Deterioration of concrete buildings in kuwait

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1.1 Introduction

In Kuwait the combined effect of the extreme climatic conditions and the salty geology makes the effect of the environment on the concrete structure more aggressive than that of any other part of the world. Extreme and harsh conditions exist because of the changing and fluctuating high temperatures and humidity at the coast and relatively lesser humidity and same high temperatures inland (Fookes, 1993). This type of aggressive and harsh environment leads to premature deterioration of the concrete buildings and structures due to depassivation, sulphate attack or by expansive cracking of the reinforcement present in the concrete by concomitant actions of chloride ions and carbonation. Therefore in order to get higher durability and reliability from the concrete buildings in such harsh environment, the concrete should be impervious and should be dense (Fookes, 1993). A lot of research has been done recently and it is found that if a concrete posses a minimum compressive strength of 50 MPa then it can be made impermeable to water, air and chloride ions in the harsh and extreme climatic conditions. The present study is a research being done on the deterioration of concrete buildings in Kuwait to find out the properties of those concrete structures, reasons for deterioration and making some suggestions and recommendations

1.2 Background

Concrete is the main construction material in the Kuwait and many other Arabian Gulf states. In the past 40 years almost all buildings had a concrete skeleton with in-fill brick walls. The use of steel frames was limited. The versatility and availability of its raw materials made concrete popular, especially during the 700's and 80's when only simple tools and unskilled labor were commonly used for mixing and pouring. Concrete made in this period normally had a high water/cement ratio and required little or no compaction. As the building industry developed in the past 20 years to meet more complex designs, heavy machinery and tighter control became necessary (Fookes, 1993)

In Kuwait buildings suffer mostly from steel corrosion due to chloride attack and/or sulphate attack, according to a field survey. The survey depended mainly on visual inspection of the structures without support from lab testing. Many experts maintain that the Gulf's environment dries out concrete during curing, mixing and pouring. However, experience of the researchers has shown damage to hardened concrete has the same causes worldwide. They are: (Rasheeduzzafar et al, 1994)

* chloride attack

* carbonation

* sulphate attack

* alkali reaction

The effect of high thermal movements due to high temperatures does not generally alter the mode of failure in concrete structures. However, use of long spans in exposed structures such as bridges should be cautiously approached. The failure of pre-stressed concrete pavement used in the 700's in some airports is an example of climate-caused deterioration in the Gulf (Rasheeduzzafar et al, 1994)

Causes of deterioration of concrete structures are normally determined through the following steps: ( Rasheeduzzafar et al, 1994)

1. Visual survey to determine the type and degree of concrete distress in the building. This is normally accompanied by extensive photographing and note taking.

2. Chemical analysis to determine chloride, pH, and soluble sulphate contents. This is usually done in a wet chemistry lab using classical methods.

3. Semi-destructive investigation by cutting cores to determine the mechanical properties.

Non-destructive testing (NDT) is used to distinguish between poor and good concrete. These tests are not normally used to produce absolute compressive strength. This is due to the inherent characteristics of concrete which influence the results and variable parameters affecting the correlation relationships between the readings and the strength. Steel reinforcement and concrete surface roughness interfere with the pulse velocity and rebound hammer tests respectively. Correlations between these tests and compression strength are normally obtained from lab prepared samples. They may not be valid for samples cut from old structures. (Nasser et al , 1987)

1.3 Problem Statement

The deterioration of the reinforcement in the concrete is common problem all over the world. But this problem is more predominant in regions of hot and dry climates of Kuwait and other Arabian Gulf countries especially coastal locations. According to the study done by Rasheeduzzafar et al, in the recent 10 - 15 years the deterioration has been seen to occur at alarming rate in the country and this problem is not only limited to some small projects. Many important and prestigious structures have also deteriorated although they were developed and designed by some of the great international construction firms.

The present study is thus aimed at evaluation of the concrete deterioration in Kuwait. An exhaustive literature review would be first carried out to find the materials of concretes, causes and effects of deterioration etc. Different deteriorated buildings in Kuwait would be surveyed and samples would be taken for analysis. Mechanical, Chemical and physical tests would be performed in order to obtain the properties of these samples. Some of the properties like depth of the carbonation, compressive strength, density etc would be obtained for the building concretes.

1.4 Aim

Evaluation and Experimental Analysis of concrete deterioration in buildings of Kuwait and suggesting recommendations for building more durable structures.

1.5 Objectives

* Exhaustive Literature Review to gain knowledge on concrete deterioration, causes, effects, materials of concrete, how to predict erosion, methods to control etc

* Survey of buildings in Kuwait to observe the nature of cracks and do the analysis

* Testing of the concrete samples from the buildings to evaluate their physical, mechanical and chemical properties

* Analysis using the standard physical chemistry techniques to obtain the causes of these deterioration

* Conclusion and suggesting recommendation on the basis of field study for bringing more durability in the concrete structures

1.6 Methodology

The methodology planned for the research is divided into 3 phases.

In the first phase a general understanding regarding the concrete, different types of materials, causes of deterioration, effects of deterioration, ways to control it etc would be developed though literature review. Some previous research in the field of concrete deterioration would also be studied through published papers in the journals. The main objective of this would be to get knowledge of the techniques and the testing procedures used by researches for measuring the properties of concrete and the techniques used in order to know the cause of the deterioration.

The second phase would involve a field study of some of the buildings in Kuwait were concrete deterioration has occurred. The concrete samples would be collected from these buildings and tests would be conducted to get the physical, chemical and mechanical properties of these concretes. The tests results would then be documented and would be analyzed.

The third phase would be based on identifying the cause of these deteriorations. Some standard techniques would be used to know the possible reasons and based on the experimental results and results of the failure causes some suggestions and recommendations would be made regarding the improvements in the durability and reliability of concrete buildings in Kuwait.

References

1. Al-Khaiat, H., 1995 Effect of pollution from Kuwait oil wells fires on concrete properties. KFAS 92-08-01

2. Aitcin, P. C., 1994 Durable concrete - current practice and future trends. AU, 144

3. Fookes, P. G., 1993 Concrete in the Middle East - past, present and future: a brief review. Concrete

4. Kayyali, 0. A. & Haque, M. N., 1988 Effect of carbonation on the chloride concentration in pore solution of mortars with and -without flyash. Cement and Concrete Research

5. Nasser, K. W. and A. A. AI-Manaseer, 1987, Comparison of Nondestructive Testers of Hardened Concrete. ACI Mat. J. 84(5) 374.

6. Neville, A. M., 1981 Properties of Concrete. The English Language Book Society and Pitman, 3rd edition,

7. Rasheeduzzafar Dakhil, F. H. & Al-Ghatani, A. S., 1984, Deterioration of concrete structures in the environment of the Middle-East. AC1 Material Journal.

8. Tomsett, H. N. In Situ Strength Evaluation of Concrete ACI. Fall Meeting, Houston, Texas. (1978).

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