G. SHINY BRINTHA, N. SAKTHIESWARAN: UTILIZATION OF SLAG POWDER AND RECYCLED CONCRETE WASTES ...
103–109
UTILIZATION OF SLAG POWDER AND RECYCLED CONCRETE
WASTES IN REACTIVE POWDER CONCRETE
UPORABA @LINDRNEGA PRAHU IN RECIKLIRANIH
BETONSKIH ODPADKOV ZA REAKTIVNI BETONSKI PRAH
G.Shiny Brintha
1
, N. Sakthieswaran
2*
1
Jaya Engineering College, Department of Civil Engineering, Thiruninravur, Tamil Nadu, India
2
E.G.S. Pillay Engineering College, Department of Civil Engineering, Nagapattinam, Tamil Nadu, India
Prejem rokopisa – received: 2022-12-01; sprejem za objavo – accepted for publication: 2023-01-16
doi:10.17222/mit.2022.701
Using recycled wastes and industrial by-products in construction materials has become mandatory to conserve the natural re-
sources and manage waste-disposal environmental problems. This experimental work investigates the workability and strength
properties of reactive powder concrete (RPC), utilizing slag powder and finely ground recycled concrete waste as the partial
substitutes for cement and quartz sand, respectively. The results for the slump flow, flexural strength, compressive strength,
split-tensile strength were analysed for varying contents of the recycled concrete waste in RPC, i.e., (0, 5, 10, 15, 20, 25 and
30) % and a constant slag-powder addition of 20 %. Furthermore, water absorption of the hardened specimens of 28 d of curing
was also examined. The results indicated a rise in the water absorption and reduced workability with the increase in the content
of recycled concrete in RPC. This was due to porous inter-particle voids in recycled concrete wastes. The strength properties of
RPC exhibited superior performance for the substitution of 15 % of quartz sand with recycled concrete waste. A low water-ce-
ment ratio and a steel-fibre addition to RPC play an important role in the strength development and durability properties of RPC.
Keywords: slag, concrete, waste, reactive powder, recycled concrete
Uporaba recikliranih odpadkov in industrijskih stranskih proizvodov postaja obveza pri izdelavi gradbenih materialov. S tem se
ohranja naravne vire in poizku{a uspe{no obvladovati okoljske probleme ob nastajanju prekomerne koli~ine odpadkov. V ~lanku
je opisana eksperimentalna raziskava lastnosti (obdelovalnosti in trdnosti) reaktivnega betonskega prahu izdelanega iz
`lindrinega prahu in fino zdrobljenega recikliranega odpadnega betona, ki naj bi slu`il kot delna zamenjava za cement oziroma
kvar~ni pesek. Dolo~ili so sipkost, tla~no, cepilno-natezno in upogibno trdnost preizku{ancev z razli~no vsebnostjo
recikliranega odpadnega betona v reaktivnem betonskem prahu: (0, 5, 10, 15, 20, 25 in 30) % ter s konstantnim 20 % dodatkom
`lindrinega prahu. Prav tako so dolo~ili absorpcijo vode v utrjenih preizku{ancih po 28-dnevnem utrjevanju. Rezultati analize so
pokazali, da se pove~uje absorpcija vode in zmanj{uje se obdelovalnost me{anic s pove~evanjem vsebnosti recikliranega betona
v reaktivnem betonskem prahu. Vzrok za to je poroznost oziroma mikro praznine nastale med delci recikliranih betonskih
odpadkov. Trdnostne lastnosti preizku{ancev so bolj{e pri dodatku reaktivnega betonskega prahu kot pri enakem (15 %) dodatku
kvar~nega peska. Za razvoj trdnosti in trajnosti preizku{ancev sta pomembna predvsem oja~itev z jeklenimi vlakni ter nizko
razmerje med vsebnostjo vode in cementom v reaktivnem betonskem prahu.
Klju~ne besede: `lindra, beton, odpad, reaktivni prah, reciklirani beton
1 INTRODUCTION
Ultra-high performance concrete (UHPC) is an excel-
lent type of high-strength concrete which possesses en-
hanced durability, high energy-absorption ability and low
permeability. An addition of fibres, especially steel
fibres, to UHPC improves the flexural behaviour, trans-
forming it into ultra-high performance fibre-reinforced
concrete (UHPFRC).
1
Many experimental attempts to en-
hance the durable and mechanical properties of concrete
are being carried out by the researchers through ad-
vanced scientific improvements and techniques. In that
category, reactive powder concrete (RPC) is an excep-
tional type of UHPFRC
2
generally produced with addi-
tions of mineral admixtures, elimination of coarse aggre-
gate, a low water-cement ratio, superplasticizer addition
and addition of steel fibres, each of which support the
advantageous strength properties
3
while the low wa-
ter-cement ratio and optimization of the particle packing
improve the durability properties of RPC.
4
Today, sustainability is the main problem associated
with the cement and concrete industry, and it is one of
the major sources of environmental issues like green-
house gas emission. To provide eco-friendly solutions for
the environmental problems, a few researchers recom-
mended certain actions such as: (1) to develop construc-
tion materials with high strength and durability, extending
the lifecycle of materials,
5
(2) to develop construction
materials with low energy consumption, for example, us-
ing industrial by-products
6
and, finally, (3) to use the re-
cycled concrete obtained from construction and demoli-
tion wastes.
7
From the environmental point of view, the
utilization of high-energy constituents in the production
shows RPC as a non-sustainable material. Consequently,
there is the need to produce an eco-friendly RPC by re-
placing the high-energy ingredients with lower-energy
Materiali in tehnologije / Materials and technology 57 (2023) 2, 103–109 103
UDK 625.821.5 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 57(2)103(2023)
*Corresponding author's e-mail:
sakthistructrichy@gmail.com (N. Sakthieswaran)

intensive materials and by using industrial by-products
and recycled concrete wastes.
8
Many research studies were carried out across the
world to introduce potential mineral admixtures in order
to replace the cement and also the silica fume, which
possess serious demerits such as high cost, increased wa-
ter demand and shrinkage.
9,10
The search for cost-effec-
tive and efficient substitutes continues day by day. In that
way, a past research study attempted to investigate the
use of alccofine, an ultra-fine form of slag, in UHPC and
found it as an effective pozzolanic material in concrete.
11
On the other hand, several research works were carried
out to study the potentiality and usage of recycled con-
crete wastes in concrete.
12,14
The impact of recycled fine
aggregates (RFA) on the mechanical strength and micro-
structure of UHPC has been studied in a recent re-
search.
15
Furthermore, several research studies suggested
the usage of RFA in the concrete production, provided
with optimum proportion and better curing condi-
tions.
16–20
A recent research work attempted to study the
RPC incorporated with the RFA obtained from two
sources, the first source is from the recycled normal con-
crete and the second source is from the recycled RPC.
21
The objectives of this present paper are to examine
the effects of exploiting the recycled concrete waste and
slag powder as partial substitutes of cement and fine ag-
gregate, respectively, on the workability, mechanical
strength and water absorption of RPC. The slag powder
replaced a constant amount of 20 % of cement in RPC
mixes, while the recycled concrete (RC) varied: dosages
of (0, 5, 10, 15, 20, 25 and 30) % in RPC were consid-
ered.
2 EXPERIMENTAL PART
2.1 Materials used
A typical material composition of RPC comprises ce-
ment, fine aggregate, mineral admixtures, steel fibres and
a superplasticizer to balance the low water-cement ratio
considered in the production of a densely packed system.
The following materials are used in this study: ordinary
Portland cement (53 grade) conforming to IS 12269:
2013,
22
quartz sand with a particle size of 600–750 μm,
used as the filler and fine aggregate, slag powder as the
cement substitute and recycled concrete (RC) wastes as
the partial alternative for quartz sand. The slag powder
(alccofine 1203) was manufactured by Counto Microfine
Products Pvt. Ltd. and supplied by commercial vendors.
The concrete wastes from the construction and demoli-
tion activities were collected, crushed and finely ground
to a particle size of 300–750 μ. Brass-coated micro-steel
fibres were used and their properties are listed in Ta-
ble 1.
A polycarboxylate-based superplasticizer (PCE) was
used and its properties are presented in Table 2. The
chemical compositions of the materials obtained with an
X-ray fluorescence (XRF) analysis are presented in Ta-
ble 3.
Table 1: Properties of steel-fibres
Type Colour Length Diameter Aspect ratio
Straight
Golden yel-
low
13 mm 0.3 mm 43.3
Table 2: Properties of the polycarboxylate superplasticizer
State
Solid con-
tent (%)
Solubility
Chloride
content
pH value
Liquid 50 % 100 % = 0.1 6.5–8.5
2.2 Mix design and sample preparation
The mix proportions for six RPC mixes incorporating
recycled wastes and industrial by-products are given in
Table 4. To simplify the discussion on the test results,
the mixes are designated based on the recycled concrete
amounts as RC0, RC5 RC10, RC15, RC20, RC25 and
RC30. For instance, RC0 denotes the control RPC mix
w i t h0%o fr e c ycled concrete; RC5 denotes the RPC
mix with 5 % of recycled concrete. Each mix includes
steel fibres, in the amount of2%byweight of cement.
The water-cement ratio was 0.3 and the PCE dosage was
2 %. The water-cement ratio, dosage of steel fibres and
PCE were constant throughout the study. The effects of
the varying content of RC on the workability and
strength of the RPC were investigated.
The preparation of RPC samples involves batching,
mixing, casting and curing. Firstly, the materials based
on the mix proportions for each mix were weigh-batched
and mixed using a Hobart laboratory mixer. Initially, the
base ingredients of RPC were put together and mixed for
about three minutes, then the substitute materials were
added and mixed in for about five minutes. The addition
of one half of the mixture and PCE was done and the du-
ration of 3 min mixing was done. Similarly, The addition
G. SHINY BRINTHA, N. SAKTHIESWARAN: UTILIZATION OF SLAG POWDER AND RECYCLED CONCRETE WASTES ...
104 Materiali in tehnologije / Materials and technology 57 (2023) 2, 103–109
Table 3: Physical and chemical properties of the materials used
Materials
Physical properties Chemical composition (w/%)
Mean particle
size (μm)
Specific
gravity
SiO2
Al
2
O
3
Fe
2
O
3 CaO MgO SO
3
Na
2
OK
2
O LOI
Cement 15.4 3.15 19.84 6.50 4.72 60.20 3.42 3.51 0.19 1.04 0.47
Slag powder 2.74 2.69 40.23 – 1.92 57.20 – – – 0.41 0.12
Quartz sand 220 2.72 99.20 0.10 0.34 - –––––
Recycled concrete 325 2.54 67.15 0.84 4.05 20.18 0.78 – – – 6.85

of the other half of water and PCE was done and the du-
ration of 3 min mixing was done. The addition of steel
fibers mixing was done for the duration of 5 min. After
assuring a uniform distribution of steel fibres without
any further delay, the wet RPC mixes were poured into
moulds greased with oil and compaction was done by
means of vibration for a period not exceeding 15 s. The
entire process of mixing and compaction took around
20 min for each mix. After 24 h, the process of de-
moulding was done for the casted specimens and sub-
jected to the standard water curing at a temperature of
27 ± 3°.
Table 4: Mix design of RPC
Materials
Weight fractions of materials
RC0 RC5 RC10 RC15 RC20 RC25 RC30
Cement 0.8 0.8 0.8 0.8 0.8 0.8 0.8
Slag powder 0.2 0.2 0.2 0.2 0.2 0.2 0.2
Quartz sand 1 0.95 0.90 0.85 0.80 0.75 0.70
RC - 0.05 0.10 0.15 0.20 0.25 0.30
2.3 Test methodologies
The experimental program investigated the work-
ability, compressive strength (after 7 d and 28 d), split-
tensile strength and flexural strength. In addition, the du-
rability of the RPC mixes was tested by means of water
absorption. The density and slump flow measurements
were carried out for each fresh RPC mix right after the
mixing process. The compressive strength and split-ten-
sile strength tests were carried out in a 1000 kN com-
pression testing machine (CTM). The flexural strength of
rectangular RPC prisms was determined by subjecting
the specimens to three-point loading in the testing ma-
chine. The specimen details and the specifications are
listed in Table 5. Triplicate specimens were used for
each testing and the average of the test results was re-
ported as the final result with a deviation of less than ±
15 %.
3 RESULTS AND DISCUSSION
3.1 Density and slump flow
Workability plays an important role in the design of
ultra-high performance concrete because of the self-com-
pacting nature.
11
The flow characteristics of the RPC
mixes were studied based on their slump values. The
changes in the density and slump flow of each RPC mix
were recorded and the results are listed in Table 6. The
results show an increase in the density with an increase
in the RC content up to RC15 and a decrease with fur-
ther increment in the RC content for RC20, RC25 and
RC30. A maximum density of 2580 kg/m
3
was attained
by RC15 and a minimum of 2475 kg/m
3
was noted for
RC30. It was revealed that RC15 possesses effective and
densely packed RPC when compared with the other RPC
mixes.
Table 6: Density and slump flow of RPC
Mix ID Density (kg/m
3
) Slump flow (mm)
RC0 2523 135
RC5 2536 121
RC10 2565 108
RC15 2580 88
RC20 2554 71
RC25 2522 52
RC30 2475 47
The slump-flow value of RPC decreased with an in-
crease in the content of RC from 135 mm to 47 mm. This
implies that the workability of RPC decreased; when in-
creasing the dosage of the quartz sand. A study by
Gautham Kishore Reddy et al.
11
revealed that the incor-
poration of alccofine increased the workability of UHPC.
This denoted the mixed effect of the slag powder and RC
on increasing and decreasing the workability of RPC. In
addition, the influence of recycled concrete on the
workability of RPC was observed to be remarkable.
3.2 Strength of RPC
The average values of the failure load of at least three
tested specimens were obtained for the compressive
strength, split-tensile strength and flexural strength and
listed in Table 7. When increasing the RC content about
15 %, the compressive strength at7da n d2 8di si n -
creased. When increasing the RC content about 20%, the
compressive strength at 7 d and 28 d is decreased. A sim-
ilar trend in the variation was observed for both the
split-tensile strength and flexural strength of RPC.
3.2.1 Compressive strength
The control RPC mix RC0 attained compressive-
strength values of 98.14 MPa and 118.72 MPa after 7 d
and 28 d, respectively, the split-tensile strength of
10.40 MPa and flexural strength of 34.12 MPa. The max-
imum compressive strength of 134.25 MPa was exhib-
G. SHINY BRINTHA, N. SAKTHIESWARAN: UTILIZATION OF SLAG POWDER AND RECYCLED CONCRETE WASTES ...
Materiali in tehnologije / Materials and technology 57 (2023) 2, 103–109 105
Table 5: Specification and specimen details
Tests Testing time Standards Specimen type and size (mm)
Slump flow – IS 1199:2018
23
Fresh mix
Compressive strength 7 d and 28 d ASTM C 109
24
Cube: 50 × 50 × 50
Flexural strength 28 d ASTM C293
25
Rectangular prism: 160 × 40 × 40
Split-tensile strength 28 d ASTM C 496
26
Cylinder: 100 × 200
Water absorption 28 d ASTM C 642
27
Cube: 50 × 50 × 50

ited by RC15. Figure 1 graphically represents the varia-
tion in the compressive strength of RPC. It was noted
that after 7 d and 28 d, the strength showed a similar
variation. The rate of change in the compressive strength
with respect to the age of curing was significant for RC0,
RC5, RC10 and RC15 when compared with RC20,
RC25 and RC30.
Table 7: Compressive strength, split-tensile strength, flexural
strength, MPa
Mix ID
Compressive strength
(MPa)
Split-tensile
strength
(MPa)
Flexural
strength
(MPa) 7d 28d
RC0 98.14 118.72 10.40 24.12
RC5 105.06 126.33 11.85 27.75
RC10 112.12 130.56 13.22 32.64
RC15 118.04 134.25 15.05 34.12
RC20 101.48 110.28 12.14 26.06
RC25 94.88 102.31 10.02 22.18
RC30 89.39 97.05 8.53 18.22
The elimination of coarse aggregates and use of fine
materials in RPC enhanced the homogeneity of the
packed materials in each RPC mix. This homogeneity of
the RPC matrix, which contributes to stronger bonding
between the materials, is one of the major reasons for the
strength enhancement up to the 15 % replacement.
About a 13 % increase in the compressive strength was
exhibited by RC15 when compared with that of RC0.
Furthermore, the slag powder acting as the supplemen-
tary cementitious material contributes to a higher pro-
duction of calcium silicate hydrates (C-S-H), which was
confirmed by a higher content of CaO (57.20 %) in the
slag powder, being almost similar to that of cement
(60.20 %).
3.2.2 Split-tensile strength
The resulting 28-day split-tensile strength of the RPC
specimens is graphically shown in Figure 2. Initially the
increment of tensile strength occurred and attained its
maximum split-tensile strength of 15.05MPa, which was
44.7 % greater than that of the control RC0 specimens.
When the RC content exceeded 15 % in RPC, the tensile
strength decreased. However, RC20 exhibited a greater
strength compared to RC0. A minimum split-tensile
strength of 8.53 MPa was noted for RC25, which al-
lowed a greater replacement of quartz sand by RC.
It is known that concrete is brittle, breaking into
pieces when subjected to compression, tension or flex-
ural loading. This explains the poor strength behaviour
of concrete, especially under tensile and flexural loads.
To make a control in crack formation and to minimize
the brittleness, steel fibres were incorporated in RPC.
This resulted in a ductile failure of the RPC specimens
without any sudden failure.
28
Furthermore, the bonding
of steel fibres with the RPC matrix was comparatively
significant at 20 % slag powder and 15 % RC incorpora-
tion in RPC.
3.2.3 Flexural strength
The obtained test results for the flexural strength of
the RPC specimens at the age of 28 d are shown in Fig-
ure 3. It was observed that the flexural strength also in-
creased with the increase in the RC content up to 15 %
and decreased at 20 % and greater levels of the replace-
ment. A maximum flexural strength of 34.12 MPa and
minimum flexural strength of 18.22 MPa were exhibited
by RC15 and RC25, respectively. Similar trends in the
variation of the compressive strength and split-tensile
strength were observed in the flexural-strength results.
Also, a maximum increase in the flexural strength of
41.5 % was noted for RC15 compared to the flexural
strength of RC0. This revealed that the mix composition
of RC15 was more efficient in enhancing the mechanical
strength of the RPC incorporating slag powder and RC
under the normal curing conditions than that of the con-
trol mix.
106 Materiali in tehnologije / Materials and technology 57 (2023) 2, 103–109
G. SHINY BRINTHA, N. SAKTHIESWARAN: UTILIZATION OF SLAG POWDER AND RECYCLED CONCRETE WASTES ...
Figure 3: Flexural-strength test results Figure 1: Compressive-strength test results
Figure 2: Split-tensile strength test results

The addition of2%ofmicro-steel fibres has great in-
fluence on improving the flexural strength by providing
ductility and increasing the energy absorption capacity
of RPC. The role of steel fibres also includes the ability
to resist and bridge the cracks when subjected to flexural
loading. The research work by Kannan Rajkumar et al.
2
explained that RPC specimens without fibres result in a
brittle failure under increasing flexural loading. The duc-
tile failure pattern observed during the flexural strength
testing confirmed the ductility provided by the inclusion
of steel fibres in RPC.
3.2.4 Impact strength
For the mix RC15, the highest impact strength value
was obtained which has 15 % replacement of RC. The
impact value of RC15 mix is 57 % more than control
mix RC0. And the second mix which has the highest im-
pact value is RC10 mix. It has the impact value 38%
more than control mix RC0. For the mix RC25, the low-
est impact strength value was obtained which has 25 %
replacement of RC. The impact value of RC25 mix is
55 % less than control mix RC0. And the second mix
which has the lowest impact value is RC30 mix. It has
the impact value 20 % less than control mix RC0. From
the test results, it is observed that the addition of RC is
more than 15 %, the impact strength is decreased be-
cause of the loose packed concrete mixture. The impact
strength values are displayed in Figure 4.
3.2.5 Bond strength
From the Figure 5, it is observed that the highest
bond strength was obtained for the mix RC10. The bond
strength for the mix RC10 is 9 % more than the control
mix RC0. The reason for the maximum bond strength
was the particle size distribution of RC with optimum
content 10 %. This leads to form the better bond between
the concrete and the bar. Up to 10 % replacement of RC,
the mechanical interlocking characteristic of concrete
mix was enhanced. After that 10 % RC replacement, the
bond strength was reduced than the normal mix.
3.2.6 Water absorption
The results of the water absorption test carried out on
the 28th day on cured RPC cubical specimens were plot-
ted graphically and shown in Figure 6. From the figure,
it is known that the water absorption increases with an
increase in the content of RC. The control mix RC0
showed about 0.98 % water absorption, which increased
linearly in a gradual manner and attained a maximum of
3.83 %. Because of the usage of fine recycled concrete,
the water absorption is increased in RPC was reported by
a few past studies.
21
This was because of the presence of
adhered cement matrix to the sand surface.
The crushed and finely ground particles of RC, how-
ever, possess inter-particle voids in the interface between
the cement and sand particles. This allows the RPC to
absorb water, retain it in minute voids and increase the
water absorption. However, the water absorption of the
RPC mixes with a maximum of 30 % of the RC substitu-
tion was found to be less than 4 %. This was mainly due
to the particle-size distribution and particle-packing effi-
ciency of the material mixture. Furthermore, the role of
the superplasticizer is remarkable, balancing the increas-
ing water demand and ensuring the homogeneity while
its potential in packing the materials results in a
self-compacting nature of the RPC material mix.
3.2.7 Sorptivity
From the Figure 7, it is known that the least value of
sorptivity was obtained for 20 % RC replacement con-
crete mix. For the addition of more than 20 % RC, the
concrete mix forms water channels and internal voids
and increases sorptivity. The reason behind this is the
closed particle efficiency and the particle size distribu-
tion of the replacement material RC. The same trend was
obtained for both 15 min and 30 min sorptivity values.
3.2.8 Porosity
The minimum value of porosity was obtained for
20 % RC replacement concrete mix. The pore diameter
is reduced and ITZ is strengthened because of the parti-
G. SHINY BRINTHA, N. SAKTHIESWARAN: UTILIZATION OF SLAG POWDER AND RECYCLED CONCRETE WASTES ...
Materiali in tehnologije / Materials and technology 57 (2023) 2, 103–109 107
Figure 4: Impact strength test results
Figure 5: Bond strength test results
Figure 6: Water absorption test results

cle size distribution of the replacement material. For the
addition of more than 20 % RC, the bleeding occurs in
concrete mix which creates internal voids and increases
porosity. This is because of loosely packed concrete of
RC concrete. The porosity values are displayed in Fig-
ure 8.
3.2.9 Acid Attack
From Figure 9, it is indicated that the mix RC5 has
the lowest loss of strength value in both HCL and H
2
SO
4
attack. For the mix RC5, the loss of strength is 82 % less
than the normal concrete for HCL acid attack specimen
and 34 % less for H2SO4 acid attack specimen. The
densified packing capacity of RC replacement concrete
generates very denser concrete that prevents the entry of
calcium sulphate salts, calcium chloride salts. This leads
to reduce the concrete degradation. For the mix RC30,
the loss of strength is 16 % more than the normal con-
crete for HCL acid attack specimen and 17% more for
H
2
SO
4
acid attack specimen. When the addition of RC is
beyond 20 %, this will lead to form more free water and
bleeding and increase the strength loss in concrete mix.
4 CONCLUSIONS
Based on the results and findings of the current ex-
perimental study, following conclusions are drawn:
• The utilization of ultrafine slag powder and fine recy-
cled concrete have decreased the workability and im-
proved the mechanical strength of RPC under normal
curing condition when added in optimum proportion.
In addition, the maximum density and the strength
properties are noted to be highly correlated. This in
turn reveals that the particle packing of the RPC in-
gredients under study, bonding behaviour of the fi-
bers and concrete matrix and the low water-cement
ratio considered in the study is the governing factors
in the strength development of RPC. A similar
strength performance was exhibited by the RPC spec-
imens of different mix combinations under compres-
sion, tension and flexural strength testing.
• The addition of micro-steel fibers by2%waseffec-
tive toenhance the mechanical properties of RPC.
This was confirmed by the ductile failure pattern of
RPC under the application of compressive, flexural
and tensile loading conditions. The higher CaO con-
tent of the slag powder obtained from the XRF analy-
sis described the role of the fine slag powder as the
supplementary cementitious material and formation
of C-S-H during the hydration reaction. The addition
of RC is more than 15 %, the impact strength is de-
creased because of the loose packed concrete mix-
ture. The bond strength is enhanced up to 10% RC
replacement.
• Recycled concrete possess inter particle voids in the
interface between the cement and silica particles
which absorbs and retains the water during mixing.
This in turn resulted in decreased slump flow and in-
creased water absorption with increasing substitution
of recycled concrete. The better results are obtained
for sorptivity and porosity values up to 20 % RC re-
placement. The addition of RC is beyond 20 %, this
will lead to form more free water and bleeding and
increase the strength loss in concrete mix. However
the addition of ultra-fine slag powder in RPC has a
significant effect in increasing the workability. It
leads the RPC to possess mixed outcome in case of
workability and the strength properties with addition
of slag powder and recycled concrete.
G. SHINY BRINTHA, N. SAKTHIESWARAN: UTILIZATION OF SLAG POWDER AND RECYCLED CONCRETE WASTES ...
108 Materiali in tehnologije / Materials and technology 57 (2023) 2, 103–109
Figure 9: Percentage loss of strength due to Acid Attack
Figure 8: Porosity test results
Figure 7: Sorptivity test results in 10
–2
mm/ s

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