Open Access

Optimised technology for repair of vertical surface of concrete bridge elements

Marijan Skazlić
Marijan Skazlić
, 
Berislav Borovina
Berislav Borovina
 and 
Ivan Gabrijel
Ivan Gabrijel
   | Dec 29, 2023
Organization, Technology and Management in Construction: an International Journal's Cover Image
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Article Category: Research Paper
Published Online: Dec 29, 2023
Page range: 233 - 242
Received: Aug 31, 2023
Accepted: Dec 08, 2023
DOI: https://doi.org/10.2478/otmcj-2023-0018
Keywords
© 2023 Marijan Skazlić et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Fig. 1:

View of Klara jug bridge (left); column used for experimental work (right).
View of Klara jug bridge (left); column used for experimental work (right).

Fig. 2:

Surface preparation by hydrodemolition under high pressure to a depth of 1.5 cm, (left) and spraying of repair mortar (right).
Surface preparation by hydrodemolition under high pressure to a depth of 1.5 cm, (left) and spraying of repair mortar (right).

Fig. 3:

Finishing of repair mortar surface (left) and curing of repair mortar (right).
Finishing of repair mortar surface (left) and curing of repair mortar (right).

Fig. 4:

Appearance of concrete surface after surface preparation by hydrodemolition under high pressure (left) and test fields before pull off testing (right).
Appearance of concrete surface after surface preparation by hydrodemolition under high pressure (left) and test fields before pull off testing (right).

Fig. 5:

Roto nozzle for washing of concrete surface.
Roto nozzle for washing of concrete surface.

Fig. 6:

Testing of concrete before repair: (A) coring of concrete; (B) pull-off test.
Testing of concrete before repair: (A) coring of concrete; (B) pull-off test.

Fig. 7:

Mortar samples for compressive and bending strength testing (left) and testing of bending strength (right).
Mortar samples for compressive and bending strength testing (left) and testing of bending strength (right).

Fig. 8:

Influence of time period between the end of surface preparation and application of the repair mortar on pull-off tensile strength.
Influence of time period between the end of surface preparation and application of the repair mortar on pull-off tensile strength.

Fig. 9:

Comparison of the pull-off tensile strength test results for two cases: with and without surface preparation by washing with a roto nozzle.
Comparison of the pull-off tensile strength test results for two cases: with and without surface preparation by washing with a roto nozzle.

Results of the mechanical and durability tests on the repair mortar.

Property Unit Individual test results Average value
Compressive strength N/mm2 71.7 70.7 75.2 71.3 70.2 74.3 72.2
Flexural strength N/mm2 8.0 8.4 8.9 8.4
Static modulus of elasticity kN/mm2 28.451 26.941 29.334 28.242
Capillary absorption coefficient kg/m2/h0.5 0.11 0.10 0.11 0.11
Chloride diffusion coefficient 10–12 m2/s 1.24 2.76 1.81 1.94

Mechanical properties of concrete from the bridge column.

Property Unit Individual test results Average value
Compressive strength N/mm2 54.6 39.0
38.6
31.4
31.3
39.3
Pull-off tensile strength N/mm2 2.20 2.04 2.24
2.68 1.90
2.45 2.05
2.27 2.44
2.03 2.35
Static modulus of elasticity kN/mm2 34.337 32.679
31.206
32.493

Results of the pull-off tensile strength tests for the case when the concrete surface is treated by hydrodemolition but without washing with a roto nozzle prior to application of the repair mortar.

Time Individual pull-off tensile strength results (N/mm2) Average pull-off tensile strength results (N/mm2)
0 min 0.19 (100% A/B) 0.16 (100% A/B) 0.83 (80% A/B, 20% B) 0.39
30 min 0.34 (80% A/B, 20% B) 1.11 (50% A/B, 50% B) 0.53 (10% A, 90% A/B) 0.66
60 min 0.45 (10% A, 90% A/B) 0.66 (80% A/B, 20% B) 0.91 (50% B, 50% A/B) 0.67
90 min 1.17 (20% A, 80% A/B) 1.39 (30% A, 70% A/B) 0.83 (20% A, 80% A/B) 1.13

Chloride concentration in concrete at different depths determined by the RCT method.

Test location Depth (mm) Chloride content (% of concrete mass)
1 0–10 0.012
10–20 0.016
2 0–10 0.034
10–20 0.021
3 0–10 0.018
10–20 0.019
4 0–10 0.006
10–20 0.005

Shrinkage of repair mortar.

Age (day) 1 3 6 8 17 28
Shrinkage (mm/m) 0.000 0.238 0.331 0.445 0.642 0.756

Results of the pull-off tensile strength tests for the case when concrete surface is prepared by hydrodemolition and washed with a roto nozzle prior to application of the repair mortar.

Time Individual pull-off tensile strength results (N/mm2) Average pull-off tensile strength result (N/mm2)
0 min 1.10 (50% A, 50% A/B) 1.32 (50% A, 50% A/B) 0.00 1.21
10 min 1.53 (20% A, 80% A/B) 1.54 (50% A/B, 50% B) 1.42 (100% A/B) 1.50
20 min 1.52 (100% A/B) 0.00 0.00 1.52
30 min 1.66 (50% A/B, 50% B) 2.18 (10% A, 90% A/B) 1.46 (20% A, 80% A/B) 1.77
40 min 1.60 (50% A/B, 50% B) 1.97 (50% A, 50% A/B) 0.00 1.79
50 min 1.69 (50% A/B, 50% A) 1.83 (10% A, 90% A/B) 0.00 1.76
60 min 1.48 (100% A/B) 2.35 (50% A/B, 50% B) 0.00 1.92
70 min 1.83 (100% A/B) 2.05 (50% A, 50% A/B) 1.90 (20% A, 80% A/B) 1.93
80 min 2.32 (100% A/B) 2.02 (60% A, 40% A/B) 2.10 (50% A, 50% A/B) 2.15
90 min 2.21 (50% A, 50% A/B) 2.59 (80% A, 20% A/B) 2.50 (80% A, 20% A/B) 2.43
100 min 1.99 (10% A, 90% A/B) 2.08 (60% A, 40% A/B) 2.17 (80% A, 20% A/B) 2.08
110 min 1.75 (50% A/B, 50% B) 1.69 (10% A, 90% A/B) 1.81 (10% A, 90% A/B) 1.75
120 min 1.51 (20% A, 80% A/B) 1.62 (50% A/B, 50% B) 1.63 (20% A, 80% A/B) 1.59
180 min 1.46 (30% A, 70% A/B) 1.70 (50% A/B, 50% B) 1.11 (20% A, 80% A/B) 1.42
240 min 1.11 (20% A/B, 80% B) 1.21 (20% A, 80% A/B) 1.87 (50% A/B, 50% B) 1.40
6 h 1.07 (100% A/B) 1.04 (100% A/B) 0.85 (100% A/B) 0.99
8 h 1.02 (20% A, 80% A/B) 0.95 (10% A, 90% A/B) 0.71 (20% A, 80% A/B) 0.89
24 h 0.82 (10% A, 90% A/B) 0.97 (20% A, 80% A/B) 0.61 (20% A, 80% A/B) 0.80
48 h 0.75 (20% A, 80% A/B) 0.55 (100% A/B) 0.80 (50% A/B, 50% B) 0.70
96 h 0.49 (100% A/B) 0.60 (50% A/B, 50% B) 0.71 (50% A/B, 50% B) 0.60
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