Page 11 - Open Access-June 2019
P. 11
120
120
120
Percentage residual compressive strength
120
100
100
100
100
100
100
100
100
80
80
80
80
80
80
80
M 30
M 30
M 30
M30
M 30
M 30
M 90
M 90
M 90
M 90
M90
M90
M 90
M 90
60
60
60
60
60
60
60
60
40
40
40
40
40
40
40
40
1520
3035
0
1015
1520
1015
2025
1520
3540
3035
4550
4045
3540
5 10
2530
2025
5 10
3540
1520
5 10
1015
2025
2530
2025
3035
2530
5 10
1015
0 5
0 5
2530
4045
3540
No. of cycles
No. of cycles
No. of cycles
No. of cycles
No. of cycles
No. of cycles
7
7
7
120
120
120
120
120
Percentage residual compressive strength
Percentage residual compressive strength
120
Percentage residual compressive strength
6
6
6
100
100
100
100
5
5
5
100
100
100
100
100
100
100
100
100 C
4
4
4
100 C
80
80
80
80
200 C
200 C
200 C
200 C
3
3
80
80
3
80
80
80
80
80
80
M 30
M 30
M 30
M 30
M 30
M 30
M 30
300 C
300 C
300 C
300 C
60
M3
2
0
60
M 30
M 90
2
60
60
2
M 90
M 90
M 90
M 90
M 90
M 90
M 90
400 C
400 C
400 C
400 C
M9
M90
0
M 90
M 90
60
60
60
60
60
60
60
60
1
1
1
40
40
0
0
0
40
40
45 50
50
40
50
0
20 25
40
40
40
25 30
50
30 35
40 0
5 10
40 0 5
2025
30 35
3540
3035
35 40
4550
0
4045
25 30
40 0
45 50
40 45
2530
40 0 5
0
4045
50
2530
2025
0 0 5 5 10 1015 1520 2025 2530 3035 3540 4045 4550 50 M 30 Percentage residual compressive strength Percentage residual compressive strength 120 120 0 0 5 5 10 1015 1520 2025 2530 3035 3540 4045 4550 50 M 30 Percentage residual compressive strength Percentage residual compressive strength Percentage residual compressive strength Percentage residual compressive strength 120 Percentage residual compressive strength 120 120 0 5 0 5 5 10 1015 1520 No. of cycles 3035 3540 4045
4550
1520
1015
0 5
5 10
2530
3540
2025
3035
50
4045
4550
1015
No. of cycles
No. of cycles
No. of cycles 1520 No. of cycles No. of cycles No. of cycles
No. of cycles
TECHNICAL PAPER
No. of cycles
No. of cycles
No. of cycles
No. of cycles No. of cycles No. of cycles No. of cycles
No. of cycles
7 6 5 7 6 7 6 5 8 7 7 6 6 8 7 7 6 6 8 7 6 8 7 6 7 6 5 7 6 5
7
Percentage residual compressive strength Percentage residual compressive strength 100 100 100 100 C Percentage residual compressive strength Percentage residual compressive strength 100 100 100 C Percentage weight loss Percentage weight loss Percentage weight loss Percentage weight loss 5 4 3 2 4 3 2 1 5 4 3 2 4 3 2 1 M 30 Percentage weight loss Percentage weight loss Percentage weight losss Percentage weight los 5 5 4 4 3 3 2 2 5 5 4 4 3 3 2 2 M 30 Percen
120
120
120
120
6
100 C
100 C
100 C
C
200 C
200 C
200 C
80
200 C
80
80
80
M 30
C
200 C
200
200 C
C
200
M 30
300 C
300 C
300 C
300 C
M 30
M 30
M 3090
M 30
M
M 90
300 C
M 90
300
C
M 90
300 C
C
300
400 C
400 C
400 C
400 C
60
60
M 90
60
60
M 90
M 90
M 90
400 C
C
400
C
400
400 C
1
1
0
0
40
40
50
25 30
20 25
30 35
15 20
20 25
25 30
10 15
0 0 5
0 5
5 10
20 25
50
45 50
40 45
35 40
30 35
25 30
30 35
20 25
25 30
35 40
30 35
45 50
20 25
30 35
25 30
40 45
0 0 5 5 10 1015 1520 2025 2530 3035 3540 4045 4550 50 40 40 0 0 5 5 10 1015 1520 2025 2530 3035 3540 4045 4550 50 1 0 0 1 0 0 0 5 5 10 10 15 15 20 20 25 25 30 30 35 35 40 40 45 45 50 50 1 1 0 0 0 0 0 5 5 10 10 15 15 20 No. of cycles 35 40 40 45 45 50 50 1 0 1 0 0 0 5 5 10 10 15 15 20 No. of cycles 35 40 40 45 45 50 50 0 0 0 0 5 5 10 10 15 15 20 No. of cycles 35 40 40 45 45 50 50
5 10
10 15
15 20
0
No. of cycles
No. of cycles
No. of cycles
No. of cycles
No. of cycles
No. of cycles
No. of cycles
No. of cycles No. of cycles No. of cycles No. of cycles
No. of cycles
No. of cycles
Figure 4.9: Variation of percentage weight loss of M 30 & M 90 Figure 4.10: Variation of percentage weight loss of M 30 & M 90
specimens exposed to temperature of 300°C. specimens exposed to temperature of 400°C.
7 7 8 8 8 8 7 7
6 5 6 5 7 6 7 6 7 6 7 6 6 5 6 5
Percentage weight loss Percentage weight loss 4 3 4 3 M 30 Percentage weight loss Percentage weight loss 5 4 3 5 4 3 M 30 Percentage weight loss Percentage weight loss 5 4 3 5 4 3 100 100 C Percentage weight loss Percentage weight loss 4 3 4 3 100 C C C
100 C
C
200 C
200
200
C
200 C
M 30
M 30
300 C
300
C
300
300 C
M 90
M 90
400 C
C
1 2 2 1 M 90 2 1 2 1 M 90 2 1 2 1 400 400 C 2 1 2 1 400 C
0 0 0 0 0 0 0 0
0 0 5 5 10 10 15 15 20 20 25 25 30 30 35 35 40 40 45 45 50 50 0 0 5 5 10 10 15 15 20 20 25 25 30 30 35 35 40 40 45 45 50 50 0 0 5 5 10 1015 1520 2025 2530 3035 3540 4045 4550 50 0 0 5 5 10 1015 1520 2025 2530 3035 3540 4045 4550 50
No. of cycles
No. of cycles
No. of cycles
No. of cycles
No. of cycles No. of cycles No. of cycles No. of cycles
Figure 4.11: Variation of percentage weight loss of M 30 with Figure 4.12: Variation of percentage weight loss of M 90 with
number of cycles. number of cycles.
2. Figure 4.11 and 4.12 show the variation of % weight loss concrete. Hence, it is suggested that NSC is good enough at
with the number of thermal cycles for the concrete specimens low temperatures up to 300°C when subjected to thermal cycles.
of M 30 and M 90 grade heated from ambient temperature A gradual loss in weight was found with increase in temperature
to elevated temperature. At first thermal cycle, M 30 grade from 100 to 400°C with repeated heating. The effect is more
concrete specimens exhibited 3.29% weight loss at 100°C and pronounced in the case of HSC than NSC which affects the
4.97% at 400°C. After 50 cycles of exposure, the specimens durability of concrete.
exhibited 5.33% weight loss at 100°C and 6.67% at 400°C. In
the case of M 90 grade, specimens exhibited 1.86% weight Based on the investigations conducted on HSC and NSC, the
loss at 100°C and 4.26% at 400°C after first thermal cycle. After following conclusions are drawn.
50 cycles of exposure, the specimens exhibited 3.43% weight
loss at 100°C and 5.87% at 400°C. This implies that weight 1. The percentage decrease of compressive strength is higher
loss increases with increase in temperature. Normal strength for higher exposure temperature irrespective of grade of
concrete (M 30) shows more loss in weight due to high porosity concrete.
than high strength concrete (M 90). The moisture present in the 2. The effect of high temperatures on compressive strength
pores gets evaporated when heated to elevated temperature of concrete decreases with an increase in thermal cycles
forming voids which results in weight loss. Hence normal except at first cycle.
strength concrete is less durable than high strength concrete.
3. Compressive strength of concrete (both HSC and NSC)
CONCLUSIONS increase at 100°C at first cycle as it loses its free water
High strength concrete with its dense structure is less resistant (water not chemically bound) which results in acceleration of
to high temperature with repeated cycling than normal strength unhydrated core in concrete.
The IndIan ConCreTe Journal | June 2019 15
