Repairs concrete

As a concrete repair and as patching mortars they are used to ... 

It is important that acrylic-modified cement mortars be marketed based on their end-use for example mortars for concrete repair and for use as ceramic tile adhesives are sold as separate products. Therefore, one should not become confused that a single mortar is used for all of the above-mentioned functions. 

Shaw, J.D.N. (1993a) Polymers for concrete repair, in The Repair of Concrete Structures (ed. S.C. Edwards), Blackie Academic Professional, Glasgow, pp. 37-55. 

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. 

A variety of techniques are employed in concrete repair, depending on the nature of the crack and the material chosen. Concrete repair professionals may be hired for this task, or instructions from the manufacturer of the repair material should be followed. 

Commercial inhibitors are frequently blends of several compounds, thus the mechanistic action can be multiple and difficult to identify. This will lead to major difficulties in the independent evaluation of corrosion inhibitors that are proposed in commercially available concrete repair systems. 

C. L. Page, V. T. Ngala, M. M. Page, Corrosion inhibitors in concrete repair systems . Magazine of Concrete Research, 2000, 52, 25-37. 

RE Weyers, EP Larson, Concrete Repair, Rehabilitation and Protection, Proc. of Inti. Conf, Univ. of Dundee, Scotland, June 27-28, 1996, RK Dhir, MR Jones, eds, E FN Spon, London, pp. 29-38. 

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. 

W. G. Smoak Polymer impregnation and polymer concrete repairs at Grand Coulee Dam. in Polymer Concrete, Uses, Materials, and Properties, SP-89, American Concrete Institute, Detroit (1985), pp.43-49. 

Y. Ohama, M. Ota and H. Tatematsu Properties of polymer-modified mortars with hydrocalumite for intelligent repair materials, in Proceedings of the International Conference on Concrete Repair, Rehabilitation and Retrofitting, Taylor Francis, London (2006), pp.931-937. 

JSCE Concrete Committee Recommendation for Concrete Repair and Surface Protection of Concrete Structures (in Japanese), Concrete Library 119, Japan Society of Civil Engineers, Tokyo (2005). 

Dimmig, A., and Kampfer, W. 2001. Investigations of the sulphate resistance of polymer-modified mortar (PCC). The Tenth International Congress on Polymers in Concrete and ICPIC/ICRlInternational Concrete Repair Workshop( Q0 ). 

Chapters 6 and 7 are then concerned with repair and rehabilitation options, first the conventional physical intervention of concrete repair, patching, overlaying and coatings. The electrochemical techniques of cathodic protection, chloride extraction and realkalization are dealt with in Chapter 7. 

Figure 4.1 Structural support system on the Midland Links Motorway elevated section (Junction 9 M6) prior to repair.The support system is jacked up to take some of the load while concrete repair is undertaken. Conductive coating cathodic protection systems can be seen on subsequent cross heads. Courtesy of Kevin Davies, Corrosion Consultant, taken December 2005.

It is common during concrete repairs for the amount of delamination to be far more extensive than delamination surveys indicate. This is partly due to the inaccuracy of the techniques available but also because of the time between survey and repair. Once corrosion has started delaminations can initiate and grow rapidly. An underestimate of 40% or more is not unusual and should be borne in mind when budgeting for repairs. 

Broomfield, J., Davies, K., Hladky, K. and Noyce, R (2003). Monitoring of Reinforcement Corrosion in Concrete Structures in the Field. Proceedings of Concrete Solutions, 1st International Conference on Concrete Repair St.-Malo, France. M. Grantham, F. Rendell, R. Jauherthie and C. Lanos (eds.) PubI Concrete Solutions (on CD ROM). 

A summary of the properties and categories of hand held pneumatic breakers is given in Vorster et al. (1992). For concrete repair work breakers usually range from about 10 to 45 kg, or a maximum of about 20 kg... 

CIRIA Technical Note 141 (CIRIA, 1993) laid down basic requirements of shrinkage, expansion due to wetting and temperature, modulus of elasticity, creep, etc. These have been taken up in standards such as the European Standard on concrete repair BSEN1504 parts 1-10. This is discussed more fully at the end of this chapter. 

Fewer and fewer materials manufacturers have their own company applicators although most have approved or recommended applicators. It is now possible to get back to back guarantees for concrete repairs to last 5-15 years, although there is a price to pay for the premium on such insurance backed guarantees. 

Corrosion inhibitors for steel in concrete are of great interest to the concrete repair community. In this section we will discuss what they are, how they work and what work is going on to assess their effectiveness. 

There is a systematic European standard to physical and chemical techniques for concrete repair of chloride contaminated structures. This is BSENl 504-9. Products and repair Systems for the Protection and repair of Concrete Structures - Definitions, requirements, quality control and evaluation of conformity. Part 9 General Principles for the use of products and systems. The earlier parts cover different classes of materials while part 10 covers site application ... 

A comprehensive Concrete Repair Manual has been developed by ACI in collaboration with BRE, ICRI and the Concrete Society (ACI, 2002). This includes the ACI, Concrete Society, BRE and ICRI guides on condition evaluation and diagnosis, patch repairing and overlaying, as well as guidance documents on protection and corrosion management. Concrete Society (1991) is part of the manual. The manual also includes Corrosion Prevention Association (CPA) monographs on electrochemical techniques, but not NACE recommended practice or technical reports. 

ACI (2002). Concrete Repair Manual. 2nd Edition. 2002 Two Vols Publ. ACI International, BRE, Concrete Society, International Concrete Repairs Institute. 

ICRI (2004). Guideline for the Preparation of Concrete Surfaces for Repair Using Hydrodemolition Methods Technical Guide G03737 International Concrete Repair Institute Des Plaines, Illinois, USA. 

Vassie, P.R. (1987). Durability of Concrete Repairs The Effect of Steel Cleaning Procedures, Research Report 109, Transport Research Laboratory, Crowthome, Berkshire, UK. 

Conductivity must be low enough to allow current to pass into the steel. A resistivity of 15 kQ-cm at 28 days under saturated conditions has been specified by the United Kingdom DoT based on successful use of materials of this resistivity on the Midland Links. There is some disagreement about this specification but it is the only quantitative information available. In the United States some applicators use salt in the concrete to even out the resistivity with the parent concrete. This practice is rarely accepted elsewhere. BSEN 12696 (2000) states that the concrete repair material shall be within 50-200% of the nominal parent concrete electrical resistivity. 

We have already determined that the chloride ion is a catalyst to corrosion (Section 3.2.3). As it is negatively charged we can use the electrochemical process to repel the chloride ion from the steel surface and move it towards an external anode. This process, called electrochemical chloride extraction (ECE), desalination or chloride removal, uses a temporary anode and a higher electrical power density than CP, but is otherwise similar (Figure 7.1). Preparation in terms of concrete repair, power supplies etc are similar to those for impressed current cathodic protection except that the power supply is temporary and may be from a temporary source such as a generator. The output is larger, up to 50 V and 2 A-m. ... 

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

Table 8.1 gives indications of the compatibilities of different repair approaches on decks and vertical surfaces based on the different requirements of the different systems. Giving global information is difficult because there are different approaches in the United States and Europe to concrete repair and the requirements of each structure and each location and microclimate must be assessed individually. 

Vibration and noise are greatly reduced during the (shortened) concrete repair phase. 

A major European standard for repair methods, selection specification and installation is nearing completion with the publication of EN1504 parts 1-10. These documents are designed to meet the harmonized products directive and are principally concerned with the materials used in non-electrochemical concrete repair, their testing prior to use and the site application. Table 8.2 lists the standards. From the point of view of selection and application of repairs parts 9 and 10 are key parts of this standard. 

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