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Service life of concrete structures in a chloride environment
RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, CBI - Cement- och betonginstitutet.ORCID-id: 0000-0002-6999-6585
1997 (Engelska)Rapport (Refereegranskat)
Abstract [en]

The purpose of this investigation was to establish the effects of various factors in order to assess the remaining service life of existing structures and the service life of new structures. We chose to study the effects of various factors on the diffusion coefficient of chloride, the threshold value for chloride and the corrosion rate once the threshold value had been reached. _x000D_ _x000D_ Decreasing water cement ratio. _x000D_ Decreasing water cement ratio has a positive effect on all three parameters. _x000D_ Decreasing RH. _x000D_ If the relative humidity of the concrete is in the range of 80-96% then a decrease in RH results in a higher threshold value and a lower corrosion rate. If however the RH value decreases in saturated concrete (RH 100%) then the chloride threshold value falls and the corrosion rate rises. _x000D_ _x000D_ Increasing micro silica content. _x000D_ In most cases increasing the concentration of micro silica results in a reduction in chloride penetration. If large amounts of micro silica (>10%) are added to the concrete this can have a negative effect on the threshold value. The corrosion rate is always reduced when micro silica is added._x000D_ _x000D_ Increasing fly ash content. _x000D_ In most cases increasing the fly ash content leads to a reduction in chloride penetration. The threshold value can be negatively affected due to the chemical composition of the fly ash. The corrosion rate is always reduced when fly ash is added to concrete.´_x000D_ _x000D_ Increasing age. _x000D_ When concrete is aged there is continuous hydration of the cement. This means that the concrete becomes denser with age, which in turn has a positive effect on chloride penetration, i.e. it proceeds less rapidly. The passive layer around the steel grows with age in a marine environment, which means that the longer it takes the chloride to reach the steel, the more difficult it is to break through the passive layer. If carbonization takes place, ageing has a negative effect on the threshold value since the passive layer is broken down. _x000D_ _x000D_ Decreasing cover. _x000D_ Decreasing cover has a negative effect on all parameters. The diffusion coefficient remains unchanged but the initiation time is reduced. _x000D_ _x000D_ Of all the factors investigated it has been found that decreasing water cement ratio has an overall positive effect on service life. Decreasing cover often leads to a shorter service life. The remaining factors have positive effects on service life in some cases and negative effects in other cases. _x000D_ _x000D_

Ort, förlag, år, upplaga, sidor
Cement och Betong Institutet , 1997. , s. 63
Serie
CBI rapport, ISSN 0346-8240 ; 1997:1
Nyckelord [en]
Chlorides, Corrosion, Service life
Nationell ämneskategori
Materialteknik
Identifikatorer
URN: urn:nbn:se:ri:diva-3014OAI: oai:DiVA.org:ri-3014DiVA, id: diva2:960619
Tillgänglig från: 2016-09-07 Skapad: 2016-09-07 Senast uppdaterad: 2023-05-23Bibliografiskt granskad

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Pettersson, Karin

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