Conventional repair

Over the years there have been several studies examining electron-curable adhesives [9-12]. Off-the-shelf acrylate adhesives were the primary focus of the studies. These adhesives, that have potential use for the repair of advanced composites using high-energy electron accelerators, offer several advantages over conventional repair systems, including [6] ... 

This chapter deals with the strategies for repair of reinforced-concrete structures damaged by carbonation or chloride-induced corrosion of the reinforcement, and outlines the most common methods. Details of conventional repair and electrochemical maintenance methods are reported in Chapters 19 and 20. The repair of prestressed concrete structures is outside the scope of this book. 

Conventional repair. The most utilised method consists in the removal of carbonated concrete and its replacement with alkaline mortar or concrete. This method is convenient when the corrosion attack is limited to zones of small extent (for example when the thickness of the concrete cover is reduced locally). In that case it is usually called patch repair. Conversely, it may be rather expensive when repair is required on large surfaces. In fact, concrete must be removed in all the zones where carbonation and subsequent corrosion of steel are expected to damage the structure within the design life of the repair. Even structurally sound concrete must be removed where the corrosion rate of the embedded steel is expected to... 

The most frequently used methods for repair of chloride-contaminated structures are shown in Figure 18.5. When the chloride level is high, conventional repair methods usually do not give a durable result In these cases, it is necessary to consider other methods such as cathodic protection or electrochemical chloride... 

The term conventional repair is used in this book to indicate a repair work made on a damaged reinforced concrete structure, which is aimed at restoring protection to the reinforcement by means of replacement of non-protective concrete with a suitable cementitious material. The durability of the repair work is due to the achievement and maintenance of passivity on the reinforcement by the contact with the protective repair material. The repair work can be divided in the following steps a) assessment of the condition of the structure b) removal of concrete in well-defined parts of the structure and for specific depths c) cleaning of the exposed rebars d) application of a suitable repair material to provide an adequate cover to the reinforcement [1-6]. Each of these steps must be carried out properly in order to guarantee the effectiveness of the whole repair work. Additional protection measures can be used to increase the durability of the repair, but they must not interfere with the protection provided by the alkahnity of the repair material. Strengthening may also be required to restore the structural safety of the structure. 

This chapter illustrates the procedure that should be followed in the design of the conventional repair to guarantee that it is effective in the aims of providing protection to the structure and preventing further corrosion damage during the... 

As illustrated in Chapter 18, even before making a decision on the use of conventional repair, the causes of deterioration and the condition of the structure have to be clearly assessed (otherwise, any repair work should only be considered a waste of time and money). If carbonation or chloride contamination is the cause of degradation and the decision of using conventional repair has been made, a more detailed analysis is required. A survey of the structure has to be carried out with the aim of identifying the extent of the areas where concrete has to be removed and the depth that should be removed. A clearly described working plan of the repair should be made. 

Many techniques are used to remove concrete in repair works, which vary from mild surface removal to destmctive methods such as blasting techniques [2,4,6], When conventional repair is used, however, only some methods are suitable to achieve the following requirements ... 

Although ordinary Portland cement mortars (or concretes) can be used as materials for conventional repair, different types of additions or admixtures may improve their performance [8,9]. The water/cement ratio is usually low (e. g. 0.4 or even... 

Surface treatment of concrete. Surface treatment of concrete may be used in association with conventional repair to achieve the required service life of the repair. A specific type of treatment may be used to delay penetration of carbonation or chlorides or to decrease the moisture content (Chapter 14) either in the original concrete or in the repair mortar. The effect of this treatment can be taken into consideration in the evaluation of the residual service fife of the structure, both in the repaired and unrepaired zones. This can lead to a reduction in the extent of the areas to be repaired or in the thickness of the repair material. 

Concrete repair to damaged areas is cheaper and easier than for conventional repairs. 

The conventional repair of severed peripheral nerves with direct suture or autografting can result in neuroma formation and poor functional recovery.2Attempts in the past several decades to provide a device to facilitate nerve regeneration have resulted in minimal success. The recent advances in material science and technology have provided an opportunity to investigate this important clinical problem with a more systematic approach. 

Laser welding Extremely accurate and much less heat intensive than conventional repair, laser welding is particularly useful for turbine blades, compressor blade leading edges, and other sensitive components. 

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