Structural deterioration assignment and Rehabilitation: Understanding Causes, Assessment, and Remediation Techniques
Question
Task: What are the primary causes of Structural deterioration assignment in concrete columns, and how can engineers effectively assess, strengthen, and repair them to ensure their longevity and safety?
Answer
Possible cause of deterioration
The initial cause of deterioration in the columns is because of direct contact with chloride contamination in water. The chloride affect and penetrate concrete, effectively in marine and aggressive environment, and start the reinforcement corrosion. However, the existing crack, spalling and exposed reinforcement suggest that the progression of that corrosion effect. In general, the chloride includes corrosion conventional occurs when the chlorides reach the steel reinforcement, that leading to the formation of the rust, that causes the concrete crack and spall as well Meda.et.al.(2016).
The deterioration process is define as degeneration or reduce in quality to an inferior state of the material. The concrete is an artificially created hard and composite construction material. In fact, the deterioration mechanism occur through erosion, change in volume of the material and change in volume of material in pores. It is also includes material dissolution and engaged with the chemical changes, and conventional biological process.
However, the possible cause of deterioration in the columns is the chloride induced corrosion. The following are suggest the procedure for deterioration.
a. Existence of chlorides ;
The chlorides are occur due to water as the result of the chemical treatment or environmental factors.
b. Chloride penetration :
The chloride ions can penetrate the concrete columns because of small size and able to mitigate through the concrete matrix.
c. Reinforcement corrosion :
Once the chlorides achieved the embedded steel reinforcement with the concrete columns, it behave with the steel to form iron chloride compounds. The chemical reaction occur because of steel corrosion.
d. Rust formation :
The steel corrodes, it expands in volume, that leading to the rust formation. However, the rust occupies the significance volume than the original steel, which exerting the pressure on the surrounding concrete Lanus.et.al.(2019).
e. Concrete spalling and cracking :
The rust expansion occur and create pressure on concrete cover.
B. maximum damage at the water level :
The maximum damage occur at the water level is credited with the fact that there is specific area where the concrete is significantly and continuously affect to the chloride contaminated water. In fact, the water is behave as the medium for the transport of chloride into the concrete. The chloride can penetrate the concrete through capillary action and diffusion effect. The existence of water accelerate that procedure, and leading intense deterioration at the water level as compared to higher level where the concrete is not in the conventional contact with the chloride contaminated water McGrath.et.al.(2019).
a.Continuous exposure to the moisture :
The column segment at the water level is continuously exposed to the moisture. However, the constant exposure occur an ideal surrounding for the chloride ions to penetrate the concrete cover.
b. Accelerated corrosion :
The chloride ions accelerate the corrosion of the embedded steel. It occurs due to moisture, oxygen, and chlorides is primary aspect in initiating and accelerating the corrosion procedure.
c. Corrosion zone :
The water level highlight at the critical zone where the corrosion process is most aggressive. This is where the chloride ions has the effective impact on the embedded steel that leading to severe corrosion and subsequent concrete decline (Kreibich, H. and Thieken, A.H., 2008).
B.experimental program for the on-site inspection;
There are various tools and techniques available for experimental inspection as considering on-site inspection. The following are some common and conventional experimental program provided for inspection.
1. Visual inspection :
Civil engineer or technical assistance at site identified defect through visual inspection, the signs would be cracks, spalling and exposed reinforcement.
2. Cover meter test :
The test has been conduct to measure the concrete cover to evaluate the extent of the concrete spalling and potential corrosion occur of the reinforcement (Sezen, H., 2012).
3. Chloride content analysis ;
It is measure the chloride concentration within the concrete to understand the extent of chloride contamination.
4. Half-cell potential test ;
The test conduct to find the likelihood of the corrosion through evaluate the electro-chemical potential of the reinforcement.
5. Carbonation depth measurement :
Evaluate the carbonation extent in the concrete that can suggested area vulnerable to corrosion.
6. Ultrasonic testing :
Finding the remaining thickness of concrete to identify area of thinning.
7. Compressive strength testing :
Evaluate the concrete strength to find the load-bearing capacity.
8. Corrosion rate measurement :
The test conduct to measure the corrosion rate through the polarization resistance or linear polarization. There are mainly two types of corrosion rate measurement technique i.e. 1. Resistivity test 2. Polarization resistance. The resistivity test develop for in-situ test, also empirical relation developed related with the resistivity to corrosion rate, and uses available data in order to find resistivity Wu.et.al.(2012). Whereas, the polarization test is considerable new and not accurate in terms of performance outcome.
9. Concrete sampling and chloride content analysis :
The test conduct with the concrete sample at the various depths to find the chloride content and evaluate the penetration effect of chloride in the concrete.
10. Carbonation depth measurement :
To find the carbonation at specific extent, as that can affect the corrosion procedure.
11. Pull-off test ;
Finding the bond strength between the concrete and reinforcement.
12. Scanning electron microscopy and energy-dispersive X-ray spectroscopy;
Evaluate the micro-structure and chemical composition of the corrosive areas Dhiman.et.al.(2022).
D. fined the Column strength:
Procedure;
Visual inspection; find the column damage through visual inspection
Reinforcement evaluation: find the diameter and cross-sectional area of the exposed longitudinal reinforcement bars.
Corrosion assessment; evaluate the corrosion extent on the exposed reinforcement. Find the pitting level, rust formation and evidence of section loss.
Compressive strength testing: carried out the series of core tests on the column. These tests include drilling cylindrical cores from the spalled region. However, the core should be effective size to contain the exposed reinforcement.
Load testing; . applied axial compressive load to the extracted cores until it failed. That will help to find the residual load carrying capacity of the column Zhouet.al.(2017).
Rebound hammer test: .evaluate the surface hardness through hammer test and integrate of the concrete choice.
Ultrasonic pulse velocity test: .this is measure the velocity of ultrasonic pulse to find the quality of concrete.
Core sampling and compression test: .extract cores from the column to find the compressive strength.
Pull-off test: . the test has been conduct to find the bond strength between concrete and reinforcement.
Lastly, strength finding:
Calculate strength of column mainly based on the load test results and concrete properties and exposed reinforcement.
1. For concrete strength, that can find the result of the compressive tests.
2. For the reinforcement strength, that includes area, diameter and corrosion level of the exposed bar.
E. column strengthen and concrete spall repair;
Procedure:
Remove loose concrete: it require to clean the spalled area, removing the loose and deteriorated concrete.
Expose and clear reinforcement: expose and clean the corroded reinforcement to remove rust and contaminants.
Applied the bonding agent or chemical: this is essential to enhance adhesion between the old and new concrete.
Reinforcement jacketing: this is encase the exposed reinforcement with the additional steel reinforcement includes steel jackets to restore strength (Bankole, O.M., 2010).
Sprayed concrete repair: applying the sprayed concrete or shotcrete to reconstruct the spalled section.
Cathodic protection system: this is essential to consider and installing the cathodic prevention system to mitigate the future corrosion.
Spall preparation: it require to remove the loose and deteriorated concrete through the spalled area. Clean and de-scale the open reinforcement to remove corrosion and rust.
Bonding agent application: that applying the bonding agent to require to clean the surface area for both concrete and exposed reinforcement. That enhances the bond between the new concrete and existing one.
Additional reinforcement: Place additional longitudinal reinforcement bars (typically steel plates or bars) around the spalled area. These bars should have sufficient overlap with the existing reinforcement to ensure adequate load transfer.
Formwork installation: this require to construct the formwork around the spalled area to contain the new concrete.
Concrete pouring: this includes the pour a high strength repair mortar or the concrete mix into the formwork, encasing the additional reinforcement and existing column surface.
Finishing: finishing the surface area to match with the existing column profile.
Curing: it is essential to essential curing to maintain the strength and durability of the repaired section.
Self-reflection questions:
a. Finding key challenges in assessing and maintenance deteriorated columns, and how were they addressed?
b. How can that preventive maintenance plan can enhance to reduce risk chloride induced corrosion in the similar structure?
c. What are the new knowledge and skills has been gained while executing the project, that can enhance the ability to identified similar structure issues in the future?
d. How can observes and recommendations from that project be uses to enhance the safety and longevity of the infrastructure in equal environments?
References
Bankole, O.M., 2010. A review of biological deterioration of library materials and possible control strategies in the tropics. Library Review, 59(6), pp.414-429.
Dhiman, N.K., Sidhu, N., Agnihotri, S., Mukherjee, A. and Reddy, M.S., 2022. Role of nanomaterials in protecting building materials from degradation and deterioration. In Biodegradation and Biodeterioration at the Nanoscale (pp. 405-475). Elsevier.
Kreibich, H. and Thieken, A.H., 2008. Assessment of damage caused by high groundwater inundation. Water Resources Research, 44(9).
Lanus, E., Colbourn, C.J. and Montgomery, D.C., 2019, April. Partitioned search with column resampling for locating array construction. In 2019 IEEE International Conference on Software Testing, Verification and Validation Workshops (ICSTW) (pp. 214-223). IEEE.
Meda, A., Mostosi, S., Rinaldi, Z. and Riva, P., 2016. Corroded RC columns repair and strengthening with high performance fiber reinforced concrete jacket. Materials and Structures, 49, pp.1967-1978.
McGrath, H., Abo El Ezz, A. and Nastev, M., 2019. Probabilistic depth–damage curves for assessment of flood-induced building losses. Natural Hazards, 97, pp.1-14.
Sezen, H., 2012. Repair and strengthening of reinforced concrete beam-column joints with fiber-reinforced polymer composites. Journal of Composites for Construction, 16(5), pp.499-506.
Wu, C., Yang, Z., Liu, Y. and Xi, W., 2012. WILL: Wireless indoor localization without site survey. IEEE Transactions on Parallel and Distributed systems, 24(4), pp.839-848.
Zhou, Y., Luo, H. and Yang, Y., 2017. Implementation of augmented reality for segment displacement inspection during tunneling construction. Automation in Construction, 82, pp.112-121.
