Visible Corrosion Damage in Carbonated Reinforced Concrete

publishedVersionPeer reviewe

Renovation of an alkali–aggregate reaction damaged swimming pool

AbstractThe alkali–aggregate reaction (AAR) is an expansion reaction of the aggregate in concrete caused by the alkalinity of hydrated cement, which may disintegrate concrete. The alkali–silica reaction (ASR) is the most general form of AAR which only rarely causes degradation in Finland. The pool at Tampere Swimming Centre was only the third such case in the country. Condition assessment by several parallel methods was used to determine the existence and extent of ASR. A total of 34 samples were drilled from the concrete structures of the swimming pool. The samples were examined by scanning electron microscopy (SEM) and an X-ray diffractometer as well as by thin section analyses and tensile and compressive strength tests of concrete.Based on the assessment, it was decided to repair the damaged concrete and stop the ASR by proper waterproofing. Tensile and compressive strength tests on the concrete indicated that a relatively light renovation method was sufficient because the deterioration of the concrete was still incipient and the target service life of the repairs was only 20–25 years. Self-compacting concrete was determined to be a good solution for concreting the narrow spaces between dense reinforcement. Self-compacting concrete was used also for concreting the splash canals and supporting consoles. The renovation was based on installing proper waterproofing between the concrete surface and the ceramic tiling

Decreasing Carbon Footprint of Block of Flats - Concrete Technology Possibilities

Construction business along with other businesses have set carbon neutrality goals in the following years. To reach these goals a lot needs to be done fairly quickly. The high impact of concrete production on carbon emissions has been known for years and solutions for this problem are studied in this paper through supplementary cementing materials. Ordinary Portland cement can be replaced partly but not completely with cement replacing materials since the strength properties are lost at replacement level higher than 80%. These replacing binders can be pulverized fly ash, blast furnace slag or silica fume. The use of the new low-carbon products can half the embodied carbon for the bearing frame of the building. The total area of a certain structure type is important since replacing its cement can have much higher impact on the total carbon footprint than replacing it for a single structure type that has fairly small area in the building.publishedVersionPeer reviewe

Julkisivujen ja parvekkeiden kestävyys muuttuvassa ilmastossa

Kuvaa 9 sivulla 19 päivitetty 24.9.2014.Ilmastonmuutoksen torjumista on eri medioissa tuotu esiin sekä poliitikkojen että ilmastotutkijoiden toimesta jo pitkään. Ilmastonmuutoksen torjumiseksi valtiot ovat sopineet varsin haasteellisia kasvihuonekaasupäästöjen vähentämistavoitteita. Eri ilmastoennusteiden mukaan Suomen ilmasto tulee joka tapauksessa muuttumaan lämpimämpään ja sateisempaan suuntaan seuraavien vuosikymmenten aikana riippumatta uudisrakentamisen energianvähennystoimista. Nykyisen useiden vuosikymmenten aikana rakennetun rakennuskannan julkisivuissa on käytetty monia erilaisia materiaaleja, joiden kestävyyttä muuttuvassa ilmastossa ei tarkkaan tunneta. Tämän lisäksi monien käytössä olevien rakenteiden lämpö- ja kosteustekninen toiminta on jo nykyisessä ilmastossa varsin vaurioherkkää. Tässä julkaisussa arvioidaan nykyisten julkisivutyyppien kestävyyttä, vaurioitumismekanismien ja vaurioitumisnopeuden muutoksia sekä korjaus- ja suojausmahdollisuuksia muuttuvassa ilmastossa. Tässä esiselvityksessä keskitytään ensisijaisesti huokoisten kiviainespohjaisten julkisivu- ja parvekemateriaalien vauriomekanismeihin sekä niiden keskeisimpiin korjaustapoihin. Pääpaino on 1960-luvulla ja sen jälkeen rakennetuissa rakennuksissa, jolloin selvitys kattaa yli 80 % rakennuskannasta. Esiselvitys perustuu tutkijoiden kokemuksiin julkisivujen vaurioitumisesta ja korjaamisesta sekä Tampereen teknillisen yliopiston (TTY) Rakennustekniikan laitoksella aiemmin tehtyihin julkisivujen vaurioitumiseen ja korjausmahdollisuuksiin liittyviin tutkimuksiin

Julkisivujen pitkäaikaisestävyyden rasitusolosuhteet

acceptedVersionPeer reviewe

Service Life of Concrete Pedestal without Air Entrainment

Service life of nine wind power unit pedestals, which concrete grades between C45 and C55, were studied with four different service life models. The exact service life could be calculated only with two of them with the initial data. The service life models that were used in calculations: Factor method Deterioration and service life prediction of concrete subjected to freeze-thaw cycles in Na2SO4 Solution -method Service life models that were considered only at theoretical level: FIB Bulletin 34 - Model Code for Service Life Design, and An equation for determining freeze-thaw fatigue damage in concrete and a model for predicting the service life. The latter two methods are more theoretical, and they require laboratory tests to obtain more information before the calculations can be properly executed. This article concludes that damage to concrete due to freeze-thaw cracking is still poorly known and a sufficiently accurate service life model has not yet been developed for its computational modeling. Therefore, there is a need to develop a service life model suitable for Finnish climate and concrete grades, which could be used for estimating the damage rate of an existing concrete structure.publishedVersionPeer reviewe

Delayed ettringite formation (DEF) and its effect on freeze-thaw damage in Finnish concrete façades

The strongest drivers causing delayed ettringite formation (DEF) and its impact as a cause of freeze-thaw damage in Finnish concrete façades is still poorly known as it has been only briefly touched as a part of one dissertation [1] and one master's thesis [2]. The conclusion of both studies was that DEF might slightly accelerate freeze-thaw damage of concrete, but how strongly or how rapidly was not stated. To complement the knowledge on that matter, this article analyses Finnish façade structures built between 1960 and 2003 using large case-study databases, weather history data and statistical methods. As a result, it was found that DEF occurs in more than half of the Finnish concrete façades, but it significantly increases the freeze-thaw damage only when it has spread widely in the pore structure of concrete. Such case has been quite rare, since the amount of widespread DEF covers only 4.4% of all observations. Wind-driven rain (WDR) was found to be one of the most significant drivers for DEF, and if the façades are either completely protected from it or oriented in the direction which are least exposed to WDR, DEF was not observed extensively at all. Façades where no DEF was detected had WDR exposure an average of 1852 mm per year. The facades where DEF was found extensively had 68% more exposure, an average of 3127 mm per year.publishedVersionPeer reviewe

Impact of ETICS on Corrosion Propagation of Concrete Facade

AbstractThe durability of reinforced concrete facades is an important field of research as the majority of dwellings in Northern and Eastern Europe were constructed 30–50 years ago. Recent condition assessments of the façades have indicated damage related to carbonation induced corrosion. Moreover, the problem might escalate since the future climate scenarios predict a significant increase of CO2 in ambient air being a driving force for carbonation.Assessment of residual service life of concrete facades is a complex phenomenon with a high level of uncertainty. A validated method used in this study combines dynamic hygrothermal simulation tool Delphin and existing corrosion models. Corrosion propagation consists of the time needed to concrete cover cracking and further expansion of a crack up to a width of 0.3mm as a limit criterion. Additional exterior thermal insulation (mostly ETICS) is applied to existing dwellings as a renovation scenario in order to decrease the heat loss, improve thermal comfort and prevent the degradation mechanism e.g. carbonation induced corrosion. Hence, reinforcement corrosion before and after installing ETICS with mineral wool, EPS or PIR has to be evaluated. Impact of boundary conditions, e.g. wind-driven rain in addition to material properties, and built-in moisture was included.The results indicate that corrosion propagation after carbonation has reached the reinforcement, is three to six years depending on the ratio of concrete cover depth against the reinforcement diameter. While applying ETICS, corrosion accelerates for a short period of time up to one year. Temperature inside the wall rises above +10°C throughout the year, meaning no more freeze-thaw damage. Corrosion of reinforcement in carbonated concrete after applying ETICS is so slow, that no cracking will develop. Drying out moisture or vapour diffusion from indoor air is not able to propagate corrosion of reinforcement in carbonated concrete

Wind-driven rain load in Finland in present and future projected climates

The amount of wind-driven rain (WDR) has been shown to have a major effect on the different deterioration mechanisms of outdoor exposed structures. For example, in recent studies of Finnish existing concrete element buildings the amount of WDR has been shown to have strong correlation with the corrosion rate of reinforcements in carbonated concrete and the freeze-thaw damage of concrete. The latter can be related to all porous stone-based materials (e.g., bricks and mortars). In addition, the amount of WDR has a major effect on mould growth potential in different materials or structures sensitive to it. Thus, the effect of the amount of WDR in present climate has been studied comprehensively. In this study, the amount of WDR is calculated for a new 30-year period (1989-2018) presenting the present climate among with two future periods presenting 2050 and 2080 climates. In future climate projections, three different CMPI5 based scenarios are used: RCP2.6, RCP4.5 and RCP8.5. All calculations take into account the wind directions and they are made for four different locations presenting Finland: coastal area, southern Finland, inland and northern Finland (Lapland). Based on the results, the WDR load in the form of rain or sleet is increasing in all locations and from every direction regardless of the used scenario. The highest relative increase is in inland and Lapland, though, the load is still significantly higher in coastal and southern parts of Finland. With all the scenarios the WDR load is still focusing on southern directions, but it will be more evenly divided for other directions than in present climate. In addition, the WDR load is increasing during autumn and wintertime, i.e., during the periods when in the latitudes the drying conditions are weak because of the lack of solar radiation and the high-level relative humidity.Peer reviewe

Elinkaariominaisuudet rakennuksen pitkäikäisyyden edistämisessä : Säilyvyys, joustavuus ja uudelleenkäytettävyys kiertotalouden välineinä

Uuteen rakentamislakiin sisältyy kestävää rakentamista tukevia velvoitteita, jotka painottavat vähähiilisyyttä ja rakennusten pitkäikäisyyttä. Jälkimmäiseen liittyy uusi olennainen tekninen vaatimus rakennuksen elinkaariominaisuuksista. Elinkaariominaisuudet käsittävät säilyvyyden, joustavuuden ja uudelleenkäytettävyyden. Näin ollen ne vaikuttavat myös rakennusten käyttöarvoon sekä taloudelliseen arvoon. Elinkaariominaisuuksien hallinnan perusedellytyksenä on, että rakennushankkeissa elinkaariominaisuuksille voidaan esittää täsmälliset ja todennettavissa olevat vaatimukset. Tämä puolestaan edellyttää elinkaariominaisuuksien ja niiden indikaattorien määrittämistä. Ympäristöministeriö käynnisti vuonna 2022 asiantuntijaprosessin, jonka tavoitteena oli täsmentää elinkaariominaisuuksien käsitteitä sekä esittää yhteenvetoa ja kehitysehdotuksia elinkaariominaisuuksien arvioinnista, suunnittelusta ja ohjauksesta. Tämä raportti tuo esiin asiantuntijaprosessissa tuotettuja sisältöjä ja ehdottaa, että elinkaariominaisuuksien tarkemman määrittelyn myötä ne tulisi sisällyttää systemaattisemmin rakentamisen hankintaan ja ohjaukseen. Raportti luo pohjaa elinkaarisuunnittelun systematiikalle ja antaa suosituksia aiheeseen liittyvistä jatkokehitysmahdollisuuksista