrete. In the reference
sample, in which the glass flour was used as its smallest
fraction, the same strength as the designed one was
observed. Both the Poisson’s ratio and Young’s modulus
confirm this relationship. The produced samples were
characterized by the strength class: C50/60, C80/95 and
C60/75, respectively.
The results of the thermal tests, i.e., the density, ther-
mal conductivity, heat capacity and thermal diffusivity,
for the samples of the cement-glass composite are
presented in Table 1.
Table 1: Thermal properties of investigated samples
No. Recipe
Density
(kg/m
3
)
Thermal
conductivity
(W/(mK))
Heat
capacity
(J/(kgK)
Thermal
diffusivity
(m
2
/s)
1 Reference 2304 1.11 727 6.63 e-7
2 Recipe 1 2095 0.98 745 6.54 e-7
3 Recipe 2 2057 0.97 760 6.30 e-7
4
Normal
quartz-
sand-based
concrete
2400 2.35 705 1.39 e-6
Reduced values of the thermal-conduction coefficient
depended mainly on the glass aggregate and glass flour
used. Comparing the cement-glass composite to the
sand-gravel concrete, the value of the thermal-conduc-
tion coefficient decreased 2.4 times. The smallest value
of this coefficient was obtained for the samples made in
accordance with Recipe 2 containing fly ash from a
power plant in its structure. All the tested samples exhib-
ited much lower thermal properties, putting the concrete
made in this was in a very advantageous position with
respect to the current EU environmental requirements.
4 CONCLUSIONS
Due to one of the most demanding methods of con-
crete design, the iterative method, the strength designed
at the C50/60 level is the highest strength obtained with
this method, requiring a very well selected detrital
composition of the mixture. Bottle soda glass, obtained
entirely from recycled glass bottles, which are not pro-
cessed due to unwanted elements in their structures, was
used. However, this material met the requirements and
allowed us to obtain very high classes of concrete
strength. The grinding-and-sifting process is time-con-
suming, but with the use of the smallest fraction of other
than the glass flour, it was proven that in addition to the
recycled glass, additions of zeolite and fly ash also
provide for an increase in the concrete strength by two
and one class, respectively, creating an opportunity for
even more waste to be included in the concrete structure.
Granulated glass, the recycled material of soda glass
(a post-consumer material), resulting from the process-
ing of cullet, can be an alternative substitute for natural
or broken rock aggregates used for concrete and other
composites based on the cement binder.
In terms of heat, the mixture was compared with the
standard sand and gravel concrete. A lower conductivity
was obtained, thus a better thermal insulation and a
lower density. The specific heat, in comparison with
concrete, increased; however, we cannot say that we
obtained accumulative properties. The decrease in the
thermal-conduction coefficient was affected by the
absence of the traditional aggregate. On this basis, it can
be deduced that the aggregate is the basic component
responsible for the thermal conductivity of concrete. The
mixtures obtained constitute a good base for future
activities towards increasing the thermal accumulation.
After a series of endurance tests performed in the
field of static loads, we plan further research on large
beam elements reinforced with composite rods of the
FRP type and studies of the dynamic impact and ex-
plosive loads applied to structural elements.
Acknowledgment
The financial support from the Research Statutory
Program financed by the Military University of
Technology, Faculty of Civil Engineering and Geodesy,
called "Research of materials and construction elements
of military infrastructure special objects", No. 886/2019,
is gratefully acknowledged.
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