Hydrodemolition technique for removing damaged concrete
The popularity of hydrodemolition is growing worldwide and was the specified solution for work on two vital Swedish links. The hydrodemolition technique, which uses high pressure water jets to remove damaged concrete from various structures, is playing a crucial role in the major restoration of the vital Central Bridge and Tunnel in the centre of Sweden's capital Stockholm. An inspection of the structures revealed water leakage in the tunnel roof and serious corrosion of the concrete reinforcing in the low part of the tunnel walls and on the bridge's concrete deck, primarily due to de-icing salt sprayed by passing traffic.
In 2005, Stockholm City Traffic Office embarked on a comprehensive programme of repairs and modernization, which included a new fire protecting sprayed concrete lining in the tunnel soffit; sacrificial precast concrete panels along the base of the tunnel walls and upgrading the lighting, ventilation and sign boards. The repairs include the removal of the concrete surface from the ceiling and lower parts of the tunnel walls, and removal of the bridge's damaged concrete deck, followed by replacement with fresh concrete.
The contractor used the smallest Conjet Robot 322 and larger Conjet 362 MPA and the latest Conjet 364 MPA, both with multi-purpose arms for high reach and fitted with the optional hydraulically driven rotor head for scarifying and the preparation of concrete surfaces. The Conjet Robot 322 was fitted with a single nozzle, which was modified to reach below road level and into the channel at the base of the tunnel walls.
High pressure water was supplied from three separate Conjet Powerpacks to each of the robots at a pressure of around 1,000 bar and flow of 200 litres / min. The larger 362 MPA and 364 MPA Robots worked on the tunnel roof with the rotor heads removing between 5-10 mm of concrete, leaving a rough and textured micro crack-free surface for bonding on the new fire repellent overlay. Along the base of the tunnel walls, the Robot 322 removed concrete up to approximate 1 m high and to depth of between 30-70 mm.
During the summer's phase the contractor had to prepare about 10,000 square m of the tunnel's damaged concrete surfaces. Hydrodemolition was followed by spraying a 35 mm thick porcelain impregnated fire retardant concrete lining to complete the soffit restoration. On the prepared tunnel walls an approximate 60 mm thick layer of stainless steel fibre reinforced concrete was sprayed, followed by a covering of abutting 2 m high, 4 m long precast concrete sacrificial panels. These can be individually and easily replaced in case of any future salt corrosion.
The team used the same hydrodemolition technique on the adjacent Central Bridge, selectively removing the damaged concrete to a depth of about 70-80 mm to leave an uneven and textured surface. The deck was replaced with 45 MPa bridge concrete, and was then covered with a waterproofing membrane prior to a final asphalt base and 50 mm wearing course for a return to traffic.
Vocabulary
1. hydrodemolition разрушение струей воды под высоким давлением
2. to remove удалять, убирать, снимать, устранять, уничтожать
3. damaged поврежденный, испорченный
4. to reveal обнаруживать, открывать
5. leakage утечка, течь, просачивание
6. reinforcing укрепление
7. de-icing предотвращающий обледенение
8. to embark начинать что-л., прибегать к чему-л.
9. lining покрытие, изоляция, отделка, обмуровка
10. sacrificial здесьзащитный
11. precast заводского изготовления; сборного типа
12. upgrading совершенствование, улучшение качества
13. optional произвольный, необязательный
14. replacement замена, замещение, обновление, модернизация
15. multi-purpose многоцелевой
16. hydraulically driven с гидравлическим приводом
17. scarifying разрыхление
18. tosupply поставлять, доставлять, возмещать, подводить
19. crack-free surface поверхность без трещин
20. bonding крепление
21. fire repellent overlay огнеупорный слой
22. approximate приблизительный
23. porcelain impregnated с вкраплениями фарфора
24. fire retardant огнестойкий
25. abutting соседний, примыкающий
Task 2. In Column B choose the right explanation of the words, used in the text:
A B
1. solution a) specimen
b) decision
c) preparation
2. vital a) sacrificial b) adequate
c) important
3. to remove a) to replace
b) to repair
c) to delete
4. crucial a) critical
b) complete
c) proof
5. to reveal a) to repeat
b) to apply
c) to disclose
6. leakage a) load
b) outflow
c) measure
7. repair (noun) a) criteria
b) safety
c) maintenance
8. approximate a) rough
b) theoretical
c) reinforced
9. adjacent a) allowable
b) contiguous
c) questionable
10. fibre a) grain
b) pier c) beam
Task 3. Give the Russian equivalents to the expressions from the text:
1. the popularity … is growing worldwide
2. to remove damaged concrete from various structures
3. water leakage in the tunnel roof
4. due to de-icing salt
5. a comprehensive programme of repairs and modernization
6. a new fire protecting sprayed concrete lining
7. sacrificial precast concrete panels
8. multi-purpose arms for high reach
9. the optional hydraulically driven rotor head for scarifying
10. leaving a rough and textured micro crack-free surface
11. the tunnel's damaged concrete surfaces
12. layer of stainless steel fibre reinforced concrete
Task 4. Find antonyms to the words from the text in the line A, among the words in the line B:
A.popularity, specified, various, restoration, to reveal, damaged, reinforcing, to complete
B.demolition, rehabilitated, obscurity, similar, to initiate, reducing, demolition, to conceal