Repair of Industrial Structures

10.1 Introduction

In most cases, repair and retrofit of a concrete structure are much more com­plicated than executing a new concrete structure, as new constructions do not require engineers with large amounts of experience and can be handled by junior engineers with reasonable amounts of experience, two to three years, for example. However, the repair of concrete structures is more chal­lenging and requires competent engineers and consultants. If the building already exists, you need to define new solutions for the problem that must match the nature of the building and owner requirements while also satisfy­ing the safety and economic requirements. The repair process for reinforced concrete structures is both very important and dangerous. Extreme care must be taken in choosing suitable repair methods and tools.

The reasons for structural deterioration can be summarized as follows:

• Codes, specifications, and precautions were not considered in the design phase.

• Codes, specifications, and precautions were not considered in the execution phase.

• A suitable protection method was not selected in the design phase.

• A suitable protection method was selected, but the execution was bad.

• No maintenance monitoring was performed.

In all previous cases, the results will be the same: The structure will deteri­orate and this will become obvious by cracks and falling of concrete cover of the different reinforced concrete elements of the structure. When cracks are present and the concrete cover is falling, the situation is very bad. Shortages occur in cross-sectional areas of the concrete member, and this situation requires repair as soon as possible to avoid the structural condition worsen­ing and likely collapsing with time.

The first and most important step for any repair is to determine accurately what should be repaired and this depends entirely on the assessment of the structure and the answer to these questions:

• What is the reason for the corrosion?

• Are the cracks and the deterioration of the structure increasing?

• What is the expected extent of the deterioration of concrete and how far does the corrosion extend into the steel?

• What is the impact of the current and expected future deterioration to the safety of the structure?

Answering these questions will require the use of structural assessment methods and methods of measurement to decide the cause of corrosion and the present and future deterioration of the structure. Chapter 4 discusses these methods of assessment and measurement in detail.

The process of repair and restoration of concrete structures, from the assessment phase to the execution phase, requires high levels of experience. Even the simplest stage, such as the evaluation stage, when it is conducted by inexperienced engineers, may lead to the wrong choice of repair method, and this is a big problem.

• When assessing structures, there are several strategies for repair mentioned in a special report by the RILEM committee (1994) that clarify the various repair strategies used in most cases.

• Reestablishment of the deteriorated member.

• Comprehensive repair of the concrete member to restore its ability to withstand full loads.

• Repair of a particular portion of the concrete member and follow-up over continuous periods.

• Strengthening of the structure by an alternative system to bear part of the loads.

In most cases, the strategy of repair is either a comprehensive repair of the concrete member or a partial repair of a concrete member. These strategies are common in the rehabilitation of concrete and depend on the structural system, external environmental factors, and the degree of structural degradation.