101
The Effect of Substitution Fly Ash with Cement and Artificial Aggregate as Gravel Material and the Addition
of Superplasticizer to the Compressive Strength of Concrete
Syafwandi, Imam Wafa
Departement of Civil Engineering, Mercu Buana University Jakarta, Indonesia
[email protected], [email protected]
Abstract
The Jakarta-Bandung High Speed Railway is one of the National Strategic Projects launched by the Government of Indonesia. The project, which is a form of cooperation between Indonesia and China, uses China's standard quality concrete as its main construction. The basic difference between Indonesia’s and China’s quality concrete is in the quality naming, where Indonesian concrete uses f'c and K, while China concrete uses C quality. One of the concrete qualities used is C50 T1-T2. Therefore, this study examined 4 conditions to determine the value of concrete compressive strength, slump, and setting time. This research was conducted by comparing the mixture of artificial stone, sand, fly ash type F, cement and additional superplasticizer with gravel, sand, fly ash type F, cement and additional superplasticizer. This study aims to determine whether artificial stone can be used as a mixture of compositions to make concrete with predetermined specifications, namely C 50 T1-T2, the method used is an experimental method using a cube test object measuring 15x15x15 cm as many as 32 pieces consisting of 4 pieces.
different compositions and tested concrete at age, 3 days, 7 days, 14 days, and 28 days. Based on this research, the maximum compressive strength of concrete was obtained at 28 days. The composition of concrete with artificial stone at the age of 28 days is 63,6 Mpa and 72,4 Mpa, while the composition of concrete with gravel at 28 days is 66,0 Mpa and 65,1 Mpa. The slump value with the addition of superplasticizer has no significant effect on the slump value. The values obtained in the composition of artificial stone are 20 and 23 cm while the slump values obtained in the composition of gravel are 20 and 23 cm. The setting time value has a significant effect on the initial setting and final setting of the concrete. The initial setting time and final setting values for the 0.8% superplasticizer dose were 107 and 165 minutes and for the 1% superplasticizer dose were 110 and 181 minutes, respectively. The higher the dose of superplasticizer, the higher the setting time value on the concrete.
Keywords:
Artificial Stone, Compressive Strength, Concrete, Setting Time, Slump
1. Introduction
In Indonesia, the concept of using fly ash and the use of low cement content in high-strength concrete mixtures for civil engineering construction structures is still not widely known and has not been widely applied.
This is because high-strength concrete is easier to achieve by using large amounts of cement but does not have good economic value in a concrete mixture.
(et al Pandaleke, 2014) The geopolymer concrete mixture has rigid viscosity properties, whereas in the casting process the workability of concrete is needed to facilitate its implementation. To overcome this problem, instead through the use of additives (additives admixtures) or superplasticizer.
According to Presidential Regulation Number 58 of 2017 concerning Amendments to Presidential Regulation Number 3 of 2016 concerning Acceleration of Implementation of National Strategic Projects, there are as many as 248 National Strategic Projects launched by the Central Government. One of them is the Jakarta- Bandung Fast Train project which is a form of collaboration between Indonesian SOEs and the Chinese Consortium which was later called PT KCIC (Indonesian China Fast Train). One of the concrete used in this 142.3km project is the quality C 50 T1-T2 which is a high quality concrete using a composition of materials, namely fine aggregate, aggregate
coarse, cement, water and admixture with the value of the compressive strength of concrete at the age of 3 days of 29.05 MPa, 59.45 MPa for 7 days, 60.05 MPa for 14 days, and 62.25 MPa for 28 days. Then a research will be carried out by replacing the predetermined composition, namely with fine aggregate, artificial aggregate, F type fly ash, cement, and additional superplasticizer to find out whether the composition of this concrete mix can be used as a design for C 50 quality in this KCIC project.
1.1. Identification of Problems
Based on the description of the background of the problem above, the identification of the problem can be made, namely by knowing the composition of the high-strength concrete C 50 used in the KCIC project, research will be carried out by replacing the predetermined composition, namely with fine aggregate, artificial aggregate, fly ash type F. , cement, and the addition of a superplasticizer to determine whether the composition of this concrete mix can be used as a design for the C 50 grade in this KCIC project.
1.2. Research Purpose and Objectives
The purpose and objectives of this research are:
1. Knowing the provisions on how to use F type fly ash as a substitute for cement and the addition of a superplasticizer to produce high-strength concrete according to Chinese standards
2. Knowing the comparison of the compressive strength of artificial concrete + fly ash type F grade I + superplasticizer and gravel + fly ash type F grade I + superplasticizer with different doses.
3. Knowing the maximum compressive strength value at a predetermined age of 3, 7, 14 and 28 days 4. Knowing the comparison of setting time on the addition of superplasticizer
2. Methodology 2.1. Research Method
In this study, researchers used an experimental method to determine the compressive strength of high- strength concrete consisting of the basic ingredients for making concrete, namely fine aggregate, artificial aggregate, F type fly ash, cement, and additional superplasticizer. This study aims to determine the maximum compressive strength of concrete at the age of 3, 7, 14, and 28 days.
2.2. Time and Research Place
j. Research PlaceThis research was conducted in the laboratory of PT Wijaya Karya Beton Tbk k. Research Time
The research was carried out in April 2021. The manufacture of test specimens up to testing the compressive strength of concrete is planned to be completed in June 2021
2.3. Research Variable
The research variables in this study consisted of two kinds. The first variable is the independent variable which is given the notation X and the second variable is the dependent variable which is given the notation Y. This study determined that the independent variable (X) was Chinese concrete which was added with type F fly ash, artificial aggregate and superplasticizer as precursors and the dependent variable (Y) is the compressive strength of concrete.
2.4. Flowchart
The stages of analysis in the calculation of this study are as described in the following figure:
103 Figure 1. Flowchart (Source: Author, 2021)
3. Result and Analysis 3.1. Mix Design Planning
1. Determination of Compressive Strength Plan
When the design compressive strength of concrete is < C60, the compressive strength test can be calculated by:
fCu,0 ≥ Cu,k + 1,645 σ fCu,0 ≥ 50 + 1,645 x 6 fCu,0 ≥ 59,87 Mpa
Start
Library Studies/Literature
Preparation of Tools and Materials
Fine and Coarse Aggregate Testing
Mix Design
Slump Testing
Test Object Creation
Therapy
Press Strong Test
Data Analysis
Conclusion
Done
2. Fas used for Chinese concrete 0.264 based on technical specifications and based on China's high-speed rail technical experience
3. The water requirement is seen based on table
Table 1. The water requirement of dry concrete (kg/m3)
‘ Pebble Size (mm) Gravel Size (mm)
Indeks 10 20 40 16 20 40
Konsistensi weibull (s)
16 – 20 175 160 145 180 170 155
11 – 15 180 165 150 185 170 160
5 – 10 185 170 155 190 180 165
Source: (JGJ 55 – 2011)
When the slump value in table 1 is less than the planned slump, then for every additional 20mm the slump value is added 5 kg of water so that the required water per m3 can be calculated as follows:
Water requirement = 215 + ((200-90) / 20) x 5
= 242,5 kg
4. When admixture is added, the water requirement per m3 of concrete (mwo) can be calculated by:
mwo = mwo’(1- ) = 242,5 (1 – 27%) = 177,025 kg
5. To find out the amount of binder material per m3 of concrete (mbo), the following calculations are carried out:
mbo =
=
= 670,55 kg
Because the maximum limit for using a binder is 480 kg, and based on experience in high-speed train construction, the water used is 123 kg, so the required binder is
mbo =
mbo =
= 465 kg
6. Calculating the amount of cement, fly ash, and admixture F type fly ash = 465 x 10% = 47 kg
Cement = 465 - 47 = 418 kg Admixture 1 = 465 x 1% = 4.65 kg Admixture 2 = 465 x 0.8% = 3.72 kg 7. Based on the S/A test used is 39.5%
8. Counting the amount of sand and gravel
9. Assuming the density of concrete for 1 m3 is 2350 kg/m3, then:
Total weight of concrete = weight of cement + weight of F type fly ash + weight of sand + weight of gravel + weight of water
Weight of sand + weight of gravel = 2350 – (47+418+123)
= 1762 kg
Weight of sand = 1762 x S/A
= 1762 x 0.395 = 696 kg
Weight of gravel = 1762 – 696 = 1066 kg
3.2. Compressive Strength Test
The compressive strength test of concrete was carried out to find out how much influence the use of artificial stone and superplasticizer had on the compressive strength of the resulting concrete. Tests were carried out on specimens aged 3 days, 7 days, 14 days, and 28 days. The steps for testing the compressive strength of concrete are as follows:
1. Conduct trial mix for the first concrete condition, namely artificial material + F type fly ash + 0.8%
superplasticizer
2. Inserting the concrete mixture into the 15 x 15 x 15 cm cube-shaped test object/mold 3. Putting the molding that has been filled with concrete mix on the vibrating table 4. Turn on the vibrating table to ensure that all parts are evenly filled
5. Adding concrete mix if it has not reached full
6. Leveling the top of the concrete mix if it has not reached full
7. Putting the molding containing the concrete mixture in the place provided
105 8. Removing the test object from the molding after 24 hours
9. Test the compressive strength of the specimens at the age of 3 days, 7 days, 14 days, and 28 days 10. Repeat test for concrete condition:
a. Artificial material + F type fly ash + 1% superplasticizer b. Gravel + F type fly ash + 0.8% superplasticizer
c. Gravel + F type fly ash + 1% superplasticizer The test results are presented in the following table:
Table 2. The result of compressive strength test
No Test age
Compressive strength C50 (Mpa) Artificial Stone +
Sand + Cement + FA tipe F+ SP 0,8%
Artificial Stone + Sand + Cement + FA tipe F + SP 1%
Gravel + Sand + Cement + FA tipe F
+ SP 0,8%
Gravel + Sand + Cement + FA tipe F
+ SP 1%
1 3 day 55,9
51,8 55,8
53 48,4
52,2 60,6
56,6
47,8 50,2 56 52,7
2 7 day 56,0
54,9 57,2
56,4 59,6
59,9 60,6
60,8
53,8 55,6 60,2 60,9
3 14 day 55,4
56,1 58,8
59,5 60,2
60,6 61,4
62,15
56,8 60,2 61,0 62,9
4 28 day 64,0
63,6 69,6
72,4 59,8
66,0 61,3
65,1
63,1 75,6 72,2 68,9
(Source: Author, 2021)
Figure 2. Compressive strength chart (Source: Author, 2021)
From table 2 shows that:
1. Concrete 1 with the addition of artificial stone + SP 0.8%, with 2 test objects has an average age of testing 3 days of 51.8 MPa, at the age of testing 7 days of 54.9 MPa, at the age of testing 14 days of 56.1 MPa
2. Concrete 2 with the addition of artificial stone + 1% SP, with 2 test objects has an average of 53 MPa at 3 days of testing, 56.4 MPa at 7 days of testing, 59.5 MPa at 14 days of testing MPa
3. Concrete 3 with the addition of gravel + SP 0.8%, with 2 test objects has an average age of testing 3 days of 52.2 MPa, at the age of testing 7 days of 59.9 MPa, at the age of testing 14 days of 60.6 MPa
4. Concrete 4 with the addition of gravel + SP 1%, with 2 test objects has an average age of testing 3 days of 56.5 MPa, at the age of testing 7 days of 60.8 MPa, at the age of testing 14 days of 62, 15 MPa
3.3. Slump Test
Tests were carried out to determine the workability of concrete with the addition of superplasticizer. And the following are the results of testing the slump value for each concrete mix composition:
51,8 54,9 53 56,4 52,2 59,9 56,5 60,8
56,1 63,6 59,5 60,6 62,15
72,4
66 65,1
0 10 20 30 40 50 60 70 80 90 100
Batu Buatan + SP 0,8%
Batu Buatan + SP 1% Kerikil + SP 0,8% Kerikil + SP 1%
Strong Press Concrete
3 hari 7 hari 14 hari 28 hari
Table 3. Slump Result
No Concrete Code SP Consumption (%) Fly ash (%) Slump fall (cm) Slump Flow (cm)
1 Artificial Stone 0,8 10 20 58
2 1 10 23 60
3 Gravel 0,8 10 20 58
4 1 10 23 60
(Source: Author, 2021)
Figure 3. Compressive strength chart (Source: Author, 2021) From table 3 can be seen:
1. The value of Slump Fall and Slump Flow in the artificial aggregate concrete code + SP 0.8% is 20 cm and 58 cm
2. The value of Slump Fall and Slump Flow in the artificial aggregate concrete code + SP 1% is 23 cm and 60 cm 3. The value of Slump Fall and Slump Flow on gravel + SP 0.8% concrete code is 20 cm and 58 cm
4. The value of Slump Fall and Slump Flow on gravel + SP 1% concrete code is 23 cm and 60 cm
This is because the use of a cement superplasticizer can be reduced while maintaining the value of the water- cement factor. Increasing the compressive strength of concrete by reducing the water-cement factor, but with a consistent cement content and the same workability ASTM C.494 (1995:254).
3.4. Setting Time Test
Bonding is the change of form from a liquid to a solid. Bonding time the initial setting time is the time from mixing cement and water until it loses its plasticity while the final setting time is the time until the paste becomes a hard mass (Kasmuri, 2019)
The setting time testing steps are carried out as follows:
1. Setting up the vicat tool to test the setting time. The first test was carried out for C50 concrete 2. Weighing:
a. cement 250 g, water 136, fly 250 g, and SP 1%
b. ement 250 g, water 134, fly ash 25 g, and SP 0.8%
3. Set the vicat tool according to the standard
4. Make mortar by mixing cement with water using a mixing tool
5. Put the mortar into the mold with a glass base as much as half of the mold then knock it until it is solid 6. Put the mortar again into the remaining half of the mold and flatten it
7. Put the mortar that is already in the mold under the vicat
8. Drop the test rod into the mortar mold with a distance of ±0.5 cm from the surface. Then record the penetration that occurs
9. Record the distance of the test rod from the glass base when the test rod stops sinking. Record the time required when the needle shows the number 6±1 (S)
10. Lift the test rod and clean it 11. Recompacting the tested mortar
12. Put the mortar into the curing box for ± 2 hours, then retest using the vicat as before and record the needle readings that occur
13. Record the distance of the test needle from the glass base when the test rod stops sinking
20 23 20 23
58 60 58 60
0 10 20 30 40 50 60 70
Agregat Buatan + SP 0,8%
Agregat Buatan + SP 1%
Kerikil + SP 0,8% Kerikil + SP 1%
Slump Value Chart
Nilai Slump Jatuh (cm) Nilai Slump Flow (cm)
107
14. Record the time obtained when the reading of the numbers is 4±1 and this is when the initial setting time occurs
15. Lift the test needle and clean it
16. Change / reverse the position of the mortar from the top to the bottom
17. Put it in the curing box for ±1 hour, then test again using the vicat tool as before
18. Final setting time occurs when the circle on the final setting test needle does not touch the mortar The results of the test are presented in the following table:
Table 4. Setting Time Result
No Compotition Initial Setting Final Setting
1 cement 250 g , water 136, fly ash 250 g, dan SP 1% 110 mnt 181 mnt 2 cement 250 g, water 134, fly ash 250 g, dan SP 0,8% 107 mnt 165 mnt
(Source: Author, 2021)
From table 4 it can be seen that the addition of superplasticizer can slow down the setting time. From the table, it is found that the addition of SP as much as 0.8% can slow down the setting time from initial setting to final setting up to 58 minutes and at 1% SP up to 71 minutes.
4. Conclussion
Based on the results of the research on the effect of substitution of fly ash with cement and artificial aggregate as gravel material and the addition of superplasticizer on the compressive strength of concrete, it can be concluded:
1. From the research, it was found that to achieve high-strength concrete specifications required fly ash type F by 10% with the addition of a superplasticizer in the range of 0.8 - 1%
2. Comparison of the compressive strength of concrete using gravel material with artificial stone material is not much different. At the age of 3 days the two concretes have met the specifications for the compressive strength of C50 T1-T2, which is 50 MPa, but at the age of 28 days the compressive strength of concrete using artificial stone material increased significantly from 59.5 MPa to 72.4 MPa of concrete compressive strength. , while for gravel material 62.15 MPa becomes 65.1.
3. The compressive strength of concrete with the composition of artificial stone + sand + fly ash type F + cement + SP0.8% at the ages of 3, 7, 14, and 28 days, respectively, is 51.8 MPa, 54.9 MPa, 56, 1 MPa, and 63.6 MPa.
The compressive strength of concrete with the composition of artificial stone + sand + fly ash type F + cement + SP 1% at the age of 3, 7, 14, and 28 days, respectively, was 53 MPa, 56.4 MPa, 59.5 MPa, and 72 ,4 MPa.
The compressive strength of concrete with the composition of gravel + sand + fly ash type F + cement + SP 0.8% at the age of 3, 7, 14, and 28 days in a row is 52.2 MPa, 59.9 MPa, 60.6 MPa , and 66.0 MPa. The compressive strength of concrete with the composition of gravel + sand + fly ash type F + cement + SP 1% at the age of 3, 7, 14, and 28 days, respectively, was 56.6 MPa, 60.8 MPa, 62.15 MPa, and 65.1 MPa.
4. So that the highest compressive strength value is obtained in the composition of artificial stone + sand + fly ash type F + cement + SP 1%, because the crush index value in artificial aggregate is very high which is a factor in the compressive strength value in concrete.
5. The addition of superplasticizer can slow down the setting time. The addition of 0.8% SP can slow down the setting time from initial setting to final setting up to 58 minutes and at 1% SP up to 71 minutes. The higher the SP dose, the longer the setting time.
References
American Standard Testing and Material. (1995). Standard Specification for Chemical Admixtures for Concrete.
C.494. 1995: 254
Et al Pandaleke. 2014. Pengaruh Variasi Kadar Superplasticizer Terhadap Nilai Slump Beton Geopolymer. Jurnal Sipil Statik Vol. 2 No. 6. Universitas Sam Ratulangi: Manado
Kasmuri, Mudiono. 2019. Pengaruh Variasi Suhu Pembakaran Abu Cangkang Sawit Sebagai Bahan Substitusi Semen Terhadap Waktu Ikat dan Kuat Tekan Mortar. Jurnal Kajian Teknik Sipil, Vol. 04, No. 1. Program Studi Teknik Sipil, UTA’45: Jakarta
Railway Industry Standard of the People’s Republic of China, 2011. JGJ 55-2011 Ordinary Concrete Mix Design Rules. China Railway Corporation, Beijing.
