Durability means concrete
can meet high security, function and appearance requirement in the estimated period as designed without much additional maintenance, taken natural environment engineering environment and structural internal factors into consideration.
It is global topic and focus in civil engineering.
Situation of durability
Fig.1 Pictures of degradation
in foreign countries
It is reported that 130 billion dollars are needed for over 29% bridges, more than 1/3 roads and 2100 unstable dam, by American Civil Engineering Society in 1998. Canada spends about 500 billion dollars in maintaining degradation destruction.
Japan spends 40 billion yuan in structure maintenance every year. Our situation is what developed countries experienced decades ago.
Aspects of durability study
- atmospheric environment
- sea environment
- soil environment
- industry environment
- corrosion of reinforcing bar
- alkali-aggregate reaction
- carbonation、fire damage、soundness
- hydrate－chemical corrosion、fire、dimensional stability
- pore structure－permeability、chlorine ion permeation、frost resistance
- model of rupture due to corrosion expansion
- model of reducing cohesion
- model of bearing strength change
Measures to enhance durability of concrete
- Basic protection
- to enhance solidity
- to increase protective thickness
- to use chemical admixture
- to use mineral admixture
- Adjunct measures
- protection of bar coating
- reinforcing corrosion-resisted bar
- electrochemical protection
- protection of concrete coating