61
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 grcm
3
. 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
62
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 50:5
25:10 2
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
grcm
3
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
Source: Tjokrodimuljo, 1992
63
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 grcm
3
. 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 grcm
3
Average of Weight Density grcm
3
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
14 days
64
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 grcm
3
. 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 grcm
3
Average of Weight Density grcm
3
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
28 days
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 grcm
3
5.4. Compressive Strength of Concrete
