Rak Production Technology of Concrete Structures (2015) Repair of Concrete Structures

Transcription

1 Rak Production Technology of Concrete Structures (2015) Repair of Concrete Structures na_paaluja_ennen_korjausta.jpg na_paaluja_powermortar-korj.jalk.1.jpg 1

2 Learning Outcomes To acquaint the student with concrete repairs eferenssit/destia_kulosaaren_silta.jpg _ jpg 2

3 General Cause: Production failures, effect of service conditions, catastrophes, bad materials, bad planning of works, negligent execution of works (handling of concrete, compaction and curing), service conditions (frost, corrosion, temperature and moisture, shrinkage etc.), etc. Damage: Cracking, movement of elements, destroyed concrete surface, corrosion of reinforcement, water erosion and collapse Dependence: Scale, location, type of structure and specification of the structure 3

4 General 4

5 European Standard EN 1504 The whole concrete repair process, from the initial identification of a problem, through to the works on site. It requires that a whole life cost approach is taken so that the anticipated future needs if the client is met. Specifies minimum performance levels Provides identifiable performance testing Provides standardized approach to design Raises application standards Removes technical barriers to trade Products and systems for the protection and repair of concrete structures Definitions, requirements, quality control and evaluation of conformity Site application of products and systems and quality control of the works 5

6 European Standard EN 1504 The 10 documents forming the EN 1504 Series are listed below: Part Content Status 1 Definitions Released Surface protection systems Released Structural and non structural repair Released Structural bonding Released Concrete injection Released Products and systems for grouting anchor reinforcement Released Reinforcement corrosion protection Released Quality control and evaluation of conformity Released General principles for use of products and system Released 1997 ENV 10 Site application of products and systems and quality control Released 2003 of the works 6

7 EN The phases of a typical repair projects Project phases Management of the Structure Process of Assessment General Planning Design of Repair Work Repair Work Acceptance of Repair Work Basic considerations and actions Conditions and history of Structure, Documentation, Commissions for maintenance Defects and their classification and causes Options, Principles and Methods Intended use of products Requirements: Substrate, Products and work Specifications and drawings Safety/Structural estimation after protection and repair Choice and use of products and equipment Tests of quality control Health and safety Acceptance testing, Remedial works and Documentation Parts and clauses of the EN 1504 series Clause 4 of EN Clause 4 of EN Clauses 5 and 6 of EN EN to EN and Clauses 6, 7 and 9 of EN Clauses 6,7, 9 & 10 of EN and EN Clause 8 of EN and EN

8 Structure management options EN :2008 (E) a) Do nothing for a certain time but monitor; b) Re-analyze the structural capacity, possibly leading to downgrading in function; c) Prevent or reduce further deterioration; d) Strengthen or repair and protect all or part of the concrete structure; e) Reconstruct or replace all or part of the concrete structure; f) Demolish all or part of the concrete structure. 8

9 Damage evaluation Condition of the structure: drawings and specification of the structure, damage rate, special reasons for the damage, examination of the materials quality, examination of the structure, possible loading tests, evaluation of execution of works, declaration of seriousness of the damage Seriousness of the damage: demolishing and building a new structure, change of maximum loading, change of usage, detailed investigation, certification and/or repairmen Concrete quality: visual evaluation, knocking with hammer, impact hammer, ultrasound measurements, mix composition analysis, drilling samples 9

10 Damage evaluation Investigation of the structure: crack formation, microscopy, dimensions, thickness of the concrete cover Preliminary measures: removal of bad concrete, design, moistening of old concrete, cleaning, protection from moving water 10

11 Repairs methods and their choice Fixing parts of the surface, when the damage is small Fracture (cracking) refitting by injections Corrosion and deep long casting defects: usage of formwork - regular concrete, dry packed concrete, self compacting concrete, special methods shotcrete, injections, fiber concrete, etc. Repairs of reinforcement, replacement of bars Repairs of joints ktiv/concreterepair/polandrepair.jpg 11

12 Dry packed concrete method Small damage formwork and injections fillings Depth >30mm Bonding layer cement dust layer or mortar Portland cement: sand 1:2,5 3,5 Water to cement ratio Compaction in 10 mm thick layers dmin/imgs/imgs_bdd/ %2009:26:11-Two-Part-Polyurethane.gif 12

13 Mortar repairs Depth mm Done by hands: cement : sand - 1 : 2,5 3; plastic consistency; setting and repairing in the shortest possible time small shrinkage; layer thickness 1-20mm; porosity 6 10% 13

14 Shotcrete Damage depth mm (with dense reinforcement mm) 14

15 Ejectors Well bonding base concrete Good compaction Maximum aggregate size 2-4mm Cement : Sand 1 : 4,5 Water to cement ratio New layer can be applied usually after half an hour 15

16 Concrete repairs Structural parts Volume of works > m3 Concrete thickness >100 mm for young concretes and more than 150 mm for old concretes Water to cement ratio the same as repaired concrete Casting in layers h<30 cm and cover >30 min break Exact vibration Casting of head box Porosity: 3-5% entrained air Bonding mortar Lying-up period of concrete 0.5 to 1.5 hours 16

17 Concrete repairs Example or repair of concrete structures using formworks and concrete 17

18 Filling with injections Protecting filling injections Applicable for wide range of patching works Thickness of a patch >150 mm Under water works or upper surfaces (ceilings etc.) Application for geotechnical works (strengthening of soils) ystems/catalog/large/086d-2012.gif 18

19 Polymer based fillers Small surfaces Fast hardening Covering of unprepared surfaces No corrosion of reinforcement Polymer is mixed with sand The epoxies are two component materials Epoxy fillers are used also as bonding layer for old and new concretes 19 Before application of this materials loose particles and impurities must be removed (sand blasting or steel brushes) The surface should be dry Temperature >10 C Reference control specimens should be produced

20 Learning Summary Repairs methods and their choice Photo%205_1.JPG efault/files/specrepair1sm.jpg 20