Building Pathology (L3) Goole Flashcards
What did you discover on-site?
There were signs of cracking and spalling of the concrete which exposed the steel reinforcement. Stalactites were also visible to the underside of the balcony.
What was the pattern of the cracking?
The cracking appeared to follow the pattern of the reinforcement mesh.
Following your inspection, what were your findings?
Following my visual inspection and pH testing, I concluded the cause of defect was due to carbonation which had caused the steel reinforcement to corrode spalling areas of concrete.
What were the remedial works you recommended to your client?
I advised the client to carry out a tap-test to establish the extent of repairs. I then advised repairs to be undertaken by:
- removing the hollow sections of concrete
- cleaning the exposed steel reinforcement and applying a corrosion resistant coating
- Fill the areas using a polymer modified mortar
- Include for applying an anti-carbonation protective coating to the balcony following the repairs
- I would advise consulting with a concrete repair specialist for a suitable and compatible product
Did you carry out any testing? What was the chemical testing which was carried out and what did this confirm?
I used a pH indicator called phenolphthalein (feenal-fayeleen) to determine the pH of the concrete. The results were low pH levels indicated to the concrete.
Fuscia/Pink – High pH level 8-12 (Good)
Clear – Low pH level < 8 (Becomes Acidic)
What led you to believe that previous repairs had been undertaken?
There were several areas where a cementitious mortar had been used. A section was removed on-site and although it appeared the previous repairs had treated the steel reinforcement, the repair product used was not suitable.
Why did you take measurements to determine the thickness of the concrete and depth of reinforcement?
To determine if the cover of reinforcement was sufficient.
What method did you use to take the measurements?
I used a spirit level to span the sections of spalled concrete and crack width ruler to record the depth measurement.
Why did you choose a schedule of approximate quanitities?
Because the extent of repairs were unknown and a schedule of approximate quantities can provide a cost to cover for the items listed in the schedule.
Why did the concrete deteriorate?
The concrete deteriorated due to expansion of the steel reinforcement. The was the result of insufficient concrete coverage to the reinforcement which allowed carbonation to occur.
How did you arrive to the unit rate for the actual repair itself?
- I went on historical rates from past projects
- Inflation
- Consulted with special manufacturer
- Consulted with other colleagues
How did you go about producing an estimate for the repairs?
Schedule of approximate quantities
How would you prevent carbonation occurring in new reinforced concrete?
- Lower the amount of water to cement ratio
- Well mechanically compacted to maximise density
- Sufficient time to cure
What other causes of concrete failure could there be?
- Insufficient cover for the steel reinforcement
- Chloride attack
What type of repair mortar did you use?
I consulted with Sika for a suitable product. I used Sika MonoTop 1010 which was a reinforcement corrosion protective coating. The mortar used was a polymer modified
