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<p>Validerat; 20130508 (global_studentproject_submitter)</p>

Betong är världens mest använda byggnadsmaterial och en stor utsläppskälla av koldioxid. Det är framför allt produktion av cementet i betongen som bidrar till koldioxidutsläppen. Globalt sett är produktionen av cement den tredje största orsaken till koldioxidutsläpp, 8 % av världens utsläpp. Därför ligger det stort intresse i att minska mängden cement i betongen för att nå lägre klimatpåverkan. Ett sätt att göra detta på är att delvis byta ut cementet mot andra tillsatsmaterial med cementliknande egenskaper, till exempel slagg. Det största problemet med detta är att betongens härdningstid förlängs. Detta arbete genomförs tillsammans med RISE för att hjälpa Hedareds Sand och Betong att ställa om till klimatförbättrad betong i sina prefabelement. För att göra detta måste härdningstiden i den klimatförbättrade betongen sänkas. Denna studie ska därför undersöka om accelererande tillsatsmedel kan korta härdningstiden i slaggbetong. För att undersöka detta användes två experimentella metoder: isotermisk kalorimetri och gjutning med tryckprovning. Resultatet från den isotermiska kalorimetrin visade att acceleratorn Master X-Seed 140 gav kortast induktionsperiod och klart högre värmeflöde än referensprovet. Resultatet från gjutningen visade att den prövade betongen nådde en tryckhållfasthet på 29,73 MPa efter 24 timmar. Vilket är 62,5 % högre än referensprovet utan accelerator och tydligt över kravet på 16 MPa efter 24 timmar. Slutsatsen som gick att dra efter detta arbete var att acceleratorn visade mycket god effekt på tryckhållfastheten och ger utökade möjligheter att använda klimatförbättrad betong inom prefabindustrin. / Concrete is the world's most widely used building material and a significant source of carbon dioxide emissions. It is primarily the production of cement in concrete that contributes to these emissions. Globally, cement production is the third-largest contributor to carbon dioxide emissions, accounting for 8 % of the world's emissions. Therefore, there is considerable interest in reducing the amount of cement in concrete to achieve lower climate impact. One way to do this is by partially replacing cement with other supplementary materials with cement-like properties, such as slag. The main challenge with this approach is that it extends the curing time of the concrete. This work is conducted in collaboration with RISE to assist Hedareds Sand and Betong in transitioning to climate-enhanced concrete in their precast elements. To achieve this, the curing time in the climate-enhanced concrete must be reduced. This study aims to investigate whether accelerating admixtures can shorten the curing time in slag concrete. Two experimental methods were used to investigate this: isothermal calorimetry and casting with pressure testing. The results from isothermal calorimetry showed that the accelerator Master X-Seed 140 had the shortest induction period and significantly higher heat flow than the reference sample. The results from casting showed that the tested concrete reached a compressive strength of 29,73 MPa after 24 hours, which is 62,5 % higher than the reference sample without accelerator and clearly exceeds the requirement of 16 MPa after 24 hours. The conclusion drawn from this work was that the accelerator demonstrated a very good effect on compressive strength and provides expanded opportunities for using climate-enhanced concrete in the precast industry.

Man vill förkorta betongs bindetid dvs. den tid då betongytan kan behandlas så att betongytan blir slät efter gjutning. Det är en stor utmaning för företag som tillverkar fabriksbetong vintertid, eftersom bindetiden förlängs ju kallare klimatet är. Syftet med denna labboration var att visa hur Kalciumnitrart fungerar som bindetidsaccelerator i betong, och om Kalciumnitrart påverkar betongens fysikaliska egenskaper.  Följande faktorer har studerats för att se hur dessa faktorer påverkar betongens bindetid i kombination med användning av Kalciumnitrat. Betongens utgångstemperartur Typ av flyttillsatsmedel i betongen Betongens utgångskonsistens Betongens lagringsklimat Även hitta rätt dosering för att denna produkt ska vara lönsamt att användas i praktiken. Alla underökningar har utförts hos Sika AB laboratorium. All data har noggrant undersökts och använts i Excel program för framtagning av tabeller och diagram. Resultaten/slutsats i underökningarna visade följande. Bindetiden kan förkortas med Kalciumnitrat utan att behöva riskera betongens fysikaliska egenskaper. Enligt bindetidsdiagram noterades att 2,0 % och 2,5 % doseringarna gav bästa resultat gällande bindetid dvs. de gav kortast bindetid. Observera att +5 graders lagringsklimat gav ologiska resultat dvs. referensbetongen utan acceleratorn gav kortast bindetid. Tryckhållfastheten påverkas inte av acceleratorn dvs. man kan använda denna produkt utan att riskera betongens bärförmåga. Resultaten visade att betongens utgångskonsistens har stor betydelse för bindetiden, ju högre konsistens värde desto längre bindetid. Även betongens utgångstemperatur har påverkan på bindetiden, ju högre betongtemperatur desto kortare bindetid. / You want to reduce the concrete’s initial setting i.e.  the time the concrete surface can be treated so that surface gets plane after molding. It’s a big challenge for the companies that produce mill concrete in winter. Since the colder the climate gets the binding process will be extended. The purpose of this lab was to show how Calcium Nitrate functions as bonding time accelerator in concrete and if Calcium Nitrate affects the physical features of the concrete. The following elements have been studied to see how these elements affect the initial setting of the concrete in combination with the use of Calcium Nitrate. The initial temperature of the concrete The type of super plasticizer in the concrete The initial consistency Concrete storage climate Even finding the right dose so that this product will be profitable to use in the practice. All investigations have been made at Sika AB laboratory. All the data have been investigated and used in excel program for the product of chart and diagram. The results of the investigations showed the following:   Bond time can be reduced with Calcium Nitrate without needing to risk the physical features of the concrete.  According to bonding time diagram it was noted that 2.0 % and 2.5% doses gave the best result valid the initial setting i.e. that gave the shortest time of initial setting, Observe that +5 degrees storage climate gave illogical results i.e. reference concrete without the accelerator gave the shortest initial setting. Compressive strength does not get affected by the accelerator i.e. you can use this product without risking the concretes carrying capacity.  The results showed that the concrete initial consistency has a big importance to bond time, the higher consistency value the longer time of initial setting. Even concrete initial temperature has influence on the bond time, the higher concrete temperature, the shorter time of initial setting.

Purpose:  The purpose is to investigate the use of concrete as a frame material and its effects on carbon dioxide emissions and energy use. Carbon dioxide emissions and energy use are examined from the production stage to the management stage 100 years in the future. In addition, investigate other material compositions in concrete to study the possibilities 0f lower carbon dioxide impact and energy use. Method: The methods used have included investigating one construction project involving two multi-family houses with the same conditions. The investigation conducted is primarily made through calculations of CO2 emission and energy use. Furthermore, a literary study has also been conducted focused on investigating what the impact concrete has on the environment and what different alternatives are available to reduce potential carbon dioxide emissions and energy use in house construction with a concrete frame. The study has focused on both the production phase and the management phase. The construction stage has been investigated primarily within the concrete production, enforcement and including transports. Whereas the management stage has been studied upon the energy use of the buildings and its effect on carbon dioxide emission.  The literature study deals with methods that can be associated with the case study but will also deal with other presumptive methods. Results: The study of the construction project shows that CO2 emission and energy use primarily comes from cement production within the production stage. Whereas, looking at the whole life cycle studied, the primary contributor to CO2 emissions and energy use over time is the management stage of the buildings. The result also shows that by using renewable steel as reinforcement can significantly effect the energy use, as well as, CO2 emission of the production phase. Conclusions: The cement production is one of the biggest causes of CO2 emissions and energy use in the production phase of the studied life cycle. While the management phase is the largest in terms of the total life cycle studied. Several methods are possible to decrease the use of energy use and CO2-emission in the production stage, and to combine those methods is an alternative that suggested