Concrete degradation

At elevated temperature a joint action of thermo-chemical concrete degradation, V, accounting for high temperature related micro-cracking and dehydration, and external load-related cracking, d, is described by the total damage parameter, D, given by [7],... 

Concrete degraded. Anchors in the brickwork, or other penetrations through membrane into concrete, allowed flow of chemicals. (3)... 

Reinforced concrete bridges suffer from corrosion of the reinforcement and, consequently, concrete degradation because of the high tensile forces exerted by... 

Glasser, E, Marchand, J., Samson, E., 2008. Durability of concrete. Degradation phenomena involving detrimental chemical reactions. Cement and Concrete Research, 38(2), pp. 226-246. 

If the project involves demolition and refurbishment, then information on the occupancy of the premises or nearby premises needs to be ascertained. A structural survey should be made of the building to investigate the types of structural defect that may be apparent during a visual inspection and explain the causes of those defects. Typical defects include corrosion of steelwork, cracking due to fatigue in structural steel and welds, cracked brickwork and concrete, concrete degradation (flaking), dropped lintels and... 

The phases in concrete degradation are first mechanical in origin, then chemical. 

As Rogers et al. [21] quoted to The U.S. Nuclear Regulatory Commission, Service Life of Concrete , conplied in 1989, there are at least seven major chemi-cal/physical factors reported to be major causes of concrete degradation ... 

Rogers et al. put it an understanding of concrete degradation may be incomplete without including the effects of microbial influenced degradation, or briefly. 

Figure 2.25 Concrete degradation processes resulting from environmental effects.

Figure 2.27 Concrete degradation caused by rebar corrosion damage in a highway structure in downtown Toronto, Ontario. Extensive repair work was underway on this structure at the time the picture was taken. The annual maintenance costs for this structure were recently reported at around 18 million.

Figure 2.28 Concrete degradation caused by rebar corrosion damage near Kingston, Ontario. This bridge underwent extensive rehabilitation shortly after this picture was taken.

An important issue in CP of reinforcing steel is how much current should be impressed between the reinforcing steel and the anode. Too little current will result in inadequate corrosion protection of the rebar, while excessive current can result in problems such as hydrogen embrittlement and concrete degradation. Furthermore, a imiform current distribution is obviously desirable. 

Besides corrosion-induced rebar damage, there are three other commonly cited forms of concrete degradation, namely, alkali-aggregate reaction, freeze-thaw damage, and sulfate attack. 

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