Improving the strength of concrete

IMPROVING THE STRENGTH OF
CONCRETE USING GLASS POWDER
Edson Jansen Pedrosa de Miranda Júnior, Helton de Jesus Costa Leite Bezerra, Flávio Salgado Politi and Antônio Ernandes Macêdo Paiva (2014)

ABSTRACT
This research analyzes the compressive strength of Portland
cement concrete in response to the incorporation of 5%, 10%, and
20% flat glass powder instead of sand, with w/c (water/cement)
ratios of 0.50, 0.55, and 0.58. Statistical analysis of variance
(ANOVA) was performed after 7, 14, and 28 days of treatment. The
compressive strength test results indicate that concrete with a w/c
ratio of 0.50 can be used for structural applications, regardless of
the glass waste content, as is the case with a 0.55 w/c ratio
containing 20% glass waste. We suggest that using flat glass
powder instead of sand in the above proportions is possible to
produce environmentally suitable and structurally applicable
concrete. However, the fluidity of the concrete and the void content
must be taken into account.

OBJECTIVES
The purpose of this study is to analyze the effect of
partial substitution of natural fine aggregates for flat
glass powder on the compressive strength of Portland
cement concrete. One difference in this research was
the use of flat glass powder. This is the first study to
focus on the application of this type of glass waste as
fine aggregate in Portland cement concrete.

INTRODUCTION
The use of glass as a fine aggregate material in
Portland cement concrete has been studied and
some countries are currently using this material.
Australia, for example, uses waste glass in
concrete for civil construction. Recommendations
for the use of this material have been made
concretely in New York State.
The main focus of the research has been the use
of glass waste in place of cement and, in a few
cases, as fine and coarse aggregates for concrete.
Only a few studies have focused on the use of
glass waste as fine aggregate in concrete for
structural purposes.

MATERIALS
EXPERIMENTAL MATERIALS
Washed river sand was used as fine
aggregate and crushed stone as
coarse aggregate.
The waste glass was supplied by a tempered
glass manufacturer (Marvite), and it came
from the process of grinding and polishing flat
glass before the tempering process of glass.
Portland cement used was pozzolanic CP IV-
32 RS; Because the concrete made from it is
less permeable and especially because it
reduces the alkaline silica reaction (ASR).

METHODS
First, waste glass was ground and oven-dried at 110 ° C. Then, the waste
glass was characterized by particle size distribution, X-ray diffraction (XRD),
and energy-dispersive X-ray spectroscopy (EDXRF).
The concrete was prepared using a mixture of 1: 1.57: 1.935: w/c ratio,
(cement: sand: crushed stone: water/cement ratio). Note that no additive was
used to homogenize the mixture. Glass waste ratios of 5%, 10%, and 20%
were used instead of sand, and weight ratios of 0.50, 0.55, and 0.58 were
used in the preparation of concrete.
Cylindrical (10 cm x 20 cm) test specimens were molded and processed.
Samples were manually collected in two layers, with 15 rammer strokes
applied to each layer of concrete. The test samples were first cured for 24 h in
the molds at an ambient temperature of 28.5 ° C. Then they were released
from the molds and immersed in water at 26.5 ° C for treatment for 7, 14, and
28 days.
The compressive strength test was applied to test samples of cast concrete
containing ratios of three w/c and 3 percentages of glass waste instead of
sand, which were treated for 7, 14, and 28 days. An unbound polychloroprene
elastomer (commercially known as neoprene) with a hardness of 70 Shore A
was used in the test samples instead of caulking.
The compressive strength tests were performed in an Emic DL30000N
universal test machine with a load capacity of 300 kN, with loading applied at
a constant rate of 0.5 MPa / s.

RESULTS
Figure 1 compares the particle size distribution of sand and glass waste. The residue rate of crushed glass (material finer than
0.075 mm) was 6.74%. This percentage is more than double that obtained for fine aggregates, which was 3.15%. A high
percentage of fine glass waste may cause increased water absorption, which impairs cement hydration.
Since the coefficient of clarity of the glass is higher than that of fine aggregate, its particles are larger, which is confirmed by the
predominance of glass particle sizes from 300 μm to 4.74 mm. Note that glass waste accounts for fewer materials that pass
through sieves with holes of 300 μm and 600 μm compared to sand.
Tables 1 and 2 describe the results of the chemical analysis of glass and cement waste
by EDXRF. As can be seen, Si and Ca predominate as the two most abundant elements.

Figures 3, 4, 5, 6, 7, and 8 show the effect of glass percentage and w/c ratio on concrete
compressive strength in each of the three processing periods. As can be seen from these figures,
the mentioned variables significantly affected the compressive strength of the concrete at each of
the treatment ages analyzed, although the variable w/c ratio exerted the greatest influence.

DISCUSSION
Increasing the ratio of glass instead of sand increased compressive strength, regardless of
processing life, with w/c ratios of 0.55 and 0.58. This behavior is attributed to the reduction
of the void ratio due to the potential improvement in the particle size distribution of waste
glass, natural fine aggregates, and pozzolanic activity of waste glass. Glass waste can act
as pozzolanic material, interacting with portlandite, resulting in C-S-H formation, which
reduces voids in concrete.
However, increasing the waste glass content of the prepared concrete with a w/c ratio of
0.50 reduces the compressive strength, although the compressive strength increases with
the lost glass content from 0% to 5%, and this behavior is attributed to the poor fluidity of
concrete containing 10% and 20 % Of glass waste and a w/c ratio of 0.50, resulting in an
increase in the percentage of void in the concrete. When the amount of glass and the size
of the glass particles increases, more water is needed for the mixture to maintain certain
workability, resulting in less compressive strength.
The graphs in Figures 3, 4, 5, 6, 7, and 8 also show other predicted behaviors, such as
increased compressive strength as a function of increasing processing life and reducing the
w/c ratio.
Concrete exhibits moderate compressive strength making it suitable for construction
applications in civil construction when prepared with a 0.50 w/c ratio, regardless of the
waste glass percentage, 0.55 w/c ratio, and 20% waste glass content.
1
4
2
3

CONCLUSION
In this study, it was found that the compressive strength of Portland
cement concrete increases in response to the use of flat glass waste
powder, which has not yet been used as a fine aggregate. Concrete
with flat glass powder was found to be suitable for construction
applications when prepared with a w/c ratio of 0.55, a waste glass
content of 20%, and a w/c ratio of 0.50, regardless of the
percentage of glass used. A w/c ratio of 0.50 showed the best
potential when sand was replaced with waste glass.
Results of ANOVA analysis confirmed the significant effect of w/c
ratio and waste glass ratio on compressive strength of concrete
treated for 7, 14, and 28 days. Additionally, it was found that the
compressive strength of concrete is affected by the w/c ratio more
than that of glass wasted in sand replacement. The formation of
new phases was not revealed in the XRD diffraction results.
The presented results indicate the promising potential of using flat
glass powder as a fine aggregate in Portland cement concrete to
produce environmentally friendly and structurally applicable
concrete. However, the limitations regarding the fluidity of the
concrete and the void content must be analyzed in future studies.

Improving the strength of concrete

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