T4-x2: Repair Products and Systems Flashcards
(26 cards)
Give an overview of patch repairs (x6)
- Remove deleterious materials
- Replace corroded reinforcement
- Apply a bonding coat
- Apply a repair mortar
- Cure the product
- Apply a surface coating
What are three issues with incipient anodes?
- Ongoing corrosion
- Further delamination
- Repeat repairs
What are the three main types of intervention options?
- Structural repair (full load case)
- Semi-structural repair (some load taken)
- Cosmetic repair (surface repairs only)
.
What do beam soffit repairs do, and why?
- Keeps bars at design depth
- For corrosion prevention
For column/wall repair:
a) what does it do to the concrete
b) what properties are important (x2)
a) keeps concrete in compression
b) creep and shrinkage important, and important to match structural properties
For a load-bearing repair (structural), what should be done (x5)?
- The repair should be in compression
- Consider creep and shrinkage of repair
- Match structural properties
- Remove live and dead loads
- Consider as a two-stage reinstatement
What are five types of structural enhancements?
- Increasing element size
- Plate bonding
- Applying external tendons
- Additional support
- Crack injection
What things should be considered for materials of concrete repair (x5)?
- Application
e.g. setting time, workability, max/max thickness - Physical factors
e.g. thermal expansion, bond, freeze-thaw, modulus - Chemical factors
e.g. attack by cement, attack in service - Barrier factors
e.g. water vapour resistance, CO2, chloride-ion resistance - Long-term factors
e.g. thermal cycling, long-term bond reduction
[NAQ] compatibility of materials Table 1
[NAQ] compatibility of materials Table 2
What is the relevance of the coefficient of thermal expansion?
To prevent differential stresses
Why do we need low chloride ion and CO2 diffusion?
To prevent bar re-activation
What is the relevance of bond strength?
For stress transfer and durability
Name two types of mortar
- Modified mortar
- Epoxy mortar
Describe the different types of materials, and their suitability for different applications
What are the structural applications of Epoxy Resin?
- what thickness of layer are they applied in?
- what features (x2) do they have?
Structural applications in thin layers
- moisture tolerant
- low cure shrinkage/high creep
What can be done to modify concrete/mortar for better performance?
Modify with polymers
- polymer-modified mortar
- polymer-modified concrete
What early lessons have been ‘re-learnt’ for standards for concrete repairs (x2)?
- The importance of cover
- The effect of chlorides
What are two features of PVA bonding coat?
- Excellent adhesion
- Breaks down on damp, alkaline surfaces
What are four features of epoxy resin repairs?
What can they become if they are over-filled?
- High tensile/compressive strength
- Porous if over-filled
- Prone to high exotherm
- Poor workmanship - voids behind the bar
What part of patch repairs are particularly prone to fail?
The edges
What are incipient anodes, and why do they occur?
- The phenomenon where corrosion is accelerated in the area surrounding a patch repair
- Due to the different electrochemical properties between the old and new concrete, creating a situation where the repair patch acts as a cathode and the surrounding concrete becomes an anode (creating corrosion)
If bars turn to rust on a building, what is likely causing the corrosion?
Chloride presence
What is a solution to creep and shrinkage issues (from concrete)?
Steel repair
