Issue 41

L. Zhang et alii, Frattura ed Integrità Strutturale, 41 (2017) 356-368; DOI: 10.3221/IGF-ESIS.41.47

The compressive strength of cement mortar with different dosages is obtained. As the accelerator dosage increases, the later strength loss tends to increase. However, if the dosage ranges from 1.5% to 4%, the later strength loss will not exceed 10%. Tab. 2 shows the compressive strength of cement mortar.

Compressive strength/MPa

Accelerator dosage/%

28d compressive strength ratio/%

1d

28d 47.8 46.9 46.1

0

7.8

100

1.5 2.0 2.5 3.0 3.5

13.6 13.9 14.5 15.1 15.8

98.1 96.4 94.1 93.3 91.4

45

44.6 43.7

4.0

14.2 90.2 Table 2 : Compressive strength of cement mortar. 43.1

N UMERICAL CALCULATION

Strength-time and elasticity modulus-time regression curve of shotcrete n the lab, the hardening characteristics of shotcrete are tested. Shotcrete adopts C25 mix proportion (selected from Changgang tunnel of Fushou Highway) of cement, sand, to stone as 469 : 912 : 912. Non-linear regression analysis is conducted on shotcrete strength and time, and then the change rules between the strength and age are obtained. Tab. 3 lists the uniaxial compressive strength of shotcrete added with the traditional accelerator. Tab. 4 lists the uniaxial compressive strength of shotcrete added with the new liquid accelerator. I

Age

8h/MPa

12h/MPa

1d/MPa

3d/MPa

7d/MPa

28d/MPa

Specimen No.

1 2 3 4 5 6 7 8 9

4.35 5.05 4.92 4.36 4.45 4.82 6.15 5.20 4.8

6.80 7.22 6.95 6.50 7.10 6.83 7.25 7.64 7.30

9.52 10.25 9.80 9.30 10.64 9.13 10.37 11.28 9.95

14.6 15.40 14.88 15.72 16.20 14.67 15.60 16.38 14.68

21.89 20.76 22.12 23.30 21.66 23.20 21.37 22.50 21.86

25.4 26.38 27.10 26.70 25.89 27.80 28.31 29.25 27.97

Table 3 : Uniaxial compressive strength of shotcrete added with the traditional accelerator.

Age

8h/MPa

12h/MPa

1d/MPa

3d/MPa

7d/MPa

28d/MPa

Specimen No.

1 2 3 4 5 6 7 8 9

7.25 7.37 7.34 6.38 7.18 7.01 7.35 8.16 7.46

8.99 9.53 9.71 9.18 9.47 8.95 9.73 9.98

12.75 14.15 13.29 12.76 14.59 12.80 13.53 14.33 13.45

19.39 20.12 19.72 20.30 20.86 19.28 19.89 20.97 19.17

27.48 26.66 27.97 28.69 27.65 28.44 27.11 27.84 27.72

31.06 31.66 32.60 32.18 31.88 33.17 34.21 34.95 33.65

10.27

Table 4 : Uniaxial compressive strength of shotcrete added with the new liquid accelerator.

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