Damaged concrete

Epoxy resin injections have been successfully employed in the repair of delaminated bridge decks (Crompton et al., 1974). It is important to remember that the effectiveness of the repair process is dependent on the ability of the epoxy resin to penetrate, under appropriate pressure, into the fine cracks of the damaged concrete (Chang, 1981). 

Repair Materials Grouts for repairing cracks and delaminalions of concrete structures, patching materials for damaged concrete structures, rustproof coatings for corroded reinforcing bars, etc. 

The destruction of concrete due to the formation of thaumasite replacing the C-S-H phase is a special case of sulphate corrosion. This process is promoted by the simultaneous intensive carbonation, or by use of limestone Portland cement, together with the low temperature. In Poland the destruction of concrete stractures due to the thaumasite formation has not been reported, however, this ean arise from the multicomponent paste composition of damaged concrete and very similar XRD pattern of thaumasite and ettringite. 

If an electrochemical technique is being used then repairs only need to reinstate damaged concrete. A clean rebar surface is needed and a simple patch to rebar depth in cracked, spalled and delaminated areas will prepare the structure for the application of the anode. In some cases the anode and overlay will fill the excavated areas as a single operation. Only a minimal repair is required as shown in Figure 5.1 becau.se the treatment itself deals with the corrosion. The repair materials must be compatible with the electrochemical treatment. These issues are fully discussed in Chapter 6. 

At the time of vriting 1996 any use of inhibitors to rehabilitate corrosion damaged concrete should be considered experimental. Trials on core.s and test areas are recommended with follow up studies using corrosion rate measurement before and after application, with control areas for comparison. 

Economic considerations have made it mandatory to look to repair the damaged concrete rather than it s total replacement. 

In the case of concrete, the main reasons for preparing the surface before bonding are similar, namely (1) to produce a close fit between the adherends (2) to remove laitance and contaminants and to expose pieces of aggregate and (3) to produce a mechanically sound surface. Any typical sequence of steps in the process of concrete surface preparation should then include the removal of any damaged concrete and its replacement with new material, and the elimination of dust and other contaminants by brushing, air blast or vacuum. In some situations, additional steps like cleaning with a solvent to eradicate specific contaminants and application of a primer may be required. 

Reproduced with permission from Georgali B. and Tsakirides P. E., Microstructure of fire-damaged concrete a case study published by... 

Land-based construction is more accurate and can be carried out usually under sea conditions that do not allow construction with the aid of barges. Moreover, the risk of damaging concrete units is lower. When both type are possible land-based... 

The aggregates may be contaminated with salts, such as Na2S04 and react with calcium aluminate hydrate to produce ettringite and also CaS04 2H20. These reactions products damage concrete by... 

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