ANALYSIS OF THE PHYSICAL-MECHANICAL CONCRETE PROPERTIES
WHEN CONCRETE WASTE ADDITIVES ARE USED IN THE MIXTURES
Olga Finoženok1, Ramunė Žurauskienė2 Rimvydas Žurauskas3
1
Vilnius Gediminas technical university, Saulėtekio ave. 11, LT-10223 Vilnius, Lithuania.
E-mail: 1olga.finozenok@vgtu.lt; 2 ramune.zurauskiene@vgtu.lt 3 rimvydas.zurauskas@vgtu.lt
Abstract. Most often construction waste in Lithuania is used for road construction. 78 % of construction waste consists of concrete waste, bricks and tiles. Concrete waste can be used for the production of higher quality products, and
this waste can be returned to the production technological cycle. In the research the variation of the properties of concrete samples is analysed when concrete waste aggregates are used. Concrete waste with various fractions was used
as coarse aggregate in the research, as well as filler aggregates from the crushed concrete waste were used. Physicalmechanical properties of the samples were analysed by comparing with reference samples where typical aggregates
were used. Sectional analysis of the samples, produced by using coarse aggregates from concrete waste, is carried out
during the research and covering areas of every integrated phase are calculated.
Keywords: normal weight concrete, demolition waste, concrete waste, recycled aggregate, filler aggregate.
However, researchers also provide the recommendations
to carry out investigations in every country and determine
the conditions for the utilisation of crushed concrete
waste to produce new products, because in a particular
country products are affected by different climatic conditions.
In Lithuania most often construction waste is used
for road construction, as secondary breakstone. The composition of this waste depends on the type of building to
be demolished and demolishing technologies implemented. When buildings are demolished after they wear
out morally and constructively, demolition waste consists
of the following materials: concrete, wood, metal, plaster
boards, oils, chemical materials and roof coverings (78 %
of waste is composed of concrete waste, bricks and tiling
(Uselytė et al. 2007)). When buildings that are in construction phase are demolished, demolition waste consists
of concrete and metals. Currently, in Lithuania the
amount of second type buildings (not exploited) is the
same as the amount of first type buildings. These not
exploited buildings are skeleton constructions of public
purpose, their construction works were not completed due
to various reasons and they are demolished (Figure 1).
Demolition works consist of the following technological
operations: crushing, sorting, metal separation, initial
sieving, milling, metals separation, sieving.
In Europe, 1/3 of secondary breakstone is produced
in the stationary systems at especially equipped sites and
2/3 is produced in mobile systems at construction sites.
Introduction
Demolition and construction waste consists of the
following waste materials: wood, concrete, bricks and
blocks, gypsum, metal, asphalt concrete, plastics, glass
and packing. The amounts of these waste materials are
different in various regions. In some regions the major
part of waste materials consists of wood waste, in other –
concrete waste. The amounts of waste materials vary
depending on the former construction traditions and on
local natural resources of these regions. Main problem of
demolition waste management is waste sorting. Only
sorted waste materials can be used for the production of
high quality products.
Over the past decade the problems of concrete waste
reprocessing problems are intensively investigated
worldwide. Reprocessing amounts of concrete and demolition waste in particular countries differ considerably.
For instance, in Taiwan (Hsiao et al. 2002), starting from
2002 to 2009 year the reprocessing of this waste had to be
increased from 50 % to 100 % in order to avoid the overload of dumps. Other researcher from Hong Kong (Tam
2009a) notes that in the overall amount of construction
and demolition waste in the region up to 70 % is concrete
waste, and the utilisation of this waste is very important.
Utilisation of crushed concrete waste is analysed
worldwide. It was determined that this waste can be used
not only as a breakstone for road construction, but also
for the production of paving-tiles (Poon and Chan 2007).
64
plied products produced from construction waste is limited to their usage for road construction. However, this
waste can be reprocessed and used for the production of
higher quality products. Based on these priorities this
research was carried out.
Following the feasibility study, prepared by “Ekokonsultacijos” UAB (Uselytė et al. 2007), over the period from
2002 and 2006 year, the reprocessing of construction
waste in Lithuania has increased 8 times and this amount
reached 50 % of overall waste. In 2007 year (Uselytė et
al. 2008) the amount of construction waste in Lithuania
was 700 thousand tonnes, and 470 thousand tonnes were
reprocessed. However, in recent years, after the slowdown of realty market and suspension of constructions of
new buildings, over 30–50 % of buildings (with uncompleted skeleton) were left non-commissioned. After the
market recovers, these buildings could be demolished,
and during the demolition huge amount of concrete and
metal waste, that is not polluted by other construction
waste, would be created.
Research materials
During the research the following raw materials
were used to prepare concrete:
Cement: limestone Portland cement CEM II/A-L
42.5 N, complying with the requirements of standard LST
EN 197-1. This cement is moderately aluminous, its
physical-mechanical properties are provided in Table 1.
Table 1. Physical-mechanical properties of the cement
Parameter
Early compressive strength after
2 days, N/mm2
Standard compressive strength after
28 days, N/mm2
Initial set, min.
Final set, min.
Specific surface, cm2/g
Specific particles’ density, g/cm3
Bulk density, g/cm3
Fig 1. Demolition
building
works
of
Value
21
47
155
288
3100
2.75
1.02
Fine aggregate: natural sand, the maximal size of
the particles thereof is smaller than 5 mm, bulk density
1.64 g/cm3, particles’ density 2.41 g/cm3, module of
coarseness 2.1.
Coarse aggregate: gravel breakstone and used
crushed concrete waste. The main characteristics of these
materials are provided in Table 2. View of crushed concrete waste is provided in Figure 2.
non-commissioned
“Lina” UAB PN can be studied as one of Lithuanian
companies, which works on the reprocessing of construction waste. In 2009 year this company put on the market
the following products, produced from construction
waste: concrete breakstone and brick-concrete breakstone
(with fractions of 0–16, 8–32, 16–45, 32–45, 0–45 mm),
as well as crushed small concrete and brick-concrete
particles of 0–5 mm fraction. These products are produced in mobile mills, with sorting line, where container
type waste is sorted. In main regions of Vilnius, Kaunas
and Klaipėda, other similar construction waste reprocessing companies carry out their activities as well.
In accordance with the directive 2008/98/EB approved at 19-11-2008 by European Parliament and Council, the following waste reprocessing targets, related to
construction waste, were determined up to 2020 year: at
least 70 % of nonhazardous construction and demolition
waste must be prepared for secondary usage and reprocessing. According to development priorities measures for
the reprocessing of secondary waste within the period of
2009-2013, the markets for the products, manufactured
from the secondary raw materials, must be established,
the support for secondary raw materials’ sorting, washing, reprocessing projects must be ensured. Creation of
high quality reprocessing capabilities and development of
existing ones must be preferred.
Considering the determined priorities, new products
produced from construction waste should be developed,
analysed and popularized. Utilisation of currently sup-
Table 2. Characteristics of coarse aggregate
Coarse
aggregate
Crushed gravel
5–20 mm
Crushed gravel
10–20 mm
Concrete waste
5–10 mm
Concrete waste
5–20 mm
Parameter and its value
Bulk density, Particles’ den- Hollowsity, g/cm3
ness, %
g/cm3
1.44
2.47
42
1.43
2.42
41
1.10
2.03
46
1.13
2.26
50
a
b
Fig 2. View of crushed concrete waste: a – 5–10 mm
fraction; b – 10–20 mm fraction
65
Table 3. Composition of concrete mixtures A, B, C and D
Concrete
marking
A
B
C
D
Cement,
kg/m³
440
440
440
405
Coarse aggregate, kg/m³
Concrete waste
Crushed gravel
–
1288
408
758
991
–
–
1288
Composition
Fine aggregate, kg/m³
356
356
556
356
Water, l/m³
189
189
189
189
Filler aggregate, kg/m³
–
–
–
35
Water /
cement ratio
0,43
0,43
0,43
0,47
were taken from each concrete batch (three batches in
total) produced at laboratory conditions.
Filler aggregate: crushed concrete waste, with particles’ size smaller than 0.125 mm, most of this aggregate
pass the sieve with the mesh size of 0.063 mm, the remaining part <10 %, according to the standard LST EN
12620:2003+A1:2008. Bulk density of the filler aggregate is 0.95 g/cm3, particles’ density 2.13 g/cm3.
Research methodology
Compressive strength of concrete samples was estimated after 28 days of hardening. Main physical and
mechanical properties were determined by applying standard methods: density of the samples was determined
according to LST EN 12390-7, compressive strength –
according to LST EN 12390-3, samples were compressed
by using hydraulic press “ALPHA 3-3000” complying
with the requirements of standard LST EN 12390-4.
Scanned view of the sample B was analysed by using image processing software. 800 dpi resolutions were
set for the scanning. Adobe Photoshop CS2 software was
used for image processing. In this software the following
phases were indicated with different colours: white –
pores, light grey – cement stone with fine aggregates,
dark grey – cement stone with fine aggregates produced
from crushed concrete waste and black – coarse aggregate produced from crushed concrete waste (rock).
X-ray diffraction analysis of the filler aggregate was
implemented by using diffraction meter DRON–2 (Cu
anode, Ni filter, monochromator, gaps 1:8:0.5 mm). Operating conditions of the pipe of diffraction meter are as
follows: U = 30 kV, I = 10 mA. The recorded diffractogram was encoded, by comparing the obtained experimental values of the interplanar distances d and relative
integral intensity I/I0 of the lines with the corresponding
values in ASTM card file.
According to the results of water absorption (after
72 h, after vacuuming) the following parameters were
calculated: effective porosity (WE, %), total open porosity
(WR, %), reserve of pore volume (R, %), degree of structural inhomogeneity (N), and capillary rate of mass flow
at normal conditions (g, g/cm2), capillary rate of mass
flow in vacuum towards freezing direction (G1, g/cm2)
and capillary rate of mass flow in vacuum perpendicular
to freezing direction (G2, g/cm2) (Mačiulaitis 1996). Considering these structural parameters, the forecasted exploitation frost resistance (after the beginning of fragmentation, in cycles) was calculated.
Compositions of the mixture analysed
During the research 4 concrete mixtures with the
markings A, B, C, D were prepared. Concrete composition was estimated in accordance with the characteristics
of raw materials by applying volume method used most
often and described in the literature. Compositions of
concrete mixtures are provided in Table 3. The selected
compressive strength class of the concrete is C30/37,
slumping factor – 3 cm.
Coarse aggregates with 5–20 mm particles’ size
were used in the research. Only in first and fourth concrete mixtures (A and D) crushed gravel was used as
coarse aggregate, in second (B) – mixture of crushed
gravel and crushed concrete waste, in third (C) – only
crushed concrete waste. During the preparation of the
mixture consisting of gravel breakstone and crushed concrete waste (B) the optimal ratio for the mixture fractions
was followed: when two mixture’s fractions are used and
maximal allowed diameter of the particles of coarse aggregate is 20 mm, then the amount of aggregate of 5–
10 mm fraction is 35 %, and 10–20 mm fraction – 65 %.
Concrete waste was crushed with jaw crusher and
sieved out with the laboratory sieves. The fractions belonging to coarse aggregates, fine aggregates and filler
aggregates were separated. In the research the crushed
concrete waste with the particles larger than 5 mm and
concrete waste particles, belonging to the group of filler
aggregates, were used. In mixture D, 8 % of cement mass
was replaced by filler aggregate. In accordance with LST
1577:1999, the ratio between the masses of filler aggregate and CEM II A Portland cement, should not exceed
15 %. During the research half of this amount was selected to add.
All concrete mixtures were mixed manually at laboratory. The prepared concrete mixture of the required
consistence was poured into the moulds. Samples were
thickened by vibrating them on the laboratory vibrating
plate for approximately 1 min. Samples were hardened in
the moulds for 24 hours, then they were taken from the
moulds and immersed into the water with temperature of
20ºC ± 2ºC, as it is specified in LST EN 12390-2 2003. In
these conditions samples were stored until the tests of
mechanical properties. Five samples (100×100×100 mm)
Experimental results and discussions
X-ray diffraction analysis for the filler aggregate
was carried out. Figure 3 shows X-ray pattern of the filler
aggregate. From this pattern it can be noticed that the
main minerals of this raw material are as follows: quartz
Q SiO2 (0.137, 0.138, 0.154, 0.167, 0.182, 0.198, 0.213,
66
Intensity
Fig 3. X-ray pattern of filler aggregate: Q – quartz; K – calcite; D – dolomite; P – Portlandite; L – feldspars;
C – tricalcium silicate; Ž – mica; X – chlorites
0.208, 0.245, 0.335, 0.425 nm), calcite K CaCO3 (0.152,
0.160, 0.162, 0.187, 0.191, 0.209, 0.208, 0.249, 0.304,
0.385 nm), dolomite D CaMg(CO3)2 (0.178, 0.180, 0.201,
0.219, 0.240, 0.266, 0.288 nm). Other minerals, such as
Portlandite P Ca(OH)2 (0.169, 0.192, 0.263, 0.490 nm),
feldspars L (0.216 0.318 0.324, 0.370 nm), cement minerals C 3CaO SiO2 (0.254, 0.278 nm), dominate as well.
Mica Ž 0.999 nm and chlorites X 0.706 nm passed to the
filler aggregate from the granite aggregates, existed in the
concrete before crushing.
Considering the results of X-ray diffraction analysis
of the filler aggregate it can be assumed that the mineralogical composition of the filler aggregate depends on the
composition of cement stone of initial material used for
the crushing and partially on the type of coarse aggregates existed in the concrete. Cement minerals, that could
not react before the crushing, could remain in the crushed
cement stone, as well as calcium hydroxide, created during the reaction.
Concrete block C (100×100×100 mm) was cut after
28 days of hardening and visual recognition of composite
materials in the block was carried out. View of the cut
block after the scanning is shown in Figure 4.
In Figure 4 we can see how crushed concrete waste
is distributed in the sample. During visual recognition it
was noticed, that half of the coarse aggregate lost contact
with the cement stone during the crushing, and half of the
grains in the mixture are bonded firmly with the cement
stone. Coarse aggregates in the concrete are distributed
evenly and in all areas they are separated by newly mixed
cement paste with the fine aggregates.
Part of the coarse aggregates from the crushed concrete waste are composed from solid particles and cement
stone parts adhered to one or several sides. Scientists,
after the microstructure analysis (Tam et al. 2005; Tam et
al. 2009b), assume that the cracks (created during the
crushing of concrete waste) in this cement stone, adhered
to the solid particle, could influence the compressive
strength of the concrete products. Additionally, sufficiently large amount of pores could exits in this cement
stone, and this amount depends on the porosity of construction waste.
Fig 4. View of concrete sample C
Scanned image was analysed by using computer
graphic software. Individual phases composing the sample are specified in different colours. Analysed view is
provided in Figure 5.
By applying special features it was possible to calculate how much area each colour in Figure 5 covers. It was
estimated that pores, indicated in white colour, cover
1.43 % area (for calculations were used those pores that
are marked and which diameter is ≥ 0.9 mm), cement
stone, indicated in light grey colour, covers 46.63 % area
and coarse aggregate from the crushed concrete waste,
indicated in dark grey and black colours, covers 50.95 %
(coarse aggregates indicated with black colour cover
27.07 %, and old crushed cement stone with fine aggregates, indicated in dark grey, covers 23.88 %). When
phases’ arrangement (of obtained area in Figure 5) in a
plane is compared with phase volumes in overall area of
the concrete samples, it would be noticed that coarse
aggregates cover 47 % area of overall concrete volume. It
can be assumed that coarse aggregates from the crushed
concrete waste are arranged evenly in overall area of the
concrete sample.
67
gates from the crushed concrete waste were used, was
the same – 3 cm. According to the data provided in the
references (Batayneh et al. 2007), concrete’s bending
strength and spalling strength remains the same when the
amount of crushed concrete waste increases.
During the analysis of the change of compressive
strength, for the case when all aggregates are replaced by
crushed concrete waste, it can be noticed that compressive strength decreases by 18 % (when waste materials
are used) comparing with the compressive strength of
reference samples. Researchers (Tabsh and Abdelfatah
2009) describe that when crushed concrete only with
considerably larger strength is used for the coarse aggregates, it is possible to produce concrete stone of the same
strength as concrete stone with the natural coarse aggregates.
When part of the cement in the concrete mixture was
replaced by filler aggregate from the crushed concrete
waste, compressive strength of the concrete decreased by
32 %, although concrete’s density decreased by only 6 %
comparing to the reference concrete samples.
Compressive strength of the concrete decreases as
well when other filler aggregates, such as fly ash, are
used. Researchers (Kosior-Kazberuk and Lelusz 2007)
describe the tests where compressive strength decreases
by 12 % when 30 % of the cement is replaced by fly ash.
During the analysis of the influence of filler aggregates
on the properties of concrete samples, each particular
case must be investigated comprehensively and the analysis must be implemented to find out how one or other
aggregate influences mechanical properties of the final
product, because the usage of fine mineral additives in
the cement grout causes physical, chemical and microstructure effects (Boudchicha et al. 2007), which must be
analysed.
Fig 5. View of concrete sample C: white colour is used
to indicate pores; light grey – newly created cement
stone with fine aggregate; dark grey and black – concrete waste (dark grey – cement stone with fine aggregates and black – coarse aggregates)
Density of the produced concrete samples is shown
in Figure 6. All concrete samples comply with density
requirements applicable for the normal concrete samples,
their density is in the range from 2.0 g/cm3 to 2.6 g/cm3.
2,35
Density, g/cm
3
2,3
2,25
2,2
2,15
2,1
60
2,05
A
B
C
D
Compressive strength, MPa
Samples’
marking
Samples' marking
Fig 6. Results of density estimation for concrete samples
Compressive strength of the concrete samples was
determined (Figure 7). It can be noticed that when the
amount of concrete waste is increased in the mixture, the
compressive strength decreases: compressive strength of
concrete samples B is 91 % comparing to the compressive strength of reference samples (marking A). According to the researchers (Batayneh et al. 2007), compressive
strength of the concrete samples decreases by 12 % when
20 % of crushed concrete waste is used for the mixture.
However, in this case concrete mixture had much larger
water/cement ratio – 0.56. As it is described also by the
researchers (Tabsh and Abdelfatah 2009), when the
crushed concrete waste is used for the concrete mixture,
the slumping factor of the concrete changes, because
concrete waste requires more water. The measured
slumping factor of concrete mixture B was 2 cm, concrete
mixture C – 1 cm. Slumping factor of the concrete mixture D, where instead of a part of cement the filler aggre-
50
40
30
20
10
0
A
B
C
D
Samples’
Samples' marking
marking
Fig 7. Results of the estimation of compressive strength
of concrete samples
Researchers (Zaharieva et al. 2004), who analysed
the durability of the concrete, produced by using concrete
waste, according to the frost resistance, had found that the
important parameter for this characteristic – water/cement
ratio of concrete mixture, must be lower than 0.55, and
the selection of the method for the estimation of frost
resistance is very important as well. Additionally, it was
found that theoretical methods for the estimation of fore68
Conclusions
casted frost resistance cannot be based only on the results
of changes of mechanical properties.
The forecasted frost resistance of constructional
concrete can be estimate through physical and structural
characteristics (Nagrockienė et al. 2004). Based on the
recommendations of the scientists (Mačiulaitis 1996 and
Nagrockienė et al. 2007), the structural characteristics of
the concrete samples were determined (Table 4) and forecasted exploitation frost resistance of the concrete samples was calculated according to the beginning of fragmentation.
From the results of the analysis (Table 4) it can be
noticed that the general porosity of all three concrete
samples is similar. Authors (Lelusz and Malaszkiewicz
2004) state that general porosity of the sample by 90 %
depends on the amount of water used for the mixing, and
this amount in our analysed mixtures is the same.
Referring to the structural characteristics of the samples, the forecasted exploitation frost resistance of the
concrete samples was calculated according to the beginning of fragmentation. Considering this parameter, it can
be noted that the maximal forecasted exploitation frost
resistance exists in the concrete samples that were produced by using natural aggregates. This parameter is
smaller when crushed concrete waste is used, as well as
for the samples, for which production the filler aggregate
from the crushed concrete waste was used.
Considering the priorities of reprocessing of secondary raw materials, demolition and construction waste,
created in the construction sector, especially concrete
slabs, should be used for the production of new, good
quality, products.
Crushed concrete waste can be used as coarse aggregates for the production of concrete products. When
this waste is used in the mixtures as replacement of the
coarse aggregate, this waste evenly distributes in overall
concrete mass, and the properties of produced samples
are as follows: density 2.2 g/cm3, compressive strength
46.2 MPa, general sample’s porosity 14.61 %, and the
calculated forecasted exploitation frost resistance according to the beginning of fragmentation is 166 cycles.
After the part of coarse natural aggregate was replaced by crashed concrete waste, concrete’s density
decreases only by 2.8 %, and strength decreases by 9 %.
When filler aggregates from the crushed concrete
waste were used, we estimated that with this additive
smaller density, smaller strength of concrete stone is
reached and the calculated forecasted exploitation frost
resistance according to the beginning of fragmentation is
smaller comparing to the reference concrete samples
produced without filler aggregates.
References
Table 4. Structural characteristics and forecasted exploitation
frost resistance of the samples
Parameter
Effective porosity WE, (%)
General sample’s porosity WR,
(%)
Reserve of pore volume R, (%)
Conditional width of the wall
of pores and capillaries D
Structure’s directional irregularity factor N
Capillary rate of mass flow in
vacuum towards freezing direction G1, (g/cm2)
Capillary rate of mass flow in
vacuum perpendicular to freezing direction G2, (g/cm2)
Capillary rate of mass flow at
normal conditions g, (g/cm2)
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beginning of fragmentation,
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