p–ISSN: 2723 – 6609 e-ISSN: 2745-5254
Vol. 5, No. 12, December 2024 http://jist.publikasiindonesia.id/

Indonesian Journal of Social Technology, Vol. 5, No. 12, December 2024 6146

Effect of Fly Ash Use on Compressive Strength and Water
Absorption of Paving Block

Nathalie Dwiana1*, Anang Kristianto2
Universitas Kristen Maranatha, Indonesia

Email: [email protected]*, [email protected]

*Correspondence
ABSTRACT

Keywords: paving block,
fly ash, strong pressure,
absorbency.

Paving block is a product of a mixture of mortar which is
generally used as a building material and ground surface
pavement that can function as a sidewalk or public road that
is often passed by pedestrians and vehicles. Mortar mixtures
have a composition of cement, fine aggregate, water, and can
use other additives. In this study, the additional material used
is fly ash. With the right composition and procedures, the
addition of fly ash as a cement substitution in the mixture
can have a good effect on the compressive strength and water
absorption of the paving block. The research was conducted
using a mixture of fly ash as much as 10%, 20%, 25%, 30%,
35%, and 40% in laboratory research and 10% and 20% fly
ash in research conducted in the field. The mixture used in
the manufacture of paving blocks has a cement:sand
composition ratio of 1:5. In the implementation of the results
of testing the quality requirements of concrete bricks, the
highest quality value was found in the range of fly ash use of
10-20%, both research conducted in the laboratory and field
research. The highest compressive strength test results in the
laboratory had a value of 20.1 MPa in the 10% and 20%
variable tests, while for field tests, the highest value was
obtained in the variable of using fly ash of 10% with a
compressive strength value of 15.74 MPa.

Introduction

Paving block is a composition of mortar mixture that is often used as a building
material that has a mixture of composition such as portland cement or materials that have
hydraulic adhesive properties, water, and fine aggregate in this case may or may not use
other additives according to SNI 03-0691-1996 (Lumingkewas, Hadiwardoyo, &
Hadiwardoyo, 2023). Paving blocks are commonly used as non-structural elements such
as covers or ground hardeners which are generally used as sidewalks, garden roads,
parking lots, and residential roads. However, in this use, the paving block needs to have
a compressive strength in accordance with the standards that have been determined as in
SNI 03-0691-1996. In the paving block production process, generally using a ratio of
cement and sand with a total of 1:3, 1:4, 1:5, 1:6, this can change if there are other

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compositions that are additives/substitutions for cement (Klarens, Indranata, & Hardjito,
2016). However, the composition used in the manufacturing process has standards that
need to be considered and tested in its use. As well as the standard for the use of fine
aggregate which can be referred to as fine aggregate if it has a maximum grain size of
4.76 mm, it can come from nature or processed stone (Weno et al., 2014). Similar to the
use of water that is not recommended has excessive levels or chemicals so that the water
used does not affect the mortar mixture.

Paving blocks (concrete bricks) also have quality classification standards that need
to be considered in their use, which is regulated in SNI 03-0691-1996 (Lahoti, Wong,
Yang, & Tan, 2018). The highest quality concrete brick, namely quality A, can be used
as a road facility, quality B concrete brick can be used as a means of parking equipment,
quality C concrete brick is a concrete brick that functions as a pedestrian facility, while
quality D concrete brick can be used as a garden road pavement and other uses (Adibroto
& Fauna, 2014). The classification has physical properties that need to be met in
achieving a certain quality with a maximum limit of water absorption in each category of
concrete brick quality. It can be seen that the higher the quality of concrete bricks, the
more waterproof the paving block must be or it can be said that the lower the water
absorption capacity will be, this can be seen in Table 1.

Table 1

Physical properties of paving blocks
Physical properties

Quality
Compressive

Strength (Mpa)
Wear resistance

(mm/min)

Max
average
water

absorption
Average Min. Average Min. (%)

A 40 35 0,090 0,103 3
B 20 17,0 0,130 0,149 6
C 15 12,5 0,160 0,184 8
D 10 8,5 0,219 0,251 10

In addition to the use of materials such as fine aggregates, cement and water as
mentioned in mortar mixtures often use other additives. One of the additional materials
that is often used in the composition of making paving blocks is fly ash. Fly ash is often
used as an additional mortar material because it is considered to have properties that are
generally possessed by Portland cement, namely pozzolanic properties. Fly ash is a non-
B3 waste in the form of fine residues produced from burning or crushing coal and
transported by hot air streams (SNI 2460, 2014). Fly ash waste can be categorized as B3
waste if the coal burning process occurs at coal-fired power plant facilities or from other
activities that use technology other than stocker boilers and/or industrial furnaces
(Government Regulation Number 22 of 2021 attachment XIV N106). One of the
producers of fly ash from coal burning in Indonesia is PT Sumber Alam Sekurau which
is located in Tanjung Selor District, Bulungan Regency, North Kalimantan Province. PT

Anggoro Ary Nugroho, Imam Salehudin

Indonesian Journal of Social Technology, Vol. 5, No. 12, December 2024 6148

Pesona Khatulistiwa Nusantara utilizes coal as a steam power plant managed by PT
Sumber Alam Sekurau. In its use, coal combustion occurs to produce steam which is used
as a turbine drive which is used to drive turbines and rotate electric generators. The
burning produces 2-3% fly ash and bottom ash (FABA) from burning as much as 9
tons/hour every day. The large number of fly ash produced has led to an innovation in the
use of fly ash as a mortar mixture for making paving block products.

The research was carried out to obtain the right mixture composition in the
manufacture of paving block products using additional materials in the form of fly ash
from PLTU PT Sumber Alam Sekurau. In addition, this study also aims to see and analyze
the effect of the use of fly ash on the quality of concrete bricks (paving blocks) by using
compressive strength testing and knowing the water absorption produced from each
variable made. With the right composition and good utilization, it is hoped that it can help
reduce the fly ash waste produced every day.

Method

The method carried out in this study is an experimental method which is basically
a method of testing and controlling the variables owned in the process. The experimental
research method aims to find out and find the influence of a treatment on a variable
(NOVIANTI, Nevrita, & Fernando, 2023). This method is considered appropriate in the
research conducted considering that the purpose of this research requires the creation of
several mixed variables that are considered perfect for use in making paving blocks with
fly ash additives. The research was carried out in two different places, namely the
laboratory and the field, this gave rise to differences in results, treatments, and
preparations that occurred in the research process (Kusdarini, Ulviandri, & Sari, 2022).

In research conducted in the laboratory, variations in the addition of fly ash were
used by 10%, 20%, 25%, 30%, 35%, and 40%. The addition of fly ash is an additional
treatment that replaces the amount of cement, therefore as the fly ash increases, the
amount of cement used will be less. The addition of fly ash reaching 40% is considered
to have aggressive waterproof properties that are moderate or can be said to be resistant
to water (Al-Husseinawi, Atherton, Al-Khafaji, Sadique, & Yaseen, 2022). Research
conducted in the field using the addition of fly ash as a substitute for cement has a range
of 10% and 20% fly ash use, this refers to the results of the best compressive strength test
that was carried out in the laboratory first. However, the use of fly ash used in field
research is fly ash that has a different moisture content, namely fly ash with a fairly high
moisture content of 28.10% (wet/wet) and fly ash which has a moisture content of 3.50%
(dry/dry). Both studies used a cement:sand ratio of 1:5.

The preparation of mortar mixtures for paving block test specimens carried out in
the laboratory uses materials in the form of fine aggregate (stone sand), Portland cement,
wet/wet fly ash, and water. The four materials used have been taken into account for their
use to be a mortar mixture with a test specimen size of length x width x height (5 cm x 5
cm x 5 cm). The mixing process is carried out using a small mixer and compaction is

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carried out manually/human-powered, using a tamper and an iron plate measuring 2.5 cm
x 2.5 cm. 25 collisions were carried out per layer (3 layers/1 test piece). Details of the use
of materials in the manufacture of laboratory test pieces are detailed by Table 2.

Table 2

Composition of laboratory paving block mixture

Variable
Fly
Ash

Sand Cement
Fly
Ash

Water Total
Test

Specimen
(%) (gr) (gr) (gr) (ml) (gr) (fruit)

P-15-0 0 1875 375 0 181,5 2250 6
P-15-10 10 1875 337,5 37,5 181,5 2250 6
P-15-20 20 1875 300 75 181,5 2250 6
P-15-25 25 1875 281,25 93,75 181,5 2250 6
P-15-30 30 1875 262,5 112,5 181,5 2250 6
P-15-35 35 1875 243,75 131,25 181,5 2250 6
P-15-40 40 1875 225 150 181,5 2250 6

Preparation was carried out from the materials used, one of which was a sieve
analysis on the fine aggregate (stone sand) used and the results were obtained that the
stone sand used was in the category of medium sand with a fineness modulus of 3.08%.
Testing of fine aggregate sludge content was carried out and obtained a result of stone
sand mud content of 1.54% with a moisture content of 2.18% (Sengkey, Kandiyoh, Slat,
& Hombokau, 2023).

The process of making test pieces in the field has wet/wet fly ash and dry/dry fly
ash materials with other materials in the form of stone sand as fine aggregate, gresik
cement, and water. Formwork used in the manufacture of test pieces in the field has
dimensions of length x width x height (20 cm x 10 cm x 8.5 cm). Table 3 shows the
variables and material details in the process of making test pieces in the field. In the
manufacturing process, a large mixer is used with an automatic press machine and
compaction is carried out as many as 2 times of pressure/4 test pieces. The preparation
was carried out in the form of testing the moisture content of the two types of fly ash used
with a wet/wet fly ash moisture content of 28.10% and dry/dry fly ash of 3.50%. A
standard test was carried out on stone sand as a fine aggregate used and the results of the
filter analysis were obtained with a fineness modulus of 3.46% and included in the
medium sand category. The moisture content and mud content of the stone sand aggregate
were 3.71% and 1.73% respectively.

Table 3
Composition of the field paving block mixture

Variable
Fly Ash

Conditions
% Fly
Ash

Test
Specimen

Sand Cement
Fly
Ash

Total Water

- - (%) - (kg) (kg) (kg) (kg) (ml)
P-W-0 Wet 0% 24 82,43 16,49 0,00 98,91 3200

P-W-10 Wet 10% 24 82,43 14,84 1,65 98,91 3200

Anggoro Ary Nugroho, Imam Salehudin

Indonesian Journal of Social Technology, Vol. 5, No. 12, December 2024 6150

P-D-10 Dry 10% 24 82,43 14,84 1,65 98,91 3200
P-W-20 Wet 20% 24 82,43 13,19 3,30 98,91 3200

The preparation was carried out in the form of testing the moisture content of the

two types of fly ash used with a wet/wet fly ash moisture content of 28.10% and dry/dry
fly ash of 3.50%. A standard test was carried out on stone sand as a fine aggregate used
and the results of the filter analysis were obtained with a fineness modulus of 3.46% and
included in the medium sand category. The moisture content and mud content of the stone
sand aggregate were 3.71% and 1.73% respectively.

Results and Discussion

The test carried out to determine the quality requirements of concrete bricks (paving
blocks) is a test of compressive strength and water absorption. This is also done to find
out the comparison between existing variables and get the variable with the best results
to use and one of the factors that affect the compressive strength of the mortar is the age
of the mortar (Siahaan, Tanjung, & Siregar, 2024). The calculation of the compressive
strength of a mortar can be calculated using the formula of equation 1 as follows:

��′�� =
��
��
(1)

where F'c = Compressive strength of the test piece (MPa), P = maximum compressive
load (N), A = surface area (mm2).

Water absorption testing is carried out on the test piece to show the percentage of
water weight that can be absorbed by the aggregate when immersed in the test piece, this
is also influenced by the size and number of pores contained in the test piece [8]. The
result is obtained through the equation formula 2:

�� =
��−��

��
�� 100%

(2)
with A= Dry weight, B= wet weight.

The compressive strength test carried out in the laboratory has a number of tests of
3 times with details of the 7th day of testing, the 28th day of testing, and the 56th day of
testing. The test was carried out using a hydraulic compressive strength test tool using
two test pieces on each variable and each test. Meanwhile, the test method in water
absorption refers to SNI 03-0691-1996 and the results obtained can be seen through the
category results according to table 1. Physical properties of paving blocks. So the results
of the compressive strength test of the test object in the laboratory are shown in Table 4
with a comparison graph of each test variable shown in Figure 1.

Table 4
Laboratory compressive strength test results

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Picture 1

Laboratory Compressive Strength Testing Chart

The results of the laboratory compressive strength test showed that the test on the
variables P-15-10 and P-15 20 had the highest compressive strength test results at the age
of 56 days with an average compressive strength result of 20.1 MPa, both variables
contained 10% fly ash and 20% fly ash. The results of the compressive strength are in
accordance with table 1. The physical properties of the paving block test piece are
included in the category of concrete brick quality B or can be used optimally as parking
equipment. The variable P-15-25 and containing 25% fly ash at the age of 56 days is
classified in category C or as a means of walking. The variable with the highest
compressive strength result has compressive strength results that increase with each test
while some other variables have results that fluctuate. Table 5 shows the results of water
absorption testing conducted in the laboratory with tests carried out 3 times.

Table 5
Laboratory Water Absorption Test Results

No. Variable

Kuat Tekan (Mpa)
Hari Ke-7 Hari Ke-28 Hari Ke-56

Benda
Uji 1

Benda
Uji 2

Rata-
rata

Benda
Uji 1

Benda
Uji 2

Rata-
rata

Benda
Uji 1

Benda
Uji 2

Rata-
rata

1 P-15-0 4 10 7 20 16,4 18,2 12,4 14,4 13,4
2 P-15-10 14,4 12 13,2 20 15 17,5 19,9 20,3 20,1
3 P-15-20 12,5 14,5 13,5 17,2 16,4 16,8 20,2 20 20,1
4 P-15-25 8 12 10 15,6 14,8 15,2 16 14 15
5 P-15-30 6 6 6 14,8 12 13,4 14,8 9,2 12
6 P-15-35 2 2 2 14 20 17 10 10 10
7 P-15-40 2 2 2 6 6 6 6 6 6

13,2 13,5
10

6
2 2

18,2 17,5 16,8 15,2
13,4

13,4

20,1 20,1
15

12
10

0
2
4
6
8

10
12
14
16
18
20
22

P-15-0 P-15-10 P-15-20 P-15-25 P-15-30 P-15-35 P-15-40K
u

at
T

e
ka

n
(

M
P

Variabel

Hasil Pengujian Kuat Tekan Paving Block
Laboratorium

Hari Ke-7 Hari Ke-28 Hari Ke-56

Anggoro Ary Nugroho, Imam Salehudin

Indonesian Journal of Social Technology, Vol. 5, No. 12, December 2024 6152

Water absorption testing is carried out on each test piece and each variable can be
seen that each variable has water absorption in accordance with the category of concrete
brick quality requirements in table 1. Properties of physics. In the variable with the
highest compressive strength, namely the variables P-15-10 and P-15-20 have water
absorption of 4.02% and 4.64% respectively, which in category B the maximum water
absorption owned by the test specimen is 6%. The highest water absorption occurs in the
P-15-25 variable which has a fly ash content of 25% of 7.06%. However, this figure is
in accordance with the category owned by the test piece, namely category C with a
maximum absorption of 8%.

In the compressive strength test carried out in the field, there were 4 tests at the age
of the test specimen 7 days, 18 days, 29 days, and 56 days. Each test was taken 3 test
pieces per variable with two curing methods , namely the water immersion method and
the no-treatment method. The results of the compressive strength testing of test objects in
the field with the water immersion curing method are shown in Table 6 with a comparison
chart of each test variable shown in Figure 2.

Table 6
Field compressive strength test results (water immersion)

Pengujian penyerapan air (Hari ke-7) Pengujian penyerapan air (Hari ke-28) Pengujian penyerapan air (Hari ke-56)

Variable No.
Berat
Awal
(gr)

Berat
Akhir
(gr)

%
Penyerapan

Rata-
rata

No.
Berat
Awal
(gr)

Berat
Akhir
(gr)

%
Penyerapan

Rata-
rata

No.
Berat
Awal
(gr)

Berat
Akhir
(gr)

%
Penyerapan

Rata-
rata

P-15-0
1 242 251 3,72

3,32
3 264 273 3,41

3,64
5 258 272 5,43

5,23
2 273 281 2,93 4 259 269 3,86 6 258 271 5,04

P-15-10
1 271 280 3,32

3,33
3 264 273 3,41

3,55
5 252 263 4,37

4,02
2 270 279 3,33 4 271 281 3,69 6 272 282 3,68

P-15-20
1 264 275 4,17

4,12
3 254 265 4,33

4,21
5 273 286 4,76

4,64
2 270 281 4,07 4 269 280 4,09 6 266 278 4,51

P-15-25
1 245 261 6,53

6,60
3 259 278 7,34

7,36
5 264 283 7,20

7,06
2 255 272 6,67 4 257 276 7,39 6 260 278 6,92

P-15-30
1 253 260 2,77

2,71
3 269 277 2,97

3,37
5 270 279 3,33

3,30
2 263 270 2,66 4 266 276 3,76 6 275 284 3,27

P-15-35
1 268 279 4,10

3,95
3 269 280 4,09

4,36
5 253 264 4,35

4,41
2 263 273 3,80 4 259 271 4,63 6 268 280 4,48

P-15-40
1 268 281 4,85

4,42
3 275 288 4,73

4,60
5 278 291 4,68

5,26
2 276 287 3,99 4 268 280 4,48 6 274 290 5,84

Variable

Hari ke-8 Hari ke-18 Hari ke-29 Hari ke-56
Rendam Air Rendam Air Rendam Air Rendam Air

Kn Mpa
Rata-
rata

(Mpa)
Kn Mpa

Rata-
rata

(Mpa)
Kn Mpa

Rata-
rata

(Mpa)
Kn Mpa

Rata-
rata

(Mpa)

P-W-0
126 8,51

10,14
247 16,26

9,94
208 14,44

10,60
163 11,13

8,70 214 14,46 95 6,25 173 12,01 155 10,59
110 7,43 111 7,31 77 5,35 64 4,37

P-W-10
167 11,28

10,25
141 9,28

8,93
188 13,06

12,45
238 16,26

14,39 154 10,41 148 9,74 156 10,83 209 14,28
134 9,05 118 7,77 194 13,47 185 12,64

P-D-10
124 8,38

7,45
70 4,61

7,33
131 9,10

7,82
98 6,69

7,49 125 8,45 127 8,36 146 10,14 123 8,40
82 5,54 137 9,02 61 4,24 108 7,38

P-W-20
193 13,04

10,63
234 15,41

10,80
218 15,14

12,31
164 11,20

11,98 121 8,18 149 9,81 173 12,01 136 9,29
158 10,68 109 7,18 141 9,79 226 15,44

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Figure 2

Field compressive strength test graph (water immersion)

The compressive strength test carried out on the paving block test piece had the
result with the highest average compressive strength of 14.39 MPa which occurred in the
P-W-10 variable with a test specimen life of 56 days. This variable has a fly ash content
of 10% and the P-W-10 variable enters the category of concrete brick quality
requirements C with the category of pedestrian facility use. In addition to the P-W-10
variable, the P-W-20 variable is also included in the paving block which can enter the
quality requirements of concrete bricks in accordance with SNI 03-0691-1996 in category
D for use as pavement, roads, gardens and other uses. The P-W-0 variable in the 28-day
age test had a compressive strength result that could enter the D quality requirement
category, but on the 56th day of the test, there was a decrease in the compressive strength
result so that it could not enter the compressive strength quality requirement of concrete
bricks along with the P-D-10 variable. The results of the compressive strength testing of
test objects in the field with the water-soaked curing method are shown in Table 7 with
a comparison chart of each test variable shown in Figure 3.

10,14 10,25

7,45

10,63
9,94

8,93
7,33

10,8010,60
12,45

7,82

12,31

8,70

14,39

7,49

11,98

0
2
4
6
8

10
12
14
16

P-W-0 P-W-10 P-D-10 P-W-20

K
u

a
t

T
e
k

a
n

(
M

P
a

)

Variabel

Hasil Pengujian Kuat Tekan Paving Block
(Rendam Air)

Hari Ke-8 Hari Ke-18 Hari Ke-29 Hari Ke-56

Anggoro Ary Nugroho, Imam Salehudin

Indonesian Journal of Social Technology, Vol. 5, No. 12, December 2024 6154

Table 7

Field compressive strength test results (no maintenance)

Figure 3

Field compressive strength test graph (without maintenance)

On the test specimen with the curing method without maintenance, it can be seen
that the variable P-W-0 is the variable with the highest average compressive strength test
result of 15.28 MPa at a test age of 56 days. Refer to table 1. The physical properties of
the variable P-W-0 are a category of quality requirements for concrete brick C with its
use as a pedestrian facility. This variable is a variable with a test piece without the use of
fly ash as the main material. However, on the 28th day of testing, the P-W-10 variable is
the variable that has the highest average compressive strength test result with a value of
15.74 MPa and is included in the quality condition category C. This variable experienced
a decrease in the average compressive strength test result on the 56th test day and only
entered the quality requirement D category or use as a pavement for garden roads and
other uses. Variable P-W-20 according to table 1. The physical properties can be
categorized as D quality concrete bricks from the 7th day of testing to the 56th day of
testing. While the P-D-10 variable at the test age of 7 days is included in category D, but
after that this variable cannot meet the quality requirements of any concrete brick. While

Variable

Hari ke-8 Hari ke-18 Hari ke-29 Hari ke-56
Tanpa Perawatan Tanpa Perawatan Tanpa Perawatan Tanpa Perawatan

Kn Mpa
Rata-
rata

(Mpa)
Kn Mpa

Rata-
rata

(Mpa)
Kn Mpa

Rata-
rata

(Mpa)
Kn Mpa

Rata-
rata

(Mpa)

P-W-0
160 10,81

11,51
177 11,65

13,63
231 16,04

13,31
222 15,16

15,28 200 13,51 248 16,33 185 12,85 286 19,54
151 10,20 196 12,90 159 11,04 163 11,13

P-W-10
182 12,30

12,23
202 13,30

15,19
237 16,46

15,74
159 10,86

11,63 172 11,62 233 15,34 218 15,14 187 12,77
189 12,77 257 16,92 225 15,63 165 11,27

P-D-10
155 10,47

10,29
66 4,35

7,75
73 5,07

9,31
87 5,94

9,49 159 10,74 89 5,86 127 8,82 132 9,02
143 9,66 198 13,04 202 14,03 198 13,52

P-W-20
139 9,39

11,19
270 17,78

14,24
166 11,53

12,11
164 11,20

13,48 143 9,66 233 15,34 158 10,97 237 16,19
215 14,53 146 9,61 199 13,82 191 13,05

11,51 12,23
10,29

11,19
13,63

15,19

7,75

14,24
13,31

15,74

9,31
12,11

15,28

11,63
9,49

13,48

0
2
4
6
8

10
12
14
16
18

P-W-0 P-W-10 P-D-10 P-W-20

K
u

a
t

T
e
k

a
n

(
M

P
a

)

Variabel

Hasil Pengujian Kuat Tekan Paving Block
(Tanpa Perawatan)

Hari Ke-8 Hari Ke-18 Hari Ke-29 Hari Ke-56

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the results of water absorption testing carried out in the field are shown in Table 8, this
can also be used as a correction factor whether the water absorption power possessed by
certain variables is proportional to the compressive strength test value obtained. The water
absorption test was carried out 4 times and the results were obtained that the test pieces
made in the field until the 4th test did not have good water absorption results and showed
very high results were also too waterproof and did not enter the water absorption standard
of the paving block which had a range of 3%-10%. The P-W-20 variable is the only
variable with sufficient absorption according to SNI 03-0691-1996 in table 1. Properties
of physics. This can be caused by several factors that cause the test piece to absorb too
much water, resulting in too high absorption such as cavities in the test piece that may be
too much and too open.

Table 8

Field water absorption test results

If you look at each test result, both compressive strength testing and water
absorption testing, of course, the results are obtained that the tests carried out in the
laboratory have better test results than the tests carried out in the field. This can be caused
by differences in the treatment carried out in the process of making test pieces or
differences in treatment when preparing for the use of materials. With the difference in
treatment that occurs in the manufacturing and preparation process, there are various
results that are considered to be able to reduce the quality both in terms of compressive
strength and water absorption. One of them is about the difference in preparation for the
use of stone sand materials, the use of stone sand as a fine aggregate certainly requires
some preparation so that the stone sand used does not pass the standard for the use of the
maximum grain size of fine aggregate. Fine aggregate itself is one of the important
components that plays a role in determining the strength of concrete bricks in general
(Nofrianto & Hutrio, 2023). Fine aggregate in the use of concrete brick making has a
maximum grain size of 4.75 mm and this is missed in the use of fine aggregate in the field
because it is not filtered with a sieve that is in accordance with the maximum size of fine
aggregate, the condition of the aggregate can be seen in Figure 4 and Figure 5
respectively. Filtration is carried out on the use of materials in the laboratory so that the
test piece in the laboratory does not have an aggregate that is more than its maximum
grain size.

Variable

Hari ke-7 Hari ke-14 Hari ke-28 Hari ke-56
Berat
Awal

Berat
Akhir

Penyerapan
Berat
Awal

Berat
Akhir

Penyerapan
Berat
Awal

Berat
Akhir

Penyerapan
Berat
Awal

Berat
Akhir

Penyerapan

(kg) (kg) (%) (kg) (kg) (%) (kg) (kg) (%) (kg) (kg) (%)
P-W-0 3 3,55 18,33 2,95 3,5 18,64 2,8 3,1 10,71 2,95 3,03 2,71

P-W-10 3,25 3,65 12,31 3,2 3,8 18,75 3 3,5 16,67 3,2 3,26 1,87
P-D-10 3,1 3,65 17,74 2,95 3,5 18,64 2,85 3,3 15,79 3 3,06 2,00
P-W-20 3,15 3,6 14,29 3,25 3,7 13,85 3,15 3,45 9,52 3,1 3,2 3,23

Government Support, Trust, and UTAUT 2 in Willingness to Adopt & Pay Smart Home
Indonesia

Indonesian Journal of Social Technology, Vol. 5, No. 12, December 2024 6157

Picture 5

Field specimen cavity

In addition to the cavities found in the test piece, the amount of fly ash used also
affects the water absorption on the paving block because referring to several studies on
the properties of fly ash, fly ash is a material that absorbs more water than cement
(Pataras, Arliansyah, Kadarsa, Fatimah, & Diningrum, 2023). So that as the number of
fly ash used in the manufacture of paving block test pieces increases, the water absorption
properties in the paving block will allegedly be higher.

Conclusion

Based on the research that has been conducted, fly ash can be used as a substitute
or substitute for cement with the right amount and procedure. The optimal use of fly ash
from coal combustion by PT Sumber Alam Sekurau for additional materials for making
paving blocks is in the range of 10%-20%. The results of laboratory tests showed that the
highest compressive strength values were obtained in the use of fly ash of 10% and 20%
(variables P-15-10 and P-15-20) with a compressive strength value of 20.1 MPa at the
age of 56 days, meeting the quality of category B concrete bricks with water absorption
of 4.02% and 4.54% respectively. Meanwhile, the results of the test in the field showed
the highest compressive strength value of 15.74 MPa in the P-W-10 variable with a
percentage of fly ash of 10%, obtained at the age of 28 days, included in the quality
category of concrete brick C, although the water absorption of 16.67% still requires
correction. Differences in the manufacturing process and material preparation are
important factors that affect the difference in test results.

Anggoro Ary Nugroho, Imam Salehudin

Indonesian Journal of Social Technology, Vol. 5, No. 12, December 2024 6158

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