Reinforced concrete repair

Figure 6.4 Dimensions of the substrate for measuring plastic shrinkage cracking using a bonded overlay, from N. Banthia.R. Gupta and S. Mindess, Development of Fiber Reinforced Concrete Repair Materials , Canadian J. of Civil Engineering, Vol. 33, No. 2,2006, pp. 126-1 33 with permssion from NRC Research Press.

There are different concrete replacement systems available for renovating reinforced concrete structures. They range from sprayed concrete without polymer additions to systems containing conducting polymers (PCC-mortar). Since with the latter alkalinity is lower, more rapid carbonization occurs on weathering [59] and the increased electrical resistivity has to be taken into account, so that with cathodic protection only sprayed concrete should be used as a repair mortar. 

Proc. 2nd International Conference on the deterioration and repair of reinforced concrete in the Arabian Gulf, Bahrain 1987. 

Tvarusku, A. and Bennett, J. E., Proc. 2nd International Conference on Deterioration and Repair of Reinforced Concrete in Arabian Gulf, Bahrain, pp. 139-154 (1987)... 

Latex-modified mortars and concretes have become promising materials for preventing chloride-induced corrosion and for repairing damaged reinforced concrete structures. In Japan and the USA, latex-modified mortar is widely used as a construction material in bridge deck overlays and patching compounds, and for finishing and repairs [99]. Polymer-cement hydrate-... 

REPAIR AND STRENGTHENING OF REINFORCED CONCRETE STRUCTURES BY EPOXY-RUBBER COATINGS [10-25]... 

Potapov, Yu., Borisov, Yu., Surovtsev, I., Figovsky, O., and Beilin, D. Increasing Repair and Crack Resistance of Reinforced Concrete Structures by Polymer Composites, Proceedings of the Second International Conference on Concrete Repair, Concrete Solution, St. Malo, France, 2006, 111-114. 

The main aim of the work presented here is to assess the performances of RPC, as a new repair material and to evaluate the strength and durability of its bond to existing reinforced concrete. 

The use of corrosion inhibitors could be a promising technique in restoring reinforced concrete structures, offering benefits as reduced costs and inconvenience of repairs. It has, however, to be taken into account that the use of corrosion inhibitors in repair systems is far less well-established than their application as admixtures in new structures. The performance of proprietary corrosion inhibitors in repair systems marketed under different trade names is not yet sufficiently documented by independent research work, especially when considering field tests. 

B. Elsener, M. Btirchler, F. Stalder, H. Bohni, "A migrating corrosion inhibitor blend for reinforced concrete - Part 2 Inhibitor as repair strategy , Corrosion, 2000, 56, 121. 

German Committee on Reinforced Concrete, Guidelines for the Protection and Repair of Concrete Component",... 

M. I. Eusebio Marques, Effectiveness of surface coatings to protect reinforced concrete in marine environments . Materials and Structures, 2000, 33, 618-626. prEN 1504-2, Products and systems for the protection and repair of Concrete Structures. Definitions -Requirements - Quality Control and Evaluation of Conformity. Part 2 Sutface Protection Systems , CEN TC 104/WG 8. 

P. Pedeferri, L. Bertolini, F. Bolzoni, T. Pastore, Behaviour of stainless steels in concrete , in Repair and Rehabilitation Reinforced Concrete Structures the State of the Art,... 

B. Elsener, Condition evaluation of reinforced concrete bridges - The benefits of potential mapping , in Proc. Int. Conf Structural Faults e[ Repair, London, Vol. 1, 47,... 

F. Hunkeler, Monitoring of repaired reinforced-concrete stmctures by means of resistivity measurements , in Repair of Concrete Structures, Svolvaer,... 

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. 

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. 

Cathodic protection of reinforced-concrete structures exposed to the atmosphere was apphed for the first time to bridge decks contaminated by de-icing salts by R. F. StratfuU in California in 1973 [1,2]. In the years following, design and protection criteria were elaborated, as well as power supply and monitoring systems completely different from those used for cathodic protection of buried steel structures or structures operating in seawater. Above all, it was proved that cathodic protection was a rehable repair technique even in the presence of high chloride contents, where traditional systems of rehabilitation are inefficient or very costly. 

M. Tettamanti, The effect of current density on anode behaviour and on concrete in the anode region , 2" Int. Conf. on Deterioration and Repair of Reinforced Concrete in the Arabian Gulf Bahrain, 11—13 October 1987. 

The adhesion or bond of latex-modified mortars to reinforcing bars is found to be very important for their use in repair work for damaged reinforced concrete structures. Figure 4.54l l illustrates the bond strength of the latex-modified mortars to the reinforcing bars, determined under direct tension by pull-out method. In general, the bond strength of the latex-... 

In the early 1980s, the corrosion of structural steel supports due to chloride ions liberated from PVDC-modified mortar which had been used to repair an old brick building, led to a civil suit in the United States l l therefore, PVDC latex is not currently used as a cement modifier in the United States and other countries. In a laboratory study, the liberation of chloride ions is observed in such a chloride-containing polymer, and a possibility of the conosion of the reinforcing bars which is induced by the chloride ions in reinforced concrete structures is suggested.l H The use of PVDC-modified mortars with polymer-cement ratios of 5% or more causes the liberation of sufficient chloride ions to exceed flie tolerable corrosion limits for the reinforcing bars in reinforced concrete structure. 

For the past seventy years or more, active research and development of polymer-modified mortar and concrete has been conducted around the world, resulting in products which are currently used as popular, important construction materials. To match the technical innovations in the construction industry in recent years, useful polymeric admixtures or polymer-modified mortar and concrete have been developed in advanced countries. There is currently great interest in using polymer-modified mortar and concrete as repair materials for deteriorated reinforced concrete structures. Polymer-modified concrete and mortar are promising construction materials for the future because of the good balance between their performance and cost compared to odier concrete-polymer composites. 

The potential of the corroding surface can be monitored periodically by means of a reference electrode. One such example is the corrosion potential measurement of reinforced steel rebar in concrete structures. Corrosion of the steel in reinforced concrete is a major factor in the deterioration of highway and bridge infrastructure. A survey of the condition ofa reinforced concrete structure is the first step toward its rehabilitation. A rapid, cost-effective, and nondestructive condition survey offers key information to evaluate the corrosion, aids in quality assurance of concrete repair and rehabilitation. 

Elsener B, Zimmermann L, Bilrchler D, Bohni H. Repair of reinforced concrete structures by electrochemical techniques - field experience. Proceedings Eurocorr 97. Trondheim, 1997. 

Wide-ranging use of repair, restoration or rehabilitation systems using polymer-modified paste, mortar and concrete for deteriorated reinforced concrete structures [72-73]... 

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