Download
1 / 16
170 likes | 485 Views
2. Introduction. Large investments in new structures in previous yearsIncreasing maintenance costsImportance of accurate forecasting for residual service lifeConcrete bridge deterioration models. 3. . Service life depends on interaction between structure and surrounding environmentTemperature changes, amount of precipitation, relative humidity, windThe most common concrete bridge deterioration in Latvia are reinforcement corrosion and its consequential damage.
E N D
1. INVESTIGATION OF CARBONATION AND CHLORIDE INGRESS IN CONCRETE BRIDGES IN LATVIA M.Sc.ing. Kristaps Gode
Dr.Sc.ing. Ainars Paeglitis
2. 2 Introduction Large investments in new structures in previous years
Increasing maintenance costs
Importance of accurate forecasting for residual service life
Concrete bridge deterioration models
3. 3 Service life depends on interaction between structure and surrounding environment
Temperature changes, amount of precipitation, relative humidity, wind
The most common concrete bridge deterioration in Latvia are reinforcement corrosion and its consequential damage
4. 4 Concrete deterioration caused by reinforcement corrosion
5. 5 Concrete carbonation
6. 6 Factors influencing the carbonation process The main factors that influence the rate of concrete carbonation are:
amount of CO2 in air
relative humidity of concrete
amount of precipitation
concrete carbonation resistance (concrete permeability, amount of Ca(OH)2 in concrete)
concrete surface position
The thickness of concrete cover
7. 7
8. 8 Modelling of carbonation The most simple carbonation model combine two processes:
diffusion of CO2 in concrete,
formation of CaCO3 (reducing of pH value)
9. 9 DuraCrete model
10. 10
11. 11 Reports show that carbonation is an issue if concrete cover is insufficient
Insuficient concrete cover (75% below 30 mm and 90% below 40 mm)
Low strength concrete
Concrete used in existing bridges provide sufficient carbonation resistance for achieving the service life of 100 years if the minimal concrete cover is 40 mm.
12. 12 Chloride ingress � De-icing salts (NaCl) are spread on roads to avoid formation of ice and increase safety on roads during the winter season.
� The mixture of chlorides and water are splashed and sprayed by traffic onto bridge surfaces.
� Chlorides initiate and accelerate the corrosion of reinforcement in concrete.
13. 13 Chloride profile
14. 14 The DuraCrete model
15. 15 Example of service life calculation Chloride profile from samples
Calculation of diffusion parameters (curve fitting)
Prediction of future behaviour
16. 16 On roads the source and amount of chlorides is very variable (unlike for structures in sea environment)
The position and shape of a structure related to source of chlorides should be considered
Chloride profiles can significantly change not only within one structure but also along one surface
Damage to reinforced concrete caused by chlorides usually appears in small portions of the structure where locally aggressive environment is created
17. 17 Conclussions Deterioration/service life/prediction models are future of modern Bridge Management Systems.
The models will help to know more about structure before inspection and will help to gain a much accurate result after bridge inspection.
At present the methods of the service life prediction are not fully developed for easy, unsophisticated use.
Currently it is possible to indicate that for example structure A will last longer than B, using described models it would be possible to predict with precision their remaining life in years.
