DISCUSSION MANAJEMEN RISIKO KONTRAK ANTARA KONTRAKTOR DENGAN SUBKONTRAKTOR.
56
CHAPTER V
DISCUSSION
5.1.Result and Discussion of material Investigation
5.1.1. Investigate the Fine Aggregate to Obtain the Results. 1. Investigation of the organic matter content.
Investigate the organic matter content is important because the organic matter content can reduce the quality of the concrete. To know whether it is possible to be used or not can be seen from the color of the sample. The relationship between the color and possibility of fine aggregate can be seen from Table 5.1.
Table 5.1 Relationship between the Color of the Solution and Organic Mater Content
No. Color Organic Mater Information
5 Light flaxen Less organic matter
content Good to be used
8 Flaxen
Rather much organic matter
content
Can be used 11 Dark Yellow
A lot of organic
matter content Not really good to be used 14 Dark Orange
A lot of organic
matter content Cannot be used 16 Dark Red A lot of organic
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(5-1) After the sand washed using NaOH 3% and kept for 24 hours, the solution is appropriate with the color of Gardner Standard Color No. 8 so that the sand can be used for the experiment.
2. Investigate the amount of mud in sand
Fine aggregate should not contain of mud until 5% greater than the density of dry oven. If the mud levels exceed 5%, the fine aggregate should be washed because the high value of mud can reduce the bind between fine aggregate and geopolymer paste. So, the quality of the concrete can be bad. The value of the investigation can be seen in Table 5.2.
Table 5.2 Investigation of Mud in the Sand. Investigation weight (gram) Weight of sand
(A) 99
So, the amount of mud in the sand can be calculated as follow:
with:
W= the amount of the mud in the sand A = the weight of sand after dried in the oven
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Based on SK SNI S-04-1989-F, fine aggregate cannot have the amount of mud more than 5%. If the mud is more than 5% so that the fine aggregate should be washed because the high content of mud will decrease the bond between sand and paste and it makes the quality will decrease.
3. Density and Absorption
The result of the density and absorption test of fine aggregate can be seen in table 5.3.
Table 5.3 Result of the Density and Absorption Test of Fine Aggregate
Information Value
A Dry Weight Sample 500 gram
B Weight Sample (SSD) 178
C Weight of Sample from the Oven 482,13 gram
D Bulk Density =
2,712
E Bulk Density SSD =
2,812
F Apparent Density =
3,001
G Absorption=
3,701%
The fine aggregate is restrained in the sieve no. 4 (4.75mm). The weight of the sample is 500gr. From the requirement, the density of the fine aggregate for the normal concrete is around 2.4-3.2 gr/cm3. The density of this test is
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2.712%. So the sand can be used in the geopolymer concrete. The absorption of the split is 3.701%
4. Water Content
The water content test of fine aggregate is equal to 1.6635 %. The calculation of the water content of fine aggregate can be seen in appendix A.3
5.1.2. Investigate the Coarse Aggregate to Obtain the Result 1. Investigation of the organic matter content.
Coarse aggregate shall not contain the mud 1% greater than the density of dry oven. If the mud levels exceed 1%, the coarse aggregate should be washed, because of the high levels of mud would reduce bond coarse aggregate in the concrete mix. The investigation value of the mud in coarse aggregate can be seen in Table 5.4.
Table 5.4 Investigation of Mud in the Coarse Aggregate
Investigation Weight
(gram) Weight of coarse aggregate
(A) 99.3
So, the amount of mud in the sand can be calculated as follow:
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with:
W= the amount of the mud in the coarse aggregate A = the weight of coarse aggregate after dried in the oven
The amount of mud in coarse aggregate is <1% so that the coarse aggregate can be used as the material of the specimen.
2. Density and Absorption
The result of the density and absorption test of coarse aggregate can be seen in table 5.5.
Table 5.5 Result of the Density and Absorption Test of Coarse Aggregate
Information Value
A Dry Weight Sample 500 gram
B Weight Sample (SSD) 505 gram
C Weight of Sample in the Water 293,5 gram
D Bulk Weight Density
) ( ) ( ) ( C B A 2,3711
E Bulk Weight Density (SSD)
) ( ) ( ) ( C B B 2,3948
F Weight Density (Apparent)
) ( ) ( ) ( C A A 2,4289
G Absorption x 100% ) ( ) ( ) ( A A B 1%
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The coarse aggregate is restrained in the sieve no. 4 (4.75mm). The weight of the sample is 500gr. From the requirement, the density of the coarse aggregate for the normal concrete is around 2.4-3 gr/cm3. The density of this test is 2.3711%. So the coarse aggregate can be used in the geopolymer concrete. The absorption of the coarse aggregate is 1%
3. Water Content
The water content test of coarse aggregate is equal to 1,342%. The calculation of the water content of coarse aggregate can be seen in appendix A.4
5.2.Slump Test
Slump test was conducted to measure the ease slump concrete mix to be done (workability). Implementation procedures described in Chapter IV. The Value of slump was affecting the strength of the concrete. The big value of slump will produce a bad concrete because it can produce a porous concrete. If the value of the slump is too small the concrete will be difficult to be mixed. The tests carried out per variant slump value at age 14 and 28 days. Slump Test results is shown in the table 5.6
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Table 5.6 The Result of Slump Test at 14 days and 28 days Varian
Slump Value (14 days)
Slump Value (28 days) Metakaolin : Silica Fume (cm)
75:5 0 0
50:5 0 0
25:10 2 0
The differences value in the experiment is because the amount of additional water to make the mixture is easy to be done. If the amount of additional water is high the mixture will be too wet and the value of the test will be higher.
5.3.Weight Density of Concrete
The types of concrete can be grouped based on the weight of the concrete type. Concrete grouping based on its density can be seen in Table 5.7.
Tabel 5.7 Specification of Weight Density of Concrete
Type Weight Density
(gr/cm3) Usage
Very Lightweight
Concrete <1,00 Non Struktur
Lightweight Concrete 1,00-2,00 Lightweight Structure
Normal Concrete 2,30-2,50 Structure
Weight Concrete >3,00 Light shield
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In this research, the age of the concrete is divided into two types; 14 days and 28 days. In day 14, the highest value of the density is in the percentage of both metakaolin and silica fume as much as 25:5. The value is 1.9519 gr/cm3. The complete value can be seen in Table 5.8 and the chart can be seen in Figure 5.1.
Tabel 5.8 Average Weight Density in 14 days
Pozzolan Weight Density
(gr/cm3)
Average of Weight Density (gr/cm3) Metakaolin : Silica Fume
25:5
1.9757
1.9519 1.9381
1.9419 50:5
1.8706
1.8974 1.8929
1.9288 75:5
1.7608
1.7176 1.6988
1.6932
Figure 5.1 Weight Density in 14 Days Chart
1,6000 1,6500 1,7000 1,7500 1,8000 1,8500 1,9000 1,9500 2,0000
25:5 50:5 75:5
Wei
g
h
t
D
e
n
si
ty
(gr
/c
m
3)
Precentage of Metakaolin and Silica Fume (%)
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In day 28, the highest value of the density is in the percentage of both metakaolin and silica fume as much as 25:5. The value is 1.9287 gr/cm3. The complete value can be seen in Table 5.9 and the chart can be seen in Figure 5.2.
Tabel 5.9 Average Weight Density in 28 days
Pozzolan Weight Density
(gr/cm3)
Average of Weight Density (gr/cm3) Metakaolin : Silica Fume
25:5
1.8616
1.9287 1.9902
1.9344 50:5
1.7159
1.8051 1.8512
1.8483 75:5
1.6783
1.6939 1.7351
1.6683
Figure 5.2 Weight Density in 28 Days Chart
1,5500 1,6000 1,6500 1,7000 1,7500 1,8000 1,8500 1,9000 1,9500
25:5 50:5 75:5
Wei
g
h
t
D
e
n
si
ty
(gr
/c
m
3)
Precentage of Metakaolin and Silica Fume (%)
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65
The value of weight density is depends on the sample. It is because of the process of the compaction from the sample itself. Based on the table above, weight density of the geopolymer concrete is belongs to lightweight concrete. The biggest value of the average weight density of concrete comes from the geopolymer concrete with the proportion of the metakaolin and silica fume; 25:5 in 14 days. The value is 1.9519 gr/cm3
5.4.Compressive Strength of Concrete
Compressive strength test is done at the age of 14 days and 28 days. The test is done by machine (UTM) with Shimadzu brands. The test results from the small cylinder (day 14) are already change into the normal size of the concrete (150 mm x 300 mm). The compressive strength value of the research can be seen in Table 5.10 and the chart of compressive strength test can be seen in Figures 5.3 and 5.4.
Table 5.10 Compressive Strength Test
Pozzolan Compressive Strength (Mpa)
Metakaolin Silica Fume 14 days 28 days
25% 5%
2.30729
2.071743
1.10814
1.149566
2.02273 1.20311
1.88520 1.13744
50% 5%
1.37959
1.229189
0.68563
0.641213
1.21979 0.61374
1.08817 0.62426
75% 5%
0.69916
0.675865
0.15911
0.178246
0.63963 0.19685
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Figure 5.3 Compressive Strength Column Chart
Figure 5.4 Compressive Strength Line Chart
Based on the test, the highest value of the compressive strength is 2.071743 MPa in day 14 with the ratio of metakaolin and silica fume as much as 25:5. From the test, it is known that the highest proportion of metakaolin, the lowest value of the test.
0 0,5 1 1,5 2 2,5
25% : 5% 50% : 5% 75% : 5%
Co
m
p
re
ssi
v
e
Str
e
n
g
th
Value
(M
Pa)
Precentage of Metakaolin and Silica Fume (%)
14 days 28 days
0 0,5 1 1,5 2 2,5
25% : 5% 50% : 5% 75% : 5%
Co
m
p
re
ssi
v
e
Str
e
n
g
th
Value
(M
Pa)
Precentage of Metakaolin and Silica Fume (%)
14 days 28 days
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The value of the mixture should be higher because both metakaolin and silica fume have higher percentage of SiO2 (Silica) and both of them also contain of Calcium Oxide (CaO). CaO will has a reaction with NaOH become Ca(OH)2. SiO2 will be react with Ca(OH)2 become Calcium Silicate Hydrate (CSH) that will be used as a paste. The mixture should be strong enough.Na2SiO3 also used as alkali of the geopolymer. The Na2SiO3 will react with NaOH and make a strong binder.
From the result, the values of the concrete are very low. According to the author, the values are low because they do not have a good proportion of CaO. So, the reaction is not properly. From the table below, it is known that all of the materials only have a good proportion in Silica, but not in Calcium Oxide while the composition of CaO in cement is really big; 64.67%. The composition of the contents can be seen in Table 5.11.
Table 5.11 Composition of the Contents
Content Name cement Metakaolin Silica Fume
SiO2 Silica 21.03% 66.39% 85%
CaO Calcium Oxide 64.67% 3.08% <1
Fe2O3 Iron Oxide 2.58% 5.00% -
MgO Magnesia 2.62% 9.64% -
Na2O Alkali 1.34% 2.97% 8,72%
5.5.1. Research Comparison
Research comparison is used to show the effect of the material in the concrete. Every research has its own result that depends on the material preparation,
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temperature, type, and environment. This research will be compared with the research from Lisantono and Hatmoko (2009) that also use metakaolin and bagasse ash as the materials. The tables of the comparison value can be seen in table 5.12 and table 5.13.
Table 5.12 Compressive Strength of the Test
Combustion of Metakaolin Time (minute) Molarity of NaOH
Pozzolan Compressive Strength (Mpa)
800°C 40 min’ 12M
Metakaolin Silica
Fume 14 days 28 days
25% 5%
2.307
2.071
1.108
1.149
2.022 1.203
1.885 1.137
50% 5%
1.379
1.229
0.685
0.641
1.219 0.613
1.088 0.624
75% 5%
0.699
0.675
0.159
0.178
0.639 0.196
0.688 0.178
Table 5.13 Compressive Strength of Lisantono and Hatmoko Research
Combustion of Metakaolin Time (minute) Molarity of NaOH
Pozzolan Compressive Strength (Mpa)
500°C 25 min’ 8M
Metakaolin Bagasse
Ash 14 days 28 days
50% -
0.715
0.560
0.759
0.721
0.467 0.507
0.497 0.898
50% 50%
0.427
0.380
0.720
0.852
0.473 0.950
0.239 0.886
- 50%
0.336
0.325
0.366
0.344
0.425 0.329
0.213 0.336
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Based on the comparison, the highest value of the compressive strength in this research is 2.071 MPa in day 14 with the ratio of metakaolin and silica fume as much as 25:5. The highest value of the compressive strength in Lisantono and Hatmoko (2009) research is 0.852 MPa in day 28 with the materials are metakaolin and bagasse ash. The tables show that the temperature of combustion, time of combustion and molarity of NaOH of both researches are different. That can be one of the reasons why the values of both researches are different. From the result of Lisantono and Hatmoko (2009), the highest proportion is in the metakaolin and bagasse ash in day 28. But, in day 14 the highest value is in the proportion of 50% of metakaolin. The lowest value of the result in Lisantono and Hatmoko (2009) is in the result from the bagasse ash. The values are 0.325 MPa in 14 days and 0.344 MPa in 28 days. There will be an effort how to increase the compressive strength of geopolymer concrete based on metakaolin. But, according to the theories and researches from the other researchers, metakaolin should be strong material from concrete.
5.5.Modulus Elasticity of Concrete
The result of modulus of elasticity is depends on the composition of the mixture. In this research the result of the modulus of elasticity can be seen in the table 5.14 and the average of modulus of elasticity value can be seen in Table 5.15.
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Table 5.14 Modulus of Elasticity Test
Concrete
Area (Ao)
Average of
Area Po
Maximum load
Average of
Compression Average
Average of strain E
(cm2) (kgf) (Mpa) (Mpa) (Mpa)
25:5
172.5683
172.5683
21.34 725 0.2131
0.2001
0.0659 3.234
171.1738 20.91 675 0.2115 0.0786 2.691
170.7103 21.04 625 0.1867 0.0698 2.675
50:5
171.6380
171.6380
20.41 625 0.1857
0.1636
0.0719 2.583
172.5683 21.34 500 0.1491 0.0643 2.319
172.8013 20.91 525 0.1560 0.0705 2.213
75:5
172.5683
172.5683
20.32 150 0.0497
0.0673
0.0552 0.900
171.8704 20.93 275 0.0885 0.0714 1.239
172.8013 20.92 200 0.0638 0.0495 1.289
Table 5.15 Average of Modulus of Elasticity Test Modulus of Elasticity Average Modulus of Elasticity
(Mpa) (Mpa)
3.234
2,866 2.691
2.675 2.583
2.371 2.319
2.213 0.900
1.143 1.239
1.289
From the result, the highest maximum load is in the mixture with the proportion of metakaolin and silica fume; 25% : 5%. The value of compression strength test is 0.2131 MPa with the value of strain is 0.0659 and the value of
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modulus of elasticity is 3.234 MPa. The highest value of strain is in the proportion of metakaolin and silica fume; 50:5. The value is 0.0719 and the value of modulus elasticity is 2.583 MPa. The highest value of modulus of elasticity is in the proportion of metakaolin and silica fume; 25% : 5%. The value is 3.234 MPa.
Based on modulus of elasticity test that has been done, the value of the average of modulus of elasticity at 28 days with comparative precursor are metakaolin and silica fume are 25% :5% = 2.866 MPa, 50% :5% = 2.371MPa, 75% : 5% = 1.143 MPa. The modulus of elasticity chart can be seen in Figure 5.6.
Figure 5.6 Modulus of Elasticity Chart
0,000 0,500 1,000 1,500 2,000 2,500 3,000 3,500
25:5 50:5 75:5
M
o
d
u
lu
s
o
f E
lasti
ci
ty
Val
u
e
(
M
Pa)
(1)
66
Figure 5.3 Compressive Strength Column Chart
Figure 5.4 Compressive Strength Line Chart
Based on the test, the highest value of the compressive strength is 2.071743 MPa in day 14 with the ratio of metakaolin and silica fume as much as 25:5. From the test, it is known that the highest proportion of metakaolin, the lowest value of the test.
0 0,5 1 1,5 2 2,5
25% : 5% 50% : 5% 75% : 5%
Co
m
p
re
ssi
v
e
Str
e
n
g
th
Value
(M
Pa)
Precentage of Metakaolin and Silica Fume (%)
14 days 28 days
0 0,5 1 1,5 2 2,5
25% : 5% 50% : 5% 75% : 5%
Co
m
p
re
ssi
v
e
Str
e
n
g
th
Value
(M
Pa)
Precentage of Metakaolin and Silica Fume (%)
14 days 28 days
(2)
67
The value of the mixture should be higher because both metakaolin and silica fume have higher percentage of SiO2 (Silica) and both of them also contain of Calcium Oxide (CaO). CaO will has a reaction with NaOH become Ca(OH)2. SiO2 will be react with Ca(OH)2 become Calcium Silicate Hydrate (CSH) that will be used as a paste. The mixture should be strong enough.Na2SiO3 also used as alkali of the geopolymer. The Na2SiO3 will react with NaOH and make a strong binder.
From the result, the values of the concrete are very low. According to the author, the values are low because they do not have a good proportion of CaO. So, the reaction is not properly. From the table below, it is known that all of the materials only have a good proportion in Silica, but not in Calcium Oxide while the composition of CaO in cement is really big; 64.67%. The composition of the contents can be seen in Table 5.11.
Table 5.11 Composition of the Contents
Content Name cement Metakaolin Silica Fume
SiO2 Silica 21.03% 66.39% 85%
CaO Calcium Oxide 64.67% 3.08% <1
Fe2O3 Iron Oxide 2.58% 5.00% -
MgO Magnesia 2.62% 9.64% -
Na2O Alkali 1.34% 2.97% 8,72%
5.5.1. Research Comparison
Research comparison is used to show the effect of the material in the concrete. Every research has its own result that depends on the material preparation,
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temperature, type, and environment. This research will be compared with the research from Lisantono and Hatmoko (2009) that also use metakaolin and bagasse ash as the materials. The tables of the comparison value can be seen in table 5.12 and table 5.13.
Table 5.12 Compressive Strength of the Test
Combustion of Metakaolin Time (minute) Molarity of NaOH
Pozzolan Compressive Strength (Mpa)
800°C 40 min’ 12M
Metakaolin Silica
Fume 14 days 28 days
25% 5%
2.307
2.071
1.108
1.149
2.022 1.203
1.885 1.137
50% 5%
1.379
1.229
0.685
0.641
1.219 0.613
1.088 0.624
75% 5%
0.699
0.675
0.159
0.178
0.639 0.196
0.688 0.178
Table 5.13 Compressive Strength of Lisantono and Hatmoko Research
Combustion of Metakaolin Time (minute) Molarity of NaOH
Pozzolan Compressive Strength (Mpa)
500°C 25 min’ 8M
Metakaolin Bagasse
Ash 14 days 28 days
50% -
0.715
0.560
0.759
0.721
0.467 0.507
0.497 0.898
50% 50%
0.427
0.380
0.720
0.852
0.473 0.950
0.239 0.886
- 50%
0.336
0.325
0.366
0.344
0.425 0.329
0.213 0.336
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Based on the comparison, the highest value of the compressive strength in this research is 2.071 MPa in day 14 with the ratio of metakaolin and silica fume as much as 25:5. The highest value of the compressive strength in Lisantono and Hatmoko (2009) research is 0.852 MPa in day 28 with the materials are metakaolin and bagasse ash. The tables show that the temperature of combustion, time of combustion and molarity of NaOH of both researches are different. That can be one of the reasons why the values of both researches are different. From the result of Lisantono and Hatmoko (2009), the highest proportion is in the metakaolin and bagasse ash in day 28. But, in day 14 the highest value is in the proportion of 50% of metakaolin. The lowest value of the result in Lisantono and Hatmoko (2009) is in the result from the bagasse ash. The values are 0.325 MPa in 14 days and 0.344 MPa in 28 days. There will be an effort how to increase the compressive strength of geopolymer concrete based on metakaolin. But, according to the theories and researches from the other researchers, metakaolin should be strong material from concrete.
5.5.Modulus Elasticity of Concrete
The result of modulus of elasticity is depends on the composition of the mixture. In this research the result of the modulus of elasticity can be seen in the table 5.14 and the average of modulus of elasticity value can be seen in Table 5.15.
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Table 5.14 Modulus of Elasticity Test
Concrete
Area (Ao)
Average of
Area Po
Maximum load
Average of
Compression Average
Average of strain E
(cm2) (kgf) (Mpa) (Mpa) (Mpa)
25:5
172.5683
172.5683
21.34 725 0.2131
0.2001
0.0659 3.234
171.1738 20.91 675 0.2115 0.0786 2.691
170.7103 21.04 625 0.1867 0.0698 2.675
50:5
171.6380
171.6380
20.41 625 0.1857
0.1636
0.0719 2.583
172.5683 21.34 500 0.1491 0.0643 2.319
172.8013 20.91 525 0.1560 0.0705 2.213
75:5
172.5683
172.5683
20.32 150 0.0497
0.0673
0.0552 0.900
171.8704 20.93 275 0.0885 0.0714 1.239
172.8013 20.92 200 0.0638 0.0495 1.289
Table 5.15 Average of Modulus of Elasticity Test
Modulus of Elasticity Average Modulus of Elasticity
(Mpa) (Mpa)
3.234
2,866 2.691
2.675 2.583
2.371 2.319
2.213 0.900
1.143 1.239
1.289
From the result, the highest maximum load is in the mixture with the proportion of metakaolin and silica fume; 25% : 5%. The value of compression strength test is 0.2131 MPa with the value of strain is 0.0659 and the value of
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modulus of elasticity is 3.234 MPa. The highest value of strain is in the proportion of metakaolin and silica fume; 50:5. The value is 0.0719 and the value of modulus elasticity is 2.583 MPa. The highest value of modulus of elasticity is in the proportion of metakaolin and silica fume; 25% : 5%. The value is 3.234 MPa.
Based on modulus of elasticity test that has been done, the value of the average of modulus of elasticity at 28 days with comparative precursor are metakaolin and silica fume are 25% :5% = 2.866 MPa, 50% :5% = 2.371MPa, 75% : 5% = 1.143 MPa. The modulus of elasticity chart can be seen in Figure 5.6.
Figure 5.6 Modulus of Elasticity Chart
0,000 0,500 1,000 1,500 2,000 2,500 3,000 3,500
25:5 50:5 75:5
M
o
d
u
lu
s
o
f E
lasti
ci
ty
Val
u
e
(
M
Pa)